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Web Services Policy 1.5 - Primer is an introductory description of the Web Services Policy language. This document describes the policy language features using numerous examples. The associated Web Services Policy 1.5 - Framework and Web Services Policy 1.5 - Attachment specifications provide the complete normative description of the Web Services Policy language.
This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.
This is the First Public Working Draft of the Web Services Policy 1.5 - Primer specification. This Working Draft was produced by the members of the Web Services Policy Working Group, which is part of the W3C Web Services Activity. The Working Group has not yet decided if it will advance this Working Draft to Recommendation Status. It represents a transcription of the original contribution into the W3C style. Several issues have already been filed on this document and are recorded in Bugzilla. The Working Group has not yet considered these issues and how they relate to the Working Group's plans to publish another document current entitled "Guidelines for Policy Assertion Authors".
Note that this Working Draft does not necessarily represent a consensus of the Working Group. Discussion of this document takes place on the public public-ws-policy@w3.org mailing list (public archive) and within Bugzilla. Comments on this specification should be made following the Description for Issues of the Working Group.
Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.
This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.
1. Introduction
2. Basic Concepts:
Policy Expression
2.1 Web
Services Policy
2.2 Simple
Message
2.3 Secure
Message
2.4 Other
Assertions
2.5 Combining Policy
Assertions
2.6 Optional Policy Assertion
2.7 Nested Policy Expressions
2.8 Referencing Policy
Expressions
2.9 Attaching Policy
Expressions to WSDL
2.10 Policy Automates Web
Services Interaction
3. Advanced
Concepts I: Policy Expression
3.1 Policy
Expression
3.2 Normal Form for Policy
Expressions
3.3 Policy
Data Model
3.4 Compatible Policies
3.5 Attaching Policy
Expressions to WSDL
3.6 Combine
Policies
3.7 Extensibility and
Versioning
4. Advanced
Concepts II: Policy Assertion Design
4.1 Role of Policy Assertions
4.2 Parts of a Policy
Assertion
4.3 When to design policy
assertions?
4.3.1 Opt-in behavior
4.3.2 Shared behavior
4.3.3 Visible behavior
4.4 Guidelines for Designing
Assertions
4.4.1 Optional Behaviors
4.4.2 Assertion vs. assertion
parameter
4.4.3 Leveraging Nested Policy
4.4.4 Minimal approach
4.4.5 QName and XML
Information Set representation
4.4.6 Policy subject and
attachment points
4.4.7 Versioning behaviors
4.4.8 Versioning Policy Language
4.4.8.1
Policy Framework
4.4.8.2
Policy Attachment
4.5 Describing Policy
Assertions
5. Conclusion
A. Security
Considerations
B. XML Namespaces
C. References
D. Acknowledgements
(Non-Normative)
E. Changes in this Version of the
Document (Non-Normative)
F. Web Services Policy 1.5 - Primer Change
Log (Non-Normative)
This document, Web Services Policy 1.5 - Primer, provides an introductory description of the Web Services Policy language and should be read alongside the formal descriptions contained in the WS-Policy and WS-PolicyAttachment specifications.
This document is:
for policy expression authors who need to understand the syntax of the language and understand how to build consistent policy expressions,
for policy implementers whose software modules read and write policy expressions and
for policy assertion authors who need to know the features of the language and understand the requirements for describing policy assertions.
This document assumes a basic understanding of XML 1.0, Namespaces in XML, WSDL 1.1 and SOAP.
Each major section of this document introduces the features of the policy language and describes those features in the context of concrete examples.
2. Basic Concepts: Policy Expression covers the basic mechanisms of Web Services Policy. It describes how to declare and combine capabilities and requirements of a Web service as policy expressions, attach policy expressions to WSDL constructs such as endpoint and message, and re-use policy expressions.
3. Advanced Concepts I: Policy Expression this is the first advanced section that provides more in-depth materials for policy implementers and assertion authors. It explains the basics of normalizing policy expressions, merging policies, determining the compatibility (intersection) of policies, the policy data model, the policy expression and the extensibility points built into the Web Services Policy language.
4. Advanced Concepts II: Policy Assertion Design this is the second advanced section that walks through the dimensions of a policy assertion for assertion authors. This section describes the role of policy assertions, parts of a policy assertion, when to design policy assertions, outlines guidelines for designing policy assertions and enumerates the minimum requirements for describing policy assertions in specifications.
This is a non-normative document and does not provide a definitive specification of the Web Services Policy language. B. XML Namespaces lists all the namespaces that are used in this document. (XML elements without a namespace prefix are from the Web Services Policy XML Namespace.)
Web services are being successfully used for interoperable solutions across various industries. One of the key reasons for interest and investment in Web services is that they are well-suited to enable service-oriented systems. XML-based technologies such as SOAP, XML Schema and WSDL provide a broadly-adopted foundation on which to build interoperable Web services. The WS-Policy and WS-PolicyAttachment specifications extend this foundation and offer mechanisms to represent the capabilities and requirements of Web services as Policies.
Service metadata is an expression of the visible aspects of a Web service, and consists of a mixture of machine- and human-readable languages. Machine-readable languages enable tooling. For example, tools that consume service metadata can automatically generate client code to call the service. Service metadata can describe different parts of a Web service and thus enable different levels of tooling support.
First, service metadata can describe the format of the payloads that a Web service sends and receives. Tools can use this metadata to automatically generate and validate data sent to and from a Web service. The XML Schema language is frequently used to describe the message interchange format within the SOAP message construct, i.e. to represent SOAP Body children and SOAP Header blocks.
Second, service metadata can describe the ‘how’ and ‘where’ a Web service exchanges messages, i.e. how to represent the concrete message format, what headers are used, the transmission protocol, the message exchange pattern and the list of available endpoints. The Web Services Description Language is currently the most common language for describing the ‘how’ and ‘where’ a Web service exchanges messages. WSDL has extensibility points that can be used to expand on the metadata for a Web service.
Third, service metadata can describe the capabilities and requirements of a Web service, i.e. representing whether and how a message must be secured, whether and how a message must be delivered reliably, whether a message must flow a transaction, etc. Exposing this class of metadata about the capabilities and requirements of a Web service enables tools to generate code modules for engaging these behaviors. Tools can use this metadata to check the compatibility of requesters and providers. Web Services Policy can be used to represent the capabilities and requirements of a Web service.
Web Services Policy is a machine-readable language for
representing the capabilities and requirements of a Web service.
These are called ‘policies’. Web Services Policy offers mechanisms
to represent consistent combinations of capabilities and
requirements, to determine the compatibility of policies, to name
and reference policies and to associate policies with Web service
metadata constructs such as service, endpoint and operation. Web
Services Policy is a simple language that has four elements -
Policy, All
, ExactlyOne
and
PolicyReference
- and one attribute -
wsp:Optional
.
Let us start by considering a SOAP Message in the example below.
Example 2-1. SOAP Message
<soap:Envelope> <soap:Header> <wsa:To>http://stock.contoso.com/realquote</wsa:To> <wsa:Action>http://stock.contoso.com/GetRealQuote</wsa:Action> </soap:Header> <soap:Body>...</soap:Body> </soap:Envelope>
This message uses message addressing headers. The
wsa:To
and wsa:Action
header blocks
identify the destination and the semantics implied by this message
respectively. (The prefix wsa
is used here to denote
the Web Services Addressing XML Namespace. B. XML Namespaces lists all the
namespaces and prefixes that are used in this document.)
Let us look at a fictitious scenario used in this document to illustrate the features of the policy language. Tony is a Web service developer. He is building a client application that retrieves real time stock quote information from Contoso, Ltd. Contoso supplies real time data using Web services. Tony has Contoso’s advertised WSDL description of these Web services. Contoso requires the use of addressing headers for messaging. Just the WSDL description is not sufficient for Tony to enable the interaction between his client and these Web services. WSDL constructs do not indicate requirements such as the use of addressing.
(The example companies, organizations, products, domain names, e-mail addresses, logos, people, places, and events depicted herein are fictitious. No association with any real company, organization, product, domain name, email address, logo, person, places, or events is intended or should be inferred.)
Providers have the option to convey requirements, such as the use of addressing, through word-of-mouth and documentation – as they always have. To interact successfully with this service, Tony may have to read any related documentation, call someone at Contoso to understand the service metadata, or look at sample SOAP messages and infer such requirements or behaviors.
Web Services Policy is a machine-readable language for representing these Web service capabilities and requirements as policies. Policy makes it possible for providers to represent such capabilities and requirements in a machine-readable form. For example, Contoso may augment the service WSDL description with a policy that requires the use of addressing. Tony can use a policy-aware client that understands this policy and engages addressing automatically.
How does Contoso use policy to represent the use of addressing? The example below illustrates a policy expression that requires the use of addressing.
Example 2-2. Policy Expression
<Policy> <wsap:UsingAddressing /> </Policy>
The policy expression in the above example consists of a
Policy
main element and a child element
wsap:UsingAddressing.
Child elements of the
Policy
element are policy assertions. Contoso attaches
the above policy expression to a WSDL binding description.
The wsap:UsingAddressing
element is a policy
assertion. (The prefix wsap
is used here to denote the
Web Services Addressing – WSDL Binding XML Namespace.) This
assertion identifies the use of Web Services Addressing information
headers. A policy-aware client can recognize this policy assertion,
engage addressing automatically, and use headers such as
wsa:To
and wsa:Action
in SOAP
Envelopes.
It is important to understand the association between the SOAP message and policy expression in the above example. As you can see by careful examination of the message, there is no reference to any policy expression. Just as WSDL does not require a message to reference WSDL constructs (such as port, binding and portType), Web Services Policy does not require a message to reference a policy expression though the policy expression describes the message.
In addition to requiring the use of addressing, Contoso requires the use of transport-level security for protecting messages.
Example 2-3. Secure Message
<soap:Envelope> <soap:Header> <wss:Security soap:mustUnderstand="1" > <wsu:Timestamp u:Id="_0"> <wsu:Created>2006-01-19T02:49:53.914Z</u:Created> <wsu:Expires>2006-01-19T02:54:53.914Z</u:Expires> </wsu:Timestamp> </wss:Security> <wsa:To>http://real.contoso.com/quote</wsa:To> <wsa:Action>http://real.contoso.com/GetRealQuote</wsa:Action> </soap:Header> <soap:Body>...</soap:Body> </soap:Envelope>
The SOAP message in the example above includes security
timestamps that express creation and expiration times of this
message. Contoso requires the use of security timestamps and
transport-level security - such as HTTPS
– for
protecting messages. (The prefixes wss
and
wsu
are used here to denote the Web Services Security
and Utility namespaces.)
Similar to the use of addressing, Contoso indicates the use of transport-level security using a policy expression. The example below illustrates a policy expression that requires the use of addressing and transport-level security for securing messages.
Example 2-4. Addressing and Security Policy Expression
<Policy> <wsap:UsingAddressing /> <sp:TransportBinding>...</sp:TransportBinding> </Policy>
The sp:TransportBinding
element is a policy
assertion. (The prefix sp
is used here to denote the
Web Services Security Policy XML Namespace.) This assertion
identifies the use of transport-level security – such as
HTTPS
- for protecting messages. Policy-aware clients
can recognize this policy assertion, engage transport-level
security for protecting messages and include security timestamps in
SOAP Envelopes.
Tony can use a policy-aware client that recognizes this policy expression and engages both addressing and transport-level security automatically.
For the moment, let us set aside the contents of the
sp:TransportBinding
policy assertion and consider its
details in a later section.
Thus far, we explored how Contoso uses policy expressions and assertions for representing behaviors that must be engaged for a Web service interaction. What is a policy assertion? What role does it play? In brief, a policy assertion is a piece of service metadata, and it identifies a domain (such as messaging, security, reliability and transaction) specific behavior that is a requirement. Contoso uses a policy assertion to convey a condition under which they offer a Web service. A policy-aware client can recognize policy assertions and engage these behaviors automatically.
Providers, like Contoso, have the option to combine behaviors for an interaction from domains such as messaging, security, reliability and transactions. Using policy assertions, providers can represent these behaviors in a machine-readable form. Web service developers, like Tony, can use policy-aware clients that recognize these assertions and engage these behaviors automatically.
Who defines policy assertions? Where are they? Policy assertions are defined by Web services developers, product designers, protocol authors and users. Like XML Schema libraries, policy assertions are a growing collection. Several WS-* protocol specifications and applications define policy assertions:
Web Services Security Policy [WS-SecurityPolicy]
Web Services Reliable Messaging Policy [Web Services Reliable Messaging Policy]
Web Services Atomic Transaction [Web Services Atomic Transaction]
Web Services Business Activity Framework [Web Services Business Activity Framework]
Devices Profile for Web Services [Devices Profile for Web Services]
A Technical Reference for Windows CardSpace [A Technical Reference for Windows CardSpace]
…
Policy assertions can be combined in different ways to express
consistent combinations of behaviors (capabilities and
requirements). There are three policy operators for combining
policy assertions: Policy
, All
and
ExactlyOne
(the Policy
operator is a
synonym for All).
Let us consider the All
operator first. The policy
expression in the example below requires the use of addressing and
transport-level security. There are two policy assertions. These
assertions are combined using the All
operator.
Combining policy assertions using the Policy
or
All
operator means that all the behaviors represented
by these assertions are required.
Example 2-5. Addressing and Security Policy Expression
<All> <wsap:UsingAddressing /> <sp:TransportBinding>…</sp:TransportBinding> </All>
In addition to requiring the use of addressing, Contoso allows
either the use of transport- or message-level security for
protecting messages. Web Services Policy language can indicate this
choice of behaviors in a machine-readable form. To indicate the use
of message-level security for protecting messages, Contoso uses the
sp:AsymmetricBinding
policy assertion (see the example
below).
Example 2-6. Asymmetric Binding Security Policy Assertion
<sp:AsymmetricBinding>…</sp:AsymmetricBinding>
The sp:AsymmetricBinding
element is a policy
assertion. (The prefix sp
is used here to denote the
Web Services Security Policy namespace.) This assertion identifies
the use of message-level security – such as WS-Security
1.0 - for protecting messages. Policy-aware clients can
recognize this policy assertion, engage message-level security for
protecting messages and use headers such as
wss:Security
in SOAP Envelopes.
To allow the use of either transport- or message-level security,
Contoso uses the ExactlyOne
policy operator. Policy
assertions combined using the ExactlyOne
operator
requires exactly one of the behaviors represented by the
assertions. The policy expression in the example below requires the
use of either transport- or message-level security for protecting
messages.
Example 2-7. Transport- or Message-Level Security Policy Expression
<ExactlyOne> <sp:TransportBinding>…</sp:TransportBinding> <sp:AsymmetricBinding>…</sp:AsymmetricBinding> </ExactlyOne>
Contoso requires the use of addressing and requires the use of
either transport- or message-level security for protecting
messages. They represent this combination using the
All
and ExactlyOne
operators. Policy
operators can be mixed to represent different combinations of
behaviors (capabilities and requirements). The policy expression in
the example below requires the use of addressing and one of
transport- or message-level security for protecting messages.
Example 2-8. Addressing and Transport- OR Message-Level Security Policy Expression
<All> <wsap:UsingAddressing /> <ExactlyOne> <sp:TransportBinding>…</sp:TransportBinding> <sp:AsymmetricBinding>…</sp:AsymmetricBinding> </ExactlyOne> </All>
Using this policy expression, Contoso gives the choice of mechanisms for protecting messages to clients (or requesters).
Through a customer survey program, Contoso learns that a significant number of their customers prefer to use the Optimized MIME Serialization (as defined in the MTOM specification) for sending and receiving messages. Contoso adds optional support for the Optimized MIME Serialization and expresses this optional behavior in a machine-readable form.
To indicate the use of optimization using the Optimized MIME
Serialization, Contoso uses the
mtom:OptimizedMimeSerialization
policy assertion (see
the example below).
Example 2-9. Optimized MIME Serialization Policy Assertion
<mtom:OptimizedMimeSerialization />
The mtom:OptimizedMimeSerialization
element is a
policy assertion. (The prefix mtom
is used here to
denote the Optimized MIME Serialization Policy namespace.) This
assertion identifies the use of MIME Multipart/Related
serialization for messages. Policy-aware clients can recognize this
policy assertion and engage Optimized MIME Serialization for
messages. The semantics of this assertion are reflected in
messages: they use an optimized wire format (MIME Multipart/Related
serialization).
Like Contoso’s optional support for Optimized MIME
Serialization, there are behaviors that may be engaged (in contrast
to must be engaged) for a Web service interaction. A service
provider will not fault if these behaviors are not engaged. Policy
assertions can be marked optional to represent behaviors that may
be engaged for an interaction. A policy assertion is marked as
optional using the wsp:Optional
attribute. Optional
assertions represent the capabilities of the service provider as
opposed to the requirements of the service provider.
In the example below, the Optimized MIME Serialization policy assertion is marked optional. This policy expression allows the use of optimization and requires the use of addressing and one of transport- or message-level security.
Example 2-10. Optional MIME Serialization, Addressing and Transport- OR Message-Level Security Policy Expression
<All> <mtom:OptimizedMimeSerialization wsp:Optional="true"/> <wsap:UsingAddressing /> <ExactlyOne> <sp:TransportBinding>…</sp:TransportBinding> <sp:AsymmetricBinding>…</sp:AsymmetricBinding> </ExactlyOne> </All>
Contoso is able to meet their customer needs by adding optional support for the Optimized MIME Serialization. An optional policy assertion represents a behavior that may be engaged.
In the previous sections, we considered two security policy assertions. In this section, let us look at one of the security policy assertions in little more detail.
As you would expect, securing messages is a complex usage
scenario. Contoso uses the sp:TransportBinding
policy
assertion to indicate the use of transport-level security for
protecting messages. Just indicating the use of transport-level
security for protecting messages is not sufficient. To successfully
interact with Contoso’s Web services, Tony must know what transport
token to use, what secure transport to use, what algorithm suite to
use for performing cryptographic operations, etc. The
sp:TransportBinding
policy assertion can represent
these dependent behaviors. In this section, let us look at how to
capture these dependent behaviors in a machine-readable form.
A policy assertion – like the sp:TransportBinding
-
identifies a visible domain specific behavior that is a
requirement. Given an assertion, there may be other dependent
behaviors that need to be enumerated for a Web Service interaction.
In the case of the sp:TransportBinding
policy
assertion, Contoso needs to identify the use of a transport token,
a secure transport, an algorithm suite for performing cryptographic
operations, etc. A nested policy expression can be used to
enumerate such dependent behaviors.
What is a nested policy expression? A nested policy expression is a policy expression that is a child element of a policy assertion element. A nested policy expression further qualifies the behavior of its parent policy assertion.
In the example below, the child Policy
element is a
nested policy expression and further qualifies the behavior of the
sp:TransportBinding
policy assertion. The
sp:TransportToken
is a nested policy assertion of the
sp:TransportBinding
policy assertion. The
sp:TransportToken
assertion requires the use of a
specific transport token and further qualifies the behavior of the
sp:TransportBinding
policy assertion (which already
requires the use of transport-level security for protecting
messages).
Example 2-11. Transport Security Policy Assertion
<sp:TransportBinding> <Policy> <sp:TransportToken> <Policy> <sp:HttpsToken RequireClientCertificate="false" /> </Policy> </sp:TransportToken> <sp:AlgorithmSuite> <Policy> <sp:Basic256Rsa15/> </Policy> </sp:AlgorithmSuite> … </Policy> </sp:TransportBinding>
The sp:AlgorithmSuite
is a nested policy assertion
of the sp:TransportBinding
policy assertion. The
sp:AlgorithmSuite
assertion requires the use of the
algorithm suite identified by its nested policy assertion
(sp:Basic256Rsa15
in the example above) and
further qualifies the behavior of the
sp:TransportBinding
policy assertion.
Setting aside the details of using transport-level security, Web service developers, like Tony, can use a policy-aware client that recognizes this policy assertion and engages transport-level security and its dependent behaviors automatically. That is, the complexity of security usage is absorbed by a policy-aware client and hidden from these Web service developers.
Contoso has numerous Web service offerings that provide
different kinds of real-time quotes and book information on
securities such as GetRealQuote
,
GetRealQuotes
and GetExtendedRealQuote
.
To accommodate the diversity of Contoso’s customers, Contoso
supports multiple WSDL bindings for these Web services. Contoso
provides consistent ways to interact with their services and wants
to represent these capabilities and requirements consistently
across all of their offerings without duplicating policy
expressions multiple times. How? It is simple - a policy expression
can be named and referenced for re-use.
A policy expression may be identified by an IRI and referenced
for re-use as a standalone policy or within another policy
expression. There are two mechanisms to identify a policy
expression: the wsu:Id
and Name
attributes. A PolicyReference
element can be used to
reference a policy expression identified using either of these
mechanisms.
Example 2-12. Common Policy Expression
<Policy wsu:Id=”common”> <mtom:OptimizedMimeSerialization wsp:Optional="true"/> <wsap:UsingAddressing /> </Policy>
In the example above, the wsu:Id
attribute is used
to identify a policy expression. The value of the
wsu:Id
attribute is an XML ID. The relative IRI for
referencing this policy expression (within the same document) is
#common
. If the policy document IRI is
http://real.contoso.com/policy.xml
then the absolute
IRI for referencing this policy expression is
http://real.contoso.com/policy.xml#common. (
The
absolute IRI is formed by combining the document IRI,
#
and the value of the wsu:Id
attribute.)
For re-use, a PolicyReference
element can be used
to reference a policy expression as a standalone policy or within
another policy expression. The example below is a policy expression
that re-uses the common policy expression above.
Example 2-13. PolicyReference to Common Policy Expression
<PolicyReference URI="#common"/>
For referencing a policy expression within the same XML
document, Contoso uses the wsu:Id
attribute for
identifying a policy expression and an IRI to this ID value for
referencing this policy expression using a
PolicyReference
element.
The example below is a policy expression that re-uses the common policy expression within another policy expression. This policy expression requires the use of addressing, one of transport- or message-level security for protecting messages and allows the use of optimization.
Example 2-14. Secure Policy Expression
<Policy wsu:Id=”secure”> <All> <PolicyReference URI="#common"/> <ExactlyOne> <sp:TransportBinding>…</sp:TransportBinding> <sp:AsymmetricBinding>…</sp:AsymmetricBinding > </ExactlyOne> </All> </Policy>
The Name
attribute is an alternate mechanism to
identify a policy expression. The value of the Name
attribute is an absolute IRI and is independent of the location of
the XML document where the identified policy expression resides in.
As such, referencing a policy expression using the
Name
attribute relies on additional out of band
information. In the example below, the Name
attribute
identifies the policy expression. The IRI of this policy expression
is http://real.contoso.com/policy/common
.
Example 2-15. Common Policy Expression
<Policy Name=”http://real.contoso.com/policy/common”> <mtom:OptimizedMimeSerialization wsp:Optional="true"/> <wsap:UsingAddressing /> </Policy>
The example below is a policy expression that re-uses the common policy expression above.
Example 2-16. PolicyReference to Common Policy Expression
<PolicyReference URI="http://real.contoso.com/policy/common"/>
A majority of Contoso’s customers use WSDL for building their client applications. Contoso leverages this usage by attaching policy expressions to the WSDL binding descriptions.
In the example below, the SecureBinding
WSDL
binding description defines a binding for an interface that
provides real-time quotes and book information on securities. (The
prefixes wsdl
and tns
are used here to
denote the Web Services Description language XML namespace and
target namespace of this WSDL document.) To require the use of
security for these offerings, Contoso attaches the secure policy
expression in the previous section to this binding description. The
WSDL binding
element is a common policy attachment
point. The secure policy expression attached to the
SecureBinding
WSDL binding description applies to any
message exchange associated with any port
that
supports this binding description. This includes all the message
exchanges described by operations in the
RealTimeDataInterface
.
Example 2-17. Secure Policy Expression Attached to WSDL Binding
<wsdl:binding name="SecureBinding" type="tns:RealTimeDataInterface" > <PolicyReference URI="#secure" /> <wsdl:operation name="GetRealQuote">…</wsdl:operation> … </wsdl:binding>
In addition to providing real-time quotes and book information
on securities, Contoso provides other kinds of data through Web
services such as quotes delayed by 20 minutes and security symbols
through Web services (for example GetDelayedQuote
,
GetDelayedQuotes,
GetSymbol
and
GetSymbols
). Contoso does not require the use of
security for these services, but requires the use of addressing and
allows the use of optimization.
Example 2-18. Open Policy Expression Attached to WSDL Binding
<wsdl:binding name="OpenBinding" type="tns:DelayedDataInterface" > <PolicyReference URI="#common" /> <wsdl:operation name="GetDelayedQuote">…</wsdl:operation> … </wsdl:binding>
In the example above, the OpenBinding
WSDL binding
description defines a binding for an interface that provides other
kinds of data such as quotes delayed by 20 minutes and security
symbols. To require the use of addressing and allow the use of
optimization, Contoso attaches the common policy expression in the
previous section to this binding description. As we have seen in
the SecureBinding
case, the common policy expression
attached to the OpenBinding
WSDL binding description
applies to any message exchange associated with any
port
that supports this binding description. This
includes all the message exchanges described by operations in the
DelayedDataInterface
.
As mentioned earlier, providers have the option to convey requirements, such as the use of addressing or security, through word-of-mouth and documentation – as they always have. The absence of policy expressions in a WSDL document does not indicate anything about the capabilities and requirements of a service. The service may have capabilities and requirements that can be expressed as policy expressions, such as the use of addressing, security and optimization. Or, the service may not have such capabilities and requirements. A policy aware client should not conclude anything (other than ‘no claims’) about the absence of policy expressions.
Service providers, like Contoso, can preserve and leverage their investments in WSDL and represent the capabilities and requirements of a Web service as policies. A WSDL document may specify varying behaviors across Web service endpoints. Web service developers, like Tony, can use a policy-aware client that recognizes these policy expressions in WSDL documents and engages behaviors automatically for each of these endpoints. Any complexity of varying behaviors across Web service endpoints is absorbed by a policy-aware client or tool and hidden from these Web service developers.
As you have seen, Web Services Policy is a simple language that
has four elements - Policy, All
,
ExactlyOne
and PolicyReference
- and one
attribute - wsp:Optional
. In practice, service
providers, like Contoso, use policy expressions to represent
combinations of capabilities and requirements. Web service
developers, like Tony, use policy-aware clients that understand
policy expressions and engage the behaviors represented by
providers automatically. A sizable amount of complexity is absorbed
by policy-aware clients (or tools) and is invisible to these Web
service developers.
Web Services Policy extends the foundation on which to build interoperable Web services, hides complexity from developers and automates Web service interactions.
In 2. Basic Concepts: Policy Expression, we covered the basics of Web Services Policy language. This is the first advanced section that provides more in-depth materials for Web Services Policy implementers and assertion authors. This section covers the following topics:
What is a policy expression?
What is the normal form of a policy expression and how to normalize policy expressions?
What is the policy data model?
How to select a compatible policy alternative?
How to attach policy expressions to WSDL constructs?
How to combine policies?
What are the extensibility points?
A policy expression is the XML representation and interoperable
form of a Web Services Policy. A policy expression consists of a
Policy
wrapper element and a variety of child and
descendent elements. Child and descendent elements from the policy
language are Policy, All
, ExactlyOne
and
PolicyReference
. Other child elements of
Policy
, All
and ExactlyOne
are policy assertions. (The Policy
element plays two
roles: wrapper element and operator.) Policy assertions can contain
a nested policy expression. Policy assertions can also be marked
optional to represent behaviors that may be engaged (capabilities)
for an interaction. The optional marker is the
wsp:Optional
attribute which is placed on a policy
assertion element.
Let us take a closer look at Contoso’s policy expression (see below) from the previous section.
Example 3-1. Contoso’s Secure Policy Expression
<Policy> <All> <mtom:OptimizedMimeSerialization wsp:Optional="true"/> <wsap:UsingAddressing /> <ExactlyOne> <sp:TransportBinding>…</sp:TransportBinding> <sp:AsymmetricBinding>…</sp:AsymmetricBinding > </ExactlyOne> </All> </Policy>
The Policy
element is the wrapper element. The
All
and ExactlyOne
elements are the
policy operators. All other child elements of the All
and ExactlyOne
elements are policy assertions from
domains such as messaging, addressing, security, reliability and
transactions.
Web Services Policy language defines two forms of policy expressions: compact and normal form. Up to this point, we have used the compact form. The compact form is less verbose than the normal form. The compact form is useful for authoring policy expressions. The normal form is an intuitive representation of the policy data model. We will look into the policy data model in the next section.
The normal form uses a subset of constructs used in the compact form and follows a simple outline for its XML representation:
Example 3-2. Normal Form for Policy Expressions
<Policy> <ExactlyOne> <All> <x:AssertionA>…</x:AssertionA> <y:AssertionB>…</y:AssertionB> … </All> <All> <x:AssertionA>…</x:AssertionA> <z:AssertionC>…</z:AssertionC> … </All> … </ExactlyOne> <Policy/>
The normal form consists of a Policy
wrapper
element and has one child ExactlyOne
element. This
ExactlyOne
element has zero or more All
child elements. Each of these All
elements has zero or
more policy assertions. The PolicyReference
element
and wsp:Optional
attribute are not used in the normal
form. And, a nested policy expression in the normal form has at
most one policy alternative.
The normal form represents a policy as a collection of policy alternatives and a policy alternative as a collection of policy assertions in a straight-forward manner.
The example below is a policy expression in the normal form. This expression contains two policy alternatives: one that requires the use of transport-level security and the other that requires the use of message-level security for protecting messages.
Example 3-3. Transport- or Message-Level Security Policy Expression in Normal Form
<Policy> <ExactlyOne> <All> <sp:TransportBinding>…</sp:TransportBinding> </All> <All> <sp:AsymmetricBinding>…</sp:AsymmetricBinding > </All> </ExactlyOne> </Policy>
A policy expression in the compact form can be converted to the normal form. Web Services Policy language describes the algorithm for this conversion.
Let us re-consider Contoso’s policy expression (see the example below). Contoso requires the use of addressing and either transport- or message-level security and allows the use of optimization. This policy expression is in the compact form and has four policy alternatives for requesters:
Requires the use of addressing and transport-level security
Requires the use of addressing and message-level security
Requires the use of optimization, addressing and transport-level security and
Requires the use of optimization, addressing and message-level security.
Example 3-4. Contoso’s Secure Policy Expression in Compact Form
<Policy wsu:Id=”secure”> <All> <PolicyReference URI=”#common”/> <ExactlyOne> <sp:TransportBinding>…</sp:TransportBinding> <sp:AsymmetricBinding>…</sp:AsymmetricBinding > </ExactlyOne> </All> </Policy> <Policy wsu:Id=”common”> <mtom:OptimizedMimeSerialization wsp:Optional="true"/> <wsap:UsingAddressing /> </Policy>
Let us look at the normal form for this policy expression. The
example below is Contoso’s policy expression in the normal form. As
you can see, the compact form is less verbose than the normal form.
The normal form represents a policy as a collection of policy
alternatives. Each of the All
operators is a policy
alternative. There are four policy alternatives in the normal form.
These alternatives map to bullets (a) through (d) above.
Example 3-5. Contoso’s Policy Expression in Normal Form
<Policy> <ExactlyOne> <All> <!-- - - - - - - - - - - - - - Policy Alternative (a) --> <wsap:UsingAddressing/> <sp:TransportBinding>…</sp:TransportBinding> </All> <All> <!-- - - - - - - - - - - - - - Policy Alternative (b) --> <wsap:UsingAddressing/> <sp:AsymmetricBinding>…</sp:AsymmetricBinding > </All> <All> <!-- - - - - - - - - - - - - - Policy Alternative (c) --> <mtom:OptimizedMimeSerialization /> <wsap:UsingAddressing/> <sp:TransportBinding>…</sp:TransportBinding> </All> <All> <!-- - - - - - - - - - - - - - Policy Alternative (d) --> <mtom:OptimizedMimeSerialization /> <wsap:UsingAddressing/> <sp:AsymmetricBinding>…</sp:AsymmetricBinding> </All> </ExactlyOne> </Policy>
The wsp:Optional
attribute, nested policy
expression and Policy
Reference
element
are converted to their corresponding normal form. The
wsp:Optional
attribute converts to two alternatives,
one with and the other without the assertion. A policy alternative
containing an assertion with a nested policy expression that has
multiple policy alternatives converts to multiple policy
alternatives where the assertion contains a nested policy
expression that has at most one policy alternative.
The PolicyReference
element is replaced with its
referenced policy expression. Just as other service metadata
languages, Web Services Policy does not mandate any specific policy
retrieval mechanism. Any combination of any retrieval mechanisms in
any order may be used for referencing policy expressions. Example
retrieval mechanisms are:
Do nothing. A policy expression with the referenced IRI is already known to be available in a local cache or chip (embedded systems).
Use the referenced IRI and retrieve an existing policy expression from the containing XML document: a policy element with an XML ID.
Use the referenced IRI and retrieve a policy expression from some policy repository (local or remote) or catalog. Policy tools may use any protocols (say Web Services Metadata Exchange) for such metadata retrieval. These protocols may require additional out of band information.
Attempt to resolve the referenced IRI on the Web. This may resolve to a policy element or a resource that contains a policy element.
If the referenced policy expression is in the same XML document
as the reference, then the policy expression should be identified
using the wsu:Id
(XML ID) attribute and referenced
using an IRI reference to this XML ID value.
In the previous section, we considered the normal form for policy expressions. As we discussed, the normal form represents a policy as a collection of policy alternatives. In this section, let us look at the policy data model.
Contoso uses a policy to convey the conditions for an interaction. Policy-aware clients, like the one used by Tony (as explained earlier in 2. Basic Concepts: Policy Expression), view policy as an unordered collection of zero or more policy alternatives. A policy alternative is an unordered collection of zero or more policy assertions. A policy alternative represents a collection of behaviors or requirements or conditions for an interaction. In simple words, each policy alternative represents a set of conditions for an interaction. The diagram below describes the policy data model.
Figure 3-1. WS-Policy Data Model
A policy-aware client uses a policy to determine whether one of these policy alternatives (i.e. the conditions for an interaction) can be met in order to interact with the associated Web Service. Such clients may choose any of these policy alternatives and must choose exactly one of them for a successful Web service interaction. Clients may choose a different policy alternative for a subsequent interaction. It is important to understand that a policy is a useful piece of metadata in machine-readable form that enables tooling, yet is not required for a successful Web service interaction. Why? Web service developers, like Tony, could use the documentation, talk to the service providers, or look at message traces to infer these conditions for an interaction. Developers continue to have these options, as they always had.
As we discussed, a policy assertion identifies a domain specific behavior or requirement or condition. A policy assertion has a QName that identifies its behavior or requirement or condition. In the XML representation, the QName of the assertion element is the QName of the policy assertion. A policy assertion may contain assertion parameters and a nested policy.
The assertion parameters are the opaque payload of an assertion. Parameters carry additional useful pieces of information necessary for engaging the behavior described by an assertion. In the XML representation, the child elements and attributes of an assertion are the assertion parameters.
We considered nested policy expressions in the context of a security usage scenario. Let us look at its shape in the policy data model. In the normal form, a nested policy is a policy that has at most one policy alternative and is owned by its parent policy assertion. The policy alternative in a nested policy represents a collection of dependent behaviors or requirements or conditions that qualify the behavior of its parent policy assertion.
A policy-aware client supports a policy assertion if the client engages the behavior or requirement or condition indicated by the assertion. A policy-aware client supports a policy alternative if the client engages the behaviors represented by all the assertions in the alternative. A policy-aware client supports a policy if the client engages the behaviors represented by at least one of the policy alternatives.
In the previous section, we saw how the normal form of a policy expression represents a policy as a collection of policy alternatives. By policy language design, the normal form of a policy expression directly maps to the policy data model:
Each child element of Policy/ExactlyOne/All
maps to
a policy assertion.
Each Policy/ExactlyOne/All
element and policy
assertions which correspond to its children map to a policy
alternative.
The Policy/ExactlyOne
element maps to a collection
of policy alternatives.
The Policy
wrapper element and policy alternatives
which correspond to the Policy/ExactlyOne
element map
to a policy.
The diagram below describes this mapping from the normal form of a policy expression to the policy data model.
Figure 3-2. Mapping from Normal Form to Policy Data Model
A provider, like Contoso, and a requester, like Tony’s policy-aware client, may represent their capabilities and requirements for an interaction as policies and want to limit their message exchanges to mutually compatible policies. Web Services Policy defines an intersection mechanism for selecting compatible policy alternatives when there are two or more policies.
The example below is a copy of Contoso’s policy expression (from 3.2 Normal Form for Policy Expressions). As we saw before, Contoso offers four policy alternatives. Of them, one of the policy alternatives requires the use of addressing and transport-level security.
Example 3-6. Contoso’s Policy Expression
<Policy> <ExactlyOne> <All> <!-- - - - - - - - - - Contoso’s Policy Alternative (a) --> <!-- - - - - - - - - - - - - - - - - - Policy Assertion (c1) --> <wsap:UsingAddressing/> <!-- - - - - - - - - - - - - - - - - - Policy Assertion (c2) --> <sp:TransportBinding>…</sp:TransportBinding> </All> … </ExactlyOne> </Policy>
Tony’s organization requires the use of addressing and transport-level security for any interaction with Contoso’s Web services. Tony represents these behaviors using a policy expression illustrated in the example below in normal form. This policy expression contains one policy alternative that requires the use of addressing and transport-level security.
Example 3-7. Tony’s Policy Expression in Normal Form
<Policy> <ExactlyOne> <All> <!-- - - - - - - - - - - - - - Tony’s Policy Alternative --> <!-- - - - - - - - - - - - - - - - - - Policy Assertion (t1) --> <sp:TransportBinding>…</sp:TransportBinding> <!-- - - - - - - - - - - - - - - - - - Policy Assertion (t2) --> <wsap:UsingAddressing/> </All> </ExactlyOne> </Policy>
Tony lets his policy-aware client select a compatible policy alternative in Contoso’s policy. How does this client select a compatible policy alternative? It is simple – it uses the policy intersection. That is, Tony’s policy-aware client uses these two policy expressions (Tony’s and Contoso’s) and the policy intersection to select a compatible policy alternative for this interaction. Let us look at the details of policy intersection.
For two policy assertions to be compatible they must have the
same QName. And, if either assertion has a nested policy, both
assertions must have a nested policy and the nested policies must
be compatible. For example, policy assertions (c2) and (t1) have
the same QName, sp:TransportBinding
. For this
discussion, let us assume that these two assertions have compatible
nested policies. These two assertions are compatible because they
have the same QName and their nested policies are compatible.
Two policy alternatives are compatible if each policy assertion in one alternative is compatible with a policy assertion in the other and vice-versa. For example, policy assertions (c1) and (c2) in Contoso’s policy alternative are compatible with policy assertions (t2) and (t1) in Tony’s policy alternative. Contoso’s policy alternative (a) and Tony’s policy alternative are compatible because assertions in these two alternatives are compatible.
Two policies are compatible if a policy alternative in one is compatible with a policy alternative in the other. For example, Contoso’s policy alternative (a) is compatible with Tony’s policy alternative. Contoso’s policy and Tony’s policy are compatible because one of Contoso’s policy alternative is compatible with Tony’s policy alternative.
For this interaction, Tony’s policy-aware client can use policy alternative (a) to satisfy Contoso’s conditions or requirements.
Similarly, policy intersection can be used to check if providers expose endpoints that conform to a standard policy. For example, a major retailer might require all their supplier endpoints to be compatible with an agreed upon policy.
In 2. Basic
Concepts: Policy Expression, we looked into how Contoso
attached their policy expressions to the WSDL binding
element. In addition to the WSDL binding
element, a
policy expression can be attached to other WSDL elements such as
service
, port
, operation
and
message
. These elements are the WSDL policy attachment
points in a WSDL document.
The WSDL attachment points are partitioned (as illustrated below) into four policy subjects: message, operation, endpoint and service. When attached, capabilities and requirements represented by a policy expression apply to a message exchange or message associated with (or described by) a policy subject.
Figure 3-3. Policy Subjects and Effective Policy in WSDL
The WSDL service
element represents the service
policy subject. Policy expressions associated with a service policy
subject apply to any message exchange using any of the endpoints
offered by that service.
The WSDL port
, binding
and
portType
elements collectively represent the endpoint
policy subject. Policy expressions associated with an endpoint
policy subject apply to any message exchange made using that
endpoint.
The WSDL binding/operation
and
portType/operation
elements collectively represent the
operation policy subject. Policy expressions associated with an
operation policy subject apply to the message exchange defined by
that operation.
The WSDL binding/operation/input
,
portType/operation/input
, and message
element collectively represent the message policy subject for the
input message. The WSDL binding/operation/output
,
portType/operation/output
, and message
element collectively represent the message policy subject for the
output message. The WSDL binding/operation/fault
,
portType/operation/fault
, and message
element collectively represent the message policy subject for the
fault message. Policy expressions associated with a message policy
subject apply only to that message.
In the example below, the policy expression is attached to an endpoint policy subject.
Example 3-8. Contoso’s Policy Expression Attached to WSDL binding Element
<wsdl:binding name="SecureBinding" type="tns:RealTimeDataInterface" > <PolicyReference URI="#secure" /> <wsdl:operation name="GetRealQuote">…</wsdl:operation> … </wsdl:binding>
If multiple policy expressions are attached to WSDL elements
that collectively represent a policy subject then the effective
policy of these policy expressions applies. The effective policy is
the combination of the policy expressions that are attached to the
same policy subject. For example, the effective policy of an
endpoint policy subject is the combination of policy expressions
attached to a WSDL port
element, policy expressions
attached to the binding
element referenced by this
port, and policy expressions attached to the portType
element that is supported by this port. Let us consider how to
combine policy expressions in the next section.
Most of the policy assertions are designated for the endpoint, operation or message policy subject. The commonly used WSDL attachment points are:
Policy Subject | Commonly used attachment point (s) |
---|---|
Endpoint | binding element |
Operation | binding/operation
element |
Message | binding/operation/input
and binding/operation/output elements |
Multiple policy expressions may be attached to WSDL constructs.
Let us consider how Contoso could have used multiple policy
expressions in a WSDL document. In the example below, there are two
policy expressions #common2
and #secure2
attached to the SecureBinding
WSDL binding and
RealTimeDataPort
WSDL port descriptions.
Example 3-9. Multiple Policy Expressions Attached to Endpoint Policy Subject
<Policy wsu:Id=”common2”> <mtom:OptimizedMimeSerialization wsp:Optional="true"/> <wsap:UsingAddressing /> </Policy> <Policy wsu:Id=”secure2”> <ExactlyOne> <sp:TransportBinding>…</sp:TransportBinding> <sp:AsymmetricBinding>…</sp:AsymmetricBinding > </ExactlyOne> </Policy> <wsdl:binding name="SecureBinding" type="tns:RealTimeDataInterface" > <PolicyReference URI="#secure2" /> <wsdl:operation name="GetRealQuote">…</wsdl:operation> … </wsdl:binding> <wsdl:service name=”RealTimeDataService”> <wsdl:port name=”RealTimeDataPort” binding=”tns:SecureBinding”> <PolicyReference URI="#common2"/> … </wsdl:port> </wsdl:service>
As we discussed before, the WSDL port
,
binding
and portType
elements
collectively represent the endpoint policy subject. In the example
above, the #common2
and #secure2
policy
expressions attached to the SecureBinding
WSDL binding
and RealTimeDataPort
WSDL port descriptions
collectively apply to any message exchange associated with the
RealTimeDataPort
WSDL port.
As in the example above, multiple policy expressions may be attached to Web service constructs that collectively represent a single policy subject. When there are multiple policy expressions attached to the same policy subject then the effective policy or combination of these policy expressions apply to the associated policy subject.
The effective policy is the combination of two or more policy
expressions attached to the same policy subject. The combination of
two policy expressions, also known as the merged policy expression,
is a new policy expression that combines these two policy
expressions using the All
policy operator.
The policy expression below is the combination of the two policy
expressions attached to the SecureBinding
WSDL binding
and RealTimeDataPort
WSDL port descriptions. The
#common2
policy expression has two policy
alternatives. The #secure2
policy expression has two
policy alternatives. The combination of these two policies is
equivalent to Contoso’s secure policy in 2. Basic Concepts: Policy
Expression and has four policy alternatives. In other
words, the combination of two policies is the cross product of
alternatives in these two policies.
Example 3-10. Effective Policy of the Endpoint Policy Subject in the Previous Example
<Policy> <All> <Policy> <mtom:OptimizedMimeSerialization wsp:Optional="true"/> <wsap:UsingAddressing/> </Policy> <Policy> <ExactlyOne> <sp:TransportBinding>…</sp:TransportBinding> <sp:AsymmetricBinding>…</sp:AsymmetricBinding > </ExactlyOne> </Policy> </All> </Policy>
Of course, the above policy expression can be normalized. There are four policy alternatives in the normal form. As we have seen in the policy data model, a policy is an unordered collection of policy alternatives. That is, the order of policy alternatives is insignificant. Therefore, the order of combining these policy expressions is insignificant.
Web Services Policy language is an extensible language by
design. The Policy
, ExactlyOne
,
All
and PolicyReference
elements are
extensible. The Policy
, ExactlyOne
and
All
elements allow child element and attribute
extensibility. The PolicyReference
element allows
attribute extensibility. Extensions must not use the policy
language XML namespace name. A consuming processor processes known
attributes and elements, ignores unknown attributes and treats
unknown elements as policy assertions.
Web Services Policy language enables simple versioning practices that allow requesters to continue the use of any older policy alternatives in a backward compatible manner. This allows service providers, like Contoso, to deploy new behaviors using additional policy assertions without breaking compatibility with clients that rely on any older policy alternatives.
The example below represents a Contoso version 1 policy expression. This expression requires the use of addressing and transport-level security for protecting messages.
Example 3-11. Contoso’s Version 1 Policy Expression
<Policy> <ExactlyOne> <All> <wsap:UsingAddressing/> <sp:TransportBinding>…</sp:TransportBinding> </All> </ExactlyOne> </Policy>
Over time, Contoso adds support for advanced behaviors: requiring the use of addressing and message-level security for protecting messages. They added this advanced support without breaking compatibility with requesters that rely on addressing and transport-level security. The example below is Contoso’s version 2 policy expression. In this version, Contoso’s adds a new policy alternative that requires the use of addressing and message-level security. The clients that rely on addressing and transport-level security may continue to interact with Contoso’s using the old policy alternative. Of course, these clients have the option to migrate from using old policy alternatives to new policy alternatives.
Example 3-12. Contoso’s Version 2 Policy Expression
<Policy> <ExactlyOne> <All> <wsap:UsingAddressing/> <sp:TransportBinding>…</sp:TransportBinding> </All> <All> <!-- - - - - - - - - - - - - - - - NEW Policy Alternative --> <wsap:UsingAddressing/> <sp:AsymmetricBinding>…</sp: AsymmetricBinding > </All> </ExactlyOne> </Policy>
When Contoso added support for advanced behaviors, they spent time to plan for the continued support for existing clients, the smooth migration from using current to advanced behaviors, and the switch to use only the advanced behaviors in the near future (i.e. sun-setting current behaviors). In this versioning scenario, policy can be used to represent current and advanced behaviors in a non-disruptive manner: no immediate changes to existing clients are required and these clients can smoothly migrate to new functionality when they choose to. This level of versioning support in policy enables the same class of versioning best practices built into WSDL constructs such as service, port and binding.
Let us look at tooling for unknown policy assertions. As service providers, like Contoso, incrementally deploy advanced behaviors, some requesters may not recognize these new policy assertions. As discussed before, these requesters may continue to interact using old policy alternatives. New policy assertions will emerge to represent new behaviors and slowly become part of everyday interoperable interaction between requesters and providers. Today, most tools use a practical tolerant strategy to process new or unrecognized policy assertions. These tools consume such unrecognized assertions and designate these for user intervention. As you would recognize, there is nothing new in this practice. This is similar to how a proxy generator that generates code from WSDL creates code for all the known WSDL constructs and allows Web service developers to fill in code for custom or unknown constructs in the WSDL.
In the previous section, we covered in-depth materials for Web Services Policy implementers. This is the second advanced section that walks through the dimensions of a policy assertion for assertion authors. This section covers the following topics:
What is the role of policy assertions?
What are the parts of a policy assertion?
When to design policy assertions?
What are the guidelines for designing policy assertions?
What are the minimum requirements for describing policy assertions?
As you have seen, Web Services Policy is a simple language that
has four elements -Policy, All
,
ExactlyOne
and PolicyReference
- and one
attribute - wsp:Optional
. Policy is a flexible
language to represent consistent combinations of behaviors using
policy operators: Policy, All
and
ExactlyOne.
Policy is an expressive language and
capable of representing behaviors from a variety of domains. Let us
look for the key parts that unlock this potential.
Service providers combine behaviors for an interaction from domains such as messaging, security, reliability and transactions. To enable clients to engage these behaviors, services require some way to advertise these behaviors. Providers require machine readable metadata pieces that identify these behaviors. A policy assertion is a machine-readable metadata piece that requires the use of a behavior identified by the assertion. Web service developers can use policy-aware clients that recognize these assertions and engage their corresponding behaviors automatically.
Policy assertions are the key parts and play a central role to unlock the potential offered by the Web Services Policy language. Assertions are defined by product designers, protocol authors, protocol implementers and Web service developers.
Policy assertion authors identify behaviors required for Web services interactions and represent these behaviors as policy assertions. By designing policy assertions, assertion authors make a significant contribution to automate Web services interactions and enable advanced behaviors.
As we discussed, a policy assertion identifies a domain specific behavior or requirement or condition. A policy assertion has a QName that identifies its behavior or requirement or condition. A policy assertion may contain assertion parameters and a nested policy.
Let us look at the anatomy of a policy assertion from the
security domain. The policy expression in the diagram below uses
the sp:IssuedToken
policy assertion. This assertion
illustrates the use of assertion parameters and nested policy.
Figure 4-1. sp:IssuedToken Policy Assertion
The sp:IssuedToken
element is a policy assertion
that identifies the use of a security token – such as SAML token -
issued by a third party for protecting messages. A policy assertion
is an XML element. The QName of this element represents the
behavior identified by this policy assertion.
The sp:IssuedToken
policy assertion has three
parameters: @sp:IncludeToken
, sp:Issuer
and sp:RequestSecurityTokenTemplate
.
The sp:IncludeToken
attribute is a parameter that
contains information on whether a security token should be included
in messages or an external reference to the key of this security
token should be used. The sp:Issuer
parameter is an
endpoint reference to a security token issuer. The
sp:RequestSecurityTokenTemplate
parameter contains the
necessary information to request a security token from the
specified issuer. Parameters are the opaque payload of a Policy
Assertion, carry useful information for engaging the behavior
described by an assertion and are preserved through policy
processing such as normalize, merge and intersection. requesters
may use policy intersection to select a compatible policy
alternative for an interaction. Assertion parameters do not affect
the outcome of policy intersection.
For the sp:Issuer
policy assertion parameter, the
assertion author uses the natural XML structural relationships (the
child elements and attributes) and encodes the relationship between
an assertion and its parameters in a machine readable form.
Assertion parameters may be represented as child XML elements or
attributes of an assertion. The policy language allows assertion
authors to strongly tie the relationship between an assertion and
its parameters using the natural XML structural relationships.
The sp:IssuedToken
policy assertion has a nested
policy expression. The sp:RequireInternalReference
element is a nested policy assertion of the
sp:IssuedToken
policy assertion. The
sp:RequireInternalReference
assertion requires the use
of an internal reference for referencing the issued token. A nested
policy assertion further qualifies a dependent behavior of its
parent policy assertion. As mentioned earlier, requesters may use
policy intersection to select a compatible policy alternative for
an interaction. Nested policy assertions affect the outcome of
policy intersection.
The sp:IssuedToken
security policy assertion
identifies a visible domain specific behavior: the use of a
security token – such as SAML token - issued by a third party for
protecting messages. This behavior is relevant to a Web service
interaction. For the sake of discussion, let us assume that Contoso
requires the use of a SAML token issued by a third party. Service
providers, like Contoso, must convey this usage and all the
necessary information to obtain this security token for Web service
developers. This is a key piece of metadata for a successful
interaction with Contoso’s Web services.
As we illustrated in the previous section, requiring the use of a security token issued by a third party is represented as a policy assertion. In simple words, a policy assertion identifies a domain specific behavior:
That is a requirement
That is relevant to an interoperable Web service interaction
That is relevant to an interaction that involves two or more Web service participants
That applies to its associated policy subject such as service, endpoint, operation and message.
Given that interoperability and automation are the motivations, policy assertions that represent opt-in, shared and visible behaviors are useful pieces of metadata. Such assertions enable tooling and improve interoperability. The key to understanding when to design policy assertions is to have clarity on the characteristics of a behavior represented by a useful policy assertion: opt-in, shared and visible.
An opt-in behavior refers to a requirement that providers and requesters must deliberately choose to engage for a successful web service interaction. Examples of such behaviors are the use of optimization, message-level security, reliable messaging and atomic transaction. Policy assertions are not necessary to interoperate on widespread assumed behaviors. An example of an assumed behavior is the use of UTF-8 or UTF-16 text encoding for XML messages.
A shared behavior refers to a requirement that is relevant to an interoperable Web service interaction and involves two or more participants. If an assertion only describes one participant’s behavior (non-shared behavior) then the assertion is not relevant to an interoperable interaction. Non-shared behaviors do not add any value for tooling or interoperability. An example of a non-shared behavior is the use of logging or auditing by the provider.
requesters may use the policy intersection to select a compatible policy alternative for a Web service interaction. If an assertion only describes one participant’s behavior then this assertion will not be present in the other participants’ policy and the policy intersection will unnecessarily produce false negatives.
A visible behavior refers to a requirement that manifests on the wire. Web services provide interoperable machine-to-machine interaction among disparate systems. Web service interoperability is the capability of disparate systems to exchange data using common data formats and protocols such as messaging, security, reliability and transaction. Such data formats and protocols manifest on the wire. Providers and requesters only rely on these wire messages that conform to such formats and protocols for interoperability. If an assertion describes a behavior that does not manifest on the wire then the assertion is not relevant to an interoperable interaction.
For example, say an assertion describes the privacy notice information of a provider and there is an associated regulatory safeguard in place on the provider’s side. Such assertions may represent business or regulatory level metadata but do not add any value to interoperability.
If an assertion has no wire- or message-level visible behavior, then the interacting participants may require some sort of additional non-repudiation mechanism to indicate compliance with the assertion. Introducing an additional non-repudiation mechanism adds unnecessary complexity to processing a policy assertion.
The policy language allows assertion authors to invent their own XML dialects to represent policy assertions. The policy language builds on natural XML nesting and leverages XML Schema validation. The policy language relies only on the QName of the policy assertion XML element. Everything else is left for the policy assertion authors to design. The policy language offers plenty of options to assertion authors such as independent assertions, dependent assertions, nested policies and assertion parameters.
The description of a policy assertion should identify a single domain specific behavior in an objective manner and answer the following questions:
What is the behavior? (In the previous section, we discussed the characteristics of a behavior represented by a useful policy assertion.)
What are the assertion parameters?
Are there any dependent behaviors, and how are they represented?
What is the assertion’s QName and XML information set representation?
What is the policy subject of this behavior?
What are the attachment points?
As you would have expected, the policy assertion design is more than a technical design. Given that interoperability and automation are the motivations, policy assertion design is a business process to reach agreements with relevant stakeholders for interoperability and tooling. Setting aside the business aspects of the design, the rest of this section walks through a few tradeoffs or dimensions to consider and provides technical guidelines for designing policy assertions.
A policy assertion identifies a domain specific behavior that is
a requirement relevant to a Web Service interaction. Policy
assertions can be marked optional using the
wsp:Optional
attribute marker to represent behaviors
that may be engaged (capabilities) for an interaction. It is
important to note that behavior (policy assertion) and optional
representation (wsp:Optional
attribute) are distinct
ideas of the Web Services Policy language. Conflating these
distinct ideas unnecessarily disrupts scenarios that depend on the
policy intersection: if an assertion indicates an optional behavior
and this assertion is not present in the other participants’ policy
then the policy intersection will unnecessarily produce false
negatives.
Best practice: use the wsp:Optional
attribute to
indicate optional behaviors.
Policy assertion parameters are the opaque payload of an assertion. Parameters carry additional useful information for engaging the behavior described by an assertion and are preserved through policy processing such as normalize, merge and policy intersection. requesters may use policy intersection to select a compatible policy alternative for an interaction. Assertion parameters do not affect the outcome of policy intersection.
In the example below, sp:Body
and
sp:Header
elements are the two assertion parameters of
the sp:SignedParts
policy assertion (this assertion
requires the parts of a message to be protected). These two
parameters identify the parts of a wire message that should be
protected. These parameters carry additional useful information for
engaging the behavior that is irrelevant to compatibility
tests.
Example 4-1. Policy Assertion with Assertion Parameters
<Policy> <sp:SignedParts> <sp:Body /> <sp:Header /> </sp:SignedParts> … </Policy>
Best practice: represent useful (or additional) information necessary for engaging the behavior represented by a policy assertion as assertion parameters.
As we have seen before, a nested policy expression further qualifies the dependent behaviors of its parent policy assertion. When we consider nested policy there is always two or more policy assertions involved. The following design questions below can help you to determine when to use nested policy expressions:
Are these assertions designed for the same policy subject?
Do these assertions represent dependent behaviors?
If the answers are yes to both of these questions then leveraging nested policy expressions is a good idea. Keep in mind that a nested policy expression participates in the policy intersection algorithm. If a requester uses policy intersection to select a compatible policy alternative then the assertions in a nested policy expression play a first class role in the outcome. There is one caveat to watch out for: policy assertions with deeply nested policy can greatly increase the complexity of a policy and should be avoided when they are not needed.
Best practice: represent dependent behaviors that apply to the same policy subject using nested policy assertions.
How big should an assertion be? How many assertion parameters should the assertion enumerate? How many dependent behaviors should the assertion enumerate? It is always good to start with a simple working policy assertion that allows extensibility. As your design work progresses, you may add more parameters or nested policy assertions to meet your interoperability needs.
Best practice: start with a simple working assertion that allows extensibility.
As mentioned before, Web Services Policy language allows assertion authors to invent their own XML dialects to represent policy assertions. The policy language relies only on the policy assertion XML element QName. This QName is unique and identifies the behavior represented by a policy assertion. Assertion authors have the option to represent an assertion parameter as a child element (by leveraging natural XML nesting) or an attribute of an assertion. The general guidelines on when to use XML elements versus attributes apply.
The syntax of an assertion can be represented using an XML outline (plus an XML schema document). If the assertion has a nested policy expression then the assertion XML outline can enumerate the nested assertions that are allowed.
Best practice: use a unique QName to identify the behavior and provide an XML outline (plus an XML schema document) to specify the syntax of an assertion.
A behavior identified by a policy assertion applies to the associated policy subject. If a policy assertion is to be used with WSDL, policy assertion authors must specify a WSDL policy subject. What is the policy subject of this behavior?
If the behavior applies to any message exchange using any of the endpoints offered by a service then the subject is the service policy subject.
If the behavior applies to any message exchange made using an endpoint then the subject is the endpoint policy subject.
If the behavior applies to any message exchange defined by an operation then the subject is the operation policy subject.
If the behavior applies to an input message then the subject is the message policy subject - similarly for output and fault message policy subjects.
For a given WSDL policy subject, there may be several attachment
points. For example, there are three attachment points for the
endpoint policy subject: the port
,
binding
and portType
element. Policy
assertion authors should identify the relevant attachment point
when defining a new assertion. To determine the relevant attachment
points, authors should consider the scope of the attachment point.
For example, an assertion should only be allowed in the
portType
element if the assertion reasonably applies
to any endpoint that ever references that portType
.
Most of the known policy assertions are designed for the endpoint,
operation or message policy subject. The commonly used attachment
points for these policy subjects are outlined in 3.5 Attaching Policy
Expressions to WSDL.
The service policy subject is a collection of endpoint policy subjects. The endpoint policy subject is a collection of operation policy subjects and etc. As you can see, the WSDL policy subjects compose naturally. It is quite tempting to associate the identified behavior to a broader policy subject than to a fine granular policy subject. For instance, it is convenient to attach a supporting token assertion (defined by the Web Services Security Policy specification) to an endpoint policy subject instead of a message policy subject. For authoring convenience, an assertion author may allow the association of an assertion to multiple policy subjects. If an assertion is allowed to be associated with multiple policy subjects then the assertion author has the burden to describe the semantics of multiple instances of the same assertion attached to multiple policy subjects at the same time. The best practice is to choose the most granular policy subject that the behavior applies to.
Best practice: specify a policy subject, choose the most granular policy subject that the behavior applies to and specify a preferred attachment point.
Over time, there may be multiple equivalent behaviors emerging in the Web Service interaction space. Examples of such multiple equivalent behaviors are WSS: SOAP Message Security 1.0 vs. 1.1 and WS-Addressing August 2004 version vs. WS-Addressing W3C Recommendation. These equivalent behaviors are mutually exclusive for an interaction. Such equivalent behaviors can be modeled as independent assertions. The policy expression in the example below requires the use of WSS: SOAP Message Security 1.0.
Example 4-2. Message-level Security and WSS: SOAP Message Security 1.0
<Policy> <sp:Wss10>…</sp:Wss10> </Policy>
The policy expression in the example below requires the use of WSS: SOAP Message Security 1.1. These are multiple equivalent behaviors and are represented using distinct policy assertions.
Example 4-3. Message-level Security and WSS: SOAP Message Security 1.1
<Policy> <sp:Wss11>…</sp:Wss11> </Policy>
Best practice: use independent assertions for modeling multiple equivalent behaviors.
Editorial note | |
The WG is contemplating moving some or all of this material into a non-normative appendix of the framework or attachment document. User feedback is solicited |
Over time, the Policy WG or third parties can version or extend the Policy Language with new or modified constructs. These constructs may be compatible or incompatible with previous versions. Some of the possible new constructs that have been mentioned previously are: new operators, operator cardinality, policy identification, compact syntax, Policy Inclusion, security, referencing, attachment points, alternative priority, effective dating, negotiation.
WS-Policy provides extensibility points on 6 elements with a combination of attribute and/or element extensibility. The possible extensibility points with their current extensibility - including some outstanding issues related to extensibility - are:
Policy: element from ##other namespace and any attribute
PolicyReference: any attribute and a proposal to add any element ExactlyOne, All: element from ##other namespace, no attribute extensibility
PolicyAttachment: element from ##other namespace and any attribute
AppliesTo: any element and any attribute
WS-Policy Framework 1.5 specifies that any element that is not known inside a Policy, ExactlyOne or All will be treated as an assertion. The default value for wsp:Optional="false", which means after normalization it will be inside an ExactlyOne/All operator.
Let us show an example with a hypothetical new operator that is a Choice with a minOccurs and a maxOccurs attributes, ala XSD:Choice, in a new namespace. We use the wsp16 prefix to indicate a hypothetical Policy Language 1.6 that is intended to be compatible with Policy Language 1.5:
Example 4-4. Policy containing 1.5 and 1.6 Policies.
<wsp:Policy> <wsp:ExactlyOne> <wsp16:Choice wsp16:minOccurs="1" wsp16:maxOccurs="2"> ... </wsp16:Choice> <wsp:All> ... </wsp:All> </wsp:ExactlyOne> </wsp:Policy>
The normalization rule for wsp:Optional="false" would be applied to the wsp16:Choice, yielding the following expression:
Example 4-5. Normalized Policy containing 1.5 and 1.6 Policies
<wsp:Policy> <wsp:ExactlyOne> <wsp:ExactlyOne> <wsp:All> <wsp16:Choice wsp16:minOccurs="1" wsp16:maxOccurs="2"> ... </wsp16:Choice> </wsp:All> </wsp:ExactlyOne> <wsp:All> ... </wsp:All> </wsp:ExactlyOne> </wsp:Policy>
Alternatively, the wsp:Optional could be set to "true" on the choice, as in:
Example 4-6. Policy containing explicit wsp:Optional="true"
<wsp:Policy> <wsp16:Choice wsp16:minOccurs="1" wsp16:maxOccurs="2" wsp:Optional="true"> ... </wsp16:Choice> </wsp:Policy>
The normalized form will be:
Example 4-7. Normalized policy
<wsp:Policy> <wsp:ExactlyOne> <wsp:All> <wsp16:Choice wsp16:minOccurs="1" wsp16:maxOccurs="2"> ... </wsp16:Choice> </wsp:All> <wsp:All/> </wsp:ExactlyOne> </wsp:Policy>
Because the wsp16:Choice alternative isn't understood in either normalized form, it will not be chosen as one of the alternatives and will effectively be ignored. Policy intersection may be more difficult with such compatible extensions. For example, the previous will "look" like it has a wsp16:Choice typed assertion. To determine intersection with a Policy that does not have the wsp16:Choice type assertion, domain specific processing would have to be done. However, there is an alternative that does not have the wsp16:Choice, so intersection would yield the expected result.
Note: it is possible to add new names to the existing namespace, such as:
Example 4-8. Policy containing 1.5 and 1.6 Policies all in the 1.5 namespace
<wsp:Policy> <wsp:ExactlyOne> <wsp:Choice wsp:minOccurs="1" wsp:maxOccurs="2"> ... </wsp:Choice> <wsp:All> ... </wsp:All> </wsp:ExactlyOne> </wsp:Policy>
Notice that using a new namespace can result in backwards and forwards compatibility if normalization results in an optional alternative.
Best practice: insert new elements in an optional alternative or mark with wsp:Optional="true".
Incompatible versions of the Policy language may be indicated by a new namespace name for at least the new and/or incompatible elements or attributes. Imagine that the Choice operator is required by a future version of Policy, then there will be a new namespace for the Policy element. We use the wsp20 prefix to indicate a hypothetical Policy Language 2.0 that is intended to be incompatible with Policy Language 1.5:
Example 4-9. Policy containing 2.0 only Policies.
<wsp20:Policy> <wsp20:ExactlyOne> <wsp20:Choice wsp:minOccurs="1" wsp:maxOccurs="2"> ... </wsp20:Choice> ... </wsp20:ExactlyOne> </wsp20:Policy>
The new Policy operator could be embedded inside an existing Policy element:
Example 4-10. Policy containing 2.0 (incompatible with 1.5) Policies embedded in wsp 1.5 Policy.
<wsp:Policy> <wsp20:Choice wsp:minOccurs="1" wsp:maxOccurs="2"> ... </wsp20:Choice> ... </wsp20:Policy>
This will be treated as an Assertion for normalization and intersection computation. This will result in only one alternative that requires the wsp20:Choice, the intended behaviour for incompatible changes.
Best practice: use a new namespace for new incompatible construct and insert inside either: new Policy element OR existing All for future incompatible policy extensions.
A future version of WS-Policy could support the current operators in the existing namespace, such as:
Example 4-11. Policy containing 1.5 operator in 2.0 Policy
<wsp20:Policy> <wsp:ExactlyOne> <wsp20:Choice wsp:minOccurs="1" wsp:maxOccurs="2"> ... </wsp20:Choice> ... </wsp:ExactlyOne> </wsp20:Policy>
It is difficult to predict whether this functionality would be useful. The future version of WS-Policy doesn't appear to be precluded from doing this.
Policy attachment provides WSDL 1.1 and UDDI attachment points. It appears that exchange of Policy will be in the context of WSDL or UDDI. WRT WSDL, the policy model is an extension of the WSDL definition. As such, it is likely that future versions of Policy will be exchanged as multiple Policy expressions within a WSDL. One alternative is that there would be a separate WSDL for each version of Policy. The problem of how to specify and query for compound documents is very difficult, so it is more likely that each version of Policy will be exchanged within a WSDL.
We show an example of a new version of policy that allows QName reference to Policies in the PolicyReference:
Example 4-12. WSDL containing 1.5 and 2.0 (compatible with 2.0) Policy References.
<wsdl11:binding name="StockQuoteSoapBinding" type="fab:Quote" > <wsoap12:binding style="document" transport="http://schemas.xmlsoap.org/soap/http" /> <wsp:Policy> <wsp:ExactlyOne> <wsp:All> <wsp:PolicyReference URI="#RmPolicy" wsdl11:required="true" /> <wsp:PolicyReference URI="#X509EndpointPolicy" wsdl11:required="true" /> </wsp:All> <wsp:All> <wsp:PolicyReferenceByQName ref="rmp:RMAssertion" wsdl11:required="true" /> <wsp:PolicyReferenceByQName ref="sp:AsymmetricBinding" wsdl11:required="true" /> </wsp:All> </wsp:ExactlyOne> </wsp:Policy> <wsdl11:operation name="GetLastTradePrice" > .... ...
The PolicyReference element is attribute extensible. One example of an addition is a list of backup URIs for the PolicyReference:
Example 4-13. WSDL containing 1.5 and 2.0 (compatible with 2.0) Policy References.
<wsdl11:binding name="StockQuoteSoapBinding" type="fab:Quote" > <wsoap12:binding style="document" transport="http://schemas.xmlsoap.org/soap/http" /> <wsp:Policy> <wsp:ExactlyOne> <wsp:All> <wsp:PolicyReference URI="" wsp16:alternateURIs="URI*" wsdl11:required="true" /> <wsp:PolicyReference URI="" wsp16:alternateURIs="URI*" wsdl11:required="true" /> </wsp:All> </wsp:ExactlyOne> </wsp:Policy> <wsdl11:operation name="GetLastTradePrice" > .... ...
The policy framework specification says that any unknown attributes are ignored. A Policy 1.5 processor will not understand the wsp16:alternateURI attribute, it will be ignored. A Policy 1.6 processor will understand the alternate URIs so it won't be ignored.
PolicyAttachment and AppliesTo also have extensibility points. We choose not to illustrate these at this time.
Thus far, we walked through the dimensions of a policy assertion and guidelines for authoring policy assertions. Let us look at what are the minimum requirements for describing policy assertions in specifications:
Description must clearly and completely specify the syntax (plus an XML Schema document) and semantics of a policy assertion.
If there is a nested policy expression, description must declare it and enumerate the nested policy assertions that are allowed.
A policy alternative may contain multiple instances of the same policy assertion. Description must specify the semantics of parameters and nested policy (if any) when there are multiple instances of a policy assertion in the same policy alternative.
If a policy assertion is to be used with WSDL, description must specify a WSDL policy subject – such as service, endpoint, operation and message.
Service providers use Web Services Policy to represent combinations of behaviors (capabilities and requirements). Web service developers use policy-aware clients that understand policy expressions and engage the behaviors represented by providers automatically. These behaviors may include security, reliability, transaction, message optimization, etc. Web Services Policy is a simple language, hides complexity from developers, automates Web service interactions, and enables secure, reliable and transacted Web Services.
Security considerations are discussed in the Web Services Policy Framework document.
The table below lists XML Namespaces that are used in this document. The choice of any namespace prefix is arbitrary and not semantically significant.
Prefix | XML Namespace | Specifications |
---|---|---|
mtom |
http://schemas.xmlsoap.org/ws/2004/09/policy/optimizedmimeserialization |
[WS-OptimizedSerializationPolicy] |
soap |
http://www.w3.org/2003/05/soap-envelope |
[SOAP 1.2 Messaging Framework] |
sp |
http://schemas.xmlsoap.org/ws/2005/07/securitypolicy |
[WS-SecurityPolicy] |
wsa |
http://www.w3.org/2005/08/addressing |
[WS-Addressing Core] |
wsap |
http://www.w3.org/2006/05/addressing/wsdl |
[WS-Addressing WSDL Binding] |
wsdl |
http://schemas.xmlsoap.org/wsdl/ |
[WSDL 1.1] |
wsp |
http://www.w3.org/2006/07/ws-policy |
[Web Services Policy Framework, Web Services Policy Attachment] |
wss |
http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd |
[WS-Security 2004] |
wst |
http://schemas.xmlsoap.org/ws/2005/02/trust |
[WS-Trust] |
wsu |
http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd |
[WS-Security 2004] |
This document is the work of the W3C Web Services Policy Working Group.
Members of the Working Group are (at the time of writing, and by alphabetical order): Dimitar Angelov (SAP AG), Abbie Barbir (Nortel Networks), Charlton Barreto (Adobe Systems Inc.), Sergey Beryozkin (IONA Technologies, Inc.), Vladislav Bezrukov (SAP AG), Toufic Boubez (Layer 7 Technologies), Paul Cotton (Microsoft Corporation), Jeffrey Crump (Sonic Software), Glen Daniels (Sonic Software), Ruchith Fernando (WSO2), Christopher Ferris (IBM Corporation), William Henry (IONA Technologies, Inc.), Frederick Hirsch (Nokia), Maryann Hondo (IBM Corporation), Tom Jordahl (Adobe Systems Inc.), Philippe Le Hégaret (W3C/MIT), Jong Lee (BEA Systems, Inc.), Mark Little (JBoss Inc.), Ashok Malhotra (Oracle Corporation), Monica Martin (Sun Microsystems, Inc.), Jeff Mischkinsky (Oracle Corporation), Dale Moberg (Cyclone Commerce, Inc.), Anthony Nadalin (IBM Corporation), David Orchard (BEA Systems, Inc.), Fabian Ritzmann (Sun Microsystems, Inc.), Daniel Roth (Microsoft Corporation), Sanka Samaranayake (WSO2), Felix Sasaki (W3C/Keio), Skip Snow (Citigroup), Yakov Sverdlov (Computer Associates), Mark Temple-Raston (Citigroup), Asir Vedamuthu (Microsoft Corporation), Sanjiva Weerawarana (WSO2), Ümit Yalçinalp (SAP AG), Prasad Yendluri (webMethods, Inc.).
Previous members of the Working Group were: Bijan Parsia (University of Manchester), Seumas Soltysik (IONA Technologies, Inc.)
The people who have contributed to discussions on public-ws-policy@w3.org are also gratefully acknowledged.
A list of substantive changes since the previous publication is below:
Replaced URI with IRI.
Added a new section - Versioning Policy Language.
Moved 'Security Considerations' section to the Web Services Policy 1.5 - Framework.
Date | Author | Description |
---|---|---|
20060816 | ASV | Created first draft per action item 2 from the Austin F2F. This draft is based on a contribution from Microsoft. |
20060829 | ASV | Implemented the resolution for issue 3561: replaced URI with IRI. |
20060919 | DBO | Implemented the action 26 to add versioning material to primer. |
20060924 | TIB | Implemented the editorial action 35 to move the Security Considerations section to the Framework document. |
20060924 | TIB | Implemented the editorial action 36 to insert a reference to the Security Considerations section from the Framework document. |
20060926 | PY | Made a first pass at the changes to address issues reported by Paul Cotton. |
20060928 | PY | Completed making remaining changes to address issues reported by Paul Cotton. Fixing up the Acknowledgements is pending |