2.1.1 The Description Component
At the abstract level, the Description component is just a
container for two categories of components: WSDL 2.0 components and
type system components.
WSDL 2.0 components are interfaces, bindings and services. Type
system components are element declarations and type
definitions.
Type system components describe the constraints on a message's
content. By default, these constraints are expressed in terms of
the [XML Information Set],
i.e. they define the [local name], [namespace name], [children] and
[attributes] properties of an element information item.
Type systems based upon other data models are generally
accommodated by extensions to WSDL 2.0; see 6. Language Extensibility. In
the case where they define information equivalent to that of a XML
Schema global element declaration, they can be treated as if they
were such a declaration.
This specification does not define the behavior of a WSDL 2.0
document that uses multiple schema languages for describing type
system components simultaneously.
An Element Declaration component
defines the name and content model of an element information
item such as that defined by an XML Schema global element
declaration. It has a {name} property that is
the QName of the element information item and a {system} property that is
the namespace IRI of the extension element information
items for the type system, e.g. the namespace of XML
Schema.
A Type Definition component defines
the content model of an element information item such as
that defined by an XML Schema global type definition. It has a
{name} property that is the QName
of the type and a {system} property that is the
namespace IRI of the extension element information items
for the type system, e.g. the namespace of XML Schema.
Interface, Binding, Service, Element Declaration, and
Type Definition components
are directly contained in the Description component and are referred
to as top-level components. The top-level WSDL 2.0
components contain other components, e.g. Interface Operation and
Endpoint, which are referred to
as nested components. Nested components may contain other
nested components. The component that contains a nested component
is referred to as the parent of the nested components.
Nested components have a {parent} property that is a reference to
their parent component.
The properties of the Description component are as
follows:
The {type
definitions} property of the Description component contains all of
the built-in datatypes defined by XML Schema Part 2: Datatypes
Second Edition [XML Schema:
Datatypes], namely the nineteen primitive datatypes
xs:string , xs:boolean ,
xs:decimal , xs:float ,
xs:double , xs:duration ,
xs:dateTime , xs:time ,
xs:date , xs:gYearMonth ,
xs:gYear , xs:gMonthDay ,
xs:gDay , xs:gMonth ,
xs:hexBinary , xs:base64 ,
xs:Binary , xs:anyURI ,
xs:QName , xs:NOTATION , and the
twenty-five derived datatypes xs:normalizedString ,
xs:token , xs:language ,
xs:NMTOKEN , xs:NMTOKENS ,
xs:Name , xs:NCName , xs:ID
, xs:IDREF , xs:IDREFS ,
xs:ENTITY , xs:ENTITIES ,
xs:integer , xs:nonPositiveInteger ,
xs:negativeInteger , xs:long ,
xs:int , xs:short , xs:byte
, xs:nonNegativeInteger , xs:unsignedLong
, xs:unsignedInt , xs:unsignedShort ,
xs:unsignedByte , xs:positiveInteger
.
The set of top-level components contained in the Description component associated with
an initial WSDL 2.0 document consists of the components defined in
the initial document and the components associated with the
documents that the initial document includes and the namespaces
that the initial document imports. The component model makes no
distinction between the components that are defined in the initial
document versus those that are defined in the included documents or
imported namespaces. However, any WSDL 2.0 document that contains
component definitions that refer by QName to WSDL 2.0 components
that belong to a different namespace MUST contain a
wsdl:import element information item for that
namespace (see 4.2 Importing
Descriptions ).†
Furthermore, all
QName references, whether to the same or to different namespaces
MUST resolve to components (see 2.19 QName
resolution ).†
In addition to WSDL 2.0 components and type system components,
additional extension components MAY be added via extensibility
6. Language
Extensibility. Further, additional properties to WSDL 2.0
and type system components MAY also be added via extensibility.
2.1.2
XML Representation of Description Component
<description
targetNamespace="xs:anyURI" >
<documentation />*
[ <import /> | <include /> ]*
<types />?
[ <interface /> | <binding /> | <service /> ]*
</description>
WSDL
2.0 definitions are represented in XML by one or more WSDL 2.0
Information Sets (Infosets), that is one or more
description element information
items.†
A WSDL 2.0 Infoset contains representations for a collection of
WSDL 2.0 components that share a common target namespace. A WSDL
2.0 Infoset that contains one or more wsdl:import
element information items 4.2
Importing Descriptions corresponds to a collection with
components drawn from multiple target namespaces.
The components directly defined or included within a Description component are said to
belong to the same target namespace. The target namespace
therefore groups a set of related component definitions and
represents an unambiguous name for the intended semantics of the
collection of components. The value of the targetNamespace
attribute information item SHOULD be
dereferenceable.†
It SHOULD
resolve to a human or machine processable document that directly or
indirectly defines the intended semantics of those
components.†
It MAY
resolve to a WSDL 2.0 document that provides service description
information for that namespace.†
If a
WSDL 2.0 document is split into multiple WSDL 2.0 documents (which
may be combined as needed via 4.1 Including
Descriptions), then the targetNamespace
attribute information item SHOULD resolve to a master WSDL
2.0 document that includes all the WSDL 2.0 documents needed for
that service description.†
This approach enables the WSDL 2.0 component designator fragment
identifiers to be properly resolved.
Imported
components have different target namespace values from the WSDL 2.0
document that is importing them.†
Thus importing is the mechanism to use components from one
namespace in definition of components from another namespace.
Each WSDL
2.0 or type system component of the same kind MUST be uniquely
identified by its qualified name. †
That is, if two distinct components of the same kind ( Interface, Binding, etc.) are in the same target
namespace, then their QNames MUST be unique. However, different
kinds of components (e.g., an Interface component and a Binding component) MAY have the same
QName. Thus, QNames of components must be unique within the space
of those components in a given target namespace.
The description element information item
has the following Infoset properties:
-
A [local name] of description .
-
A [namespace name] of "http://www.w3.org/2006/01/wsdl".
-
One or more attribute information items amongst its
[attributes] as follows:
-
A REQUIRED targetNamespace attribute
information item as described below in 2.1.2.1 targetNamespace
attribute information item.
-
Zero or more namespace qualified attribute information
items whose [namespace name] is NOT
"http://www.w3.org/2006/01/wsdl".
-
Zero or
more element information items amongst its [children], in
order as follows:†
-
Zero or more documentation element information
items (see 5.
Documentation).
-
Zero or more element information items from among the
following, in any order:
-
Zero or more include element information
items (see 4.1 Including
Descriptions)
-
Zero or more import element information
items (see 4.2 Importing
Descriptions)
-
Zero or more namespace-qualified element information
items whose [namespace name] is NOT
"http://www.w3.org/2006/01/wsdl".
-
An OPTIONAL types element information item
(see 3. Types).
-
Zero or more element information items from among the
following, in any order:
2.1.2.1
targetNamespace attribute information
item
The targetNamespace attribute information
item defines the namespace affiliation of top-level components
defined in this description element information
item. Interface, Binding and Service are top-level components.
The targetNamespace attribute information
item has the following Infoset properties:
The type of the targetNamespace attribute
information item is xs:anyURI. Its value MUST be an
absolute IRI (see [IETF RFC
3987]) and should be dereferenceable.†