Web Services

Follow-up on work from:

• HTTP-NG
• ebXML
• Corba

Is about:

• Service Oriented Architecture
• Interoperability
• Tooling

Service Oriented Architecture

Principles:

• Application as a set of services
• Service Metadata

Benefits

• Reuse
• Cost Reductions
• Agility

Participants

Vendors:
IBM, BEA, webMethods, IONA, TIBCO, SAP, CA, Oracle, Microsoft, Sun, etc.

Users:
Citigroup, BT, Canon, Xerox, NACS, HL7, etc.

Web Services

Web Services Protocol

Web Services Description

Messaging Framework

SOAP 1.2:

• basic XML Framework for exchanging structured and typed information in machine-to-machine interaction
• necessitate the use of a transport protocol, such as HTTP/1.1
• improved interoperability, processing model, and protocol independence since SOAP 1.1
• already deployed in all major toolkits and several Web services extensions

W3C Recommendation since June 2003. Slow but steady transition.

SOAP 1.2

<soap:Envelope>

  <soap:Headers>
    <wsa:To>http://www.example.org/MyService</wsa:To>
    <wsa:Action>http://www.example.org/Update</wsa:Action>
  </soap:Headers>
  <soap:Body>
    …
  </soap:Body>
</soap:Envelope>

Addressing (1/2)

Addressing (2/2)

Web Services Addressing 1.0:

• define service endpoint references
• direct messages to the service endpoints, including replies or faults.
• relates messages using URIs

W3C Recommendation (Core and SOAP Binding)

WSDL Binding interoperability ongoing

Web Services Addressing 1.0 Interoperability

Next is Addressing 1.0 Policy assertion.

Message Transmission Optimization Mechanism (1/2)

Message Transmission Optimization Mechanism (2/2)

SOAP Message Transmission Optimization Mechanism (MTOM):

• enables the optimization, at the transport protocol level, of the transmission and wire format used to transfer binary data in a SOAP message.
• ideal for large binary attachments:
  • save bandwith: binary files are sent as-is on the wire (33% gain)
  • better performance: no conversion binary-to-XML and XML-to-binary for the transmission
• compatible with specifications built on top of the Infoset, such as XML Signature

W3C Recommendation since January 2005.

Web Services Description

WSDL 2.0 (1/3)

WSDL 2.0: Define a basic description of a Web Service

• the interface and its operations, including the types of the data being exchanged
• the transport protocol binding(s) associated with the operations
• the endpoints associated with each transport protocol bindings

WSDL 2.0 (2/3)

• Reusable definitions: import, include, inheritance, bindings
• Advanced support for SOAP 1.2 and HTTP 1.1

Candidate Recommendation

Second Interoperability event in November (Dinard, France)

Removed recently: feature/properties, 6 MEPs

(see also dashboard)

WSDL 2.0 (3/3)

<description …>

  <types>
    <xs:schema …>
      <xs:element name="checkAvailability" type="tCheckAvailability"/>    
      <xs:complexType name="tCheckAvailability">     
        <xs:sequence>      
          <xs:element  name="checkInDate" type="xs:date"/>      
          <xs:element  name="checkOutDate" type="xs:date"/>      
          <xs:element  name="roomType" type="xs:string"/>      
        </xs:sequence>     
      </xs:complexType>            
      <xs:element name="checkAvailabilityResponse" type="xs:double"/>        
      <xs:element name="invalidDataError" type="xs:string"/>    
    </xs:schema>    
  </types>
  
  <interface  name="reservationInterface" >
    <fault name="invalidDataFault"
            element="ghns:invalidDataError"/>    
    <operation name="opCheckAvailability" 
            pattern="http://www.w3.org/2006/01/wsdl/in-out" 
            style="http://www.w3.org/2006/01/wsdl/style/iri"
            wsdlx:safe="true">
        <input messageLabel="In" 
              element="ghns:checkAvailability" />
        <output messageLabel="Out" 
              element="ghns:checkAvailabilityResponse" />
        <outfault ref="tns:invalidDataFault" messageLabel="Out"/>
    </operation>
  </interface>

  <binding name="reservationSOAPBinding" 
          interface="tns:reservationInterface"
          type="http://www.w3.org/2006/01/wsdl/soap"
          wsoap:protocol="http://www.w3.org/2003/05/soap/bindings/HTTP">
    <fault ref="tns:invalidDataFault" 
      wsoap:code="soap:Sender"/>
    <operation ref="tns:opCheckAvailability" 
      wsoap:mep="http://www.w3.org/2003/05/soap/mep/soap-response"/>
  </binding>

  <service name="reservationService" interface="tns:reservationInterface">
     <endpoint name="reservationEndpoint" 
               binding="tns:reservationSOAPBinding"
               address ="http://greath.example.com/2004/reservation"/>        
  </service>

</description>

WS-Policy 1.5 (1/2)

• Framework for policy assertions: All, ExactlyOne
• Attachment mechanisms for policy: UDDI 2.0/3.0, WSDL 1.1/2.0
• Not defining policy assertions
• Not defining policy negotiation
• Started in June
• Last Call Public Working Drafts comming soon
• W3C Recommendation by end of 2007

(see also Web Services Policy 101)

WS-Policy 1.5 (2/2)

<wsp:Policy>

  <wsap:AddressingRequired />
  <mtom:OptimizedMimeSerialization
          wsp:Optional="true"/>
  <wsp:ExactlyOne>
    <sp:TransportBinding>…</sp:TransportBinding>
    <sp:AsymmetricBinding>…</sp:AsymmetricBinding>
  </wsp:ExactlyOne>
</wsp:Policy>

Choreography

WS-CDL 1.0: Describe interaction among atomic Web Services

• Complex messages exchanges
• Composition of Web Services: linking business via Web Services

Candidate Recommendation

XML Schema Patterns for Databinding

• Provides a set of simple XML Schema 1.0 patterns
• Describe XML representations of commonly used data structures: Enumeration, Collection, Vector, etc.

First Working Draft for XML Schema Patterns for Databinding published on May 12.

XML Schema Patterns for Databinding (1/2)

• Provides a set of simple XML Schema 1.0 patterns
• Describe XML representations of commonly used data structures: Enumeration, Collection, Vector, etc.

First Working Draft for XML Schema Patterns for Databinding published on May 12.

XML Schema Patterns for Databinding (2/2)

<xs:complexType name="Collection">
  <xs:sequence>
    <xs:element name="name" type="xs:string"/>
    <xs:element name="shade" type="xs:string"/>
    <xs:element name="length" type="xs:int"/>
  </xs:sequence>
  <xs:attribute name="id" type="xs:string"/>
  <xs:attribute name="inStock" type="xs:int"/>
</xs:complexType>

Semantic Web Services

Generic Semantic Annotation mechanism for WSDL

• Working Group started in April
• Mechanism to enable annotation of Web services descriptions: operations, inputs, outputs, types

  <interface name="CheckItemAvailability">
          sawsdl:modelReference="PurchaseOrderServices/ItemAvailability"
      <operation name="InStock"
         pattern="http://www.w3.org/2006/01/wsdl/in-out">
          <input messageLabel="In"
              element="tns:ItemDescription"/> 
          <output messageLabel="Out"
             element="tnsItemDescriptionAvaibility"/>
      </operation>
  
  </interface>

Semantic Web Services (2/3)

urn:Electronics rdf:type categorization:Category;
     categorization:haveValue "443112";
     categorization:usesTaxonomy <http://naics.com> . 

<wsdl:interface name="CheckItemAvailability">
  <wsdl:operation name="CheckItemAvailabilityOperation" sawsdl:modelReference="categorization#Electronics"
    ...
  </wsdl:operation>
</wsdl:interface>

Semantic Web Services (3/3)

<xs:exlement name="CheckInventoryServiceRequest">
  <xs:complexType>
    <xs:sequence>
      <xs:element name="UPC" type="xsd:string"
        sawsdl:modelReference="SampleRetailOntology#UPCCode"/>
      <wsdl:element name="DeliveryDate" type="xs:string"
        sawsdl:modelReference="SampleRetailOntology#DeliveryDate"/>
      <wsdl:element name="numBundles" type="xs:float"
        sawsdl:modelReference="SampleRetailOntology#NumBundles/>
    </xs:sequence>
  </xs:complexType>
</xs:element>

<SampleRetailOntology.owl#> rdf:type owl:Ontology  .
  :PartNumber rdf:type owl:Class;
     rdfs:subClassOf owl:Thing;
     owl:equivalentClass :UPC .
  :UPC rdf:type owl:Class;
     owl:equivalentClass :PartNumber .
  :NumBundles rdf:type owl:Class;
     owl:equivalentClass :Quantity .
  :Quantity rdf:type owl:Class;
     rdfs:subClassOf owl:Thing;
     owl:equivalentClass :NumBundles; .
  :DeliveryDate rdf:type owl:Class;
     rdfs:subClassOf owl:Thing;
     owl:equivalentClass owl:DueDate .
  :DueDate rdf:type owl:Class;
     owl:equivalentClass :DeliveryDate .

WS2: SPARQL + WSDL Demonstrator

Adding WSDL annotations for SPARQL Queries

• SPARQL: SQL-like RDF query language

  SELECT ?tile WHERE { ?response tnss:doctitle ?title }

• XPath: identify locations in a document

  aws:ItemSearchResponse/aws:Items/aws:Item/aws:Title

• WSDL: associate messages (documents) with services

  <definitions><types><element name="ItemSearchResponse"></element></types>...
      <message name="ItemSearchResponseMsg"/></definitions>

Ties RDF data to locations in a Web Services message.:

<xs:element name="Item" spat:SPAT='?book tns:doctitle xpath("aws:Title")'/>

Demo

PREFIX tnss: <http://webservices.amazon.com/AWSECommerceService/2004-11-10>
SELECT ?asin ?title WHERE {
 ?X tnss:id "0FWYBWB91M5S26YBE382" ;
    tnss:keywords "cola" ;
    tnss:index "Books" ;

    tnss:asin ?asin ;
    tnss:doctitle ?title }

Service Oriented Architecture

Principles:

• Application as a set of services
• Service Metadata

Benefits

• Reuse
• Cost Reductions
• Agility

Web Architecture: Principles

• Global Identifiers (Use URI)
• Interaction: Safe retrieval, Reference does not imply dereference
• No principles for data formats
• Orthogonality
• Error recovery

From Architecture of the World Wide Web, Volume One

SOA/Web: What's missing?

• Better protocol: query, insert, replace, subscribe, lookup, update, ...
• Security: digital signature, encryption, identity, non-repudiation, etc.
• End-to-end reliability or state query ?
• Service Description: Application modelling and visualization, code generation, configuration, resource management, orchestration, semantic, etc.

SOA/Web Services: What's missing?

Going beyond SOAP/WSDL 1.1…

• sadly, Interoperability
• Service Description: resource management.
• End-to-end reliability or state query ?
• Guidelines, industry profiles

Services on the Web

• Separation between Web Architecture and Web Services Architecture?
• Web stack needs improvement
• Web services stack needs improvement

• Could we identify the Web services gaps with a workshop?
• Best practices, usage scenarios, and findings

Web of Services for Enterprise Computing

facilitate the processing of business transactions and interactions with systems and address the need to interconnect intranet and/or extranet services using Web technologies.

W3C Workshop on Web of Services for Enterprise Computing (end of February 2007)

Efficient XML Interchange (EXI)

EXI: Improving the XML pipeline

• XML problematic in some cases: floating point arrays in energy industry, sensor processing, data synchronization, etc.
• Produce an alternate representation of XML, relaxing some original XML goals: human-legible and reasonably clear, and emphasize conciseness/terseness
• We ought to:
  • Maintain compatibility with existing XML applications and specifications;
  • Establish confidence in the proposed format;
  • Produce a non-proprietary binary format.
  • Maintain the interoperability and strong brand of XML

EXI: Test cases

Scientific

AVCL, GAML, HepRep, MAGE-ML, Seismic, XAL, Misc/periodic

Financial

FixML, FpML, Invoice

Document

OpenOffice, SVGTiny, Misc/factbook

Web Services

Google, WSDL, epicsArchiver

…, Military (ASMTF, JTLM), Broadcast (CBMS), Storage (DataStore), Sensor (LocationSightings)

From Analysis of EXI Measurement Results, by Jaakko Kangasharju

EXI: Compaction document+schema

EXI: Latest news

• Picked Efficient XML as starting point
• Some possible improvements:
  • Type Facets restrictions
  • Restricted Character Sets with escaping
  • Add whitespace event
  • Support IEEE-754 floats/doubles/quads
  • Bounded string tables
  • Strict schema processing
  • …
• First public Working Draft at the end of January

Thank you

More information at:

http://www.w3.org/2002/ws/