Foundations And Future Directions of Web Services

Hugo Haas <[email protected]>
W3C Web Services Activity Lead

Charlton Barreto, Adobe Systems Inc.
Member of the W3C Web Services Description & Choreography Working Groups

ECOWS 2005, Växjö, Sweden, 14 November 2005

Outline

Motivations for Web services
Infrastructure developed at W3C
What's ahead of us

Example of use of Web services

Web merchant

Miscellaneous partners
- Banks
- Manufacturers
- Delivery services
Use services from those partners to do business with customers
Desires well-defined and easy integration with those services

What Web services are trying to achieve

Ease of integration
Extensibility
Interoperability
Machine-to-machine communication
Scalability

A lot of buzzwords…

… translating to an architecture

… justifying some choices:

XML-based messages: for platform-independent machine processing
Framework focused on extensibility: facilitating interoperability
Machine-processable descriptions: facilitating integration
Loose coupling: maximizing scalability

Traditional Web interaction

Web services interaction

Web services at W3C

Stack of W3C Web services technologies

Messages

Messaging framework
Description formats
Looking in the future

Messaging framework for Web services

Built on top of Web technologies:

Messaging framework

SOAP Version 1.2

Core of the messaging framework
- XML-based
- Extensible
Defines:
- An envelope
- A processing model
- A binding framework

SOAP message

XML document
Represented abstractly as an XML Infoset

The SOAP envelope

SOAP message

SOAP message path

One-way message
Going from a sender to a receiver, possible via intermediaries
SOAP body is for the ultimate recipient
SOAP header blocks may be targeted at anybody along the message path

SOAP message path

Example of a SOAP message

<?xml version='1.0' ?>
<env:Envelope xmlns:env="http://www.w3.org/2003/05/soap-envelope"> 
 <env:Header>
  <m:reservation xmlns:m="http://travelcompany.example.org/reservation" 
          env:role="http://www.w3.org/2003/05/soap-envelope/role/next"
          env:mustUnderstand="true">
   <m:reference>uuid:093a2da1-q345-739r-ba5d-pqff98fe8j7d</m:reference>
   <m:dateAndTime>2001-11-29T13:20:00.000-05:00</m:dateAndTime>
  </m:reservation>
 </env:Header>
 <env:Body>
  <p:itinerary
    xmlns:p="http://travelcompany.example.org/reservation/travel">
   …
  </p:itinerary>
 </env:Body>
</env:Envelope>

Message exchange patterns

One-way exchanges can be combined
Template that establishes a pattern for the exchange of messages between SOAP nodes
Examples:
- Request response
- Response: SOAP message following a non-SOAP request

Underlying protocols binding

Need to carry the XML document that a SOAP message is
Duty of a binding to an underlying protocol:
- Serialization of the Infoset
- Transmission
- Reconstruction of the Infoset
Can implements features:
- Message exchange pattern (MEP)
- Optimization
- …

SOAP 1.2 HTTP Binding

Carries SOAP messages in an HTTP message
Implements 2 MEPs
- SOAP Request-Response: HTTP POST
- SOAP Response: HTTP GET
Implements the SOAP Web Method feature:
- POST
- GET
Allows for REST-ful interactions

Simple addition service

public class MathService
{
    static int total=0;

    // Add an integer and return the total
    public int add(int a)
    {
        total += a;
        return total;
    }
    
    // Get the total of all the additions
    public int total()
    {
        return total;
    }
    
}

Deployed with Axis 1.3

Simple addition client

import org.apache.axis.client.Call;
import org.apache.axis.encoding.XMLType;
import org.apache.axis.soap.SOAPConstants;
import javax.xml.rpc.ParameterMode;

public class AddClient
{
   public static void main(String [] args) throws Exception {

       if (args == null || args.length != 1) {
           System.err.println("Usage: AddClient <int>");
           return;
       }
       
       Call call = new Call("http://localhost:8080/axis/MathService.jws");
       call.setSOAPVersion(SOAPConstants.SOAP12_CONSTANTS);

       Integer i = new Integer(args[0]);

       call.setOperationName("add");
       call.addParameter("a", XMLType.XSD_INT, ParameterMode.IN);
       call.setReturnType(XMLType.XSD_INT);

       Integer ret = (Integer) call.invoke(new Object [] { i });
       
       System.out.println("Added " + i + ". Current total: " + ret);
   }
}

POST example: adding a value

hugo@jibboom ~/ws-setup% java AddClient 432
Added 432. Current total: 3468

produces the following HTTP request:

POST /axis/MathService.jws HTTP/1.0
Content-Type: application/soap+xml; charset=UTF-8
Accept: application/soap+xml, application/dime, multipart/related, text/*
User-Agent: Axis/1.3
Host: 127.0.0.1:8080
Cache-Control: no-cache
Pragma: no-cache
SOAPAction: ""
Content-Length: 363

<?xml version="1.0" encoding="UTF-8"?>
<soapenv:Envelope xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope"
   xmlns:xsd="http://www.w3.org/2001/XMLSchema"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <soapenv:Body>
    <add soapenv:encodingStyle="http://www.w3.org/2003/05/soap-encoding">
      <a xsi:type="xsd:int">432</a>
    </add>
  </soapenv:Body>
</soapenv:Envelope>

resulting in the following HTTP reply:

HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
Set-Cookie: JSESSIONID=16ADA5B3AB2CBE3BA1582201B4F8BC28; Path=/axis
Content-Type: application/soap+xml;charset=UTF-8
Date: Wed, 19 Oct 2005 14:34:48 GMT
Connection: close

<?xml version="1.0" encoding="UTF-8"?>
<soapenv:Envelope xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope"
   xmlns:xsd="http://www.w3.org/2001/XMLSchema"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <soapenv:Body>
    <addResponse soapenv:encodingStyle="http://www.w3.org/2003/05/soap-encoding">
      <ns1:result xmlns:ns1="http://www.w3.org/2003/05/soap-rpc">addReturn</ns1:result>
      <addReturn xsi:type="xsd:int">3468</addReturn>
    </addResponse>
  </soapenv:Body>
</soapenv:Envelope>

GET example: retrieving the total

GET /axis/MathService.jws?method=total HTTP/1.1
Host: 127.0.0.1:8080
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20050922 Firefox/1.0.7 (Debian package 1.0.7-1)
Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
Accept-Language: en-us,en;q=0.8,fr;q=0.6,de;q=0.4,es;q=0.2
Accept-Encoding: gzip,deflate
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
Cookie: JSESSIONID=9B2EB217BEA1C3EB8DEE1FE1F5E283B9

returns:

HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
Cache-Control: no-cache
Pragma: no-cache
Content-Type: text/xml;charset=ISO-8859-1
Content-Length: 410
Date: Wed, 19 Oct 2005 14:40:30 GMT

<?xml version="1.0" encoding="UTF-8"?>
<soapenv:Envelope xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope"
    xmlns:xsd="http://www.w3.org/2001/XMLSchema"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <soapenv:Body>
    <totalResponse soapenv:encodingStyle="http://www.w3.org/2003/05/soap-encoding">
      <totalReturn xsi:type="xsd:int">3468</totalReturn>
    </totalResponse>
  </soapenv:Body>
</soapenv:Envelope>

Note about encoding of the message

Examples show Axis's default, using SOAP encoding:

<?xml version="1.0" encoding="UTF-8"?>
<soapenv:Envelope xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope"
    xmlns:xsd="http://www.w3.org/2001/XMLSchema"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <soapenv:Body>
    <totalResponse soapenv:encodingStyle="http://www.w3.org/2003/05/soap-encoding">
      <totalReturn xsi:type="xsd:int">3468</totalReturn>
    </totalResponse>
  </soapenv:Body>
</soapenv:Envelope>

Possibility to use document style interaction:

<?xml version="1.0" encoding="UTF-8"?>
<soapenv:Envelope xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope"
    xmlns:xsd="http://www.w3.org/2001/XMLSchema"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <soapenv:Body>
    <ns1:totalResponse xmlns:ns1="http://localhost:8080/axis/services/MathServiceDL">
      <ns1:totalReturn>3468</totalReturn>
    </ns1:totalResponse>
  </soapenv:Body>
</soapenv:Envelope>

when deployed with:

style="wrapped" use="literal"

SOAP Extensibility: SOAP modules

Identified by a URI
Headers can be added to have extra processing done to the message; e.g.:
- Integrity checks
- Encryption
One can ensure that a header will be processed as intended:
- Optional extensions
- Mandatory extensions; e.g.:
  - Process header block in a particular order, or don't do anything

SOAP extensibility: SOAP features

Abstract piece of functionality: e.g. correlation
Can be implemented by a module, or by a binding

mustUnderstand example: updated client

import org.apache.axis.client.Call;
import org.apache.axis.encoding.XMLType;
import org.apache.axis.soap.SOAPConstants;
import javax.xml.rpc.ParameterMode;
import org.apache.axis.message.SOAPHeaderElement;
import org.apache.axis.Constants;

public class AddClientMU
{
   public static void main(String [] args) throws Exception {
       
       if (args == null || args.length != 1) {
           System.err.println("Usage: AddClient <int>");
           return;
       }
       
       Call call = new Call("http://localhost:8080/axis/MathService.jws");
       call.setSOAPVersion(SOAPConstants.SOAP12_CONSTANTS);

       SOAPHeaderElement header = new SOAPHeaderElement("http://example.com/header",
                                                        "very-important-info", "blah");
       header.setMustUnderstand(true);
       header.setActor(Constants.URI_SOAP12_ULTIMATE_ROLE);


       call.addHeader(header);

       Integer i = new Integer(args[0]);

       call.setOperationName("add");
       call.addParameter("a", XMLType.XSD_INT, ParameterMode.IN);
       call.setReturnType(XMLType.XSD_INT);

       Integer ret = (Integer) call.invoke(new Object [] { i });
       
       System.out.println("Added " + i + ". Current total: " + ret);
   }
}

gives on error:

hugo@jibboom ~/ws-setup% java AddClientMU 2
Exception in thread "main" AxisFault
 faultCode: {http://www.w3.org/2003/05/soap-envelope}MustUnderstand
 faultSubcode:
 faultString: Did not understand "MustUnderstand" header(s):{http://example.com/he
ader}very-important-info
 faultActor:
 faultNode:
 faultDetail:
        {http://xml.apache.org/axis/}stackTrace:Did not understand "MustUnderstand" header(s):{http://example.com/header}very-important-info
        at org.apache.axis.message.SOAPFaultBuilder.createFault(SOAPFaultBuilder.java:222)
        at org.apache.axis.message.SOAPFaultBuilder.endElement(SOAPFaultBuilder.java:129)
        at org.apache.axis.encoding.DeserializationContext.endElement(DeserializationContext
.java:1087)
[…]

Triggering a mustUnderstand fault

POST /axis/MathService.jws HTTP/1.0
Content-Type: application/soap+xml; charset=UTF-8
Accept: application/soap+xml, application/dime, multipart/related, text/*
User-Agent: Axis/1.3
Host: 127.0.0.1:8080
Cache-Control: no-cache
Pragma: no-cache
SOAPAction: ""
Content-Length: 616

<?xml version="1.0" encoding="UTF-8"?>
<soapenv:Envelope
   xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope"
   xmlns:xsd="http://www.w3.org/2001/XMLSchema"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
 <soapenv:Header>
  <ns1:very-important-info
     soapenv:role="http://www.w3.org/2003/05/soap-envelope/role/ultimateReceiver"
     soapenv:mustUnderstand="true"
     xsi:type="xsd:string"
     xmlns:ns1="http://example.com/header">
      blah
  </ns1:very-important-info>
 </soapenv:Header>
 <soapenv:Body>
  <add soapenv:encodingStyle="http://www.w3.org/2003/05/soap-encoding">
   <a xsi:type="xsd:int">2</a>
  </add>
 </soapenv:Body>
</soapenv:Envelope>

mustUnderstand fault

HTTP/1.1 500 Internal Server Error
Server: Apache-Coyote/1.1
Content-Type: application/soap+xml;charset=UTF-8
Date: Fri, 04 Nov 2005 12:38:56 GMT
Connection: close

<?xml version="1.0" encoding="UTF-8"?>
<soapenv:Envelope
   xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope"
   xmlns:xsd="http://www.w3.org/2001/XMLSchema"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
 <soapenv:Header>
  <soapenv:NotUnderstood qname="ns1:very-important-info"
   soapenv:role="http://schemas.xmlsoap.org/soap/actor/next"
   soapenv:mustUnderstand="false"
   xmlns:ns1="http://example.com/header"/>
 </soapenv:Header>
 <soapenv:Body>
  <soapenv:Fault>
   <soapenv:Code>
     <soapenv:Value>soapenv:MustUnderstand</soapenv:Value>
   </soapenv:Code>
   <soapenv:Reason>
    <soapenv:Text xml:lang="en">
      Did not understand &quot;MustUnderstand&quot; header(s):{http://example.com/header}very-important-info
    </soapenv:Text>
   </soapenv:Reason>
   <soapenv:Detail>
    <ns2:hostname xmlns:ns2="http://xml.apache.org/axis/">jibboom</ns2:hostname>
   </soapenv:Detail>
  </soapenv:Fault>
 </soapenv:Body>
</soapenv:Envelope>

SOAP 1.2 status

W3C Recommendation since June 2003
Basis of the messaging framework

Addressing information: Web Services Addressing 1.0

SOAP is very generic: no addressing information provided in its core capabilities
Typical interaction: HTTP request-response
Other scenarios:
- protocol without appropriate addressing capabilities
- protocol which doesn't provide correlation facilities
- send the response to an alternate location

Addressing from and to endpoints

Messages travel between endpoints
Concept of an endpoint reference (EPR):
- destination address
- reference parameters: bag of information related to an interaction
- metadata about the endpoint

Example of an EPR

<wsa:EndpointReference
     xmlns:wsa="http://www.w3.org/2005/04/addressing"
     xmlns:fabrikam="http://example.com/fabrikam"
     xmlns:wsdli="http://www.w3.org/2005/05/wsdl-instance"
     wsdli:wsdlLocation="http://example.com/fabrikam
       http://example.com/fabrikam/fabrikam.wsdl">
  <wsa:Address>
    http://example.com/fabrikam/acct
  </wsa:Address>
  <wsa:Metadata>
    <wsaw:InterfaceName>
      fabrikam:Inventory
    </wsaw:InterfaceName>
  </wsa:Metadata>
  <wsa:ReferenceParameters>
    <fabrikam:CustomerKey>
      412
    </fabrikam:CustomerKey>
  </wsa:ReferenceParameters>
</wsa:EndpointReference>

Message addressing properties

Similar to email headers
SOAP header blocks indicating source and destinations:
- wsa:From
- wsa:To
- wsa:ReplyTo
- wsa:FaultTo
Addressing metadata:
- wsa:MessageId
- wsa:RelatesTo
- wsa:Action

Example of use

Web services example

Example request message

<soap:Envelope
    xmlns:soap="http://www.w3.org/2003/05/soap-envelope"      
    xmlns:wsa="http://www.w3.org/2005/03/addressing">
  <soap:Header>
    <wsa:To>
      http://example.com/fabrikam/Purchasing
    </wsa:To>
    <wsa:Action>
      http://example.com/fabrikam/SubmitPO
    </wsa:Action>
    <wsa:MessageID>
      http://example.com/6B29FC40-CA47-1067
    </wsa:MessageID>
    <wsa:RelatesTo
        RelationshipType="http://www.w3.org/2005/03/addressing/reply">
      http://example.com/fabrikam/mid/1234
    </wsa:RelatesTo>
    <wsa:ReplyTo>
      <wsa:Address>
        mailto:[email protected]
      </wsa:Address>
    </wsa:ReplyTo>
  </soap:Header>
  <soap:Body>
    …
  </soap:Body>
</soap:Envelope>

Example response message using `wsa:Reply-To`

<soap:Envelope
    xmlns:soap="http://www.w3.org/2003/05/soap-envelope"      
    xmlns:wsa="http://www.w3.org/2005/03/addressing">
  <soap:Header>
    <wsa:To>
      mailto:[email protected]
    </wsa:To>
    <wsa:Action>
      http://example.com/fabrikam/POAcceptance
    </wsa:Action>
    <wsa:From>
      <wsa:Address>
        http://example.com/fabrikam/Purchasing
      </wsa:Address>
    </wsa:From>
    <wsa:MessageID>
      mid:[email protected]
    </wsa:MessageID>
    <wsa:RelatesTo
        RelationshipType="http://www.w3.org/2005/03/addressing/reply">
      http://example.com/6B29FC40-CA47-1067
    </wsa:RelatesTo>
  </soap:Header>
  <soap:Body>
    …
  </soap:Body>
</soap:Envelope>

WS-Addressing 1.0 status

Core and SOAP binding: Candidate Recommendation, i.e. implementation testing
Description of the extension (WSDL binding): still under work, covered later

Handling non-XML data

SOAP messages are XML documents
What to do with legacy binary data?
- Bitmap images (e.g. PNG)
- Other document binary formats (e.g. PDF)
Need to be part of the SOAP envelope to benefit from the SOAP processing model
Solution: include Base64-encoded data of type xs:base64Binary in the SOAP envelope

Optimizing transmission

Base64-encoding has significant processing and space overhead

Transmission issue: Transmission can be optimized
Processing issue: Base64 representation is only a logical view

XOP & MTOM

XML-binary Optimized Packaging
- An alternate serialization of the Infoset
- Optimizes serialization of binary content
SOAP Message Transmission Optimization Mechanism
- How to use XOP in SOAP

SOAP message containing binary parts

<soap:Envelope
    xmlns:soap='http://www.w3.org/2003/05/soap-envelope' 
    xmlns:xmlmime='http://www.w3.org/2004/11/xmlmime'>
  <soap:Body>
    <m:data xmlns:m='http://example.org/stuff'>
      <!-- Two binary components: a photo and a signature -->
      <m:photo>/aWKKapGGyQ=</m:photo>
      <m:sig>Faa7vROi2VQ=</m:sig>
    </m:data>
  </soap:Body>
</soap:Envelope>

SOAP message packaged with MTOM

MTOM packaging

Optimized message

MIME-Version: 1.0
Content-Type: Multipart/Related;boundary=MIME_boundary;
    type="application/xop+xml";
    start="<[email protected]>";
    startinfo="application/soap+xml; action=\"ProcessData\""
Content-Description: SOAP message with my pic and sig in it

--MIME_boundary
Content-Type: application/xop+xml; 
    charset=UTF-8; 
    type="application/soap+xml; action=\"ProcessData\""
Content-Transfer-Encoding: 8bit
Content-ID: <[email protected]>

<soap:Envelope
    xmlns:soap='http://www.w3.org/2003/05/soap-envelope'
    xmlns:xmlmime='http://www.w3.org/2004/11/xmlmime'>
  <soap:Body>
    <m:data xmlns:m='http://example.org/stuff'>
      <!-- Two binary components: a photo and a signature -->
      <m:photo><xop:Include 
    xmlns:xop='http://www.w3.org/2004/08/xop/include' 
    href='cid:http://example.org/me.jpg'/></m:photo>
      <m:sig><xop:Include 
    xmlns:xop='http://www.w3.org/2004/08/xop/include' 
    href='cid:http://example.org/my.hsh'/></m:sig>
    </m:data>
  </soap:Body>
</soap:Envelope>

--MIME_boundary
Content-Type: image/jpeg
Content-Transfer-Encoding: binary
Content-ID: <http://example.org/me.jpg>

// binary octets for JPEG image

--MIME_boundary
Content-Type: application/pkcs7-signature
Content-Transfer-Encoding: binary
Content-ID: <http://example.org/my.hsh>

// binary octets for signature

--MIME_boundary--

Resource Representation SOAP Header Block

Associates a URI with some Base64 encoded data
Allow to carry a representation of a Web resource
Internet media type can be expressed: Describing Media Content of Binary Data in XML
Useful for receivers that have limited connectivity

RRSHB example

<soap:Envelope
    xmlns:soap='http://www.w3.org/2003/05/soap-envelope'
    xmlns:rep='http://www.w3.org/2004/08/representation'
    xmlns:xmlmime='http://www.w3.org/2005/05/xmlmime'>
 <soap:Header>
  <rep:Representation resource='http://example.org/me.jpg'>
   <rep:Data
   xmlmime:contentType='image/jpeg'>/aWKKapGGyQ=</rep:Data>
  </rep:Representation>
 </soap:Header>
 <soap:Body>
  <x:MyData xmlns:x='http://example.org/mystuff'>
   <x:name>John Q. Public</x:name>
   <x:img src='http://example.org/me.jpg'/>
  </x:MyData>
 </soap:Body>
</soap:Envelope>

XOP/MTOM/RRSHB status

Released as a W3C Recommendation in January 2005

Doing something with this messaging framework

SOAP+WS-Addressing+MTOM allows complex exchange of rich information
Message exchange can be enhanced with added processing

But:

How do you know what messages are accepted by an endpoint?
How to do things with Web services?

Description

Messaging framework
Description formats
Looking in the future

Describing Web services

Loose coupling: simple tasks are exposed as stand-alone services
In order to use those services and do useful things:
- Need to describe how to interact with a service: WSDL 2.0
- Need to describe interactions between a set of services: WS-CDL 1.0

What is WSDL 2.0?

Machine-processable language for describing Web services
Derived from WSDL 1.1
Standardized at W3C by the Web Services Description Working Group

Web service description (WSD)

WSD governing interaction between a requester agent and provider agent

"Provider agent" implements a Web service
"Requester agent" (a.k.a. "client") makes use of that Web service
WSD represents a "contract"
Specifies the message formats, transport protocols, locations

WSDL 2.0 Structure

Description document:

<description targetNamespace="…">

Message formats (schema types):

  <types> … </types>

Abstract interface of the service:

  <interface>
    <operation> … </operation>*
  </interface>

Binding of these messages to a protocol:

  <binding> … </binding>

Location of the service:

  <service>
    <endpoint> … </endpoint>*
  </service>

</description>

New Features in WSDL 2.0

Reusability: inheritance
Extensibility: MEPs, F&P
Web-friendly: safe operations, complete HTTP/1.1 support
SOAP 1.2 binding

Inheritance

An interface may inherit from one or more other interfaces:

WSD A inherits from WSD B and WSD C

Extension Mechanisms

Open content model [old]
- Can mix XML into WSDL from other namespaces
- @wsdl:required attribute tells WSDL processor whether it must be understood
Message Exchange Patterns [new]
Features and Properties [new]

Example of open content model extensibility

Specifying that WS-Addressing 1.0 must be used:

<binding name="reservationSOAPBinding" 
    interface="tns:reservationInterface"
    type="http://www.w3.org/2005/08/wsdl/soap12"
    wsoap:protocol="http://www.w3.org/2003/05/soap/bindings/HTTP">
  <wsaw:UsingAddressing wsdl:required="true" 
        xmlns:wsaw="http://www.w3.org/2005/03/addressing/wsdl"/>
  <operation ref="tns:opCheckAvailability"
      wsoap:mep="http://www.w3.org/2003/05/soap/mep/request-response" />
  <fault ref="tns:invalidDataFault" wsoap:code="soap:Sender" />
</binding>

Message Exchange Patterns (MEPs)

<operation> specifies logical message exchange
MEP defines a pattern of interaction between agents
- sequence
- cardinality
- direction
Base set of MEPs:
- In-Out, In-Only, Out-In, Out-Only
- Robust-In-Only, Robust-Out-Only (permit optional fault)
- Out-Optional-In, In-Optional-Out (reply is optional)
Extensible: other MEPs can also be used (identified by URI)

MEP example: In-Out

<operation name="location" wsdlx:safe="true"
           pattern="http://www.w3.org/2004/08/wsdl/in-out">
  <input element="s:location"
    style="http://www.w3.org/2005/05/wsdl/style/uri-style"/>
  <output element="s:temperature"/>
</operation>

Marking Operations as Safe

"Safe": requester agent incurs no obligation beyond invoking the operation
- Analogous to HTTP GET
- Can be implemented by with SOAP 1.2's SOAP-Response MEP or HTTP GET
Permits:
- Pre-fetch
- Re-fetch
- Safe exploration

<operation name="location" wsdlx:safe="true"
           pattern="http://www.w3.org/2005/05/wsdl/in-out">
  <input element="s:location"
    style="http://www.w3.org/2005/05/wsdl/style/uri-style"/>
  <output element="s:temperature"/>
</operation>

Bindings

Binding specifies transport protocol details
Bindings are defined for:
- SOAP 1.2
- HTTP/1.1 including over SSL
- SOAP 1.1 (for backwards compatibility only)

SOAP 1.2 Binding

Can specify use of SOAP 1.2 modules
Can describe SOAP Response MEP
Supports (new) SOAP 1.2 fault description format
Can specify underlying protocol to use (e.g. HTTP): reuse of HTTP binding mechanisms

SOAP 1.2 Binding Example

<binding name="SoapBinding" interface="m:CompleteInterface"
  type="http://www.w3.org/2005/05/wsdl/soap"
  wsoap:protocol="http://www.w3.org/2003/05/soap/bindings/HTTP/"/>
  <!-- Use of MTOM -->
  <wsoap:module
   uri="http://www.w3.org/2004/08/soap/features/http-optimization"/>
  <operation ref="m:location"/>
  <operation ref="m:set">
    <input messageLabel="In">
      <!-- Required use of a security extension -->
      <wsoap:module required="true"
      uri="http://accurateweather.example/mySecurityExtension"/>
    </input>
    <output messageLabel="Out"/>
  </operation>
</binding>

Back to our Axis example: http://localhost:8080/axis/MathService.jws?wsdl

Only WSDL 1.1 is supported by Axis 1.3:

<?xml version="1.0" encoding="UTF-8"?>
<wsdl:definitions
    targetNamespace="http://localhost:8080/axis/services/MathServiceDL"
    xmlns:apachesoap="http://xml.apache.org/xml-soap"
    xmlns:impl="http://localhost:8080/axis/services/MathServiceDL"
    xmlns:intf="http://localhost:8080/axis/services/MathServiceDL"
    xmlns:tns1="http://doclit"
    xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/"
    xmlns:wsdlsoap="http://schemas.xmlsoap.org/wsdl/soap/"
    xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<!--WSDL created by Apache Axis version: 1.3
Built on Oct 05, 2005 (05:23:37 EDT)-->
 <wsdl:types>
  <schema elementFormDefault="qualified" targetNamespace="http://doclit" xmlns="http://www.w3.org/2001/XMLSchema">
   <element name="add">
    <complexType>
     <sequence>
      <element name="in0" type="xsd:int"/>
     </sequence>
    </complexType>
   </element>
   <element name="addResponse">
    <complexType>
     <sequence>
      <element name="addReturn" type="xsd:int"/>
     </sequence>
    </complexType>
    </element>
   <element name="total">
    <complexType/>
   </element>
   <element name="totalResponse">
    <complexType>
     <sequence>
      <element name="totalReturn" type="xsd:int"/>
     </sequence>
    </complexType>
   </element>
  </schema>
 </wsdl:types>

   <wsdl:message name="totalResponse">
      <wsdl:part element="tns1:totalResponse" name="parameters"/>
   </wsdl:message>

   <wsdl:message name="totalRequest">
      <wsdl:part element="tns1:total" name="parameters"/>
   </wsdl:message>

   <wsdl:message name="addResponse">
      <wsdl:part element="tns1:addResponse" name="parameters"/>
   </wsdl:message>

   <wsdl:message name="addRequest">
      <wsdl:part element="tns1:add" name="parameters"/>
   </wsdl:message>

   <wsdl:portType name="MathServiceDL">

      <wsdl:operation name="add">
         <wsdl:input message="impl:addRequest" name="addRequest"/>
         <wsdl:output message="impl:addResponse" name="addResponse"/>
      </wsdl:operation>

      <wsdl:operation name="total">
         <wsdl:input message="impl:totalRequest" name="totalRequest"/>
         <wsdl:output message="impl:totalResponse" name="totalResponse"/>
      </wsdl:operation>
   </wsdl:portType>

   <wsdl:binding name="MathServiceDLSoapBinding" type="impl:MathServiceDL">

      <wsdlsoap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http"/>

      <wsdl:operation name="add">
         <wsdlsoap:operation soapAction=""/>

         <wsdl:input name="addRequest">
            <wsdlsoap:body use="literal"/>
         </wsdl:input>
         <wsdl:output name="addResponse">
            <wsdlsoap:body use="literal"/>
         </wsdl:output>
      </wsdl:operation>

      <wsdl:operation name="total">
         <wsdlsoap:operation soapAction=""/>
         <wsdl:input name="totalRequest">
            <wsdlsoap:body use="literal"/>
         </wsdl:input>
         <wsdl:output name="totalResponse">
            <wsdlsoap:body use="literal"/>
         </wsdl:output>
      </wsdl:operation>

   </wsdl:binding>

   <wsdl:service name="MathServiceDLService">
      <wsdl:port binding="impl:MathServiceDLSoapBinding" name="MathServiceDL">
         <wsdlsoap:address location="http://localhost:8080/axis/services/MathServiceDL"/>
      </wsdl:port>
   </wsdl:service>
</wsdl:definitions>

Our Axis example in WSDL 2.0: heading

<?xml version="1.0" encoding="UTF-8"?>
<description
    targetNamespace="http://localhost:8080/axis/services/MathServiceDL" 
    xmlns:tns="http://localhost:8080/axis/services/MathServiceDL"
    xmlns:sns="http://doclit"
    xmlns="http://www.w3.org/2005/08/wsdl"
    xmlns:wsdlsoap="http://schemas.xmlsoap.org/wsdl/soap/"
    xmlns:xsd="http://www.w3.org/2001/XMLSchema"
    xmlns:wsoap="http://www.w3.org/2005/08/wsdl/soap"
    xmlns:whttp="http://www.w3.org/2005/08/wsdl/http"
    xmlns:wsdlx= "http://www.w3.org/2005/08/wsdl-extensions">

Our Axis example in WSDL 2.0: messages

   <types>
    <xsd:schema targetNamespace="http://doclit">

      <xsd:element name="total"/>

      <xsd:element name="totalResponse">
        <xsd:complexType>     
	  <xsd:sequence>      
	    <xsd:element name="totalReturn" type="xsd:int"/>
	  </xsd:sequence>
	</xsd:complexType>
      </xsd:element>

      <xsd:element name="add">
        <xsd:complexType>
	  <xsd:sequence> 
	    <xsd:element name="a" type="xsd:int"/>
	  </xsd:sequence>
	</xsd:complexType>
      </xsd:element>
            
      <xsd:element name="addResponse">
        <xsd:complexType>
	  <xsd:sequence>      
	    <xsd:element name="addReturn" type="xsd:int"/>
	  </xsd:sequence>
	</xsd:complexType>
      </xsd:element>
            
    </xsd:schema>    
   </types>

Our Axis example in WSDL 2.0: interface

   <interface name="MathService">

      <operation name="add" pattern="http://www.w3.org/2005/08/wsdl/in-out"
                       style="http://www.w3.org/2005/08/wsdl/rpc">
         <input element="sns:add"/>
         <output element="sns:addResponse"/>
      </operation>

      <operation name="total" pattern="http://www.w3.org/2005/08/wsdl/in-out"
                      wsdlx:safe="true">
         <input element="sns:total"/>
         <output element="sns:totalResponse"/>
      </operation>

   </interface>

Our Axis example in WSDL 2.0: SOAP binding

   <binding name="MathServiceSoapBinding"
            type="http://www.w3.org/2005/08/wsdl/soap"
            wsoap:protocol="http://www.w3.org/2003/05/soap/bindings/HTTP">

     <operation ref="add" wsoap:mep="http://www.w3.org/2003/05/soap/mep/request-response/"/>

     <operation ref="total" whttp:location="?method=total"
                     wsoap:mep="http://www.w3.org/2003/05/soap/mep/soap-response/"/>

   </binding>

Our Axis example in WSDL 2.0: service

   <service name="MathServiceService"
            interface="tns:MathService">

     <endpoint binding="tns:MathServiceSoapBinding" name="MathEndpoint"
              address="http://localhost:8080/axis/services/MathServiceDL"/>
   </service>

</description>

Generating a Web service client from a WSDL document

hugo@jibboom ~/ws-setup% java org.apache.axis.wsdl.WSDL2Java \
http://localhost:8080/axis/services/MathServiceDL\?WSDL

hugo@jibboom ~/ws-setup% ls localhost/axis/services/MathServiceDL
MathServiceDL.class         MathServiceDLServiceLocator.class
MathServiceDL.java          MathServiceDLServiceLocator.java
MathServiceDLService.class  MathServiceDLSoapBindingStub.class
MathServiceDLService.java   MathServiceDLSoapBindingStub.java

Generating a Web service client from a WSDL document (continued)

import localhost.axis.services.MathServiceDL.*;

public class WSDLMathClientDL {
    public static void main(String[] args) {
             Integer i = new Integer(args[0]);

             try {
               MathServiceDLService service = new MathServiceDLServiceLocator();
               MathServiceDL endpoint = service.getMathServiceDL();
               int ret = endpoint.add(i);

               System.out.println("Added " + i + ". Current total: " + ret);
             } catch (Exception e) {
               System.err.println("Exception caught: " + e);
             }
    }
}

HTTP Binding

Much more complete than in WSDL 1.1
Supports GET, POST, PUT, DELETE, as well as all other HTTP methods
Can specify:
- Input, output and fault serialization
- Transfer codings
- Authentication requirements
- Use of cookies
- Use of HTTP over TLS (https)

Also provides a URL replacement syntax:

whttp:location="http://ws.foo.example/{country}/{city}"

can be serialized as:

http://ws.foo.example/Sweden/V%C3%A4xj%C3%B6

Status of the WSDL 2.0

Working Drafts in Last Call:
- Core language
- Predefined extensions: MEPs, SOAP 1.2 and HTTP bindings, SOAP 1.1 binding
- Primer
Addressed all comments received
Nearing implementation testing

Web Services Choreography Description Language 1.0

Presentation by Charlton Barreto, Adobe Systems Inc.

Slides

What's ahead of us

Messaging framework
Description formats
Looking in the future

Looking into the future

Additional messaging extensions
Increased description capabilities

Policies: constraints and capabilities

Heterogeneous set of extensions implemented
Requirements on facets of those
Need to find a common set of extensions used to interact
Held a workshop in October 2004

Semantics in Web services descriptions

Different levels of description:
- Service taking an integer as an argument
- Service using a ISBN number as an argument
- Service giving the availability of a book identified by an ISBN number
Semantics for a service can be:
- Implied
- Expressed in human-understandable form
- Expressed in machine-readable form
More expressive descriptions; e.g.:
- Intent of a service
- Kind of data being deal with

Semantics: setting expectations

Will make people's life easier
Examples of use:
- Connect two services, ensuring that they speak the same language with same meaning
- Merge data from different sources (e.g. title & titre)
- Out of a list of 50 existing services, get only the 2 candidates that actually do what the user wants
- Automatic recovery from failure, etc.
Held a workshop in June

Internationalization

Web Services Internationalization: WS-I18N
Preferences and configuration information to provide culturally sensitive or multi-lingual operation
SOAP and WSDL extensions

<env:Envelope>
 <env:Header>
  <i18n:international>
   <i18n:locale>en-US</i18n:locale>
   <i18n:preferences>
    <ldml:collation>
     <ldml:alias source="de_DE" type="phonebook"/>
    </ldml:collation>
   </i18n:preferences>
  </i18n:international>
  …
 </env:Header>
 <env:Body>
  …
 </env:Body>
</env:Envelope>

Privacy

Looked at expressing privacy statements in WSDL 2.0
Using The Platform for Privacy Preferences 1.1 (P3P1.1)
Simple proposal

    <operation
     name="OperationAddr" 
     pattern="http://www.w3.org/2003/11/wsdl/in-out"
     p3patt:p3p="http://example.com/p3p-pol1.xml">
      <input message="mytypes:addrUpdate"/>
      <output message="mytypes:updateResp"/>
    </operation>

References

W3C Web Services Activity page: http://www.w3.org/2002/ws/
This talk: http://www.w3.org/2005/Talks/1114-hh-ecows/
Linked from http://www.w3.org/Talks/

Foundations And Future Directions of Web Services

Outline

Example of use of Web services

What Web services are trying to achieve

… translating to an architecture

Traditional Web interaction

Web services interaction

Web services at W3C

Messages

Messaging framework for Web services

SOAP Version 1.2

SOAP message

The SOAP envelope

SOAP message path

Example of a SOAP message

Message exchange patterns

Underlying protocols binding

SOAP 1.2 HTTP Binding

Simple addition service

Simple addition client

POST example: adding a value

GET example: retrieving the total

Note about encoding of the message

SOAP Extensibility: SOAP modules

SOAP extensibility: SOAP features

mustUnderstand example: updated client

Triggering a mustUnderstand fault

mustUnderstand fault

SOAP 1.2 status

Addressing information: Web Services Addressing 1.0

Addressing from and to endpoints

Example of an EPR

Message addressing properties

Example of use

Example request message

Example response message using wsa:Reply-To

WS-Addressing 1.0 status

Handling non-XML data

Optimizing transmission

XOP & MTOM

SOAP message containing binary parts

SOAP message packaged with MTOM

Optimized message

Resource Representation SOAP Header Block

RRSHB example

XOP/MTOM/RRSHB status

Doing something with this messaging framework

Description

Describing Web services

What is WSDL 2.0?

Web service description (WSD)

WSDL 2.0 Structure

New Features in WSDL 2.0

Inheritance

Extension Mechanisms

Example of open content model extensibility

Message Exchange Patterns (MEPs)

MEP example: In-Out

Marking Operations as Safe

Bindings

SOAP 1.2 Binding

SOAP 1.2 Binding Example

Back to our Axis example: http://localhost:8080/axis/MathService.jws?wsdl

Our Axis example in WSDL 2.0: heading

Our Axis example in WSDL 2.0: messages

Our Axis example in WSDL 2.0: interface

Our Axis example in WSDL 2.0: SOAP binding

Our Axis example in WSDL 2.0: service

Generating a Web service client from a WSDL document

Generating a Web service client from a WSDL document (continued)

HTTP Binding

Status of the WSDL 2.0

Web Services Choreography Description Language 1.0

What's ahead of us

Looking into the future

Policies: constraints and capabilities

Semantics in Web services descriptions

Semantics: setting expectations

Internationalization

Privacy

Example response message using `wsa:Reply-To`