Leading Web Services To Their Full Potential

Hugo Haas <hugo@w3.org>
W3C Web Services Activity Lead

Presentation at the JP Meeting, Tokyo, Japan, 12 July 2002

Slides available at:
http://www.w3.org/2002/Talks/0712-hh-jpm/

Overview

• History
• Goals
• Challenges
• Standardization work at W3C

History

• World Wide Web originally designed for people to share information
• Since early days: people have been using HTML forms as interfaces to access programs (CGI programs)
• More recently: machine to machine interaction

Web service:

• Application
• For use by another application
• Accessed via the Web (URI / XML)

An example of a Web service: travel agent usage scenario

• Travel agent service sells vacation packages
• Uses other Web services: credit card WS, hotel WS, airline WS

Example (continued): advantages

• Low cost for new airlines, hotels, credit card companies to sell products
• Travel agent service has access to more options
• Customers get better deals

Challenges faced

A whole set of technologies to design:

• communication protocol
• description of services
• enable security and privacy
• describe complex interactions
• ...

Integration to the World Wide Web

The Web has architectural principles

Set of resources that are:

• identified (URI)
• retrieved using certain rules (e.g. HTTP GET)
• structured (e.g. XML)

Design of Web services technologies must be done in a Web-friendly way

The need for semantics

Web services characteristics:

• Machine to machine interaction
• Dynamic agreements
• No a priori knowledge

Need to understand particular XML vocabularies:

• Make sense of the information
• Merge information

Ontologies

• Ontologies: formal description of concepts and their relationships

  Examples:

  • Definition of "plane ticket" and "non-refundable plane ticket"
  • A "non-refundable plane ticket" is a kind of "plane ticket"
• Communication of concepts

The Semantic Web

• Vision: having a machine-processable Web
• Simple machine processable way of expressing information:
  
• Unambiguous definitions: use of URIs
• Allow to find, share and combine information more easily

Standardization work

• Core technologies have been worked on for a long time:
  • XML: XML 1.0, XML Schema, ...
  • Security foundation: digital signatures, encryption, key management
  • Privacy: P3P
  • Etc.
• Semantic Web Activity: RDF, Web Ontology, ...
• Web Services Activity: Web services technologies

Web Services Activity

• Created in January 2002
• Subsumes the XML Protocol Activity started in September 2000
• Large Activity: more than 65 Member organizations
• All the work is done in public: mailing list archive, meeting records, editors' copies
• Technologies developed under Royalty-Free terms
• Organization:

  3 Working Groups:

  • Web Services Architecture Working Group
  • XML Protocol Working Group
  • Web Services Description Working Group

  1 Coordination Group

Web Services Architecture

• Work started in January 2002
• Developed by the Web Services Architecture Working Group
• 76 participants representing 52 Member organizations
• Goal: define the Web services architecture
  • What are we trying to achieve?
  • What technology is needed?
• Define the scope of each technology and its relationship with others
• Output used to scope proposals for new Working Groups

Requirements of the Web services architecture

• Enable interoperability
• Reliable:
  • Well defined
  • Set of metrics, e.g. for measuring quality of service
• Clean integration in the Web
• Security and privacy
• Scalability and extensibility:
  • Modular
  • Extensible, open-ended

Status of the Web Services Architecture Working Group

Documents listed on the Working Group's page:

• Requirements for the Web services architecture: Working Draft
• Usage scenario document: editors' copy
• Architecture document: editors' copy
• Glossary: editors' copy

Communicating between machines

• Need for a messaging protocol allowing complex machine to machine interactions
• Information of complex type
• Extensibility is key; support for:
  • Security extensions
  • Reliability extensions
  • Caching extensions
  • Etc.

An XML-based protocol: SOAP version 1.2

• Work started in September 2000
• Result of growing interest in the use of XML in distributed applications communication
• XML Protocol Working Group: 62 participants representing 34 Member organizations
• Technical solutions proposed by the SOAP/1.1 submission evaluated

SOAP version 1.2 in a nutshell

• SOAP message:
  • Envelope
  • Composed of a header and a body

    

• Processing model
• Sent from a sender to a receiver, possibly via intermediaries
• Headers:
  • Can be addressed to certain intermediaries
  • Can be marked as mandatory
• Can be transfered from one node to another any underlying protocol (e.g. HTTP)

Status of the work on SOAP version 1.2

Started from SOAP/1.1; more than 200 issues found and then solved

Documents produced:

• SOAP version 1.2, Part 1: Messaging Framework: Last Call Working Draft
  • Processing Model
  • Envelope
  • Protocol Binding Framework
• SOAP version 1.2, Part 2: Adjuncts: Last Call Working Draft
  • Data Model
  • Encoding
  • RPC Convention
  • Binding and Feature Description Convention
  • Message Exchange Pattern (MEP)
  • HTTP Binding

Status of the work on SOAP version 1.2 (continued)

Documents produced (continued):

• XML Protocol (XMLP) Requirements Document: Working Draft
• XML Protocol Usage Scenarios: Working Draft
• XML Protocol Abstract Model: Working Draft
• SOAP version 1.2, Part 0: Primer: Last Call Working Draft
• SOAP Version 1.2 Specification Assertions and Test Collection: Last Call Working Draft
• SOAP Version 1.2 Email Binding: Note

A language to describe Web services: motivations

• Work started in January 2002
• Done by Web Services Description Working Group
• 50 participants representing 33 Member organizations

Problem: I want to use your Web Service

• Where can I find it?
• What messages are accepted / generated? What syntax?
• How should they be transmitted?

Need standard format for describing Web Services

WSDL 1.1 (W3C Submission) used as a starting point

Status of the Web Services Description Working Group

• Requirements document published:
  • Based on the XML Information Set
  • Use W3C XML Schema but allow other schema languages
  • Simple interaction between Web Services: one-way, request-response, solicit-response, and faults
  • Binding to SOAP 1.2 and HTTP/1.1
  • Extensibility and versioning
• Published a set of usage scenarios
• Just published a first Working Draft of the description language:
  • Web Services Description Language (WSDL) Version 1.2
  • Web Services Description Language (WSDL) Version 1.2: Bindings

Next steps

• Architecture:
  • continue architecture definition
  • propose new work
• SOAP version 1.2 to Recommendation
• Description work: address issues found against WSDL 1.1, design binding to SOAP Version 1.2, develop an RDF mapping

References

This presentation: http://www.w3.org/2002/Talks/0712-hh-jpm/

W3C Web Services Activity: http://www.w3.org/2002/ws/