One of the requirements for the development of Web services is the ability to describe the interface, the boundary across which applications (Web services user agents and Web services) communicate. Applications can then interoperate using this interface.
The Web Services Description Working Group, part of the Web Services Activity, is chartered to design the following components of the interface:
Furthermore, the following three general requirements must be met by the work produced by this Working Group:
The remainder of this section describes the requirements and deliverables in more detail.
The Working Group shall start by developing a requirements document detailing and refining the scope of its work, which is the scope of the WSDL 1.1 specification. It will then proceed by evaluating the technical solutions offered by WSDL 1.1.
If in this process the Working Group finds solutions that are agreed to be improvements over solutions suggested by WSDL 1.1, those improved solutions should be used. However, the Working Group should not make arbitrary changes, i.e. without technical reasons, and it should be easy to convert a WSDL 1.1 description into the new format designed.
In addition to the specification of a description language, the Working Group will produce a primer in order to help novices familiarize themselves with this technology.
A test suite will be developed by the Working Group in order to assess advancement to Proposed Recommendation stage and to promote interoperability. The Working Group is expected to demonstrate two interoperable implementations during the Candidate Recommendation phase. Conformance requirements must be clearly stated in the specification produced.
Simplicity is a key element in making distributed systems easy to
understand, implement, maintain, and evolve. Although simplicity can only
be measured in relative terms, the Working Group must ensure that the
complexity of any solution produced is comparable to that of other current
and widespread Web solutions. Note that simplicity should not be confused
being easy to understand.
It is believed that limiting its scope to exclude bindings to existing programming languages will put the Working Group in a better position to achieve its goal of producing a simple mechanism for describing the functionality made available by an application to communicating peers.
Another important aspect of simplicity is ease of deployment. The Working Group will look at various ways of deploying the Web services descriptions in a manner that is compatible with the existing Web infrastructure (see the relationship with other external groups).
Web services are modeled as interfaces between applications on the World Wide Web. In order to make use of a Web service, one needs to know what information is expected and in what form.
Therefore, the interface needs to be explained for use by remote parties. The structure of the messages accepted and/or generated needs to be described.
The Working Group will define a description language expressed in XML. The description language must describe the messages available via the interface, accepted and generated by the Web service. The language must also describe the error messages generated, if any.
The data exchanged is usually typed and structured. This increases interoperability by having applications agreeing on semantics and also provides some level of error detection.
It is expected that developers will want to use different mechanisms for describing data types and structures, depending on the purpose of the Web service. The Working Group should allow different mechanisms, and must define one based on XML Schema. The Working Group will also take into account the encoding work going on in the XML Protocol Working Group, and will make sure that SOAP Version 1.2's extensibility mechanism can be expressed.
The description language designed will be used both by applications in order to automatically communicate between each other as well as by programmers developing Web services themselves. The language should therefore provide, in addition to the raw XML definition of the interface, human-readable comment capabilities to allow both applications and developers to make use of them.
Developers are likely to want to extend the functionality of an existing Web service. The Working Group will look into extending interface descriptions in a decentralized fashion, i.e. without priori agreement with the original interface designers.
Interacting using an interface can be done in different ways. Some Web services may accept an incoming message and return a response, others may only generate messages, etc.
The Working Group will define a mechanism which will allow a Web service to describe the following set of operations: one-way messages (to and from the service described), request-response and solicit-response, as described in WSDL 1.1's port types.
The information exchanged to and from a Web service can be carried in a large number of different ways. The action of carrying some XML-based communication in an underlying protocol is called, in the XML Protocol jargon, a binding.
The description language defined should therefore describe how to reach the Web Service in a form which is orthogonal to its message exchange patterns and its messages.
It is expected that in the near-term future, Web services will be accessed largely through SOAP Version 1.2 (the XML-based protocol produced by the XML Protocol Working Group) carried over HTTP/1.1, or by means of simple HTTP/1.1 GET and POST requests. The Working Group will describe the following bindings:
The Working Group will also ensure that other SOAP bindings can be described.
The Semantic Web aims at transforming the Web into a completely machine-processable information space. Web services are aiming at enabling automated distributed computing on the World Wide Web. The work of this Working Group is essentially the provision of an ontology for Web services.
One of the tools used by Semantic Web-enabled technologies is RDF. The Working Group will provide a mapping to RDF so that the information described can be easily merged with that of other applications. This mapping will be developed with the help of the RDF Interest Group.
The Working Group shall produce the following deliverables:
The area of Web services is very broad as it includes everything between a simple remote procedure call using an XML-based protocol to a sequence of N different services interacting in order to provide very advanced functionalities (e.g. a travel reservation service making use of individual services).
It is therefore important to clearly limit the scope of the Working Group.
This section describes out-of-scope work items. In general, the Working Group will also consider items out of scope that are being addressed as part of other W3C Activities, and it will reuse existing specifications wherever possible, including XML Namespaces and XML Schemas, Parts One and Two.
Web services are composed of interfaces to applications, which can be written in different programming languages. The purpose of the Working Group is to provide a framework that supports a wide variety of applications and programming languages, and is not geared towards any programming language. Given the wide variety of programming languages, the Working Group should not define mappings to any programming languages.
Several individual Web services can be composed to provide more complex functionalities. The goal of the Web Services Description Working Group is to describe individual Web services.
Although the Working Group needs to ensure Web services descriptions can be referenced unambiguously and that the language designed does not preclude the description of the composition of individual services, the way two or more services could be composed is considered out of scope.
Once the World Wide Web is populated with Web services, an important aspect will be the discovery of Web services. The Web Services Description Working Group will not look into Web services discovery.
These are subject to revision due to editorial needs and external scheduling issues; updates will be negotiated with the related groups and recorded on the Web Services Description Working Group home page. Meeting dates are mentioned here for planning purposes.
The target duration of the Working Group is 2 years, through January 2004. Experience suggests that 6 months of contingency should be allowed to accommodate unexpected obstacles to progress.
XML and XML derived activities have become a strategic technology in W3C and elsewhere. Each deliverable of any Working Group must satisfy the dependencies from other W3C Working Groups before it can advance to Candidate Recommendation.
The Web Services Architecture Working Group is chartered to come up with a document describing the architecture of Web services. The Working Group will take this document into account while designing the description language in order to make sure that Web services can be deployed in an optimal way, as recommended by the Web Services Architecture Working Group.
The Working Group must describe services accessible via SOAP Version 1.2 defined by the XML Protocol Working Group.
It is expected that other Working Groups will be formed to deal with different aspects of the Web services architecture. The Working Group will closely coordinate its work with any other Working Group formed within the Web Services Activity and generally in the Web services area.
The Working Group will participate in the Web Services Coordination Group.
The Working Group will develop a mapping of the language developed to RDF with the help of the RDF Interest Group.
The typing of the messages must be possible using XML Schema. While no dependencies other than the one with the XML Schema Working Group are presently identified, the Web Services Description Working Group should be prepared to coordinate with the XML Activity as necessary.
The Working Group will develop a primer and a test suite in order to improve the quality of the documents produced and their implementations.
The Internationalization Working Group will review work to ensure that principles developed by that group are consistently applied.
The work of the Working Group will be subject to review by this project.
XForms can be seen as providing a user interface for Web services. The Working Group will call for requirements from the XForms Working Group, if any.
The Web Services Description Working Group should liaise with at least the following groups outside W3C (see also W3C liaisons with other organizations):
The Working Group will attempt to liaise with the Global Grid Forum. The Global Grid Forum is a community-initiated forum of individual researchers and practitioners working on distributed computing technologies.
The Working Group will attempt to liaise with work going on at OMG. OMG is a consortium that produces and maintains computer industry specifications for interoperable enterprise applications and which has experience in distributed, object-based systems interface description (CORBA, IDL).
To join the Web Services Description Working Group, please follow the instructions of section 4.2.3 of the Process Document, sending email to the Working Group Chair and the W3C Team contact. The nomination must include explicit agreement to this charter, including its goals, an IPR disclosure and the level of effort required of the representative.
Each Member organization may have at most two participants in the Working Group. Only Working Group participants may engage in formal votes on substantive issues. When a formal vote is required, each Member organization or group of related Members is allowed one vote, even though the Member may have several participants in the Working Group.
The W3C Team is expected to have at most two participants in the Working Group (including the Team contact). When a formal vote is required, the Team is allowed one vote.
Membership is also open to invited experts from the community, selected by the Chair in order to balance the technical experience of the group.
Each participant should expect to spend one day per week on work for this Working Group.
The Working Group will utilize a public mailing list <email@example.com> for its technical email communications. It is referred to in the rest of this document as the Working Group mailing list.
A Member-only mailing list <firstname.lastname@example.org> is available for administrative purposes only.
The Working Group has a home page that records the history of the group, provides access to the archives, meeting minutes, updated schedule of deliverables, membership list, and relevant documents and resources. The page is available to the public and should be maintained by the Chair in collaboration with the W3C Team contact.
The Working Group will have distributed and face-to-face meetings.
A one- to two-hour Working Group distributed meeting will be held every week. When necessary to meet agreed-upon deadlines, distributed meetings may be held twice a week.
The Working Group may schedule face-to-face meetings in a manner that maximizes co-location with events that Working Group members would be attending anyway.
Participation in meetings (distributed or face-to-face) is limited to participants in good standing and individuals invited at the discretion of the Chair to specific meetings.
Decisions taken in meetings must be announced on the Working Group mailing list. Observers may take part in decision-making at the discretion of the Chair.
Meeting records must include attendance, the results of group decisions, and action items. They must be made publicly available except for non-technical issues that do not directly affect the output of the Working Group. The Chair will decide which issues are not made public.
To be successful, we expect the Working Group to have approximately 10 to 15 active participants. A large public review group that will participate in the mailing list discussions is expected.
The Chair for the Web Services Description Working Group will be Jonathan Marsh (Microsoft).
The W3C Team expects to dedicate the time of the services of one Team Contact, full-time, for the 2-year duration of the Working Group. Philippe Le Hégaret will provide this effort with the help of a new engineer.
W3C promotes an open working environment. Whenever possible, technical decisions should be made unencumbered by intellectual property right (IPR) claims. W3C's policy for intellectual property is set out in section 2.2 of the W3C Process document.
Members of the Working Group are expected to disclose any intellectual property they have in the area. This WG will work on a royalty-free basis, as defined in the W3C Current Patent Practice document. The Working Group is thus obliged to produce a specification which relies only on intellectual property available on a royalty-free basis.
If it proves impossible to produce specifications implementable on a royalty-free basis, then a Patent Advisory Group will be launched as described in the W3C Current Patent Practice document.
Members disclose patent and other IPR claims by sending email to <email@example.com>, an archived mailing list that is readable by Members and the W3C Team. Members must disclose all IPR claims to this mailing list but they may also copy other recipients. IPR disclosures are expected to be made public; Members should specify if their disclosure is confidential.