* Semantic Web
ActivityAs of July 2003, this is obsolete in favor of new charter.
This Working Group, part of the Semantic Web Activity, will focus on the development of a language to extend the semantic reach of current XML and RDF meta-data efforts. In particular, in a recent talk on the Semantic Web, Tim Berners-Lee, Director of the W3C, outlined the necessary layers for developing applications that depend on an understanding of logical content, not just human-readable presentation. This working group will focus on building the ontological layer and the formal underpinnings thereof.
Such language layers are crucial to the emerging Semantic Web, as they allow the explicit representation of term vocabularies and the relationships between entities in these vocabularies. In this way, they go beyond XML, RDF and RDF-S in allowing greater machine readable content on the web. A further necessity is for such languages to be based on a clear semantics (denotational and/or axiomatic) to allow tool developers and language designers to unambiguously specify the expected meaning of the semantic content when rendered in the Web Ontology syntax.
Specifically, the Web Ontology Working Group is chartered to design the following component:
The March 2001 DAML+OIL specification, discussed in some detail in section 1.1 below serves as an example of an ontology language - a comparison of DAML+OIL to XML, XML-schema, and RDF-Schema is available.
Furthermore, the following general requirements must be met by the work produced by this Working Group:
The Working Group shall start by evaluating the technical solutions proposed in the DAML+OIL draft. If in this process the Working Group finds solutions that are agreed to be improvements over solutions suggested by DAML+OIL, those improved solutions should be used.
The Working Group will be chaired by Jim Hendler (Univ of Maryland) .
The remainder of this section describes the requirements and deliverables in more detail.
The term ontology has many meanings and shades of meaning. In the contest of this work, we refer to what is sometimes called a "structural" ontology -- a machine readable set of definitions that create a taxonomy of classes and subclasses and relationships between them. The purpose of this WG is not to define ontological knowledge in any or all domains (except for example purposes). Rather, the goal is to define a machine-readable markup language, based on current semantic web standards that will allow adopters to define their own ontological content. This will allow the interoperation of tools and techniques that manipulate the ontology language for any set of content that users provide.
Recently, a number of research groups have been developing languages in which to express ontological expressions on the web. In an effort to bring these together, a number of researchers, supported by the US Defense Advanced Research Projects Agency (DARPA) released a draft language known as the DARPA Agent Markup Language Ontology notations (DAML-ONT). Since then, an ad hoc group of researchers has formed the Joint US/EU committee on Agent Markup Languages and released a new version of this language which merges DAML with the Ontology Interface Layer (OIL) developed by European researchers. The new language was released under the name DAML+OIL. This language is based on the Resource Description Framework (RDF) and discussion of its features is conducted on www-ret-logic, an open mailing list. The DAML project includes details of the language and a repository of numerous ontologies and annotated web pages.
The language they have defined, DAML+OIL, fits the requirement specified above, and should be considered as a starting draft for this particular WG product.
As well as the actual specification, the working group will produce products necessary to support its use including: the specification, examples of use, reference materials, and supporting documents with respect to the formal semantics of the language.
Within the communities of researchers working on the creation of the semantic web, there are many different visions of what ontologies are and how they can be used. This working group will strive to be as general as possible in supporting multiple approaches and techniques. It should be noted, however, that generality is not used here in the same sense as "expressiveness" -- that is the ability to say more things does not necessarily map to the ability to support many kinds of users. Trade-offs between expressivity and compactness, computational complexity, and simplicity of use will need to be made by the working group.
Moreso than for a traditional programming language, a knowledge representation language needs a formal semantics to clearly delineate what is, and is not, entailed from any particular language construct or combination thereof. Such a formal semantics may be in a denotational or axiomatic form. Examples of both of these have been produced for DAML+OIL, providing examples of what is necessary for the WebONT language products.
The general area of semantic web technologies is very broad as it can potentially include any controlled vocabulary for markup, or XML and/or RDF metadata. Therefore, only those work items that we find absolutely essential for a usable web ontology are listed in the proposed 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. The co-chairs and editors of this working group will coordinate with those of the RDF Core Working Group to avoid duplicating work with respect to concrete data types, schema definitions, and other products which may fall into those areas where the RDF and Ontology Language layers come into contact. In addition, the working group chairs will work with the W3C's Semantic Web Coordination Group to help assure that work in this effort is compatible with other ongoing semantic web development efforts wherever possible.
Also out of scope will be:
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 WebONT Working Group home page. Meeting dates are mentioned here for planning purposes.
The expected duration of the working group is about 1.5 years, through March 2003.
Note that public working drafts will be made available at least once every three months, per W3C Process.
XML and XML-derived activities, and now RDF 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.
At the current time, the primary dependency with other W3C work is with the ongoing RDFSchema activity in the RDF Core working group. Coordination with this group is specified above, and will be carried out as an ongoing activity as part of the W3C Semantic Web Coordination Group.
The Working Group will also attempt to liaise via cross-participation with a number of groups interested in service descriptions on the web. It is clear that ontologies can play a role in such descriptions, and the potential overlap between these activities is described on a vision paper about agents on the web.. Some proposed ideas for the use of ontologies for service langauges can be found at the DAML Services description page.
The Web Ontology Working Group will do its best to track work in as many other groups that are doing related work as we can. Two groups that have already been identified as doing work that relates to web ontology are:
To become a member of the Web Ontology Working Group, a representative of a W3C Member organization must be nominated by their Advisory Committee Representative (details on how to join are on the group home page). The nomination must include explicit agreement to this charter, including its goals, and the level of effort required and an IPR disclosure.
Membership is also open to invited experts from the community, selected by the chair or co-chair in order to balance the technical experience of the group.
Participation is expected to consume at least one day per week of each Working Group member's time.
The mailing list for group communication is www-webont-wg@w3.org. An archive of www-webont-wg is available to the public.
The Working Group will have 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 will be available to the public and will be maintained by one of the co-chairs in collaboration with the W3C team contact.
The Working Group will hold teleconferences approximately weekly. Participation in phone conferences is limited to members of the working group. The Chair may, at his discretion, invite guest experts to attend particular phone conferences. An IRC channel may be used to supplement teleconferences.
Meeting records should be made available within two days of each telephone meeting.
Participation in face-to-face meetings is limited to working group members and observers invited by the Chair. Observers may take part in decision-making at the discretion of the Chair.
In addition to the required three annual face-to-face meetings, the Working Group may schedule other face-to-face meetings in a manner that maximizes co-location with events that Working Group members might be attending anyway.
The Chair makes Working Group meeting dates and locations available to the group at least eight weeks before the meeting, per W3C Process.
To be successful, we expect the Working Group to have approximately 10 to 20 active principal members for its 18-month duration. We also expect a large public review group that will participate in the mailing list discussions.
The W3C Team expects to dedicate the services of one engineer, 1/3rd time, for the 1.5-year duration of the Working Group. Dan Connolly is the W3C Team contact.
W3C promotes an open working environment. Whenever possible, technical decisions should be made unencumbered by intellectual property right (IPR) claims.
This is a Royalty Free Working Group, as described in W3C's Current Patent Practice, dated 24 January 2002.
Working Group participants disclose patent claims by sending email to patent-issues@w3.org; please see Current Patent Practice for more information about disclosures.
status: complete. Dan Connolly, W3C Team Contact
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