[February 11, 2000] The SHOE project is under development in the Parallel Understanding Systems Group, Department of Computer Science, University of Maryland at College Park. The updated the SHOE Specification (February 03, 2000) 1.01, includes an appendix on using SHOE with XML. SHOE is an SGML/XML 'HTML-based' knowledge representation language -- "a superset of HTML which adds the tags necessary to embed arbitrary semantic data into web pages. SHOE tags are divided into two categories. First, there are tags for constructing ontologies. SHOE ontologies are sets of rules which define what kinds of assertions SHOE documents can make and what these assertions mean. For example, a SHOE ontology might say that a SHOE document can declare that some data entity is a 'dog', and that if it does so, that this 'dog' is permitted to have a 'name'. Secondly, there are tags for annotating web documents to subscribe to one or more ontologies, declare data entities, and make assertions about those entities under the rules proscribed by the ontologies. For example, a SHOE document subscribing to the SHOE ontology above might then declare that it's all about a dog named 'Fido'..."
The intent of the specification "is to make it possible for user-agents, robots, etc., to gather truly meaningful information about web pages and documents, enabling significantly better search mechanisms and knowledge-gathering. The general way one goes about this is as follows: (1) First, define an ontology describing valid classifications of web objects, and valid relationships between web objects and other web objects or data. This ontology may borrow from other ontologies. (2) Annotate HTML pages to describe themselves, other pages, or subsections of themselves, as having attributes as described in one or more ontologies. We're playing a bit fast-and-loose with the term ontology here. In this specification, 'ontology' simply means an ISA hierarchy of classes/categories, plus a set of atomic relations between these categories, and a set of inferential rules in the form of simplified horn clauses. Categories inherit relations defined for parent categories. User agents following this specification should be aware that assertions made by HTML pages are not facts, but claims..."
A 'SHOE' DTD is available online. The first two element declarations: (1) <!ELEMENT shoe (ontology | instance)* > and <!ELEMENT ontology (use-ontology | def-category | def-relation | def-rename | def-inference | def-constant | def-type)* >.
[August 26, 2000] "Semantic Interoperability on the Web." By Jeff Heflin and James Hendler (University of Maryland). Paper presented at the Extreme Markup Languages 2000 Conference (August 13 - 18, 2000, Montréal, Canada). Published in the proceedings volume, pages 111-120. "XML will have a profound impact on the way data is exchanged on the Internet. An important feature of this language is the separation of content from presentation, which makes it easier to select and/or reformat the data. However, due to the likelihood of numerous industry and domain specific DTDs, those who wish to integrate information will still be faced with the problem of semantic interoperability. In this paper we discuss why this is not solved by XML, and then discuss why the Resource Description Framework is only a partial solution. We then present the SHOE language, which we feel has many of the features necessary to enable a semantic web, describe an existing set of tools that make it easy to use the language. [...] if the growing proliferation of DTDs is indicative, then web developers will still be faced with the problem of semantic interoperability, i.e., the difficulty in integrating resources that were developed using different vocabularies and different perspectives on the data. To achieve semantic interoperability, systems must be able to exchange data in such a way that the precise meaning of the data is readily accessible and the data itself can be translated by any system into a form that it understands. The benefits of semantic interoperability would be numerous. For example, search can often be frustrating because of the limitations of keyword-based matching techniques. Users frequently experience one of two problems: they either get back no results or too many irrelevant results. The problem is that words can be synonymous (that is, two words have the same meaning) or polysemous (a single word has multiple meanings). However, if the languages used to describe web pages were semantically interoperable, then the user could specify a query in the terminology that was most convenient, and be assured that the correct results were returned, regardless of how the data was expressed in the sources. Intelligent internet agents could also benefit from semantic interoperability. Currently, such agents are very sensitive to changes in the format of a web page. Although these agents would not be affected by presentation changes if the pages were available in XML, they would still break if the XML representation of the data was changed slightly (for example if the element <PRICE> was renamed to <UNITPRICE>). Semantic interoperability would allow agents to be more robust. A useful function for internet agents would be the ability to automatically integrate information from multiple sources. For example, a travel-planning agent might need to access data from airlines, hotels, rental car companies, weather sites, and tourist sites, each of which may have different ways of representing the relevant data. Such an agent would be faced with the problem of translating the different vocabularies and representations for this data into a common format that it could work with. [...] Conclusion: SHOE is not the only AI language for the Web. The Ontobroker project uses a language to describe data that is embedded in HTML, but relies on a centralized broker for ontology definitions. The Ontology Markup Language (OML) and Conceptual Knowledge Markup Language (CKML) are used together for semantic markup that is based on the theories of formal concept analysis and information flow. However, both of the languages are basically web syntaxes for more traditional KR languages, and neither considers the special characteristics of the Web to the degree that SHOE does. XML will revolutionize the Web, but semantic interoperability is needed to achieve the Web's true potential. We have discussed the limitations of XML and RDF with respect to semantic interoperability, and presented the SHOE language. In describing the basic elements of SHOE, we have explained how it is better suited for semantics on the Web than either XML DTDs or RDF. In order to demonstrate SHOE, we have built a suite of tools for its use and have described those tools here." Also in PostScript format. [cache]
[November 09, 2000] SHOE software and libraries are available in the [new] Downloads section.
SHOE and DAML - "The DARPA Agent Markup Language (DAML) is a recent program by DARPA to develop a language and toolset for the Semantic Web. It has grown out of projects such as SHOE, RDF, Ontobroker, and OIL. Here we provide resources for those who are interested in how DAML relates to SHOE, or wish to use the large set of SHOE ontologies and content pages with their own DAML projects." Includes discussions (1) SHOE/DAML Comparison; (2) SHOE Ontologies in DAML Format; (3) SHOE Content in DAML Format." See "DARPA Agent Mark Up Language (DAML)."
SHOE/DAML Comparison. "The following table shows how to translate a set of SHOE tags into DAML. We have automated this process with a software tool that can be provided upon request. Note that this is only one possible translation; since DAML is based on RDF, and RDF allows multiple syntaxes for stating things, there are other equivalent translations. Please send any comments or questions about this table to Jeff Heflin."
"Dynamic Ontologies on the Web." By Jeff Heflin and James Hendler. In Proceedings of the Seventeenth National Conference on Artificial Intelligence (AAAI-2000). AAAI/MIT Press, Menlo Park, CA, 2000. pages 443-449. "We discuss the problems associated with managing ontologies in distributed environments such as the Web. The Web poses unique problems for the use of ontologies because of the rapid evolution and autonomy of web sites. We present SHOE, a web-based knowledge representation language that supports multiple versions of ontologies. We describe SHOE in the terms of a logic that separates data from ontologies and allows ontologies to provide different perspectives on the data. We then discuss the features of SHOE that address ontology versioning, the effects of ontology revision on SHOE web pages, and methods for implementing ontology integration using SHOE's extension and version mechanisms." Also in PostScript format. [cache]
"SHOE: A Knowledge Representation Language for Internet Applications." By Jeff Heflin, James Hendler, and Sean Luke. Technical Report CS-TR-4078. Department of Computer Science, University of Maryland at College Park. Also available as UMCP-CSD Technical Report CS-TR-4078, or UMCP-UMIACS Technical Report UMIACS-TR-99-71, accessible online at the Library of the Department of Computer Science, University of Maryland at College Park. "It is our contention that the World Wide Web poses challenges to knowledge representation systems that fundamentally change the way we should design KR languages. In this paper, we describe the simple HTML Ontology Extensions (SHOE), a KR language which allows web pages to be annotated with semantics. We present a formalism for the language and discuss the features which make it well suited for the Web. We describe the syntax and semantics of this language, and discuss the differences from traditional KR systems that make it more suited to modern web applications. We also describe some generic tools for using the language and demonstrate its capabilities by describing two prototype systems that use it. We also discuss some future tools currently being developed for the language. The language, tools, and details of the applications are all available on the World Wide Web at http://www.cs.umd.edu/projects/plus/SHOE/." Also in PostScript. [cache
"Ontology-based Web Agents." By Sean Luke, Lee Spector, David Rager, and James Hendler. In Proceedings of the First International Conference on Autonomous Agents (Autonomous Agents '97). W. L. Johnson, ed. New York: Association for Computing Machinery. 59-66. "This paper describes SHOE, a set of Simple HTML Ontology Extensions which allow World-Wide Web authors to annotate their pages with semantic knowledge such as 'I am a graduate student' or 'This person is my graduate advisor'. These annotations are expressed in terms of ontological knowledge which can be generated by using or extending standard ontologies available on the Web. This makes it possible to ask Web agent queries such as 'Find me all graduate students in Maryland who are working on a project funded by DoD initiative 123-4567', instead of simplistic keyword searches enabled by current search engines. We have also developed a web-crawling agent, Exposée, which interns SHOE knowledge from web documents, making these kinds queries a reality."
Ontology-Based Knowledge Discovery on the World-Wide Web." By Sean Luke, Lee Spector, and David Rager. "This paper describes SHOE, a set of Simple HTML Ontology Extensions. SHOE allows World-Wide Web authors to annotate their pages with ontology-based knowledge about page contents. We present examples showing how the use of SHOE can support a new generation of knowledge-based search and knowledge discovery tools that operate on the World-Wide Web. Also PDF and PostScript.
Exposée - A web robot written in Java which searches out web pages with SHOE entries, gathers the associated knowledge, and loads it into PARKA, University of Maryland's high-speed knowledge representation system.
See also: "DARPA Agent Mark Up Language (DAML)."