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S  H  O  E :  Simple HTML Ontology Extensions


SHOE Publications

Parallel Understanding Systems Group
Department of Computer Science
University of Maryland at College Park


Title: Towards the Semantic Web: Knowledge Representation in a Dynamic, Distributed Environment
Authors: Jeff Heflin
Abstract: The World Wide Web is an information resource with virtually unlimited potential. However, this potential is relatively untapped because it is difficult for machines to process and integrate this information meaningfully. Recently, researchers have begun to explore the potential of associating web content with explicit meaning, in order to create a Semantic Web. Rather than rely on natural language processing to extract this meaning from existing documents, this approach requires authors to describe documents using a knowledge representation language.

Although knowledge representation can solve many of the Web's problems, existing research cannot be directly applied to the Semantic Web. Unlike most traditional knowledge bases, the Web is highly decentralized, changes rapidly, and contains a staggering amount of information. This thesis examines how knowledge representation must change to accommodate these factors. It presents a new method for integrating web data sources based on ontologies, where the sources explicitly commit to one or more autonomously developed ontologies. In addition to specifying the semantics of a set of terms, the ontologies can extend or revise one another. This technique permits automatic integration of sources that commit to ontologies with a common descendant, and when appropriate, of sources that commit to different versions of the same ontology.

The potential of the Semantic Web is demonstrated using SHOE, a prototype ontology language for the Web. SHOE is used to develop extensible shared ontologies and create assertions that commit to particular ontologies. SHOE can be reduced to datalog, allowing it to scale to the extent allowed by the optimized algorithms developed for deductive databases. To demonstrate the feasibility of the SHOE approach, we describe a basic architecture for a SHOE system and a suite of general purpose tools that allow SHOE to be created, discovered, and queried. Additionally, we examine the potential uses and difficulties associated with the SHOE approach by applying it to two problems in different domains.

Citation: Heflin, J. Towards the Semantic Web: Knowledge Representation in a Dynamic, Distributed Environment. Ph.D. Thesis, University of Maryland, College Park. 2001.
Formats: This dissertation is available in two versions: the official version follows the formatting conventions of the University of Maryland and is identical to the original dissertation. The reformatted version uses single-line spacing and smaller margins to reduce the number of pages of the document.

Official - Compressed Postscript (504K)
Official - PDF (976K)
Reformatted - Compressed Postscript (512K)
Reformatted - PDF (928K)


Title: A Portrait of the Semantic Web in Action
Authors: Jeff Heflin and James Hendler
Abstract: Without semantically enriched content, the Web cannot reach its full potential. The authors discuss tools and techniques for generating and processing such content, thus setting a foundation upon which to build the Semantic Web. In particular, they put a Semantic Web language through its paces and try to answer questions about how people can use it, such as, How do authors generate semantic descriptions? How do agents discover these descriptions? How can agents integrate information from different sites? How can users query the Semantic Web? The authors present a system that addresses these questions and describe tools that help users interact with the Semantic Web. They motivate the design of their system with a specific application: semantic markup for computer science.
Citation: Heflin, J. and Hendler, J. A Portrait of the Semantic Web in Action. IEEE Intelligent Systems, 16(2):54-59, 2001.
Available: From IEEE Intelligent Systems, with electronic subscription


Title: Semantic Interoperability on the Web
Authors: Jeff Heflin and James Hendler
Abstract: 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.
Citation: Heflin, J. and Hendler, J. Semantic Interoperability on the Web. In Proceedings of Extreme Markup Languages 2000. Graphic Communications Association, 2000. pp. 111-120.
Formats: Postscript (744K)
PDF (89K)


Title: Dynamic Ontologies on the Web
Authors: Jeff Heflin and James Hendler
Abstract: 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.
Citation: Heflin, J. and Hendler, J. Dynamic Ontologies on the Web. In Proceedings of the Seventeenth National Conference on Artificial Intelligence (AAAI-2000). AAAI/MIT Press, Menlo Park, CA, 2000. pp. 443-449.
Formats: Postscript (464K)
PDF (62K)


Title: Searching the Web with SHOE
Authors: Jeff Heflin and James Hendler
Abstract: Although search engine technology has improved in recent years, there are still many types of searches that return unsatisfactory results. This situation can be greatly improved if web pages use a semantic markup language to describe their content. We have developed SHOE, a language for this purpose, and in this paper describe a scenario for how the language could be used by search engines of the future. A major challenge to this system is designing a query tool that can exploit the power of a knowledge base while still being simple enough for the casual user. We present the SHOE Search tool, which allows the user to specify a context for his or her query, and then uses the context to help the user build a query by example.
Citation: Heflin, J. and Hendler, J. Searching the Web with SHOE. In Artificial Intelligence for Web Search. Papers from the AAAI Workshop. WS-00-01. AAAI Press, Menlo Park, CA, 2000. pp. 35-40.
Formats: Postscript (1016K)
PDF (60K)


Title: SHOE: A Knowledge Representation Language for Internet Applications
Authors: Jeff Heflin, James Hendler, and Sean Luke
Abstract: 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.
Citation: Heflin, J., Hendler, J., and Luke, S. SHOE: A Knowledge Representation Language for Internet Applications. Technical Report CS-TR-4078 (UMIACS TR-99-71), Dept. of Computer Science, University of Maryland at College Park. 1999.
Formats: Postscript (680K)
PDF (384K)


Title: Coping with Changing Ontologies in a Distributed Environment
Authors: Jeff Heflin, James Hendler, and Sean Luke
Abstract: We discuss the problems associated with versioning ontologies in distributed environments. This is an important issue because ontologies can be of great use in structuring and querying internet information, but many of the Internet's characteristics, such as distributed ownership, rapid evolution, and heterogeneity, make ontology management difficult. We present a scheme for classifying ontology revisions based upon the effect these changes would have on the data sources that reference the ontology. We also discuss how to manage these changes, especially when they are the result of integrating ontologies. Finally, we describe the simple elements of SHOE, a web-based knowledge representation language, that allow us to revise shared ontologies while maintaining consistency with web pages that already reference them.
Citation: Heflin, J., Hendler, J., and Luke, S. Coping with Changing Ontologies in a Distributed Environment. Ontology Management. Papers from the AAAI Workshop. WS-99-13. AAAI Press, 1999. pp. 74-79.
Formats: Postscript (896K)
PDF (67K)


Title: Applying Ontology to the Web: A Case Study
Authors: Jeff Heflin, James Hendler, and Sean Luke
Abstract: This paper describes the use of Simple HTML Ontology Extensions (SHOE) in a real world internet application. SHOE allows authors to add semantic content to web pages and to relate this content to common ontologies that provide contextual information about the domain. Using this information, query systems can provide more accurate responses than are possible with the search engines available on the Web. We have applied these techniques to the domain of Transmissible Spongiform Encephalopathies (TSEs), a class of diseases that include "Mad Cow Disease". We discuss our experiences and provide lessons learned from the process.
Citation: Heflin, J., Hendler, J., and Luke, S. Applying Ontology to the Web: A Case Study. In: J. Mira, J. Sanchez-Andres (Eds.), International Work-Conference on Artificial and Natural Neural Networks, IWANN'99. Proceedings, Volume II. Springer, Berlin, 1999. pp. 715-724.
Formats: Postscript (2240K)
PDF (91K)


Title: Reading Between the Lines: Using SHOE to Discover Implicit Knowledge from the Web
Authors: Jeff Heflin, James Hendler, and Sean Luke
Abstract: This paper describes how SHOE, a set of Simple HTML Ontological Extensions, can be used to discover implicit knowledge from the World-Wide Wide Web (WWW). SHOE allows authors to annotate their pages with ontology-based knowledge about page contents. In previous papers, we discussed how the semantic knowledge provided by SHOE allows users to issue queries that are much more sophisticated than keyword search techniques, including queries that require retrieval of information from many sources. Here, we expand upon this idea by describing how SHOE's ontologies allow agents to understand more than what is explicitly stated in Web pages through the use of context, inheritance and inference. We use examples to illustrate the usefulness of these features to Web agents and query engines.
Citation: Heflin, J., Hendler, J., and Luke, S. Reading Between the Lines: Using SHOE to Discover Implicit Knowledge from the Web. In AI and Information Integration. Papers from the 1998 Workshop. WS-98-14. AAAI Press, 1998. pp. 51-57.
Formats: Postscript (1056K)


Title: Ontology-based Web Agents
Authors: Sean Luke, Lee Spector, David Rager, and James Hendler
Abstract: 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, Exposť, which interns SHOE knowledge from web documents, making these kinds queries a reality.
Citation: Luke, S., L. Spector, D. Rager, and J. Hendler. Ontology-based Web Agents. In Proceedings of the First International Conference on Autonomous Agents (Agents97). W. L. Johnson, ed. Association for Computing Machinery, New York, 1997, 59-66.
Formats: Postscript (784K)
Gzipped PostScript Format (50K)


Title: Web Agents That Work
Authors: Sean Luke and James Hendler
Abstract: There are two kinds of information-seekers currently wandering the World-Wide Web. First there are us humans, the web-surfers for whom the Web was designed. Second, there are increasing numbers of automated systems, Web agents, which gather information from the Web on our behalf. At the present time, humans far outnumber web agents, but this could soon change: as the sheer volume of information on the Web increases,and the ratio of junk to useful information continues to grow, we will increasingly rely on agents to dig through all that muck to find our gems for us.
Citation: Luke, S. and J. Hendler. Web Agents That Work. IEEE Multimedia 4:3 (July-September 1997) 76-80.
Formats: Gzipped Postscript (168K)
Gzipped Postscript without Figures 1 through 3 (15K)
Postscript without Figures 1 through 3 (38K)


Title: Ontology-Based Knowledge Discovery on the World-Wide Web
Authors: Sean Luke, Lee Spector, and David Rager
Abstract: 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.
Citation: Luke, S., L. Spector, and D. Rager. Ontology-Based Knowledge Discovery on the World-Wide Web. In Working Notes of the Workshop on Internet-Based Information Systems at the 13th National Conference on Artificial Intelligence (AAAI96). A. Franz and H. Kitano, eds. AAAI Press, 1996, 96-102.
Formats: HTML (29K)
Postscript (1344K)
Gzipped PostScript (112K)