WebOnt Requirements

This document describes the functionality that I believe is essential for a complete web ontology language. This is a working draft.

Use Cases

Here are some high-level use cases for a web ontology language. Note that I do not describe domain specific applications, but have instead listed functionality that could be useful in many different domains.

• context sensitive web search
• inter-domain web search
• question answering on the Web
• communication between heterogeneous agents

Requirements

These requirements describe the features needed by complete Web Ontology language. I have developed this list over time as a result of lessons I learned from my experiences with SHOE and DAML+OIL. Some of these requirements may be out of scope of the WebOnt Working Group, and instead should be saved for later "layers" of the Semantic Web. Nevertheless, identifying them now can help us to ensure that design of the Ontology layer does not prohibit the addition of them later.

• shared meaning
• data sources commit to common ontologies
• ontology reuse
• something like daml:imports
• management of ontology evolution [HH00, KF01, Hef01 (Section 3.4)]
• version numbers or revises relation
• semantic backward-compatibility
• deprecation
• interoperability of heterogeneous ontologies
• features for mapping between ontologies
• synonyms
• including synonyms for individuals!
• subclass / superclass
• inverse relationships
• conjunction, disjunction, implication
• arithmetic functions
• grouping
• string manipulation
• procedural attachments?
• Java?
• management of inconsistency
• inconsistency is inevitable in large, distributed systems
• need standard meaning in face of inconsistency
• ontologies of trust/belief
• prioritized conflict handling [GLC99]
• assumption-based truth maintenance systems (ATMSs) [dK86]
• non-monotonicity
• other methods?
• scalability
• limit expressivity?
• expect incomplete reasoning algorithms?
• user-friendly
• you shouldn't need a Ph.D. in AI to understand the language
• handle variability in persistence of data
• some data has short "lifetime"
• e.g., stock prices
• http expires?
  • may be too clumsy
  • not included in semantic model

References

[dK86] J. de Kleer. An Assumption-based TMS. Artificial Intelligence, 28(2), pp. 127-162, 1986.

[GLC99] B. Grosof, Y. Labrou, and H. Chan. A Declarative Approach to Business Rules in Contracts: Courteous Logic Programs in XML. In Proc. 1st ACM Conf. on Electronic Commerce (EC-99), 1999. (PDF)

[Hef01] J. Heflin. Towards the Semantic Web: Knowledge Representation in a Dynamic, Distributed Environment. Ph.D. Thesis, University of Maryland, College Park. 2001. (PDF)

[HH00] J. Heflin and J. Hendler. 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. (PDF)

[KF01] M. Klein and D. Fensel. Ontology Versioning on the Semantic Web. In First International Semantic Web Working Symposium (SWWS'01), 2001. (PDF)