Identity relations are at the foundation of many logic-based knowledge representations. We argue that the traditional notion of equality, is unsuited for many realistic knowledge representation settings. The classical interpretation of equality is too strong when the equality statements are re-used outside their original context. On the Semantic Web, equality statements are used to interlink multiple descriptions of the same object, using owl:sameAs assertions. And indeed, many practical uses of owl:sameAs are known to violate the formal Leibniz-style semantics. We provide a more flexible semantics to identity by assigning meaning to the subrelations of an identity relation in terms of the predicates that are used in a knowledge-base. Using those indiscernability-predicates, we define upper and lower approximations of equality in the style of rought-set theory, resulting in a quality-measure for identity relations.
Harald Sack is Professor for Information Services Engineering at two of the most renowned research institutions in Europe: FIZ Karlsruhe and AIFB. He is a part of SEMANTiCS' research and innovation track program committee as well as of the conference's permanent advisory board. His publications include more than 130 papers in international journals and conferences and three standard textbooks on networking technologies. In this interview he speaks about the limited capabilities of search engines, the necessity of data being open and the coffee culture in Vienna. You have been working in many research areas such as semantic web technologies, knowledge representations, multimedia analysis & retrieval.
The machine understandable semantic of information, achieved by using an RDF(S) structure and common-shared vocabularies (ontologies) is the big step in enabling the machine-agent interoperability on the Web. Machine agents can crawl annotated web pages, search for useful information from various sources, use the information to solve tasks at hand by using the internal reasoning mechanism and background knowledge. In order to enhance their inference capabilities, machine- (and also human-) agents need to update their knowledge, using relevant knowledge sources as much as possible. One of the possible scenarios is to search for relevant knowledge on the (Semantic) Web. In this paper we discuss the prerequisites for design, and present an approach for representing rules in the machine understandable form, which is based on the current efforts in achieving the machine understandable semantic of information. Such representation of rules can serve as the backbone for a web-enabled knowledge management process. In the presented usage scenario we focus on the knowledge sharing phase in that process, i.e. on the searching for relevant knowledge (rules) on the Web.
Service-oriented architectures have brought significant progress for more flexible realization of business processes integrating functionality from heterogeneous sources. While more and more businesses adopt the new technology it becomes obvious that many questions are still not addressed to make it keep its promises, especially in the area of human efforts involved in business process composition. We introduce a framework for a possible next generation enterprise software based on, but going beyond that of service-oriented architectures utilizing logic programming taking advantage of formalized explicit policies as substantial constituents of enterprise systems.
Description Logics (DLs) provide a clear and broadly accepted paradigm for modeling and reasoning about terminological knowledge. However, it has been often noted, that although DLs are well-suited for representing a single, global viewpoint on an application domain, they offer no formal grounding for dealing with knowledge pertaining to multiple heterogeneous viewpoints — a scenario ever more often approached in practical applications, e.g. concerned with reasoning over distributed knowledge sources on the Semantic Web. In this paper, we study a natural extension of DLs, in the style of two-dimensional modal logics, which supports declarative modeling of viewpoints as contexts, in the sense of McCarthy, and their semantic interoperability. The formalism is based on two-dimensional semantics, where one dimension represents a usual object domain and the other a (possibly infinite) domain of viewpoints, addressed by additional modal operators and a metalanguage, on the syntactic level. We systematically introduce a number of expressive fragments of the proposed logic, study their computational complexity and connections to related formalisms.