Friday, June 29, 2007

Epistemological extension to ontologies: a key of realizing Semantic Web?

(updated Dec. 21, 2007)

epistemology When discussing Semantic Web, we often think of ontologies. Ontology contains formal specifications of conceptualizations. By linking world facts to ontological declarations, machines can "understand" the meanings of these facts. Moreover, machines can reason on ontology declarations to derive latent conclusions based on explicit ontological expressions. These logical computations form the foundation of the Semantic Web.

But there is a problem. The process of linking world facts to ontology declarations is often ambiguous and subjective. This process, also normally addressed as the process of semantic annotation, is related to another branch of philosophy---epistemology. It short, epistemology studies how we know what we know. A narrower definition of epistemology could be expressed as the study of how we recognize what we know. Human recognition is often subjective.

Besides the distinction of subjectiveness and objectiveness, epistemology is more about the knowledge of recognition. This knowledge of recognition is generally bound to the superficial side of meanings, such as the form and the display, in contrast to that ontology is more about the intrinsic side of concepts themselves. The knowledge in ontologies should not be affected by its external representations, such as the form and the display. The understanding of this distinction is critical to the understanding of semantic annotation.

We should equip machines with not only ontologies but also epistemologies to realize the Semantic Web. Without epistemologies, machines with standard ontologies by themselves can neither recognize new facts, nor verify the correctness of their assigned facts. Hence they must rely on external procedures (such as data extraction routines) to accomplish these missing functions. This type of external procedures are hard to be modified and updated. As a result, we may ask why we must adopt the epistemological declarations produced by others for our own ontology declarations. To solve this problem, we need declarative (but not hard-coded programming subroutines) epistemological extensions to ontologies.

Epistemological extensions of ontologies allow individuals to specify different things of recognition with respect to the same ontology. This requirement is common in our real society. For example, different people may have varied external interpretations of an agreed, shared definition of the concept "beauty." By separating epistemological declarations and ontological declarations, we can have a better and more flexible handling of semantics. This is a key of realizing Semantic Web.

For readers who are interested in exploring more on this topic. Here is a recently accepted paper by the First International workshop on Ontologies and Information Systems for the Semantic Web (ONISW 2007) collocated with ER 2007.

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