Multi-Poset-Based Ontologies for Real World Knowledge Discovery Cliff Joslyn (featuring Susan Mniszewski, Karin Verspoor, George Papcun, and Michael Wall) Computer and Computational Sciences Los Alamos National Laboratory September 29, 2003 Old Dominion University Ontologies have become an increasingly important concept in modern knowledge systems, and are cast as one of the foundations of the Semantic Web. Characterized generally as a "formalization of a domain of knowledge", they have many different technical realizations, and ontological concepts have leaked into everything from simple function typologies to database schemata to object-oriented data structures to full-up agent-based AI. One of the very few domains where ontological concepts have escaped the laboratory and come into their own is computational biology. In this context, we have been working with ontologies, such as the Gene Ontology (GO) and the Enzyme Commission (EC) database, which take the particular mathematical form of large multi-posets, and can be understood as collections of hierarchical, taxonomic, categorizations of genes and proteins. Although these are of an intermediate level of technical complexity, in particular avoiding signficiant logical capabilities, they are foundational, and of sufficient size and value to warrant significant attention. In this talk we will introduce basic concepts in ontologies and multi-posets, show some of the particulars about the GO and the EC, and then describe some of our recent research in this area. In particular, we will discuss pseudo-distance approaches to categorization in ontologies, methods to regularize mappings among different ontologies, and the role and value of lexical semantic approaches in interaction with ontological structures.