Electronic catalog contains rich semantics associated with products, and serves as a challenging domain for ontology application. Ontology is concerned with the nature and relations of being. It can play a crucial role in e-commerce as a formalization of e-Catalogs. Description Logics provide a theoretical core for most of the current ontology languages. In this paper, we present an ontological model of e-Catalogs. Our goal is to represent the semantic information of e-Catalog in a conceptual model, and then to construct a formally sound ontology. We take an Extended Entity Relationship approach to denote the fundamental set of modeling constructs, and present corresponding description logic representation for each construct. Additional semantic knowledge can be represented directly in description logic.