Ontology translation is one of the most difficult problems that web-based agents must cope with. An ontology is a formal specification of a vocabulary, including axioms relating its terms. Ontology translation is best thought of in terms of ontology merging. The merge of two related ontologies is obtained by taking the union of the terms and the axioms defining them. We add bridging axioms not only as “bridges” between terms in two related ontologies but also to make this merge into a complete new ontology for further merging with other ontologies. Translation is implemented using an inference engine (OntoEngine), running in either a demand-driven (backward-chaining) or data-driven (forward chaining) mode. We illustrate our method by describing its application in an online ontology translation system, OntoMerge, which translates a dataset in the DAML notation to a new DAML dataset that captures the same information, but in a different ontology. A uniform internal representation, Web-PDDL is used for representing merged ontologies and datasets for automated reasoning.