This document describes a language for ontology exchange. The language, called XOL, is designed to provide a format for exchanging ontology definitions among a set of interested parties. The ontology definitions that XOL is designed to encode include both schema information (meta-data), such as class definitions from object databases as well as non-schema information (ground facts) such as object definitions from object databases. The syntax of XOL is based on XML. The semantics of XOL are based on OKBC-Lite, which is a simplified form of the knowledge model for the OKBC (Open Knowledge Base Connectivity).