XML is gaining acceptance as a universal data format, as more and more workflow systems are taking XML as their basic data format for workflow process definition, data type definition, and control information definition. For XML-based workflow systems, an XML repository is used to manage XML object resources in a safe and efficient way. RepoX, an XML repository, has been developed for the METEOR workflow system. It maps XML documents to a relational-object database at the backend and also provides extraction/retrieval, version control, check in/check out, and searching and query functions. In addition, it has support for adaptive workflows, which may need workflow definition information from the repository at runtime, in a dynamically changing environment. RepoX is used in a bioinformatics applicationthe fungal genome project to support and manage workflow designs and specifications.