XAS: a system for accessing componentized, virtual XML documents

XML is emerging as an important format for describing the schema of documents and data to facilitate integration of applications in a variety of industry domains. An important issue that naturally arises is the requirement to generate, store and access XML documents. It is important to reuse existing data management systems and repositories for this purpose. We describe the XML Access Server (XAS), a general purpose XML based storage and retrieval system which provides the appearance of a large set of XML documents while retaining the data in underlying federated data sources that could be relational, object-oriented, or semi-structured. XAS automatically maps the underlying data into virtual XML components when mappings between DTDs and underlying schemas are established. The components can be presented as XML documents or assembled into larger components. XAS manages the relationship between XML components and the mapping in the form of document composition logic. The versatility in its ways to generate XML documents enables XAS to serve a large number of XML components and documents efficiently and expediently.