A tree-structured query interface for querying semi-structured data

XML is a semi-structured data format that is quickly becoming the standard means of communication across the Internet. We introduce a simple, powerful, unambiguous tree-structured user-interface for querying semi-structured data. It emphasizes ease-of-use and provides generic access to XML repositories. An implementation of this interface called the Pathways Explorer has been built in the context of biological pathways. The implementation illustrates some basic capabilities, such as selection, projection, equijoins, and self-joins. It builds efficient queries using SQL, and it has been shown that XQuery's performance would be comparable. Future implementations might allow semantic client-side caching, aggregation and grouping, recursion, and set operations.