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The Quest for an XML Query Standard

March 02, 1999

  Last December, the W3C convened a workshop on query languages called QL'98 and invited companies to identify the problems and opportunities involved in creating or adapting a query language capable of handling XML.   Lisa Rein has talked to QL'98 organizers and participants to find out how people agree and disagree, and where they might go from here.

If XML has the power to transform the Web itself into a giant, distributed database, how shall we "interrogate" that database?

Well, a lot depends on whether you view the structure of that database as a tree or a table.

SQL (the Structured Query Language) is a well-established and standardized language that is designed for retrieving relational data.   This is data stored as a collection of tables in a relational database management system (RDBMS).   XML presents a different  but not necessarily opposing view.   Its data model is a hierarchical tree of elements and attributes.   There is increasing interest in developing an XML-aware query language to take advantage of XML's data model while enabling the kinds of applications that SQL provides for databases.   An XML query language could make it easier to process large  collections of XML documents and extract relevant information.   It might also increase the precision of searching in documents because queries could utilize the document's structure.   In short, such a query language would be an improvement over current approaches to full-text searching.

In the sections that follow, we are going to look at QL'98 in more detail and discuss the different proposals that were presented there.

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