XML and Databases

The first question you need to ask yourself when you start thinking about XML and databases is why you want to use a database in the first place. Do you have legacy data you want to expose? Are you looking for a place to store your Web pages? Is the database used by an e-commerce application in which XML is used as a data transport? The answers to these questions will strongly influence your choice of database and middleware (if any), as well as how you use that database.
For example, suppose you have an e-commerce application that uses XML as a data transport. It is a good bet that your data has a highly regular structure and is used by non-XML applications. Furthermore, things like entities and the encodings used by XML documents probably aren't important to you -- after all, you are interested in the data, not how it is stored in an XML document. In this case, you'll probably need a relational database and software to transfer the data between XML documents and the database. If your applications are object-oriented, you might even want a system that can store those objects in the database or serialize them as XML.
On the other hand, suppose you have a Web site built from a number of prose-oriented XML documents. Not only do you want to manage the site, you would like to provide a way for users to search its contents. Your documents are likely to have a less regular structure and things such as entity usage are probably important to you because they are a fundamental part of how your documents are structured. In this case, you might want a product like a native XML database or a content management system. This will allow you to preserve physical document structure, support document-level transactions, and execute queries in an XML query language.

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