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by microtonal 4569 days ago
It's not about indexing paths you indicate, XML databases are about indexing the whole structure (remember, XML is not relational, but are graphs). Besides that they provide XPath/XQuery processing and optimization. You can query large XML documents or sets of documents, like you'd query them with e.g. XQilla.

Of course, it is possible to implement all of this on top of existing database technology. E.g. Oracle's Berkeley DB XML is implemented on top of Berkeley DB. But, a relational database with some indexing of XML does not provide the same functionality as an XML database.
2 comments
taspeotis 4569 days ago
> It's not about indexing paths you indicate, XML databases are about indexing the whole structure

From my first link, MSSQL does both:

    The primary XML index indexes all tags, values, and paths within the XML instances in an XML column
    ...
    To enhance search performance, you can create secondary XML indexes. A primary XML index must first exist before you can create secondary indexes
And it supports some reasonable subset of XQuery [1].

[1] http://technet.microsoft.com/en-us/library/ms187854.aspx

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sixbrx 4569 days ago
Oracle for one does allow full document xml indexing (via XMLIndex) which is trivial to implement, also a rather full featured XQuery integrated with SQL.
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