From: Peter Eisentraut <peter_e@gmx.net>
To: Bruce Momjian <bruce@momjian.us>
Subject: Re: New XML section for documentation
Date: Sat, 26 Aug 2006 08:08:12 +0200
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Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>,
	PostgreSQL-documentation <pgsql-docs@postgresql.org>
References: <200608252346.k7PNkvT15748@momjian.us>
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Bruce Momjian wrote:
> XML Document Support
> ====================
> XML support is not one capability, but a variety of features
> supported by a database.

database system

> Storage
> -------
> PostgreSQL stores XML documents as ordinary text documents.

It is "possible" to do that, but this sounds like it's done 
automatically or implicitly.  Maybe:

"PostgreSQL does not have a specialized XML data type.  The recommended 
way is to store XML documents as text."

> Import/Export
> -------------
> Because XML documents are stored as normal text documents, they can
> be imported/exported with little complexity.

Import/export refers to exporting schema data with XML decorations.  Of 
course you can export column data trivially, but that's not what this 
is about.

> Validation
> ----------
> /contrib/xml2 has a function called xml_valid() that can be used in
> a CHECK constraint to enforce that a field contains valid XML.  It
> does not support validation against a specific XML schema.

Then this is not validation but only checking for well-formedness.  The 
xml2 README says so, in fact.

> Indexing
> --------

I think the expression index capability combined with contrib/xml2 is 
more relevant here than the full-text search capability.

> Transforming
> ------------
> /contrib/xml2 supports XSL transformations.

That's XSLT.

> XML to SQL Mapping
> -------------------
> This involves converting XML data to and from relational structures.
> PostgreSQL has no internal support for such mapping, and relies on
> external tools to do such conversions.

Are there instances of such tools?

-- 
Peter Eisentraut
http://developer.postgresql.org/~petere/