Re: XML ouput for psql

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Peter Eisentraut wrote:
> 1. Look into the SQL/XML standard draft (ftp.sqlstandards.org) to find out
> whether the standard addresses this sort of thing.

The URL you gave leads to a site curiously content-free and full of dead links.
I've looked around a bit, but found nothing definitive. One good resource I
did find was this:

http://www.wiscorp.com/sql/SQLX_Bringing_SQL_and_XML_Together.pdf

The article mentions a lot of links on the sqlstandards.org and iso.org sites, none
of which work or are restricted. If anyone knows of some good links, please
let me know. (especially ISO 9075). From what I've read of the SQLX stuff, the
format in my patch should be mostly standard:

<row>
 <name>Joe Sixpack</name>
 <age>35</age>
 <state>Alabama</state>
</row>

One problem is that the recommended way to handle non-standard characters
(including spaces) is to escape them like this:

foobar baz => <foobar_x0020_baz>

This also includes escaping things like "_x*" and "xml*". We don't have
anything like that in the code yet (?), but we should probably think about
heading that way. I think escaping whitespace in quotes is good enough
for now for:

foobar baz => <"foobar baz">

The xsd and xsi standards are also interesting, but needlessly complicated
for psql output, IMO.

> Incidentally, the HTML table model is such an established and standardized
> XML and SGML table model, so the easiest way to get the task "add XML
> output to psql" done is to update the HTML output to conform to XHTML.
> That way you get both the strict XML and you can look at the formatted
> result with any old (er, new) browser.

I don't agree with this: XML and XHTML are two different things. We could
certainly upgrade the HTML portion, but I am pretty sure that the XML
standard calls for this format:

<columnname>data here</columnname>

..which is not valid XHTML and won't be viewable by any browser. The other
suggested XML formats are even further from XHTML than the above. The HTML
format should be "html table/layout" specific and the XML should be
"schema/data" specific.

- --
Greg Sabino Mullane greg@turnstep.com
PGP Key: 0x14964AC8 200302280938

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