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From "Laura Stewart" <scotsmat...@gmail.com>
Subject Re: XML type description - possible changes?
Date Tue, 29 Aug 2006 18:30:23 GMT
On 8/29/06, Daniel John Debrunner <djd@apache.org> wrote:
> Army wrote:
> > Daniel John Debrunner wrote:
> >
> > <snip old XML type text>
> >
> >>
> >> That seems wrong to me, the use of "store Unicode character-based", any
> >> implementation details are not important here. Also the use of "large"
> >> is not relevant, what about small XML documents?
> >
> >
> > I have to admit, I'm guilty of copy-paste here.  The current
> > documentation for the CLOB type has the following sentence, which is the
> > root of the questions raised in this email:
> >
> > <begin quote>
> >
> > A CLOB (character large object) value can be up to 2,147,483,647
> > characters long. A CLOB is used to store unicode character-based data,
> > such as large documents in any character set.
> >
> > <end quote>
> >
> > I copied that as my starting point and failed to clean it up...sorry.
> >
> >> Looking at the other type definitions it seems something like this would
> >> match, though it seems unwieldy.
> >>
> >> "XML provides for storage of Extensible Markup Language (XML) documents,
> >> that conform to the SQL/XML definition of a well-formed
> >> XML(DOCUMENT(ANY)) value."
> >
> >
> > I agree, I think this is a better wording.  My one reservation is that
> > the XML type can also be used transiently for XML values that are not
> > well-formed documents.  In particular, the XMLQUERY operator returns a
> > value of type XML that is not guaranteed to be XML(DOCUMENT(ANY)).
> >
> > So while I agree with the new text proposal, I think it'd be good (or at
> > least, more accurate) to mention that XML is not restricted to "storage
> > of ... well-formed XML(DOCUMENT(ANY)) values"; it also provides for
> > transient use of XML(SEQUENCE) values, which may or may not be
> > well-formed XML(DOCUMENT(ANY)) values.
>
> I agree with your reservation. It can also be applied to most, if not
> all of the data type decriptions. Many talk about "providing storage"
> but they can all be used for transient types.
>
> Dan.
>
>
>

Another way to word the description is:

The XML data type is used to store an internal representation of
Extensible Markup Language (XML) documents. The documents in an XML
column must conform to the SQL/XML definition of well-formed XML
documents.

FYI - I would prefer to keep the phrase "data type" in the title and
first paragraph of this file as a qualifier.  In the near future (post
10.2) I intend to update all of the other files that describe data
types to add this qualifier.  There are many files in Derby that don't
have qualifiers in the titles and it makes locating the correct info
difficult for Derby users.

-- 
Laura Stewart

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