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From "Bryan Pendleton (JIRA)" <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-1759) XMLSERIALIZE operator doesn't follow SQL/XML spec in some areas when serializing a sequence.
Date Sat, 09 Sep 2006 04:42:23 GMT
    [ http://issues.apache.org/jira/browse/DERBY-1759?page=comments#action_12433561 ] 
            
Bryan Pendleton commented on DERBY-1759:
----------------------------------------

I'm afraid I don't have much to offer regarding the sequence-of-attribute-values issue.

The patch applied and built cleanly. My derbyall run was also successful. With Xalan 2.7,
I got the expected results for lang/xmlBinding.java and lang/xml_general.sql. The
patch description is clear and makes sense, and the code in the patch appears to
match the patch description.

I committed this patch to subversion as revision 441740. Thanks as usual for the
clear patch description, the careful commenting and attention to detail in the code,
and the test cases. Reviewing such changes is a pleasure!

Do we need to merge this change to 10.2?

> XMLSERIALIZE operator doesn't follow SQL/XML spec in some areas when serializing a sequence.
> --------------------------------------------------------------------------------------------
>
>                 Key: DERBY-1759
>                 URL: http://issues.apache.org/jira/browse/DERBY-1759
>             Project: Derby
>          Issue Type: Bug
>    Affects Versions: 10.2.1.0, 10.2.2.0, 10.3.0.0
>            Reporter: A B
>         Assigned To: A B
>             Fix For: 10.2.2.0, 10.3.0.0
>
>         Attachments: d1759_v1.patch, d1759_v1.stat
>
>
> The SQL/XML specification dictates that, when serializing a sequence of XML items, the
XMLSERIALIZE operator must first "normalize" the sequence based on the rules defined here:
>   http://www.w3.org/TR/xslt-xquery-serialization/#serdm
> The current Derby implementation doesn't perform such normalization, which leads to two
ways in which the results of an XMLSERIALIZE operator may not agree with the required behavior:
>   1. Sequences of atomic values will not have spaces between, but
>      the space is required as part of step 3 of the normalization
>      rules at the above link.
>   2. Derby will allow serialization of a sequence even if it has
>      a top-level Attribute node in it, but the rules of normalization
>      dictate that an error should be thrown instead (step 7).
> Both of these behaviors can be seen with the following query.
> values
>   xmlserialize(
>     xmlquery('/ageinfo/@*' passing by ref
>       xmlparse(
>         document '<ageinfo age="48" birthdate="1900-02-08"/>'
>         preserve whitespace
>       )
>       empty on empty
>     )
>     as char(50)
>   )
> Derby will currently return the following result from this statement:
> 1
> --------------------------------------------------
> 481900-02-08
> This result does not abide by SQL/XML specification because a) Derby allowed serialization
of a sequence having a top-level attribute node (actually, the sequence had two), and b) the
atomic values produced from the attributes were displayed without a space between them.
> The correct behavior for the above example is to return a serialization error caused
by the presence of an Attribute node in the sequence.
> If the example was rewritten as, say:
> -    xmlquery('/ageinfo/@*' passing by ref
> +    xmlquery('fn:data(/ageinfo/@*)' passing by ref
> then the attribute nodes are no longer present--we only have their atomic values, which
is allowed.  Thus the correct result should then be:
> 1
> --------------------------------------------------
> 48 1900-02-08
> Note, though, that Xalan doesn't appear to support the "fn:data" function, so this rewritten
query won't actually work.  I tried using Xalan's built-in string function, as follows:
> -    xmlquery('/ageinfo/@*' passing by ref
> +    xmlquery('string(/ageinfo/@*)' passing by ref
> but Xalan only returns the first attribute in that case; it doesn't return the second
one.  So part of this Jira issue is probably going to involve figuring out how to allow a
user to retrieve a sequence of attribute *values* (as opposed to attribute nodes) using Xalan
and still abide by the SQL/XML rules.

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