From georg.piewald at siemens.com  Tue Sep  2 09:57:12 2008
From: georg.piewald at siemens.com (Piewald, Georg)
Date: Mon Sep  1 23:57:53 2008
Subject: [xquery-talk] Changing the content of an XML document
Message-ID: <EC7423A1DA34E340978D0CC83F9120F00531F132@nets13ja.ww300.siemens.net>

Another beginner's question:

In my application, the client requests an XML document from the server.
Since the document is rather big (and there are actually a few different
ones), I'd like to keep it as a separate file on the server (not part of
the Xquery file). This means, in the script I load the XML file into a
local variable using the doc() function and return the result to the
client.

But now, occationally some of the content of the file has to be altered.
Is there any possiblility to do this except placing the entire file
inside the script?

Thanks for answers,
Georg


PS: I'm using eXist Database 1.2.4

From wolfgang at exist-db.org  Tue Sep  2 10:39:14 2008
From: wolfgang at exist-db.org (Wolfgang)
Date: Tue Sep  2 00:39:49 2008
Subject: [xquery-talk] Changing the content of an XML document
In-Reply-To: <EC7423A1DA34E340978D0CC83F9120F00531F132@nets13ja.ww300.siemens.net>
References: <EC7423A1DA34E340978D0CC83F9120F00531F132@nets13ja.ww300.siemens.net>
Message-ID: <48BCEDA2.9030009@exist-db.org>

> This means, in the script I load the XML file into a
> local variable using the doc() function and return the result to the
> client.
 >
 > But now, occationally some of the content of the file has to be altered.

I'm not sure I completely understand the question. Is the document 
stored in the db or do you load it from the filesystem? And do you only 
need to temporarily change some content of that file (in which case I 
would probably call an XSLT) or permanently (use XQuery update extensions)?

Wolfgang
From georg.piewald at siemens.com  Tue Sep  2 10:59:18 2008
From: georg.piewald at siemens.com (Piewald, Georg)
Date: Tue Sep  2 00:59:54 2008
Subject: [xquery-talk] Changing the content of an XML document
In-Reply-To: <48BCEDA2.9030009@exist-db.org>
References: <EC7423A1DA34E340978D0CC83F9120F00531F132@nets13ja.ww300.siemens.net>
	<48BCEDA2.9030009@exist-db.org>
Message-ID: <EC7423A1DA34E340978D0CC83F9120F00531F133@nets13ja.ww300.siemens.net>

 

> Wolfgang [mailto:wolfgang@exist-db.org] wrote:
> 
> > This means, in the script I load the XML file into a
> > local variable using the doc() function and return the result to the
> > client.
>  >
>  > But now, occationally some of the content of the file has 
> to be altered.
> 
> I'm not sure I completely understand the question. Is the document 
> stored in the db or do you load it from the filesystem? And 
> do you only 
> need to temporarily change some content of that file (in which case I 
> would probably call an XSLT) or permanently (use XQuery 
> update extensions)?

Actually I can reduce my question to the following: Assuming I have a
variable which stores a node-tree like that

let $tree :=
  <node>
    <subnode>
      some text
    </subnode>
  </node>

In reality $tree is the entire XML file which I want to send back to the
client. Now, depending on some conditions I want to change the content
of <subnode> "some text" to "some other text", before sending it. I
don't actually want to alter the file in the database, just the message
that I'm sending.

If I placed the XML-file inside the script, I would write something like

<node>
  <subnode>
  {
    if ($condition)
    then "some text"
    else "some other text"
  }
  </subnode>
</node>

But since I have a couple of not too small XML files I fear that this
will get a bit overcrwoded.
Do you understand what I mean?

Best,
Georg

From wolfgang at exist-db.org  Tue Sep  2 11:26:51 2008
From: wolfgang at exist-db.org (Wolfgang)
Date: Tue Sep  2 01:27:26 2008
Subject: [xquery-talk] Changing the content of an XML document
In-Reply-To: <EC7423A1DA34E340978D0CC83F9120F00531F133@nets13ja.ww300.siemens.net>
References: <EC7423A1DA34E340978D0CC83F9120F00531F132@nets13ja.ww300.siemens.net>	<48BCEDA2.9030009@exist-db.org>
	<EC7423A1DA34E340978D0CC83F9120F00531F133@nets13ja.ww300.siemens.net>
Message-ID: <48BCF8CB.2080809@exist-db.org>

> Actually I can reduce my question to the following: Assuming I have a
> variable which stores a node-tree like that
> 
> let $tree :=
>   <node>
>     <subnode>
>       some text
>     </subnode>
>   </node>
> 
> In reality $tree is the entire XML file which I want to send back to the
> client. Now, depending on some conditions I want to change the content
> of <subnode> "some text" to "some other text", before sending it. I
> don't actually want to alter the file in the database, just the message
> that I'm sending.

Ok, I see. If you just need to filter out or change a few nodes, I would 
probably write a simple transformation function, e.g.:

declare function f:filter-entry($node as node(), $newText as xs:string) {
     typeswitch ($node)
         case $subnode as element(subnode) return
             <subnode>{$newText}</subnode>
         case $elem as element() return
             element { node-name($elem) } {
                 $elem/@*, for $child in $elem/node() return 
f:filter-entry($child, $newText)
             }
         default return
             $node
};

Wolfgang
From cschlaefcke at wms-network.de  Tue Sep  2 12:03:26 2008
From: cschlaefcke at wms-network.de (Christian Schlaefcke)
Date: Tue Sep  2 02:03:30 2008
Subject: [xquery-talk] Changing the content of an XML document
In-Reply-To: <EC7423A1DA34E340978D0CC83F9120F00531F133@nets13ja.ww300.siemens.net>
References: <EC7423A1DA34E340978D0CC83F9120F00531F132@nets13ja.ww300.siemens.net>
	<48BCEDA2.9030009@exist-db.org>
	<EC7423A1DA34E340978D0CC83F9120F00531F133@nets13ja.ww300.siemens.net>
Message-ID: <59616.80.85.196.22.1220346206.squirrel@www.wms-network.de>

Hi Georg,

take a look at this thread:
http://www.stylusstudio.com/xquerytalk/200808/002828.html

I had a similar problem exept I wanted to delete certain nodes instead of
replacing them.

Espacially the "identity transform"
(http://en.wikipedia.org/wiki/Identity_transform) hint was very helpful
and it sounds as it could help you with your problem too.

Best regards,

Christian


>> Wolfgang [mailto:wolfgang@exist-db.org] wrote:
>>
>> > This means, in the script I load the XML file into a
>> > local variable using the doc() function and return the result to the
>> > client.
>>  >
>>  > But now, occationally some of the content of the file has
>> to be altered.
>>
>> I'm not sure I completely understand the question. Is the document
>> stored in the db or do you load it from the filesystem? And
>> do you only
>> need to temporarily change some content of that file (in which case I
>> would probably call an XSLT) or permanently (use XQuery
>> update extensions)?
>
> Actually I can reduce my question to the following: Assuming I have a
> variable which stores a node-tree like that
>
> let $tree :=
>   <node>
>     <subnode>
>       some text
>     </subnode>
>   </node>
>
> In reality $tree is the entire XML file which I want to send back to the
> client. Now, depending on some conditions I want to change the content
> of <subnode> "some text" to "some other text", before sending it. I
> don't actually want to alter the file in the database, just the message
> that I'm sending.
>
> If I placed the XML-file inside the script, I would write something like
>
> <node>
>   <subnode>
>   {
>     if ($condition)
>     then "some text"
>     else "some other text"
>   }
>   </subnode>
> </node>
>
> But since I have a couple of not too small XML files I fear that this
> will get a bit overcrwoded.
> Do you understand what I mean?
>
> Best,
> Georg



From john.snelson at oracle.com  Tue Sep  2 12:02:18 2008
From: john.snelson at oracle.com (John Snelson)
Date: Tue Sep  2 03:02:53 2008
Subject: [xquery-talk] Changing the content of an XML document
In-Reply-To: <59616.80.85.196.22.1220346206.squirrel@www.wms-network.de>
References: <EC7423A1DA34E340978D0CC83F9120F00531F132@nets13ja.ww300.siemens.net>	<48BCEDA2.9030009@exist-db.org>	<EC7423A1DA34E340978D0CC83F9120F00531F133@nets13ja.ww300.siemens.net>
	<59616.80.85.196.22.1220346206.squirrel@www.wms-network.de>
Message-ID: <48BD0F2A.1020300@oracle.com>

Hi Georg,

The identity transform will work, and is essentially the same as the 
transformation function that Wolfgang suggests. However I think a 
transform expression is easier to understand if eXist supports XQuery 
Update:

copy $a := $tree
modify replace value of node $a//subnode with
   if($condition) then "some text" else "some other text"
return $a

John

Christian Schlaefcke wrote:
> Hi Georg,
> 
> take a look at this thread:
> http://www.stylusstudio.com/xquerytalk/200808/002828.html
> 
> I had a similar problem exept I wanted to delete certain nodes instead of
> replacing them.
> 
> Espacially the "identity transform"
> (http://en.wikipedia.org/wiki/Identity_transform) hint was very helpful
> and it sounds as it could help you with your problem too.
> 
> Best regards,
> 
> Christian
> 
> 
>>> Wolfgang [mailto:wolfgang@exist-db.org] wrote:
>>>
>>>> This means, in the script I load the XML file into a
>>>> local variable using the doc() function and return the result to the
>>>> client.
>>>  >
>>>  > But now, occationally some of the content of the file has
>>> to be altered.
>>>
>>> I'm not sure I completely understand the question. Is the document
>>> stored in the db or do you load it from the filesystem? And
>>> do you only
>>> need to temporarily change some content of that file (in which case I
>>> would probably call an XSLT) or permanently (use XQuery
>>> update extensions)?
>> Actually I can reduce my question to the following: Assuming I have a
>> variable which stores a node-tree like that
>>
>> let $tree :=
>>   <node>
>>     <subnode>
>>       some text
>>     </subnode>
>>   </node>
>>
>> In reality $tree is the entire XML file which I want to send back to the
>> client. Now, depending on some conditions I want to change the content
>> of <subnode> "some text" to "some other text", before sending it. I
>> don't actually want to alter the file in the database, just the message
>> that I'm sending.
>>
>> If I placed the XML-file inside the script, I would write something like
>>
>> <node>
>>   <subnode>
>>   {
>>     if ($condition)
>>     then "some text"
>>     else "some other text"
>>   }
>>   </subnode>
>> </node>
>>
>> But since I have a couple of not too small XML files I fear that this
>> will get a bit overcrwoded.
>> Do you understand what I mean?
>>
>> Best,
>> Georg
> 
> 
> 
> _______________________________________________
> talk@x-query.com
> http://x-query.com/mailman/listinfo/talk


-- 
John Snelson, Oracle Corporation            http://snelson.org.uk/john
Berkeley DB XML:            http://oracle.com/database/berkeley-db/xml
XQilla:                                  http://xqilla.sourceforge.net
From wolfgang at exist-db.org  Tue Sep  2 13:10:54 2008
From: wolfgang at exist-db.org (Wolfgang)
Date: Tue Sep  2 03:11:29 2008
Subject: [xquery-talk] Changing the content of an XML document
In-Reply-To: <48BD0F2A.1020300@oracle.com>
References: <EC7423A1DA34E340978D0CC83F9120F00531F132@nets13ja.ww300.siemens.net>	<48BCEDA2.9030009@exist-db.org>	<EC7423A1DA34E340978D0CC83F9120F00531F133@nets13ja.ww300.siemens.net>	<59616.80.85.196.22.1220346206.squirrel@www.wms-network.de>
	<48BD0F2A.1020300@oracle.com>
Message-ID: <48BD112E.8010905@exist-db.org>

> The identity transform will work, and is essentially the same as the 
> transformation function that Wolfgang suggests. However I think a 
> transform expression is easier to understand if eXist supports XQuery 
> Update:
> 
> copy $a := $tree
> modify replace value of node $a//subnode with
>   if($condition) then "some text" else "some other text"
> return $a

Right now, updates are only supported on documents stored in the db (we 
directly modify the persistent dom). To use this approach, the document 
fragment would need to be saved first, which is probably too much 
overhead for a one-time use.

Wolfgang
From andrew.j.welch at gmail.com  Tue Sep  2 12:22:50 2008
From: andrew.j.welch at gmail.com (Andrew Welch)
Date: Tue Sep  2 03:23:21 2008
Subject: [xquery-talk] Changing the content of an XML document
In-Reply-To: <48BD0F2A.1020300@oracle.com>
References: <EC7423A1DA34E340978D0CC83F9120F00531F132@nets13ja.ww300.siemens.net>
	<48BCEDA2.9030009@exist-db.org>
	<EC7423A1DA34E340978D0CC83F9120F00531F133@nets13ja.ww300.siemens.net>
	<59616.80.85.196.22.1220346206.squirrel@www.wms-network.de>
	<48BD0F2A.1020300@oracle.com>
Message-ID: <74a894af0809020322o6089071em9e198e65924b9480@mail.gmail.com>

> The identity transform will work, and is essentially the same as the
> transformation function that Wolfgang suggests. However I think a transform
> expression is easier to understand

The XSLT 2.0 identity transform is perhaps a little more intuitive:

<xsl:template match="element()">
  <xsl:copy>
    <xsl:apply-templates select="@*,node()"/>
  </xsl:copy>
</xsl:template>

<xsl:template match="attribute()|text()|comment()|processing-instruction()">
  <xsl:copy/>
</xsl:template>

XQuery and XSLT should compliment each other - and the task of
modifying sections of a single document in a single pass is definitely
a job for XSLT.


-- 
Andrew Welch
http://andrewjwelch.com
Kernow: http://kernowforsaxon.sf.net/
From georg.piewald at siemens.com  Tue Sep  2 13:58:24 2008
From: georg.piewald at siemens.com (Piewald, Georg)
Date: Tue Sep  2 03:58:58 2008
Subject: [xquery-talk] Changing the content of an XML document
In-Reply-To: <48BD112E.8010905@exist-db.org>
References: <EC7423A1DA34E340978D0CC83F9120F00531F132@nets13ja.ww300.siemens.net>	<48BCEDA2.9030009@exist-db.org>	<EC7423A1DA34E340978D0CC83F9120F00531F133@nets13ja.ww300.siemens.net>	<59616.80.85.196.22.1220346206.squirrel@www.wms-network.de>
	<48BD0F2A.1020300@oracle.com> <48BD112E.8010905@exist-db.org>
Message-ID: <EC7423A1DA34E340978D0CC83F9120F00531F134@nets13ja.ww300.siemens.net>

 

Wolfgang [mailto:wolfgang@exist-db.org] wrote:
>
>> The identity transform will work, and is essentially the 
>> same as the 
>> transformation function that Wolfgang suggests. However I think a 
>> transform expression is easier to understand if eXist 
>> supports XQuery 
>> Update:
>> 
>> copy $a := $tree
>> modify replace value of node $a//subnode with
>>   if($condition) then "some text" else "some other text"
>> return $a
> 
> Right now, updates are only supported on documents stored in 
> the db (we 
> directly modify the persistent dom). To use this approach, 
> the document 
> fragment would need to be saved first, which is probably too much 
> overhead for a one-time use.
> 

Ok, XQuery Update looks most convenient to me and I don't mind if I
actually do alter the files stored in the db. But I still can't get it
to work, as I don't really understand the required syntax (as described
at http://exist.sourceforge.net/update_ext.html).

I tried the following, which is obviously wrong:

declare function local:alter() {
let $myfile := doc('/db/myfile.xml')
return update value $myfile/subnode/text() with
	'some other text'
};

I'm neither sure how to specify the document I want to alter (the doc()
function is surely wrong since it loads the file into memory) nor how to
select the textnode using XPath (is /text() required here?).

Thanks for all the good answers so far!
Georg

From john.snelson at oracle.com  Tue Sep  2 13:17:15 2008
From: john.snelson at oracle.com (John Snelson)
Date: Tue Sep  2 04:17:53 2008
Subject: [xquery-talk] Changing the content of an XML document
In-Reply-To: <74a894af0809020322o6089071em9e198e65924b9480@mail.gmail.com>
References: <EC7423A1DA34E340978D0CC83F9120F00531F132@nets13ja.ww300.siemens.net>	<48BCEDA2.9030009@exist-db.org>	<EC7423A1DA34E340978D0CC83F9120F00531F133@nets13ja.ww300.siemens.net>	<59616.80.85.196.22.1220346206.squirrel@www.wms-network.de>	<48BD0F2A.1020300@oracle.com>
	<74a894af0809020322o6089071em9e198e65924b9480@mail.gmail.com>
Message-ID: <48BD20BB.6050300@oracle.com>

Andrew Welch wrote:
>> The identity transform will work, and is essentially the same as the
>> transformation function that Wolfgang suggests. However I think a transform
>> expression is easier to understand
> 
> The XSLT 2.0 identity transform is perhaps a little more intuitive:
> 
> <snip>
> 
> XQuery and XSLT should compliment each other - and the task of
> modifying sections of a single document in a single pass is definitely
> a job for XSLT.

I disagree. As in this case I see lot of people saying "I want to change 
X in this document", and XQuery Update's transform expression gives them 
a way to write "change X".

Doing the same in XSLT requires an understanding of how the identity 
transform will copy an entire document, and how you can introduce 
exceptions to what is copied. That's at least one level of abstraction 
away from the user's requirements.

John

-- 
John Snelson, Oracle Corporation            http://snelson.org.uk/john
Berkeley DB XML:            http://oracle.com/database/berkeley-db/xml
XQilla:                                  http://xqilla.sourceforge.net
From wolfgang at exist-db.org  Tue Sep  2 14:18:22 2008
From: wolfgang at exist-db.org (Wolfgang)
Date: Tue Sep  2 04:19:01 2008
Subject: [xquery-talk] Changing the content of an XML document
In-Reply-To: <EC7423A1DA34E340978D0CC83F9120F00531F134@nets13ja.ww300.siemens.net>
References: <EC7423A1DA34E340978D0CC83F9120F00531F132@nets13ja.ww300.siemens.net>	<48BCEDA2.9030009@exist-db.org>	<EC7423A1DA34E340978D0CC83F9120F00531F133@nets13ja.ww300.siemens.net>	<59616.80.85.196.22.1220346206.squirrel@www.wms-network.de>	<48BD0F2A.1020300@oracle.com>
	<48BD112E.8010905@exist-db.org>
	<EC7423A1DA34E340978D0CC83F9120F00531F134@nets13ja.ww300.siemens.net>
Message-ID: <48BD20FE.1050102@exist-db.org>

> I tried the following, which is obviously wrong:
> 
> declare function local:alter() {
> let $myfile := doc('/db/myfile.xml')
> return update value $myfile/subnode/text() with
> 	'some other text'
> };

No, that's basically ok. Just make sure that $myfile/subnode/text() 
returns something. I guess you may need $myfile//subnode/text() instead.

Note: eXist's update syntax is still based on some old proposals (the 
implementation nevertheless works very well). The first XQuery update 
drafts were published later and I had no time to adopt this stuff yet 
(it doesn't have the highest priority for me personally).

> I'm neither sure how to specify the document I want to alter (the doc()
> function is surely wrong since it loads the file into memory) nor how to
> select the textnode using XPath (is /text() required here?).

doc("/db/myfile.xml") doesn't "load" the document into memory (it is a 
persistent document whose nodes reside on disk). It just returns a 
reference to that document.

Wolfgang
From georg.piewald at siemens.com  Tue Sep  2 14:51:18 2008
From: georg.piewald at siemens.com (Piewald, Georg)
Date: Tue Sep  2 04:51:43 2008
Subject: [xquery-talk] Changing the content of an XML document
In-Reply-To: <48BD20FE.1050102@exist-db.org>
References: <EC7423A1DA34E340978D0CC83F9120F00531F132@nets13ja.ww300.siemens.net>	<48BCEDA2.9030009@exist-db.org>	<EC7423A1DA34E340978D0CC83F9120F00531F133@nets13ja.ww300.siemens.net>	<59616.80.85.196.22.1220346206.squirrel@www.wms-network.de>	<48BD0F2A.1020300@oracle.com>
	<48BD112E.8010905@exist-db.org>
	<EC7423A1DA34E340978D0CC83F9120F00531F134@nets13ja.ww300.siemens.net>
	<48BD20FE.1050102@exist-db.org>
Message-ID: <EC7423A1DA34E340978D0CC83F9120F00531F135@nets13ja.ww300.siemens.net>

 

> Wolfgang [mailto:wolfgang@exist-db.org] wrote:
> 
>> I tried the following, which is obviously wrong:
>> 
>> declare function local:alter() {
>> let $myfile := doc('/db/myfile.xml')
>> return update value $myfile/subnode/text() with
>> 	'some other text'
>> };
> 
> No, that's basically ok. Just make sure that $myfile/subnode/text() 
> returns something. I guess you may need 
> $myfile//subnode/text() instead.
> 
> Note: eXist's update syntax is still based on some old proposals (the 
> implementation nevertheless works very well). The first XQuery update 
> drafts were published later and I had no time to adopt this stuff yet 
> (it doesn't have the highest priority for me personally).
> 
> > I'm neither sure how to specify the document I want to 
> alter (the doc()
> > function is surely wrong since it loads the file into 
> memory) nor how to
> > select the textnode using XPath (is /text() required here?).
> 
> doc("/db/myfile.xml") doesn't "load" the document into memory 
> (it is a 
> persistent document whose nodes reside on disk). It just returns a 
> reference to that document.

Great, now it works perfectly fine!

Just one thing that I find a bit strange: the entire "update value ..."
expression doesn't seem to actually return anything (though the file in
the db is altered as expected). So instead I had to introduce a
dummy-variable like this:

let $myfile := doc('/db/myfile.xml')
let $dummy := update value $myfile//subnode/text() with
	'some other text'
return $myfile

Is it supposed to be like that?
However, I'm happy with the current solution, thanks a lot for helping!
Georg

From p.vijayasekar at gmail.com  Thu Sep  4 12:42:55 2008
From: p.vijayasekar at gmail.com (Vijayasekar Palaniswamy)
Date: Wed Sep  3 23:12:47 2008
Subject: [xquery-talk] XQuery Try Catch
Message-ID: <ca31c2cb0809032312p1c1bdc4bt5b10e00f7a4a87a7@mail.gmail.com>

Hello,

Does XQuery support Try & Catch Block? or any way to create error pages?

Thanks.

-- 
Regards,

Vijayasekar. P,
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From james.fuller.2007 at gmail.com  Thu Sep  4 09:27:52 2008
From: james.fuller.2007 at gmail.com (James Fuller)
Date: Wed Sep  3 23:27:36 2008
Subject: [xquery-talk] XQuery Try Catch
In-Reply-To: <ca31c2cb0809032312p1c1bdc4bt5b10e00f7a4a87a7@mail.gmail.com>
References: <ca31c2cb0809032312p1c1bdc4bt5b10e00f7a4a87a7@mail.gmail.com>
Message-ID: <a0ad8ffe0809032327h3e2554a0p90ca3c1129739b9f@mail.gmail.com>

no, but XQuery does have the ability to throw an error using the
error() function.

also, some XQuery implementations have extension instructions to
enable try/catch like behavior.

hth, Jim Fuller

On Thu, Sep 4, 2008 at 8:12 AM, Vijayasekar Palaniswamy
<p.vijayasekar@gmail.com> wrote:
> Hello,
>
> Does XQuery support Try & Catch Block? or any way to create error pages?
>
> Thanks.
>
> --
> Regards,
>
> Vijayasekar. P,
>
>
> _______________________________________________
> talk@x-query.com
> http://x-query.com/mailman/listinfo/talk
>
From matthias.brantner at 28msec.com  Thu Sep  4 11:54:48 2008
From: matthias.brantner at 28msec.com (Matthias Brantner)
Date: Thu Sep  4 01:54:37 2008
Subject: [xquery-talk] XQuery Try Catch
In-Reply-To: <ca31c2cb0809032312p1c1bdc4bt5b10e00f7a4a87a7@mail.gmail.com>
References: <ca31c2cb0809032312p1c1bdc4bt5b10e00f7a4a87a7@mail.gmail.com>
Message-ID: <A772AE5D-DB40-4F8F-A2D7-C838B349F5C7@28msec.com>

Hello,

as far as I know, there will be a try-catch feature in an evolving  
XQuery recommendation.
The Zorba XQuery Processor already implements the latest try-catch  
proposal.

The grammar and some examples can be found on Zorba's webpage at:

http://www.zorba-xquery.com/doc/zorba-0.9.2/zorba/html/trycatch.html

Regards,
Matthias

On 04.09.2008, at 08:12, Vijayasekar Palaniswamy wrote:

> Hello,
>
> Does XQuery support Try & Catch Block? or any way to create error  
> pages?
>
> Thanks.
>
> -- 
> Regards,
>
> Vijayasekar. P,
>
> _______________________________________________
> talk@x-query.com
> http://x-query.com/mailman/listinfo/talk

From james.fuller.2007 at gmail.com  Thu Sep  4 12:04:54 2008
From: james.fuller.2007 at gmail.com (James Fuller)
Date: Thu Sep  4 13:05:17 2008
Subject: [xquery-talk] XQuery Try Catch
In-Reply-To: <A772AE5D-DB40-4F8F-A2D7-C838B349F5C7@28msec.com>
References: <ca31c2cb0809032312p1c1bdc4bt5b10e00f7a4a87a7@mail.gmail.com>
	<A772AE5D-DB40-4F8F-A2D7-C838B349F5C7@28msec.com>
Message-ID: <a0ad8ffe0809040204s19bdafe2t85aa3a62ac88cce8@mail.gmail.com>

On Thu, Sep 4, 2008 at 10:54 AM, Matthias Brantner
<matthias.brantner@28msec.com> wrote:
> Hello,
>
> as far as I know, there will be a try-catch feature in an evolving XQuery
> recommendation.

I think you are speaking about working drafts, not recommendations ;)

> The Zorba XQuery Processor already implements the latest try-catch proposal.
>
> The grammar and some examples can be found on Zorba's webpage at:
>
> http://www.zorba-xquery.com/doc/zorba-0.9.2/zorba/html/trycatch.html

good stuff, will take a look at this processor.

cheers, Jim Fuller
From michael.reiche at oracle.com  Thu Sep  4 14:20:44 2008
From: michael.reiche at oracle.com (Michael Reiche)
Date: Thu Sep  4 13:21:48 2008
Subject: [xquery-talk] XQuery Try Catch
In-Reply-To: <a0ad8ffe0809040204s19bdafe2t85aa3a62ac88cce8@mail.gmail.com>
References: <ca31c2cb0809032312p1c1bdc4bt5b10e00f7a4a87a7@mail.gmail.com>	<A772AE5D-DB40-4F8F-A2D7-C838B349F5C7@28msec.com>
	<a0ad8ffe0809040204s19bdafe2t85aa3a62ac88cce8@mail.gmail.com>
Message-ID: <20080904132044312.00000001852@mreiche05>

 
Oracle Data Service Integrator (formerly BEA Aqualogic Data Services Platform) has a try/catch statement in XQSE.

http://e-docs.bea.com/aldsp/docs30/xquery/xqse.html#wp1026739

It also has fail-over and time-out functions in Xquery.

http://e-docs.bea.com/aldsp/docs30/xquery/extensions.html#wp1301838


Mike


From matthias.brantner at 28msec.com  Thu Sep  4 13:35:14 2008
From: matthias.brantner at 28msec.com (Matthias Brantner)
Date: Thu Sep  4 13:38:57 2008
Subject: [xquery-talk] XQuery Try Catch
In-Reply-To: <555522.27836.qm@web23008.mail.ird.yahoo.com>
References: <555522.27836.qm@web23008.mail.ird.yahoo.com>
Message-ID: <F11FF0E0-D89D-49FA-89D8-F1B2AACFD033@28msec.com>

>> The grammar and some examples can be found on Zorba's webpage at:
>
>> http://www.zorba-xquery.com/doc/zorba-0.9.2/zorba/html/trycatch.html
>
>  The grammar looks weird.  I guess:
>
>    TryCatchExpr ::= CatchClause+
>
> should rather be:
>
>    TryCatchExpr ::= TryClause CatchClause+
Thanks! I've fixed the page.

Matthias
From ron.hitchens at marklogic.com  Thu Sep  4 14:45:30 2008
From: ron.hitchens at marklogic.com (Ron Hitchens)
Date: Thu Sep  4 13:44:24 2008
Subject: [xquery-talk] XQuery Try Catch
In-Reply-To: <ca31c2cb0809032312p1c1bdc4bt5b10e00f7a4a87a7@mail.gmail.com>
References: <ca31c2cb0809032312p1c1bdc4bt5b10e00f7a4a87a7@mail.gmail.com>
Message-ID: <62EC9CB4-FF1F-4027-AC57-43CD99DCE0F9@marklogic.com>


   Mark Logic has had try/catch for years.  Customizable
error page handlers (which let you tailor an error response
without changing the code that throws the exception) are
planned for our upcoming release.

On Sep 3, 2008, at 11:12 PM, Vijayasekar Palaniswamy wrote:

> Hello,
>
> Does XQuery support Try & Catch Block? or any way to create error  
> pages?
>
> Thanks.
>
> -- 
> Regards,
>
> Vijayasekar. P,
>
> _______________________________________________
> talk@x-query.com
> http://x-query.com/mailman/listinfo/talk

---
Ron Hitchens {ron.hitchens@marklogic.com}  650-655-2351




From lists at fgeorges.org  Thu Sep  4 13:26:45 2008
From: lists at fgeorges.org (Florent Georges)
Date: Thu Sep  4 14:32:18 2008
Subject: [xquery-talk] XQuery Try Catch
In-Reply-To: <A772AE5D-DB40-4F8F-A2D7-C838B349F5C7@28msec.com>
Message-ID: <555522.27836.qm@web23008.mail.ird.yahoo.com>

Matthias Brantner wrote:

  Hi

>The grammar and some examples can be found on Zorba's webpage at:

>http://www.zorba-xquery.com/doc/zorba-0.9.2/zorba/html/trycatch.html

  The grammar looks weird.  I guess:

    TryCatchExpr ::= CatchClause+

should rather be:

    TryCatchExpr ::= TryClause CatchClause+

  ;-)

  Regards,

--drkm






















      
From mike at saxonica.com  Mon Sep  8 13:25:06 2008
From: mike at saxonica.com (Michael Kay)
Date: Mon Sep  8 04:25:07 2008
Subject: [xquery-talk] Need some theory help
Message-ID: <835A3C3322A74A71BE251BBA87E0CC08@Sealion>

I've asked this in the past on other lists without success; in the hope that
this list is a better place to find some theoreticians, I'll ask it again
here.

Given general expressions E,F,G, I believe it is true that the following two
expressions are equivalent:

E/F union E/G <=> E/(F union G)

(That is, union distributes through "/")

But this is not true for "except".

$a/descendant::*/child::b except $a/descendant::*/(child::c/child::b)

is not the same as

a/descendant::*/(child::b except child::c/child::b)

(easily seen because child::c/child::b will not select any nodes that are
selected by child::b).

Questions:

(a) How would you prove that "union" distributes through "/" and "except"
does not? (Assuming my conjecture is correct, of course)

(b) What about "intersect": does it distribute or not?

(c) Is there a restricted class of path expressions for which "except" does
distribute through "/" (for example, path expressions that only use the
child axis)? How large can you make that class?

Clearly these questions are all directly relevant to the expression rewrites
that an optimizer can perform safely.

Michael Kay
Saxonica




From lists at fgeorges.org  Mon Sep  8 15:08:53 2008
From: lists at fgeorges.org (Florent Georges)
Date: Mon Sep  8 05:09:30 2008
Subject: [xquery-talk] Need some theory help
In-Reply-To: <835A3C3322A74A71BE251BBA87E0CC08@Sealion>
Message-ID: <236755.36200.qm@web23002.mail.ird.yahoo.com>

Michael Kay wrote:

  Hi Michael,

> Given general expressions E,F,G, I believe it is true that
> the following two expressions are equivalent:

> E/F union E/G <=> E/(F union G)

> (That is, union distributes through "/")

> But this is not true for "except".

> $a/descendant::*/child::b except $a/descendant::*/(child::c/child::b)

> is not the same as

> a/descendant::*/(child::b except child::c/child::b)

> (easily seen because child::c/child::b will not select any
> nodes that are selected by child::b).

  I am not really a theoretician, but I feel this problem is
related to the descendant axis rather than the set operations
(union, except...)

  Intuitively, I would say that "E//F x E//G" (for some
operator x) is not the same as "E//(F x G)" because in the
later "F x G" is 'anchored' at particular nodes, where in the
former two sequences are built then the operator is applied.

  For the union, I guess this leads into the same result
(intuitively again), but it doesn't with the difference (the
except operator.)

  Maybe using only a subset of axises to try to prove your
assertions could help find the way?

  Regards,

--drkm





















      
From davidc at nag.co.uk  Mon Sep  8 14:19:31 2008
From: davidc at nag.co.uk (David Carlisle)
Date: Mon Sep  8 05:20:08 2008
Subject: [xquery-talk] Need some theory help
In-Reply-To: <835A3C3322A74A71BE251BBA87E0CC08@Sealion> (mike@saxonica.com)
References: <835A3C3322A74A71BE251BBA87E0CC08@Sealion>
Message-ID: <200809081219.m88CJVI1015337@edinburgh.nag.co.uk>


> (b) What about "intersect": does it distribute or not?

I think not, for the same reason that except does not.

$a/descendant::*/child::b intersect $a/descendant::*/(child::c/child::b)

is

$a/descendant::*/(child::c/child::b)

but 

a/descendant::*/(child::b intersect child::c/child::b)

is empty, because

> (easily seen because child::c/child::b will not select any nodes that are
> selected by child::b).


> (a) How would you prove that "union" distributes through "/" and "except"
> does not? (Assuming my conjecture is correct, of course)

something along the lines of semantics of

E/F is Union{f(e) | e in E} where you think of F as a function from a single
item e in E to a node set so
E/F union E/G is Union{f(e) | e in E} union Union{g(e) | e in E}
wheras
E/(F union G) is Union{fug(e) | e in E}
where fug is the function from a node to a node set defined by
fug(e) = f(e) union g(e).

then some general mutterings about union distributing over union.

(this is using xpath 1 node set terminology, but xpath2 sequence +
implied removal of duplicates for path operators is supposed to model
set semantics here.

David

________________________________________________________________________
The Numerical Algorithms Group Ltd is a company registered in England
and Wales with company number 1249803. The registered office is:
Wilkinson House, Jordan Hill Road, Oxford OX2 8DR, United Kingdom.

This e-mail has been scanned for all viruses by Star. The service is
powered by MessageLabs. 
________________________________________________________________________
From int19h at gmail.com  Mon Sep  8 19:11:14 2008
From: int19h at gmail.com (Pavel Minaev)
Date: Mon Sep  8 07:11:48 2008
Subject: [xquery-talk] Type system extensions: best syntax for foreign
	generic types
In-Reply-To: <d5c61a20809080702of7bc36n739aea057ae94d55@mail.gmail.com>
References: <d5c61a20809080702of7bc36n739aea057ae94d55@mail.gmail.com>
Message-ID: <d5c61a20809080711vafea33dgb12085e208596b47@mail.gmail.com>

Hi,

I'm working on a conforming XQuery implementation for the .NET
platform. Naturally, to be useful, it would require first-class
interop with .NET libraries, both stock and third-party. I've seen the
way Saxon does it, but I'd rather have the entire .NET type system
available for use in XQuery - so that you could not just call a .NET
method, but declare an XQuery function that takes a reference to a
.NET object, and so on. It seems that XQuery spec gives specific
permission to do this sort of thing:

"An XQuery implementation may augment the type system of [XQuery/XPath
Data Model (XDM)] with additional types that are designed to
facilitate exchange of data with host programming languages, or it may
provide mechanisms for the user to define such types. For example, a
type might be provided that encapsulates an object returned by an
external function, such as an SQL database connection. These
additional types, if defined, are considered to be derived by
restriction from xs:anyAtomicType."

So far, so good. Initially, I wanted to map .NET namespaces directly
to XML namespaces (using the same "clr-namespace" URI schema that
Microsoft uses for XAML for the same purpose), .NET types directly to
xs:anyAtomicType-derived final XML Schema types, and methods to
functions by prefixing their names with class name and dot. An example
of such mapping would be:

 declare namespace sys = "clr-namespace:System;assembly=mscorlib";
 declare function local:foo(s as sys:String) {
   sys:String.ToLower(s)
 };

This seems to work fine and look nice, but problems begin when generic
types are brought into the picture. XQuery has its own set of what are
effectively parametrized types (e.g., element(...)), but it is a
closed, non-extensible set. I considered a language extension,
something along these lines:

 (: The corresponding .NET type is System.Func<System.String, System.Int32> :)
 declare function local:foo(fun as generic-instance(sys:Func,
sys:String, sys:Int32)) { ... };

The problem is that there is nothing in XQuery spec to guarantee that
this won't clash with any future language developments. Nor does it
seem to be possible to namespace-qualify "generic-instance" here in an
extensible way (who's to say that a future XQuery version won't allow
something like xs:integer(1, 100) as a type?). And I would really like
to stay within the boundaries permitted, either explicitly or
implicitly, by the standard.

It seems that a more "proper" way to handle this is via "declare
option". Perhaps something along the lines of:

 (: Instantiate and bind to name :)
 declare option my:generic-instance "local:FuncOfStringToInt32 =
sys:Func(sys:String, sys:Int32)";
 (: Use the bound name :)
 declare function local:foo(fun as local:FuncOfStringToInt32) { ... };

However, this seems to be a particularly verbose and ugly way of doing it.

I'm also considering just dropping the idea of mapping namespaces
altogether, and requiring fully qualified names for everything, all
mapped to a single namespace such as "clr". Some name mangling could
be devised for generics, as well. For example:

 declare namespace clr = "urn:uuid:...";
 declare function local:foo(fun as
clr:System.Action-of-System.String-and-System.Int32) as
clr:System.Object { ... }

Also verbose, but still (IMO) easier to understand than the mapping.

Which approach would you recommend? Is one of the methods outlined
above preferrable, or perhaps there is some other more intuitive
schema? Or, perhaps some extensibility hooks in XQuery spec that I've
missed that allow me to do what I want?
From mike at saxonica.com  Mon Sep  8 17:04:24 2008
From: mike at saxonica.com (Michael Kay)
Date: Mon Sep  8 08:04:59 2008
Subject: [xquery-talk] Type system extensions: best syntax for
	foreigngeneric types
In-Reply-To: <d5c61a20809080711vafea33dgb12085e208596b47@mail.gmail.com>
References: <d5c61a20809080702of7bc36n739aea057ae94d55@mail.gmail.com>
	<d5c61a20809080711vafea33dgb12085e208596b47@mail.gmail.com>
Message-ID: <1482D79CD6904AD693C5C955209E2839@Sealion>

> I'm working on a conforming XQuery implementation for the 
> .NET platform. Naturally, to be useful, it would require 
> first-class interop with .NET libraries, both stock and 
> third-party. I've seen the way Saxon does it, but I'd rather 
> have the entire .NET type system available for use in XQuery 
> - so that you could not just call a .NET method, but declare 
> an XQuery function that takes a reference to a .NET object, 
> and so on.

Saxon can in fact do this. But it doesn't yet handle generics.

> An example of such 
> mapping would be:
> 
>  declare namespace sys = "clr-namespace:System;assembly=mscorlib";
>  declare function local:foo(s as sys:String) {
>    sys:String.ToLower(s)
>  };

For method calling, Saxon maps an XML namespace to each .NET class, not to
each external package or namespace. And for the name of the type, it uses a
single namespace http://saxon.sf.net/clitype. So this would be (without
generics)

declare namespace dotnet="http://saxon.sf.net/clitype";
declare namespace System.String = "clitype:System.String?asm=mscorlib";
declare function local:foo(s as dotnet:System.String) {
   System.String:ToLower(s)
};

This can potentially lead to a lot of namespaces; but it that's the case,
then I think you are over-using the facility for calling extension functions
and should reexamine your application design.
> 
> This seems to work fine and look nice, but problems begin 
> when generic types are brought into the picture. 

Agreed, there's no easy answer to this. I think my preferred solution is to
not bring them into the picture. Mappings to external type systems are never
going to be perfect. Alternatively, I would be inclined to use "declare
option" to declare a local name for an external type:

declare option saxon:type-alias "my:listOfString =
System.Collections.List<System.String>";

declare function local:foo(s as my:listOfString) {
  ...
}

or perhaps even to define some kind of mapping language that contains these
type mappings in an external file, which can then be imported. XSD 1.1
allows user-defined primitive types, so that could provide the basis of a
mechanism.

> I considered a language extension, something along these lines:
> 
>  (: The corresponding .NET type is System.Func<System.String, 
> System.Int32> :)  declare function local:foo(fun as 
> generic-instance(sys:Func, sys:String, sys:Int32)) { ... };

There seems to be an attitude among XQuery implementors that extending the
syntax is OK. Personally I regard it as very undesirable. It's not possible
for Saxon in any case, because I am implementing XSLT as well as XQuery, and
private syntax in XSLT is both banned by the spec, and considered
unacceptable by the user community. 
> 
> The problem is that there is nothing in XQuery spec to 
> guarantee that this won't clash with any future language 
> developments. 

Which is one reason why XSLT bans it...
> 

Michael Kay
http://www.saxonica.com/

From int19h at gmail.com  Tue Sep  9 23:15:39 2008
From: int19h at gmail.com (Pavel Minaev)
Date: Tue Sep  9 11:14:02 2008
Subject: [xquery-talk] Type system extensions: best syntax for
	foreigngeneric types
In-Reply-To: <1482D79CD6904AD693C5C955209E2839@Sealion>
References: <d5c61a20809080702of7bc36n739aea057ae94d55@mail.gmail.com>
	<d5c61a20809080711vafea33dgb12085e208596b47@mail.gmail.com>
	<1482D79CD6904AD693C5C955209E2839@Sealion>
Message-ID: <d5c61a20809091115l6fb40de3w9b641a60a00ea016@mail.gmail.com>

On Mon, Sep 8, 2008 at 7:04 PM, Michael Kay <mike@saxonica.com> wrote:
>> .NET platform. Naturally, to be useful, it would require
>> first-class interop with .NET libraries, both stock and
>> third-party. I've seen the way Saxon does it, but I'd rather
>> have the entire .NET type system available for use in XQuery
>> - so that you could not just call a .NET method, but declare
>> an XQuery function that takes a reference to a .NET object,
>> and so on.
>
> Saxon can in fact do this. But it doesn't yet handle generics.

Actually, it is half-way there. This works on Saxon 9.1 for .NET:

 declare namespace nul = "clitype:System.Nullable`1[System.Int32]";
 let $x := nul:new(123)
 return nul:HasValue($x)

though there is still no way to use generic type name on its own in a
declaration or a cast.

> For method calling, Saxon maps an XML namespace to each .NET class, not to
> each external package or namespace. And for the name of the type, it uses a
> single namespace http://saxon.sf.net/clitype. So this would be (without
> generics)
>
> declare namespace dotnet="http://saxon.sf.net/clitype";
> declare namespace System.String = "clitype:System.String?asm=mscorlib";
> declare function local:foo(s as dotnet:System.String) {
>   System.String:ToLower(s)
> };

Ah, I do apologize; I was aware of the function/method mapping from my
past experience with Saxon XSLT (it proved to be very handy back
then), but I was not aware about the types, probably because they
aren't really all that useful on their own.

> This can potentially lead to a lot of namespaces; but it that's the case,
> then I think you are over-using the facility for calling extension functions
> and should reexamine your application design.

Well, let me explain why I want the feature in the first place, and
why it is an important one for the scenarios considered. I'm not
merely trying to write yet another XQuery implementation in .NET; what
I want is to come up with an implementation that is an (almost)
first-class .NET citizen, with XQuery modules being statically
compiled to .NET assemblies with straightforward mapping, XDM types
mapped to .NET types where possible, and so on. The intended use case
is to refactor complex XML processing into XQuery modules, which are
compiled to .NET classes that are immediately usable from C#/VB/... -
so you could write this:

 module namespace foo = "clr-namespace:Acme.Foo";
 import schema namespace mytypes = "mytypes.xsd";
 declare function foo:Bar($customer as
schema-element(mytypes:customer)) as xs:int { ... };

and then use it like this:

 using Acme.Foo;
 XmlDocument doc = new XmlDocument();
 doc.Load("customer.xml");
 doc.Schemas.Add(null, "mytypes.xsd");
 doc.Validate();
 Module foo = new Module();
 int bar = foo.Bar(doc.DocumentElement);

With this approach, it's much more common for foreign code to call
into XQuery code than vice versa. However, it would be a typical
scenario to have XQuery functions that would take raw or typed XML
nodes, parse or otherwise process them, and build object graphs from
the data, e.g.:

 declare namespace acme = "clr-namespace:Acme";
 declare function parse-customer($cust as element(Customer)) as
acme:Customer? { ... };

and this requires an expressive way to use arbitrary .NET types in
function signatures.

> There seems to be an attitude among XQuery implementors that extending the
> syntax is OK. Personally I regard it as very undesirable.

That was the main reasoning behind my post. No matter what, I consider
compliance to the spec first priority; therefore, while I would like
an easy way out, I'm not going to take one that is not permissible
within the boundaries of the spec. I was just wondering whether I
indeed correctly understood their restrictiveness.

By the way, it seems rather strange to me that there are explicit
extensibility points for some elements of the language - "declare
option" for global stuff, and expression-scope pragmas - but no
similar mechanisms to decorate type references, or function
declarations. Is it a deliberate design decision, or just something
that was not considered because of the (then) seeming lack of need of
such a thing?
From rob at koberg.com  Tue Sep  9 21:58:42 2008
From: rob at koberg.com (Robert Koberg)
Date: Tue Sep  9 17:57:00 2008
Subject: [xquery-talk] cross implementation XQuery
Message-ID: <8A8763F1-F500-4007-9D2E-AA0C4F6F48F6@koberg.com>

Hi,

How do you write XQuery in a cross processor/implementation way? It  
seems (to me) that you need extension functions. For example, you want  
to write a XQuery based webapp that might be be used by 2 or more  
processors/XMLDBs.

Do you keep webapp logic out of your XQuery?

Is there a cross processor equivalent to XSL's function-available()?

Do you create generic functions mapping to various impl specific  
functions, place those in impl specific import modules, and use a  
custom URIResolver to resolve imports based on the impl? Do  
implementations have a standard way to assign these resolvers?

Other ways?

best,
-Rob
From rob at koberg.com  Tue Sep  9 22:01:36 2008
From: rob at koberg.com (Robert Koberg)
Date: Tue Sep  9 17:59:50 2008
Subject: [xquery-talk] FLOR or FLWOR
Message-ID: <889FFFD6-3BBB-435A-A9B3-679797354799@koberg.com>

Hi,

Where would you use 'where' that couldn't be handled by XPath? In  
other words, why is there a where?

best,
-Rob
From mike at saxonica.com  Wed Sep 10 09:53:16 2008
From: mike at saxonica.com (Michael Kay)
Date: Wed Sep 10 00:51:39 2008
Subject: [xquery-talk] FLOR or FLWOR
In-Reply-To: <889FFFD6-3BBB-435A-A9B3-679797354799@koberg.com>
References: <889FFFD6-3BBB-435A-A9B3-679797354799@koberg.com>
Message-ID: <B04A1CC488BE4552ACA9D2329D37CF5E@Sealion>

> 
> Where would you use 'where' that couldn't be handled by 
> XPath? In other words, why is there a where?
> 

Because people coming from the world of SQL and other database query
languages (e.g. OQL) thought that anything that calls itself a query
language ought to have a WHERE clause.

Apparently people who have spent years writing SQL not only find it easy to
bundle together all the search conditions into one humungous boolean
expression, they actually come to believe it is a good idea.

Historically, remember that early proposals for XQuery (based on XQL etc)
didn't build on XPath, they were developed independently. 

Michael Kay
http://www.saxonica.com/

From mike at saxonica.com  Wed Sep 10 09:59:02 2008
From: mike at saxonica.com (Michael Kay)
Date: Wed Sep 10 00:57:20 2008
Subject: [xquery-talk] cross implementation XQuery
In-Reply-To: <8A8763F1-F500-4007-9D2E-AA0C4F6F48F6@koberg.com>
References: <8A8763F1-F500-4007-9D2E-AA0C4F6F48F6@koberg.com>
Message-ID: <145E6E5A315A431E893E20BD2DA5CA64@Sealion>


Personally, I don't think you should try to write entire applications in
XQuery. You should use XQuery for tasks that it is good at, and then
integrate the application using some other level of technology, for example
a pipeline processor. This way I think there is far less need to do anything
platform-dependent in the XQuery logic, and you end up with XQuery code that
is much more versatile and reusable.

Perhaps the main reason for this view is the absence of any dynamic despatch
mechanism in XQuery. This makes it very hard to write XQuery code that is
capable of doing more than one job, or of doing the same job in different
circumstances.

I've seen it done by compile-time manipulation of "import module" in the way
you suggest, but it's no fun.

Michael Kay
http://www.saxonica.com/ 

> -----Original Message-----
> From: talk-bounces@x-query.com 
> [mailto:talk-bounces@x-query.com] On Behalf Of Robert Koberg
> Sent: 10 September 2008 01:59
> To: talk@x-query.com
> Subject: [xquery-talk] cross implementation XQuery
> 
> Hi,
> 
> How do you write XQuery in a cross processor/implementation 
> way? It seems (to me) that you need extension functions. For 
> example, you want to write a XQuery based webapp that might 
> be be used by 2 or more processors/XMLDBs.
> 
> Do you keep webapp logic out of your XQuery?
> 
> Is there a cross processor equivalent to XSL's function-available()?
> 
> Do you create generic functions mapping to various impl 
> specific functions, place those in impl specific import 
> modules, and use a custom URIResolver to resolve imports 
> based on the impl? Do implementations have a standard way to 
> assign these resolvers?
> 
> Other ways?
> 
> best,
> -Rob
> _______________________________________________
> talk@x-query.com
> http://x-query.com/mailman/listinfo/talk

From timothymarc at freenet.de  Wed Sep 10 12:02:27 2008
From: timothymarc at freenet.de (timothymarc@freenet.de)
Date: Wed Sep 10 02:08:31 2008
Subject: [xquery-talk] FLOR or FLWOR
Message-ID: <E1KdLal-0006WR-A8@www3.emo.freenet-rz.de>

Hey Rob,

i have had a situation in where the XPath predicate selection does not fit my requirements. I think it was something concerning a query, that combines to sequences, but i'm not sure. It is a long time ago and i can't find the example.

But the where is essential in some case. But you're right, most of the selections can be done with XPath.

HTH
Timothy
----- original Nachricht --------

Betreff: [xquery-talk] FLOR or FLWOR
Gesendet: Mi 10 Sep 2008 03:02:44 CEST
Von: "Robert Koberg"<rob@koberg.com>

> Hi,
> 
> Where would you use 'where' that couldn't be handled by XPath? In  
> other words, why is there a where?
> 
> best,
> -Rob
> _______________________________________________
> talk@x-query.com
> http://x-query.com/mailman/listinfo/talk
> 

--- original Nachricht Ende ----


From remi at gide.net  Wed Sep 10 12:35:05 2008
From: remi at gide.net (=?UTF-8?Q?R=C3=A9mi_Dewitte?=)
Date: Wed Sep 10 02:33:20 2008
Subject: [xquery-talk] FLOR or FLWOR
In-Reply-To: <E1KdLal-0006WR-A8@www3.emo.freenet-rz.de>
References: <E1KdLal-0006WR-A8@www3.emo.freenet-rz.de>
Message-ID: <2184b2340809100235x3a888637gcce672cce9a6dd4c@mail.gmail.com>

Hi,
I do have an example. Correct ?

for $v in distinct-values($values) where count($values[. = $v]) > 2 return
$v

R?mi

On Wed, Sep 10, 2008 at 11:02 AM, <timothymarc@freenet.de> wrote:

> Hey Rob,
>
> i have had a situation in where the XPath predicate selection does not fit
> my requirements. I think it was something concerning a query, that combines
> to sequences, but i'm not sure. It is a long time ago and i can't find the
> example.
>
> But the where is essential in some case. But you're right, most of the
> selections can be done with XPath.
>
> HTH
> Timothy
> ----- original Nachricht --------
>
> Betreff: [xquery-talk] FLOR or FLWOR
> Gesendet: Mi 10 Sep 2008 03:02:44 CEST
> Von: "Robert Koberg"<rob@koberg.com>
>
> > Hi,
> >
> > Where would you use 'where' that couldn't be handled by XPath? In
> > other words, why is there a where?
> >
> > best,
> > -Rob
> > _______________________________________________
> > talk@x-query.com
> > http://x-query.com/mailman/listinfo/talk
> >
>
> --- original Nachricht Ende ----
>
>
> _______________________________________________
> talk@x-query.com
> http://x-query.com/mailman/listinfo/talk
>
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From mike at saxonica.com  Wed Sep 10 12:01:15 2008
From: mike at saxonica.com (Michael Kay)
Date: Wed Sep 10 02:59:36 2008
Subject: [xquery-talk] FLOR or FLWOR
In-Reply-To: <2184b2340809100235x3a888637gcce672cce9a6dd4c@mail.gmail.com>
References: <E1KdLal-0006WR-A8@www3.emo.freenet-rz.de>
	<2184b2340809100235x3a888637gcce672cce9a6dd4c@mail.gmail.com>
Message-ID: <B8D6AAC6B77B4DA1B64D2D63D48D6577@Sealion>

There are some cases where using a predicate may be inconvenient, but it is
always possible. This query is equivalent to 
 
distinct-values($values)[let $v := . return count($values[. = $v] > 2]
 
or if you prefer (or if you are restricted to XPath 2.0 syntax)
 
distinct-values($values)[exists(index-of($values, .))[3]]
 
Michael Kay
http://www.saxonica.com/
 
 


  _____  

From: talk-bounces@x-query.com [mailto:talk-bounces@x-query.com] On Behalf
Of R?mi Dewitte
Sent: 10 September 2008 10:35
To: timothymarc@freenet.de
Cc: Robert Koberg; talk@x-query.com
Subject: Re: [xquery-talk] FLOR or FLWOR


Hi,
I do have an example. Correct ?

for $v in distinct-values($values) where count($values[. = $v]) > 2 return
$v

R?mi


On Wed, Sep 10, 2008 at 11:02 AM, <timothymarc@freenet.de> wrote:


Hey Rob,

i have had a situation in where the XPath predicate selection does not fit
my requirements. I think it was something concerning a query, that combines
to sequences, but i'm not sure. It is a long time ago and i can't find the
example.

But the where is essential in some case. But you're right, most of the
selections can be done with XPath.

HTH
Timothy
----- original Nachricht --------

Betreff: [xquery-talk] FLOR or FLWOR
Gesendet: Mi 10 Sep 2008 03:02:44 CEST
Von: "Robert Koberg"<rob@koberg.com>

> Hi,

>
> Where would you use 'where' that couldn't be handled by XPath? In
> other words, why is there a where?
>

> best,
> -Rob

> _______________________________________________
> talk@x-query.com
> http://x-query.com/mailman/listinfo/talk
>


--- original Nachricht Ende ----



_______________________________________________
talk@x-query.com
http://x-query.com/mailman/listinfo/talk



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From davidc at nag.co.uk  Wed Sep 10 12:11:20 2008
From: davidc at nag.co.uk (David Carlisle)
Date: Wed Sep 10 03:09:39 2008
Subject: [xquery-talk] FLOR or FLWOR
In-Reply-To: <2184b2340809100235x3a888637gcce672cce9a6dd4c@mail.gmail.com>
	(remi@gide.net)
References: <E1KdLal-0006WR-A8@www3.emo.freenet-rz.de>
	<2184b2340809100235x3a888637gcce672cce9a6dd4c@mail.gmail.com>
Message-ID: <200809101011.m8AABKHA007267@edinburgh.nag.co.uk>



> I do have an example. Correct ?


> for $v in distinct-values($values) where count($values[. = $v]) > 2
> return $v

But that is a typical example where the where clause is not needed.

it is

distinct-values($values)[let $v := . return count($values[. = $v]) > 2]

or simpler

distinct-values($values)[let $v := . return $values[. = $v][2]]


It is possible to come up with cases where where is theoretically more
expressive as it has access to the full tuple stream, but they temd to
be rather artificial.

David



________________________________________________________________________
The Numerical Algorithms Group Ltd is a company registered in England
and Wales with company number 1249803. The registered office is:
Wilkinson House, Jordan Hill Road, Oxford OX2 8DR, United Kingdom.

This e-mail has been scanned for all viruses by Star. The service is
powered by MessageLabs. 
________________________________________________________________________
From mike at saxonica.com  Wed Sep 10 13:40:07 2008
From: mike at saxonica.com (Michael Kay)
Date: Wed Sep 10 04:38:26 2008
Subject: [xquery-talk] FLOR or FLWOR
In-Reply-To: <200809101011.m8AABKHA007267@edinburgh.nag.co.uk>
References: <E1KdLal-0006WR-A8@www3.emo.freenet-rz.de><2184b2340809100235x3a888637gcce672cce9a6dd4c@mail.gmail.com>
	<200809101011.m8AABKHA007267@edinburgh.nag.co.uk>
Message-ID: <12DAFF3D859849B1B203974DC850E066@Sealion>

> 
> or simpler
> 
> distinct-values($values)[let $v := . return $values[. = $v][2]]
> 

I think you need an exists() call there - a value might be 0 or "" or
false().

Michael Kay
http://www.saxonica.com/

From davidc at nag.co.uk  Wed Sep 10 13:48:27 2008
From: davidc at nag.co.uk (David Carlisle)
Date: Wed Sep 10 04:41:54 2008
Subject: [xquery-talk] FLOR or FLWOR
In-Reply-To: <12DAFF3D859849B1B203974DC850E066@Sealion> (mike@saxonica.com)
References: <E1KdLal-0006WR-A8@www3.emo.freenet-rz.de><2184b2340809100235x3a888637gcce672cce9a6dd4c@mail.gmail.com>
	<200809101011.m8AABKHA007267@edinburgh.nag.co.uk>
	<12DAFF3D859849B1B203974DC850E066@Sealion>
Message-ID: <200809101148.m8ABmRKg008948@edinburgh.nag.co.uk>


> I think you need an exists() call there - a value might be 0 or "" or
> false().

blurg. Who's idea was it to allow atomic values in node sets//////
sequences:-)

You are quite right of course, also it should be [3] not [2] to match
the original expression.

David

________________________________________________________________________
The Numerical Algorithms Group Ltd is a company registered in England
and Wales with company number 1249803. The registered office is:
Wilkinson House, Jordan Hill Road, Oxford OX2 8DR, United Kingdom.

This e-mail has been scanned for all viruses by Star. The service is
powered by MessageLabs. 
________________________________________________________________________
From hrennau at yahoo.de  Mon Sep 15 04:49:00 2008
From: hrennau at yahoo.de (Hans-Juergen Rennau)
Date: Sun Sep 14 20:49:41 2008
Subject: [xquery-talk] FLOR or FLWOR
Message-ID: <896798.43388.qm@web27104.mail.ukl.yahoo.com>

>> 
>> or simpler
>> 
>> distinct-values($values)[let $v := . return $values[. = $v][2]]
>> 

>I think you need an exists() call there - a value might be 0 or "" or
>false().
>
>Michael Kay
>http://www.saxonica.com/


Not to mention the danger of $values containing atomic values of a type for which the Effective Boolean Value is not defined, that is, any non-numeric type other than xs:string or xs:boolean!

With kind regards,
Hans-Juergen Rennau


__________________________________________________
Do You Yahoo!?
Sie sind Spam leid? Yahoo! Mail verf?gt ?ber einen herausragenden Schutz gegen Massenmails. 
http://mail.yahoo.com 

From hrennau at yahoo.de  Mon Sep 15 05:54:42 2008
From: hrennau at yahoo.de (Hans-Juergen Rennau)
Date: Sun Sep 14 21:55:21 2008
Subject: [xquery-talk] RE: FLOR or FLWOR
Message-ID: <368715.86375.qm@web27105.mail.ukl.yahoo.com>

Hello, Rob,

it seems to me important to remember two facts about FLWOR expressions:
a) they may not only create loops but procure intermediate results (via let clause)
b) to remove a tuple from the tuple stream, a predicate has to be placed in a for clause

If the filter condition refers to such an intermediate result, it is very convenient that we have the where, because otherwise we would have to create the intermediary twice: once to procure the predicate (as part of a for loop), and once to be used later on (as a let clause).

As an illustration consider this query:

(:---------------------------------------------------------------------------------------:) 
  string-join(
   for $owner in distinct-values(//ContainerDataList/@EIGT)
   let $nrs := distinct-values(//ContainerDataList[@EIGT eq $owner]/@CONR)
   where count($nrs) le 2
   order by $owner 
   return (
     concat($owner, "  (", count($nrs), ")"),
     for $n in $nrs return concat("            ", $n)
   )
, "&#xA;")
(:---------------------------------------------------------------------------------------:) 


 The intermediate ($nrs) is definitely needed later on, and the filter condition refers to it. To replace the where by a predicate, one would end up with something like this:

 (:---------------------------------------------------------------------------------------:) 
 string-join(
   let $in := .
   for $owner in distinct-values(//ContainerDataList/@EIGT)
      [let $o := . return count(distinct-values($in//ContainerDataList[@EIGT eq $o]/@CONR)) le 2]
   let $nrs := distinct-values(//ContainerDataList[@EIGT eq $owner]/@CONR)
   order by $owner 
   return (
     concat($owner, "  (", count($nrs), ")"),
     for $n in $nrs return concat("       ", $n)
   )
, "&#xA;")
(:---------------------------------------------------------------------------------------:) 

which is horrible, isn't it? The alternative would be to introduce an artificial for clause:

(:---------------------------------------------------------------------------------------:) 
  string-join(
   for $owner in distinct-values(//ContainerDataList/@EIGT)
   let $nrs := distinct-values(//ContainerDataList[@EIGT eq $owner]/@CONR)
   for $dummy in 1[count($nrs) le 1]
   return (
     concat($owner, "  (", count($nrs), ")"),
     for $n in $nrs return concat("       ", $n)
   )
, "&#xA;")
(:---------------------------------------------------------------------------------------:) 


If anyone considers this an acceptable alternative to a where clause, I give up.

With kind regards -
Hans-Juergen Rennau

> Message: 2
>Date: Tue, 9 Sep 2008 21:01:36 -0400
>  From: Robert Koberg <rob@koberg.com>
> Subject: [xquery-talk] FLOR or FLWOR
> To: talk@x-query.com
> Message-ID: <889FFFD6-3BBB-435A-A9B3-679797354799@koberg.com>
> Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes
>
> Hi,
> 
> Where would you use 'where' that couldn't be handled by XPath? In  
> other words, why is there a where?
>
> best,
> -Rob
***********************************


__________________________________________________
Do You Yahoo!?
Sie sind Spam leid? Yahoo! Mail verf?gt ?ber einen herausragenden Schutz gegen Massenmails. 
http://mail.yahoo.com 

From kennorth at sbcglobal.net  Fri Sep 19 13:21:08 2008
From: kennorth at sbcglobal.net (Ken North)
Date: Fri Sep 19 12:21:52 2008
Subject: [xquery-talk] Call for speakers for DataServices World closes 26
	September 2008
Message-ID: <006601c91a8c$e11eb740$2301a8c0@DURANTE>

Following the successful launch of DataServices World in New York City, we're
running the Fall event on November 20, 2008. It is co-located with SOAWorld
2008, Virtualization Conference and Cloud Computing Conference and Expo.
--------------------------------------------------------------
Call for Speakers Closes September 26, 2008

DataServices World Fall 2008
San Jose, California (November 20, 2008)

The complexities of distributed processing and the importance of middleware can
elude even senior technical people, including enterprise architects, IT
managers, consultants and designers. Enterprise developers embraced the
separation of presentation, data services and application logic. Internet
computing, cloud computing, web services and service-oriented architecture
(SOA) continue a trend towards moving data access and data integration logic
into a separate data services layer.

The data services layer, databases and data access are the focus of DataServices
World. We're looking for technical presentations about architecture and
solutions for data access and data integration from heterogeneous data sources
including XML, SQL tables, geo-coded data, content management systems,
enterprise resource planning (ERP) systems, data warehouses, and web data.

Topics of interest include:

?        Information as a service
?        Grid and cloud data services
?        Data services development: architecture, tools
?        Essential capabilities for effective, robust, secure  data services
?        Data services enabling technology: JDBC, JNDI, Hibernate,
JAX-WS, JAX-RS, DWR, LINQ, ADO.NET Entity Framework
?        End-to-end performance optimization: (database, metadata, data
distribution, caching, query tuning, load balancing, protocols, data
services)

If you're interested in speaking, you must submit a proposal by September 26,
2008.
Send your proposal to videoscribe21st-dsworld@yahoo.com. Please include:

- The presentation title and a brief abstract (< 200 words).
- Your name, title, a brief biography and complete contact information.
- A summary of your speaking experience.

Presentations and video from DataServices World in New York City (June 24,
2008):
http://www.dataservicesworld.com



======== Ken North ===========
www.KNComputing.com

www.DataServicesWorld.com
www.CloudComputingSummit.com
www.LinkedDataSummit.com
www.WebServicesSummit.com
www.SQLSummit.com
www.GridSummit.com


From D.McBeath at elsevier.com  Tue Sep 23 09:04:04 2008
From: D.McBeath at elsevier.com (McBeath, Darin W (ELS-STL))
Date: Tue Sep 23 06:05:21 2008
Subject: [xquery-talk] Leverage your XQuery skills in the Article 2.0 Contest
Message-ID: <C5EB1FEE51C01C4697222F890D5E97E603420B07@ELSSTLEXCP03VA.science.regn.net>

Elsevier Labs is inviting creative individuals who have wanted the
opportunity to view and work with scientific journal article content on
the web to enter the Elsevier Article 2.0 Contest. Each contestant will
be provided online access to approximately 7,500 full-text XML articles
from Elsevier journals, including the associated images, and the
Elsevier Article 2.0 API to develop a unique yet useful web-based
journal article rendering application.  The sample apps (including
source code) we have provided on the Article 2.0 Contest web site were
developed in XQuery.  While the contest does not mandate the use of
XQuery, our experience has shown the technology is a natural fit for
building these types of applications.

 

If you are interested in the contest, please visit the web site
(http://article20.elsevier.com <http://article20.elsevier.com/> ) and
apply for an Article 2.0 API Key.  

 

If you have any questions about the contest, drop us an email at
info-article20@elsevier.com.

 

Thanks.

 

Elsevier Labs.

 

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From remi at gide.net  Wed Sep 24 16:42:21 2008
From: remi at gide.net (=?UTF-8?Q?R=C3=A9mi_Dewitte?=)
Date: Wed Sep 24 10:06:37 2008
Subject: [xquery-talk] XQuery memoization
Message-ID: <2184b2340809240642s4c99f2fsc59e1c2e5cda606a@mail.gmail.com>

Hi all,
Is there something to apply memoization on a function to speed up multiple
calls with same arguments ?

I am using saxon 9.

Cheers,
R?mi
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From mike at saxonica.com  Wed Sep 24 22:23:52 2008
From: mike at saxonica.com (Michael Kay)
Date: Wed Sep 24 13:24:52 2008
Subject: [xquery-talk] XQuery memoization
In-Reply-To: <2184b2340809240642s4c99f2fsc59e1c2e5cda606a@mail.gmail.com>
References: <2184b2340809240642s4c99f2fsc59e1c2e5cda606a@mail.gmail.com>
Message-ID: <A3088ED7CFE44BBD8CA8218B4791F607@Sealion>

Yes. Use "declare option saxon:memo-function", see
 
http://www.saxonica.com/documentation/using-xquery/extensions.html
 
Michael Kay
Saxonica


  _____  

From: talk-bounces@x-query.com [mailto:talk-bounces@x-query.com] On Behalf
Of R?mi Dewitte
Sent: 24 September 2008 14:42
To: talk@x-query.com
Subject: [xquery-talk] XQuery memoization


Hi all,
Is there something to apply memoization on a function to speed up multiple
calls with same arguments ?

I am using saxon 9.

Cheers,
R?mi


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From remi at gide.net  Wed Sep 24 23:38:08 2008
From: remi at gide.net (=?UTF-8?Q?R=C3=A9mi_Dewitte?=)
Date: Wed Sep 24 13:39:02 2008
Subject: [xquery-talk] XQuery memoization
In-Reply-To: <A3088ED7CFE44BBD8CA8218B4791F607@Sealion>
References: <2184b2340809240642s4c99f2fsc59e1c2e5cda606a@mail.gmail.com>
	<A3088ED7CFE44BBD8CA8218B4791F607@Sealion>
Message-ID: <2184b2340809241338r634c35at3d23264b5f907300@mail.gmail.com>

That's great !

R?mi



On Wed, Sep 24, 2008 at 10:23 PM, Michael Kay <mike@saxonica.com> wrote:

>  Yes. Use "declare option saxon:memo-function", see
>
> http://www.saxonica.com/documentation/using-xquery/extensions.html
>
> Michael Kay
> Saxonica
>
>  ------------------------------
> *From:* talk-bounces@x-query.com [mailto:talk-bounces@x-query.com] *On
> Behalf Of *R?mi Dewitte
> *Sent:* 24 September 2008 14:42
> *To:* talk@x-query.com
> *Subject:* [xquery-talk] XQuery memoization
>
>  Hi all,
> Is there something to apply memoization on a function to speed up multiple
> calls with same arguments ?
>
> I am using saxon 9.
>
> Cheers,
> R?mi
>
>
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