LISTSERV mailing list manager LISTSERV 16.0

Help for ZNG Archives


ZNG Archives

ZNG Archives


[email protected]


View:

Message:

[

First

|

Previous

|

Next

|

Last

]

By Topic:

[

First

|

Previous

|

Next

|

Last

]

By Author:

[

First

|

Previous

|

Next

|

Last

]

Font:

Monospaced Font

LISTSERV Archives

LISTSERV Archives

ZNG Home

ZNG Home

ZNG  March 2005

ZNG March 2005

Subject:

Xpath indexes, was: Re: Regular Expressions

From:

Marc Cromme <[log in to unmask]>

Reply-To:

[log in to unmask]

Date:

Thu, 3 Mar 2005 16:35:13 +0100

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (100 lines)

Dr Robert Sanderson wrote:

>> Just when we are about it - an xpath expression on CQL ?? Something like
>> /this/that[@attribute="xyz"]=somestuff
>
>
> We can sort of already do this if the CQL parser allows for quoted,
> dynamic indexes. Equally, the value could be hacked into a relation
> modifier value with a magical index.
>
> foo.magical any/foo.xpath="/this/that[@attribute='xyz']" somestuff

I did miss the possibility of quoted, dynamic indexes. This is of course
the way to go!

>
>
> However it does not fit the abstract data model of SRW nor CQL, as we
> cannot determine several crucial things required to process the above
> query:
>
> * Schema that the server uses internally, if any
> * Schema that the XPath expression should be applied to
> * Namespaces for the XPath expression
>
I am aware of these restrictions - it is pretty clear that _if_ you want
to have the slightest chance to make xpath queries suceed, you have to
know the data model into details.

> Secondly, XPath over the wire is practically never the right solution.
>
Well, I can imagine quite a lot of system integration tasks where we at
the moment make the 'de-route' of indexing xpath expressions into bib1
attr sets, and asking in the client with CCL/CQL and a CCL/CQL parser,
just to translate the stuff into PQF @attr this=that queries.

It would be much cleaner to be able to make xpath index queries
directly, wihtout the need of translations all the time.

Off course, xpath queries are _not_ the right solution for a end user
GUI, but given the nice syntax of CQL, it's a shame not to use it for
system integration, where I have all the information needed.

> If you control the server, then you can define an index in a profile
> which
> resolves to that XPath.

Only for predefined xpath queries - not for arbitrary xpath queries

> If you don't know the data, then you can't tell
> what to use in the XPath. If the data changes, your query is suddenly
> inaccurate (eg going from one version of a schema to another) or if the
> data is heterogeneous (MODS data and MARCXML data in the same database)
>
> So the only situation in which it would be useful would be:
>
> * The server only supplies one schema, or can determine which schema to
> use from the XPath expression
> * The records do not use namespaces
> * The client knows the data and the schema
> * The data is completely homogeneous
>
> Hence there isn't an official XPath query type.


Thanks for the thoughts and input on this issue. I will investigate
'dynamic quoted' xpath indexes in future!

Marc Cromme

>
> Rob
>
> ,'/:. Dr Robert Sanderson ([log in to unmask])
> ,'-/::::. http://www.o-r-g.org/~azaroth/
> ,'--/::(@)::. Dept. of Computer Science, Room 805
> ,'---/::::::::::. University of Liverpool
> ____/:::::::::::::. L5R Shop: http://www.cardsnotwords.com/
> I L L U M I N A T I
>


--

Marc Cromme, cand. polyt, Ph.D
Senior Developer, Project Manager

Index Data Aps
Købmagergade 43, 2
1150 Copenhagen K.
Denmark

tel: +45 3341 1000
fax: +45 3341 0101

http://www.indexdata.com

INDEX DATA Means Business
for Open Source and Open Standards

Top of Message | Previous Page | Permalink

Advanced Options


Options

Log In

Log In

Get Password

Get Password


Search Archives

Search Archives


Subscribe or Unsubscribe

Subscribe or Unsubscribe


Archives

July 2017
October 2016
July 2016
August 2014
February 2014
December 2013
November 2013
October 2013
February 2013
January 2013
October 2012
August 2012
April 2012
January 2012
October 2011
May 2011
April 2011
November 2010
October 2010
September 2010
July 2010
June 2010
May 2010
April 2010
March 2010
February 2010
January 2010
December 2009
October 2009
September 2009
August 2009
July 2009
May 2009
April 2009
March 2009
February 2009
December 2008
November 2008
October 2008
September 2008
August 2008
July 2008
June 2008
May 2008
April 2008
March 2008
February 2008
January 2008
December 2007
November 2007
October 2007
September 2007
August 2007
July 2007
June 2007
May 2007
April 2007
March 2007
January 2007
December 2006
November 2006
October 2006
September 2006
August 2006
July 2006
June 2006
May 2006
April 2006
March 2006
February 2006
January 2006
December 2005
November 2005
October 2005
September 2005
August 2005
July 2005
June 2005
May 2005
April 2005
March 2005
February 2005
January 2005
December 2004
November 2004
October 2004
September 2004
August 2004
July 2004
June 2004
May 2004
April 2004
March 2004
February 2004
January 2004
December 2003
November 2003
October 2003
September 2003
August 2003
July 2003
June 2003
May 2003
April 2003
March 2003
February 2003
January 2003
December 2002
November 2002
October 2002
September 2002
August 2002
July 2002
June 2002
May 2002
April 2002
March 2002
February 2002
January 2002
December 2001
November 2001
October 2001
September 2001
August 2001
July 2001

ATOM RSS1 RSS2



LISTSERV.LOC.GOV

CataList Email List Search Powered by the LISTSERV Email List Manager