Hello,
I want to query a BaseX XML Database via Python (BaseXClient.py). Therefore I write a XQuery script, which executes a FLOWR expression combined with a few self-written functions. A bunch of options, which are generated within my Python script, have to externally bind to this query.
For convenience it would be appropriate to have optional external variables which I do not have necessarily to bind, but which will have default values specified in the XQuery script. Is there a possibility to do this?
I thought about an alternative, that is to declare the options with the help of a XML snippet. But then I could not figure out how to bind this snippet as a node instead of a string, because XQuery itself does not have a function to convert a String containing a XML document to a node. Of course I could create before each request a new options document in the database, but this seems to be a bit unhandy.
All in all I have the impression, that those are quite easy problems, but for some reason I could not find any solution on the web, so I were glad about reading a solution to one of those problems.
All the best, Ronny
Hi Ronny I use BaseX to do some transformatins over Pyton binding.
In case I test it in GUI, I have in my current collection one source document. When I process it remtoely, I pass the data as string and convert it into xml document.
So in my XQuery code I have this:
(: let $xml := collection()[1] :) let $xml := util:eval($xmlString)
The later is used in production and is converting incoming string into xml doc.
Jan
*Jan Vlčinský* TamTam Research s.r.o. Slunečnicová 338/3, 734 01 Karviná Ráj, Czech Republic tel: +420-597 602 024; mob: +420-608 979 040 skype: janvlcinsky; GoogleTalk: jan.vlcinsky@gmail.com http://cz.linkedin.com/in/vlcinsky
On 13 March 2012 17:08, Ronny Möbius moebius@physik.hu-berlin.de wrote:
Hello,
I want to query a BaseX XML Database via Python (BaseXClient.py). Therefore I write a XQuery script, which executes a FLOWR expression combined with a few self-written functions. A bunch of options, which are generated within my Python script, have to externally bind to this query.
For convenience it would be appropriate to have optional external variables which I do not have necessarily to bind, but which will have default values specified in the XQuery script. Is there a possibility to do this?
I thought about an alternative, that is to declare the options with the help of a XML snippet. But then I could not figure out how to bind this snippet as a node instead of a string, because XQuery itself does not have a function to convert a String containing a XML document to a node. Of course I could create before each request a new options document in the database, but this seems to be a bit unhandy.
All in all I have the impression, that those are quite easy problems, but for some reason I could not find any solution on the web, so I were glad about reading a solution to one of those problems.
All the best, Ronny _______________________________________________ BaseX-Talk mailing list BaseX-Talk@mailman.uni-konstanz.de https://mailman.uni-konstanz.de/mailman/listinfo/basex-talk
Hi Jan, Hi Ronny,
maybe you might want to use the following approach:
declare variable $a external; let $default := "<b>I am default</b>" let $vals := ( try { $a } catch * {()}, $default )[1] return parse-xml($vals)
the try clause tries to assign $a to $vals, and if catched assigns the empty sequence to $vals. The [1] predicate selects the first element of this sequence, as empty subsequences are flattened, the value for $default is returned if $a has been set to the empty sequence.
I chose parse-xml instead instead of util:eval; might be both a little faster and definitely more secure :-)
Hope this helps (and works ;-)).
Kind Regards
Michael
Am 13.03.2012 um 17:20 schrieb Jan Vlčinský (TamTam Research):
let $xml := util:eval($xmlString)
Hi Jan, Hi Michael,
thank you both very much. I was not aware of the parse-xml function, because I only read a reference of XQuery2 functions.
The try .... catch statement is also very helpful.
Thanks a lot! Ronny
On 03/13/2012 06:35 PM, Michael Seiferle wrote:
Hi Jan, Hi Ronny,
maybe you might want to use the following approach:
declare variable $a external; let $default := "<b>I am default</b>" let $vals := ( try { $a } catch * {()}, $default )[1] return parse-xml($vals)
the try clause tries to assign $a to $vals, and if catched assigns the empty sequence to $vals. The [1] predicate selects the first element of this sequence, as empty subsequences are flattened, the value for $default is returned if $a has been set to the empty sequence.
I chose parse-xml instead instead of util:eval; might be both a little faster and definitely more secure :-)
Hope this helps (and works ;-)).
Kind Regards
Michael
Am 13.03.2012 um 17:20 schrieb Jan Vlčinský (TamTam Research):
let $xml := util:eval($xmlString)
basex-talk@mailman.uni-konstanz.de
-
Jan Vlčinský (TamTam Research) -
Michael Seiferle -
Ronny Möbius