[CWB] Any way to filter out some preceding tokens in a CQP query?

[Ray Wu]

Hi Stefan,

Thanks for your suggestion. That helps.  And forgive me for making your name into something different.. (blush)


Best,
Ray




At 2012-10-17 06:34:13,"Stefan Evert" <stefanML at collocations.de> wrote:
>
>> CQP's zero-width assertions are quite handy when we want to filter out some tokens after a CQP query. A typical example is given in Stephen's "Inside the IMS Corpus Workbench" presentation to find clausal verb complement:
>> [pos="VB.*"] "that" [:pos!= "JJ.*| N.*":]
>> 
>> My question is: is there a way in CQP to limit the content BEFORE a CQP query? I guess that mechanism might be equally handy in other situations.
>
>No, unfortunately not.  These "zero-width assertions" were implemented for an entirely different purpose (being able to make assertions similar to the global constraint at arbitrary places within a CQP query), and the ability to check one additional token after the end of the match is just a useful side-effect.
>
>If you're working directly with CQP or with an interface that's under your control, you can easily filter out unwanted matches after running the query, like so:
>
>	A = [pos="VB.*"] "that" [:pos!= "JJ.*| N.*":];
>	set A keyword nearest [pos = "N.*"] within left 1 word;
>	delete A with keyword;
>
>etc.  This mechanism is much more flexible than zero-width assertions, of course, but it cannot be used through a Web interface (such as BNCweb or CQPweb) that only allows users to enter plain CQP queries.
>
>Hope this helps
>Stefan
>
>	
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