Re: SRU/CQL requirements

Thanks Ray, it is much clearer now.

Ivan



> On 01 May 2015, at 15:58 , Denenberg, Ray <rden@loc.gov> wrote:
> 
> Hi Ivan;
> 
> > Is my understanding correct that CQL is some sort of a framework?
> > Framework in the sense that we have to define which indexes are usable in
> > our environment and how they translate onto the model?
> 
> While I would not characterize CQL as a "framework" (it has substantial teeth), it is true, you define indexes for your particular environment.   These sets of indexes (and other objects)  are called "context sets".  A list of known context sets (those I know about) are at http://www.loc.gov/standards/sru/cql/contextSets/listOfContextSets.html
> 
> 
> > Another question/comment is on the '=' operator like 'body = cat' in your
> > example. Is this defined to be an exact match, or a submatch, or something
> > similar?
> 
> There is both "=" and "==".   Here is what the spec says about these:
> 
> "=
>  This is the default relation, and the server can choose any appropriate relation or means of comparing the query term with the terms from the data being searched."
> 
>     ==
> This relation is used for exact equality matching. The term in the data is exactly equal to the term in the search.  A relation modifier may be included to specify how whitespace (trailing, preceding, or embedded) is to be treated  (for example, the CQL relation modifier ‘honorWhitespace’).  "
> 
> 
> 
> .... I would expect that some sort of a (possibly simplified) regular
> > expression match may be more useful for our purposes. I do not know
> > whether CQL has this facility.
> 
> Yes, CQL has several built-in matching functions, including:
> 
> "
> *     A single asterisk (*) is used to mask zero or more characters.
> 
> ?        A single question mark (?) is used to mask a single character, thus N consecutive question-marks means mask N characters.
> 
> ^        Carat/hat (^) is used as an anchor character for terms that are word lists, that is, where the relation is 'all' or 'any', or 'adj'. It may not be used to anchor a string, that is, when the relation is '==' (string matches are, by default, anchored). It may occur at the beginning or end of a word (with no intervening space) to mean right or left anchored."^" has no special meaning when it occurs within a word (not at the beginning or end) or string but must be escaped nevertheless.
> 
> \        Backslash (\) is used to escape '*', '?', quote (") and '^' , as well as itself. Backslash not followed immediately by one of these characters is an error.
> 
> "
> 
> Ray


----
Ivan Herman, W3C
Digital Publishing Activity Lead
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