= MDService Example Queries =
Collection of Real-world queries  (but not all of them tested yet) and related issues.

Showing both CQL queries and XPath-translations.

MDRepository provides three interfaces:
{{{
  getCollections()
  queryModel()
  searchRetrieve()
}}}


== Basic facets ==
!  needs queryModel - Values

 profile overview::
  important starting question: which profiles are actually used:
{{{ 
   ?operation=queryModel&q=//CMD/Components
}}}
   however this returns only the root elements, which may not unambiguously refer to the profiles.[[BR]]
   `CMD/Header/MdProfile` should refer to the correct profile, but may not be always filled. (+ requires queryModel to return Values!)
{{{
   ?operation=queryModel&q=//MdProfile
   ?operation=queryModel&q=//CMD/Components/MdProfile
}}}   

 language overview::
{{{
   ?operation=queryModel&q=language
}}}
 continent/country::
{{{
   ?operation=queryModel&q=Location
}}}

== View collections == 
There is a special param `collection`, but this is currently unstable, as it relied on the exist's own collection mechanism.
A safe alternative is the use of element `IsPartOf` (full path: `/CMD/Resources/IsPartOfList/IsPartOf`)
{{{
  cql:   IsPartOf = test-hdl:1839/00-0000-0000-0001-494F-5

  xpath: //IsPartOf[.='test-hdl:1839/00-0000-0000-0001-494F-5']
         //IsPartOf[.='clarin-at:aac-test-corpus:sozialismus']
}}}
So to get the whole collection (all resources of the collection) we use `operation=searchRetrieve` and query element `IsPartOf`:[[BR]]
[http://demo.spraakdata.gu.se/clarin/cmd/model/stats?operation=searchRetrieve&query=//IsPartOf%5B.=%27clarin-at:aac-test-corpus:sozialismus%27%5D collection(clarin-at:aac-test-corpus:sozialismus) ]

As the `IsPartOf`-relation is fully expanded (every resource references via `IsPartOf` every ancestor-collection CMD-record, not just the parent), the simple quey as introduced above returns all descendants, not only children, which should actually be the default behaviour. One possible resolution would be to add an attribute `@ancestor-level` or similar, which would allow to distinguish the depth of the `IsPartOf`-relation. Querying just the children would be accomplished by:
{{{
  //IsPartOf[@ancestor-level=1][.='clarin-at:aac-test-corpus:sozialismus']
}}}
This would even allow for flexible maximum depth of the query wrt to the collection-hierarchy.

Querying multiple collections translates to a `OR`-query:
{{{
   xpath: //IsPartOf[.='{handle-coll1}' or .='{handle-coll2}']
          //IsPartOf[@ancestor-level=1][.='{handle-coll1}' or .='{handle-coll2}']
}}}

== Simple Search Clauses ==

 Index ANY term::
{{{
 Title any the
}}}
 Phrase ::
{{{
 Country = "United States" /* not working yet in MDService*/
 Description any "Free play in a family context"
 "data collection"
  (: but works in XPath:  :)
  //title[contains(.,'a machine-readable transcription')] 
}}}

 comparitors ::
   does not work yet
{{{
 Date < 2005 /* especially tricky as the Date-format YYYY-MM-DD (or even other) */
}}}

== Boolean ==
Boolean CQL-queries are easily conversible into XPath, they just have to be contextualised with some same ancestor node, like this:
{{{
 //Session[contains(Date,'2005')][contains(.//Description,'participant')]
}}}
Currently it may not be the root node `CMD` itself, because MDRepository searches for the `ancestor::CMD` of the XPath
So this will result in 0 (irrespective of the actual conditions)
{{{
 ! //CMD[contains(.//Title,'year')][.//Date='2001-11-21']
}}}
But this would work:
{{{
 //CMD/Components[contains(.//Title,'year')][.//Date='2001-11-21']
 //CMD/*[contains(.//Title,'year')][.//Date='2001-11-21']
 //Components[contains(.//Title,'year')][.//Date='2001-11-21']
}}}
Usually using `Components` as starting point is best, if searching in the actual metadata. This however does not cover the `/CMD/Header` and `/CMD/Resources` part of the MD-records. This is especially the case when constraining the collections with `IsPartOf`:
{{{
 //CMD/*[contains(.//Title,'year')][.//Date='2001-11-21'][.//IsPartOf='{handle-coll1}']
 (: this wouldn't work: :)
 !  //CMD/Components[contains(.//Title,'year')][.//Date='2001-11-21'][.//IsPartOf='{handle-coll1}']
}}}

Boolean queries:
 AND::
{{{
 biling_data: ( ( Date any 2005 ) ) and ( ( Description any participant ) )
 biling_data: ( ( Date any 2005 ) ) and ( ( Description any part ) ) and ( ( Country any United ) ) 
}}}
 brackets are not necessary, as long as they are not necessary ;). This should work as well :
{{{
 biling_data: Date any 2005 and Description any participant
}}}

 AND OR::
{{{
 biling_data: ( ( Date any 2005 ) or ( Country any United ) ) and ( ( Description any part ) ) 
 //CMD/Components[.//Date[contains(.,'2005')] or .//Country[contains(.,'United')]][.//Description[contains(.,'part')]]
}}}

 AND NOT ::
  seems very expensive, not sure about the syntax
{{{ 
 biling_data: ( ( Date any 2005 ) not ( Country = Japan) )

 //CMD[.//imdi-corpus][not(.//ResourceType[.='Metadata'])]
}}}