felix@3033: The datacages behaviour is defined in the file conf/meta-data.xml .
felix@3033: 
felix@3033: The datacage serves two purposes.
felix@3033: It handles automatic 'recommendations', which are instructions
felix@3033: sent by the client to add newly created artifacts to the collection.
felix@3033: From a user perspective, these artifacts mainly represent curves or data
felix@3033: points in the resulting diagrams.
felix@3033: The second task is to let the user add already existing artifacts (i.e.
felix@3033: previous calculations) or new artifacts with access to related data.
felix@3033: 
felix@3033: Irrelevant of the type of elements (recommendations or user picked data) the
felix@3033: datacage can iterate over possible artifacts by accessing its own database.
felix@3033: Thus, to create a list of matching entries, database queries are used.
felix@3033: 
felix@3033: In meta-data.xml, database queries are defined as <dc:statement> elements,
felix@3033: for example
felix@3033:                 <dc:statement>
felix@3033:                   SELECT id          AS prot_id,
felix@3033:                          description AS prot_description
felix@3033:                   FROM wsts WHERE kind = 1 AND river_id = ${river_id}
felix@3033:                 </dc:statement>
felix@3033: 
felix@3033: As can be seen from the example, the datacage configuration file can maintain
felix@3033: its own stack of variables (${river_id} in above example).