Composite Record Attributes
^^^^^^^^^^^^^^^^^^^^^^^^^^^

With this feature we create an abstraction on top of the Record Attribute
infrastructure to allow the aggregation of multiple, cross-Attribute values
under a single search filter value, accessible through new, dynamic filters.

Each QueryParser filter will be created by the addition of a Composite Record
Attribute Definition. For instance, one may wish to create a Composite Record
Attribute Definition for an abstract "Item Type" interface component that
uses information from the item_type, vr_format, bib_level and item_form
Record Attribute Definitions, with each Composite Record Attribute Value
having a different combination of Record Attribute Values from some or all of
these Record Attribute Definitions. In this way, as single interface
component might be presented as a dropdown with options such as "All Books",
"All video recordings", "DVDs", "VHS Tapes", "E-Books", "Audio Books" and
"Large Print Books". Of particular note are the "DVDs" and "VHS Tapes"
entries, which include information from Record Attribute Definitions
completely separate from the others. Additionally, the Composite Record
Attribute Values defined by this Composite Record Attribute Definition
can be used to drive behavioral logic, such as alternate icon display or
link generation, in upgrade-friendly template adjustments.

Included in this development is a replacement for the single-attribute
Format filter supplied for basic search.  Instead, a Composite Attribute
is used to combine the values from Item Type, Item Form and Videorecording
Format in various ways that provide a more patron-friendly set of choices.

This new Format filter can be adjusted, or even replaced with a completely
local one, through configuration and without template adjustment.