Material catalogs offer several features.
Allow persistent definition of materials, including all material properties.
Materials defined in the material catalog can be referenced using a simple ID, rather than a set of material properties.
Provide defaults for certain request attributes, such as the JPEG quality or a default reply image size.
Manage vignettes, ICC profiles, and request templates.
Even if no specific material catalogs are defined, all features of material catalogs are available by way of the default catalog ( default.ini).
While render materials may be specified explicitly in requests using material attributes, often it is more desirable to hide the details of materials from the web site by using material catalogs. src= commands accept catalog references instead of explicit file paths. A catalog entry consists of
[ *catId*/] *itemId*, where
*catId* identifies a material catalog and
*itemId* identifies a record in the catalog. If
*catId* is not specified, the session catalog is used (see below).
A catalog record is matched successfully if (a)
*catId* matches the
attribute::RootId value of a material catalog and (b)
*recId* matches the catalog::Id value in the same catalog. If there is a successful match, the attributes of the material (including
src=) are set to the data from the catalog record. If the MSS includes additional attributes for this material besides src=, they override the values from the catalog record.
*recId* cannot be matched to a catalog entry, then
*catId* is replaced with
attribute::RootPath from the catalog and the resulting path is then assumed to be a simple file path. Other default attributes (for example,
attribute::Resolution) may also be inherited from the material catalog.
Vignettes and ICC profiles can be itemized in material catalogs similar to the materials themselves, and given properties. In addition, the vignette map also provides the container for templates.
Material Catalog Reference,