Provided are a method, system, and program for defining asset classes in a digital library. At least one asset class is defined to include at least one attribute and attributes are defined for each asset class to have an attribute object type. The attribute object type is defined to indicate one of a plurality of different data structure formats that are searchable through separate application programs, wherein the attribute object types in one asset class are implemented in different data structure formats. A asset object instance is generated for each asset class and information is generated in the asset object instance on a file location of attribute objects providing the attributes for the generated asset object instance.