Identifying Objects 
An object to be stored in the cache, manipulated, or invalidated can be identified by the application program using one of the following attributes:
The fully specified cache key, consisting of the URL and the various context-dependent fields, such as SAP language and SAP theme
Example/sap/bc/bsp/sap/public/bc/bsp/styles/sapbsp.css&de&&A6E90000&
End of the example.
CautionAlthough the application can identify objects using the cache key, this is not recommended. Use the URL prefix or e-tag as described below.
End of the caution.A <prefix>* wildcard pattern that selects all objects with a matching <prefix>
Example/sap/bc/bsp/sap/public/bc/bsp/styles/*
End of the example.The e-tag - a unique key (GUID) assigned to an object when that object is created. You can use the GUID_CREATE ABAP function module to generate a unique GUID for your object.
NoteThe e-tag is required so that logically identical objects that are physically stored a number of times under different URLs (but with the same e-tags) can be identified. When the object is being invalidated, the application uses the e-tag to access all copies of the object simultaneously.
End of the note. CautionThe e-tag is not automatically assigned to every object by the system (such as the cache key), but is a GUID that the application programmer can assign if he or she wants to access this object at a later date (to invalidate it, for instance).
End of the caution.