For the STORE project, its core library (crypto/store/store_lib.c) needs the following functionlity:

• STORE_load, a function that loads objects the STORE library supports, given a URI. It returns a STACK_OF(STORE_INFO) containing all the information it's been able to retrieve (a PEM file can contain quite a few items, for example).
• STORE_INFO, an opaque structure holding details on what has been loaded.
• functions to retrieve data of specific type from a STORE_INFO reference.
• functions to manipulate a STORE_INFO.
• functions to register and unregister loaders, which are handlers for each URI scheme that needs support.