There are several components that should be considered essential to Document Store but are not part of the very core of the functionality. One in particular, The Library, may be considered indispensable, a killer app which provides the functionality that people really need from a Document Store, without which it can be seen as simply a complicated database system. The SuperStore provides a mechanism for multiplexing several Document Stores into one logical system. FIXME: expand this idea. The Library may be the lynch-pin of the Document Store system. It provides the mechanism to track, index and search documents within the Document Store. Its interface is identical to that of the StoreFront, although it provides additional functions for searching the index based on meta-data that is already associated with the Documents. The Library acts as a sort of indexing layer, sitting between the client object and the actual Document Store and automatically gathering information about documents as they are manipulated in the Document Store. FIXME: expand this idea