The join is the creation of a single directory entry that contains or references attributes from multiple related entries. By providing it, we solve the issue of disparate locations, while sidestepping the need to provide an enterprise directory from scratch. It must be able to communicate via LDAP, since this is the lingua franca of directory interaction. It must be capable of dealing with extensible schema. Schemas are the definitions of the structure and form of information held in a directory or database.
Meta directory requires flexible schemas many directories come with hard-coded data definitions.
Polling for change means that only the elements that have been updated need to be reflected in the Meta directory. The GartnerGroup has identified three different basic technologies that can be used to provide Meta directory solutions, each of which has its merits and disadvantages. The most common Meta directory solutions use a replication based model to copy attributes from each of the proprietary servers to build an entry in the central directory which contains all the attributes. Able to use existing directory technology existing standards, protocols and products can be used to deliver this type of directory solution. Proven there are many examples of organizations that have implemented Meta directory solutions using existing X.500 and LDAP directory products in this manner.