Directories were once viewed as a potentially general-purpose IT building block. In practice, they have never been used in this way. There are a variety of reasons for this.
- Directory vendors didn't make directories either available or easily usable for this purpose. For example, Microsoft's Active Directory until relatively recently (see Active Directory Application Mode - ADAM) was too tightly integrated with Windows security to be employed as an IT building block.
- Existing and ubiquitous relational database management systems provided alternative IT building blocks, albeit it ones without standardized schemas, or protocol-level interfaces. While these were easy to create, this approach has led to information both duplicated and scattered across many often incompatible database tables.
- As organizations now drive towards maintaining single logical repositories of multi-application data, they are employing Web Services (WS) as opposed to directory protocols such as LDAP, as protocol-level building blocks.
... Nick Shelness