Tom,
Directories have structure, schema, and DNs must fit within
this schema. So, a directory operator has a great deal of interest in
making sure that any entries you register with him fit the schema
established for his directory. For interoperability purposes, e.g.,
in constructing useful search queries and being able to interpret
returned entries, it is very useful to have commonly accepted schema
across a wide range of directory system operators.
Finally, re your earlier message, no, the IANA has not
established the "common attribute" list yet, something that was
agreede upon by the PEM and directory WGs. However, I assume you must
be joking when you ask if there IS an IANA.
Steve