larry@JPL-VLSI.ARPA (11/28/85)
The SYSTEM package is part of a larger problem. Despite AJPO's "There
shall be no supersets" policy, the fact is that the LRM itself explicitly
allows supersets in several ways. Representation specs are optional,
pragmas and attributes beyond the "kernel" set are allowed, etc.
I believe this is desirable; Ada will be no use unless it can be expanded
and tailored to suit specific applications and environments. The problems
this causes are obvious, but lessened by various mechanisms to control
supersets (or whatever word you choose to avoid "superset"). They include:
extensions beyond the kernel must be described in Appendix F; the package
feature lets us insulate application/ environment specifics from the rest
of a system; the real-time working group is channeling effort to expand
Ada's real-time capability; and a new LRM is planned for every five years.
But more work does need to be done to control Ada expansion. I'm less
concerned about vendor efforts (which tends to be conservative) than I am
about utility libraries which can be created by any programmer. I'm not
sure what the answer here is.
Larry @ jpl-vlsi