!ASIS Issue #006
!topic Unification between Element Nodes and Compilation Unit Nodes
!reference ASIS95-ASIS
!from D. Ehrenfried 95-03-08
!keywords Elements, Compilation Units
!discussion

This issue was submitted on 1 January 1995 for discussion at the March
1995 ASISWG meeting. The original email had 2 issues. Issue #006
captures the first issue while Issue #008 captures the second issue.

First Issue =>

1. The one glaring problem with the current interface is the lack of
unification of element nodes and compilation unit nodes.  If one asks
for the parent_compilation_unit, one should get an asis.element, not
some other type.  It forces compilations for traversal and all sorts of
queries that one might want to define (Most need two interfaces, one for
each type).  Clearly this can be programmed around, but it is an
unnecessary wart in my opinion, making both the interface and client code
much more complicated.

!resolution Rejected.
!date 95-03-08
!Notes from minutes

Issues discussed at this ASISWG meeting

     ASIS provides two views of compilation units; a "black box" view is
     abstracted with the Compilation_Unit type, and a "white box" view is
     abstracted with the Element type.

     During the discussion of this issue, it was brought out that we
     should keep ASIS as primitive as possible, and let additional
     functionality be included in higher level or "Secondary Layer" of
     interfaces -- the ATIP project defined Secondary Layer for
     particular application areas as a Program View Layer (PVL).  We
     could use so-called non-primitive, secondary layer, functions that
     are removed from ASIS 95 as examples of usage of ASIS that could
     be put into the public domain.  Vendors are encouraged to
     contribute such secondary functions as examples.  For background
     information, the following information is provided from a previous
     description of the ASIS/PVL ATIP:

	Views are effectively abstractions of ASIS information that
	focus on different aspects of an Ada program structure.  At the
	start of the ATIP, candidate PVL Views discussed included:
	Control Flow, Reference (set of entities referenced in a
	declarative region), "Chunk" (identify transfer of control
	resulting from calls and propagated exceptions), Name Space,
	and Data Flow.  The actual ASIS/PVL ATIP project has created
	four views: the Region View, Name Space View, Reference View,
	and Control Flow View.