J3/00-130

Date:		28th February 2000
To:		J3
From:		Malcolm Cohen
Subject:	Abstract interface blocks

1. Missing semantics

There is no specification as to how abstract interfaces get their
characteristics, and what the relationship is between an abstract interface and
an explicit interface created by a PROCEDURE statement.

Also, some of the old semantics for an interface body assume that it is always
creating an explicit specific interface.

Also, there is unnecessary duplication of semantics between an explicit
specific interface created by an interface body and one created by a PROCEDURE
statement - we should just say that these are the same.

Also, there is an editorial fixup.

2. Edits - intro

Part 1 of the solution is to split the paragraph at [247:14-21] into two, the
first of which tackles issues common to abstract interfaces and explicit
specific interfaces, the second of which addresses explicit specific interfaces
only.

Also, the prohibition against ENTRY appearing in an interface block (sic -
should be body) is better done as a constraint.

3. Edits

[246:11+] Insert constraint
"Constraint: An interface body shall not contain an ENTRY statement."
{If this is not desirable as a constraint it needs to be re-inserted into
the main text.}

[247:4] Delete ";".
{Editorial fixup.}

[247:14-21] Replace with the following two paragraphs:
"An interface body specifies all of the characteristics of the explicit
specific interface or abstract interface.  The specification part of an
interface body may specify attributes or define values for data entities that
do not determine characteristics of the procedure.  Such specifications have no
effect.

If an explicit specific interface is created by an interface body or a
procedure declaration statement for an external procedure, the characteristics
shall be consistent with those specified in the procedure definition except
that the interface may specify a procedure that is not pure if the procedure is
defined to be pure.  An interface for a procedure defined by an ENTRY statement
may be specified by using the entry name as the procedure name in the interface
body.  A procedure shall not have more than one explicit specific interface in
a given scoping unit."
{Split into common case and specific case.
 Add explicit inclusion of procedure declaration statement.}

[253:17+] Insert
"All of the characteristics of the explicit specific interface are specified by
the <proc-interface>, and are those of the abstract interface."
{Specify where the characteristics come from.}

[253:17-20] Delete "If <proc-name> ... pure."
{Delete now redundant requirements.}

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