IEEE 200X Fast Track Change Proposal

ID:      FT-27

Proposer:     Stephen Bailey
email:        sbailey@model.com

Status:       Proposed
Proposed:     01/04
Analyzed:     Date
Resolved:     Date

Related issues:  
Relevant LRM sections:   
    1.1.2 Entity declarative part
    1.1.3 Entity statement part



Enhancement/Requirements Summary:
-------------------------------------------------------- 
Eliminate the restriction that entity statement part
must contain only passive concurrent procedure calls
and passive process statements.  (That is, make the
need for an architecture optional.)


Enhancement/Requirements  Detail: 
-------------------------------------------------------- 
In many cases, separating a block or module into separate
entities and architectures is not needed.  There is no
intention or need to have multiple implementations of the
same entity interface.  When such separation is not required
it would be significantly more convenient to simply put the
implementation (architecture) together with the entity interface
specification.

If the restriction on passive concurrent statements is eliminated,
the language must also allow for non-passive (active?) concurrent
statements in both the entity and architecture in the event
that a user still desires to separate some of the implementation
from the entity.  In this case, the active concurrent state-
ments would be common to any implementation (architecture)
for the entity.


Implementation Summary: 
---------------------------- 
Remove the restrictions documented in the 2002 LRM on entity
declarative items and entity statement parts.  Whatever is
legal in an architecture in both cases should also be legal
in the entity.


Implementation Details: 
----------------------------
Section 1.1.2 Entity declarative part
Replace the current entity_declarative_item BNF production with:

entity_declarative_item ::=
  { block_declarative_item }

Move the block_declarative_item BNF production from section 1.2.1
to section 1.1.2 as this will become the 1st reference to a
block_declarative_item.

Section 1.1.3 Entity statement part
Replace the current entity_statement BNF production with:

entity_statement ::=
  { concurrent_statement }

Replace the paragraph "It is an error if any statements ..."
With:

"All of the statements in the entity statement part are concurrent
statements which execute asynchronously with respect to one another.
The various kinds of concurrent statements are described in Clause 9."

Annex A:
The BNF productions for entity_declarative_part and
entity_statement need to be modified consistent with the
above discussion.


Discussion:
----------------------------
There is no good reason to enforce the current restrictions on
entity declarative and statement parts.  The affect of the
restrictions is to enforce a specific coding style.  While
it is fine for the language to support such a coding style
(separation of interface and implementation), it should not
dictate coding styles.  This change allows both a good
coding style of interface/implementation separation while
also allowing more efficient coding when there is no
perceived benefit of following such a coding style.

The restriction does not simplify tool implementations nor
make them more efficient.

Analysis/LRM Changes
----------------------------
See above.

Note:  This change is backward compatible.


Resolution:
----------------------------
[To be performed by the 200X Fast Track Working Group]