Frames, Transactions, and Elements

Greetings ITC Techies,

Another issue that became apparent at the face-to-face
and today is that we need to develop a consistent terminology
for what is a transaction, what is an element, what is a fragment,
what is a thing marked by EOM, etc.

I would like to propose the following terminology to
be used. I'm not claiming this is universally correct
terminology. In fact I don't think there is a universally
correct definition of a transaction.

But, within the realm of the SCE-MI world, let's at least
use consistent terminology and something upward
compatible with SCE-MI 1.

Transaction:

I would like to propose that we define transaction
generally as "the amount of data" passed in a single
DPI function call.

This definition has generally served us well since
SCE-MI 1, and all the way through plain DPI. Where it
becomes fuzzy is when data shaping and VLM become
involved.

As we know with data shaping, elements of transactions
can be passed in single calls at one (narrow) end of a
nozzle or funnel.

So, with that in mind, let's qualify the definition of
transaction above as above as "the data passed in a
single call of a DPI function, or in the case of a nozzle
or funnel transaction pipe, the data passed at the larger
end of that pipe."

Element:

That segues us nicely into the definition of an element
as simply the data passed at the smaller end of a
nozzle or funnel. In other words 1 or more elements
of a transaction can be passed in single calls to
transaction pipes.

Frame:

Let's refer a sequence of transactions marked by an eom
as a "frame". Transmissions of frames require multiple
calls that pass a transaction in each call to conventional
pipes (both ends same size). Or to the larger end of
a data shaping pipes in the sense of a nozzle or funnel.

So, with this in mind, the general granularity of data
organization in the SCE-MI 2 context from coarsest
to finest is:

Frames
   contain one or more
     Transactions
       contain one of more
         Elements

And, except for the special case of elements used in data
shaping, transactions are defined in what is passed in a
single call to a pipe.

How does this sound ? I think it scales well to more
traditional definitions of transactions in the SCE-MI 1
and plain DPI senses.

-- johnS

______________________________/\/            \     \
John Stickley                   \             \     \
Principal Engineer               \             \________________
Mentor Graphics - MED             \_
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