Ryan Farrell <ryan.farrell.ctr@nrl.navy.mil> · 19/07/2011 19:12

If
presentBit is zero, then A1 has zero occurences
For anyone that was at the 19/07  phone meeting,
this is what Adam Fox 

and I were trying to find a solution to. If anyone knows of a solution,

please contact me or adam.fox@nrl.navy.mil.

----------------------------------------------------------------------------------------------------

Please see the attached xml schema while reading this message.

The problem we want to solve is how to represent a structure that can 

have a variable amount of occurences (even zero), and the amount of 

repeats is controlled by a one bit field, which we will call"repeatBit".

The repeating structure in this case is "A1". The element before
it, 

"presentBit", determines if there is at least one occurence of
A1. If 

presentBit is zero, then A1 has zero occurences. If presentBit is one,

then A1 has AT LEAST one occurence.

The first element in A1 is "repeatBit". What repeatBit does is
tells us 

if there will be another occurence of A1 after the current occurence. 

When repeatBit is zero, then that means we will read through the rest of

A1, then that is the last occurence of A1. As long as repeatBit 

continues to be one however, we will read through the rest of A1, then

start a new occurence.

I have included all the known required DFDL notation. Please let me know

what is missing.

        EXAMPLE INPUT (results are in base 10):

        NOTE: Not all bits are used in these examples.
Unused bits 

should be ignored for the purpose of the examples.

        1) 0111 0101

        presentBit = 0

        aFieldAfterA1 = 3

        2) 1011 1010

        presentBit = 1

        A1

        -repeatBit = 0

        -someField = 3

        aFieldAfterA1 = 2

        3) 1101 0110 0000 0000

        presentBit = 1

        A1

        -repeatBit = 1

        -someField = 1

        A1

        -repeatBit = 0

        -someField = 3

        aFieldAfterA1 = 0

[attachment "repeat_example.xsd" deleted by Steve Hanson/UK/IBM]
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From:	Ryan Farrell <ryan.farrell.ctr@nrl.navy.mil>
To:	dfdl-wg@ogf.org
Date:	19/07/2011 19:12
Subject:	[DFDL-WG] [wg-all] Repeating groups in DFDL
Sent by:	dfdl-wg-bounces@ogf.org