Re: Mutually Exclusive Values in Set Hanno Klein / Deutsche Börse Systems <> 7 Nov 2008 7:56AM ET
Why wouldn't the enum attribute within the set serve the same purpose. The enum attribute is for single values and requires the same number of bits. What is the advantage of introducing another attribute?
> Many times there are large groups of values which are mutually exclusive
> in a MultiValueString. The example field used, TradeCondition, is likely
> to have many mutually exclusive subsets of values.
>
> The set extension should allow for a definition of these mutually
> exlusive fields. Let's use the 20 A* values for TradeCondition and
> assume that they are mutually exclusive. Only one of the A* values can
> be set at a time. Using a single bit for each value would require 3
> bytes in the Set encoding. Using an option declaration this can be
> reduced to 5 bits.
>
> AB >
> The presence attribute indicates whether null should be accepted as
> value or if the option should always be present. In this case:
>
> 00000 represents no value 00001 represents AA 00010 represents AB
>
> The example above would take 1 byte in the worst case.
