Tag uniqueness and Parsing repeating groups

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Imported from previous forum

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Hi there -

I have two questions about the FIX protocol 4.2/4.3 message defns.

  1. Are tags guaranteed to be unique (represent the same data) across messages. eg. in the "New Order - Single" message the tag value 1 = Account. Can I assume it will represent account in every message in which it occurs?

  2. There appears to be no terminator for repeating groups, which makes it impossible to generically parse a message; the parser MUST work based on definitions of messages, in order to know where a repeating group ends when there is only one ‘repeat’. Is my understanding correct, or have I missed something?

Thanks!
Peter

3

  1. Yes. The FIX tag number represents the same field defined in the FIX Field Reference/Data Dictionary across FIX messages.

  2. Repeating groups are ordered and the first field of the repeating group is required if that repeating group is specified. Thus you can use the re-occurance of the first field as the delimiter for the last instance. Please refer to “Repeating Groups:” in FIX 4.3 Volume 1’s “COMMON FIX SYNTAX RULES”.

> Hi there -
>
> I have two questions about the FIX protocol 4.2/4.3 message defns.
>
> 1) Are tags guaranteed to be unique (represent the same data) across messages. eg. in the “New Order - Single” message the tag value 1 = Account. Can I assume it will represent account in every message in which it occurs?
>
> 2) There appears to be no terminator for repeating groups, which makes it impossible to generically parse a message; the parser MUST work based on definitions of messages, in order to know where a repeating group ends when there is only one ‘repeat’. Is my understanding correct, or have I missed something?
>
> Thanks!
> Peter
>

4

Thanks for the quick response.

Although the first field will delimit the beginning of a repeating group, when there are multiple fields being repeated in the group there is no way to find the end of the last group - except by knowing which fields make up the group and looking for the first field which is not valid for the group. Then the end of the last repeating group is at n-1. Or have I missed something?

Also, is each message body potentially a repeating group? eg. for message type D: New Order - Single, is it valid to have multiple sets of the fields defined for this message between a single standard header/footer pair?

Regards,
Peter

> 1) Yes. The FIX tag number represents the same field defined in the FIX Field Reference/Data Dictionary across FIX messages.
>
> 2) Repeating groups are ordered and the first field of the repeating group is required if that repeating group is specified. Thus you can use the re-occurance of the first field as the delimiter for the last instance. Please refer to “Repeating Groups:” in FIX 4.3 Volume 1’s “COMMON FIX SYNTAX RULES”.
>
>
> > Hi there -
> >
> > I have two questions about the FIX protocol 4.2/4.3 message defns.
> >
> > 1) Are tags guaranteed to be unique (represent the same data) across messages. eg. in the “New Order - Single” message the tag value 1 = Account. Can I assume it will represent account in every message in which it occurs?
> >
> > 2) There appears to be no terminator for repeating groups, which makes it impossible to generically parse a message; the parser MUST work based on definitions of messages, in order to know where a repeating group ends when there is only one ‘repeat’. Is my understanding correct, or have I missed something?
> >
> > Thanks!
> > Peter
> >
>