FIXML implementation of custom data

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Imported from previous forum

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New to FIXML. How do I provide custom data in an XML document not defined in FIXML’s order.dtd?

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[ original email was from John Goeller - john.goeller@ssmb.com ]
Check out the Design Rules document in the FIXML Archive. It gives an example.
> New to FIXML. How do I provide custom data in an XML document not defined in FIXML’s order.dtd?
>
>

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I’ve seen the custom tags in many places in the DTDs and read the design rules document, but I don’t see how this will work in the long run. Isn’t the DTD the interface between firms? How then can one firm make changes to the DTD and still be true FIXML compliant? If two firms have different custom extensions how can they ever send FIXML to each other?

I know custom tags are part of FIX but shouldn’t they be omitted from FIXML?

> Check out the Design Rules document in the FIXML Archive. It gives an example.
> > New to FIXML. How do I provide custom data in an XML document not defined in FIXML’s order.dtd?
> >
> >
>

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[ original email was from Shalom Reich - shalom.reich@neonsoft.com ]
> I’ve seen the custom tags in many places in the DTDs and read the design rules document, but I don’t see how this will work in the long run. Isn’t the DTD the interface between firms? How then can one firm make changes to the DTD and still be true FIXML compliant? If two firms have different custom extensions how can they ever send FIXML to each other?
>

Just as firms change the FIX tags in a message and remain FIX compliant they can change DTD and remain FIXML compliant. Everything is govorned by bilateral agreements.

> I know custom tags are part of FIX but shouldn’t they be omitted from FIXML?
>

Every firm has a something special that they offer. This usually requires additional information that needs to be put into custom fields - so I don’t think this will happen in the real world.