RE: EXI in XMPP: schema negotiations

Hello Youenn,

Thanks for your input. See my responses below.

> Hi Daniel, Peter,
>
> There may be more to define than uploading a XML schema document.
> You probably need to take care of all include/import in a proper way so that everything is unambiguous.

Correct. The next revision will include a method for how to create a "main schema" in an unambiguous way, that will import the schemas agreed on during schema negotiation. We're working on this revision. It will also include a new binary-only transport.

> Uploading a compressed XML schema document give benefits on the network side but it does not give any benefit on the processing side. Processing a schema document is generally difficult and will probably be restricted to XMPP servers?

The schemas uploaded will probably be internal to the xmpp server and not used for other purposes than EXI compression/decompression. However, it's a good point.

>  Having a simpler format would help (better compression, better processing) but would need some significant extra definition work.

Do you know of any such formats?

> As for QName and prefix preservation, whenever you have an attribute whose type is QName, the whole attribute value is encoded as a string (except for @xsi:type values). Therefore the decoder needs to know how to resolve the prefix that is embedded in the string representation to a URI. 
> If preserving prefixes, you guarantee that the information is available to the decoder. 
> But other alternatives, for instance conventions specifically defined to the XMPP environment, may be envisioned.

I think the solution of preserving prefixes during schema negotiation is a good choice and is easy to implement/understand. If you see better alternatives, please feel free to elaborate.

> Regards,
>	Youenn

Thanks again for your input,
Sincerely,
Peter Waher

Received on Thursday, 18 April 2013 15:54:08 UTC