Re: [apps-discuss] +exi

Zach Shelby <> Sat, 17 December 2011 19:34 UTC

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Date: Sat, 17 Dec 2011 21:34:20 +0200
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Subject: Re: [apps-discuss] +exi
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On Dec 17, 2011, at 12:41 PM, Carine Bournez wrote:

> It seems that you could use application/foo and the content-encoding: exi
> instead of registering a different media type. Is your application using a
> protocol that has no content-encoding?

This is one aspect, these applications are often aimed at CoAP, where content-encodings are more difficult. 

> or do you mean that you use a 
> different schema for the exchange of a foo serialized in EXI than a 
> text foo?

Yes, this is entirely possible for some applications as strict schema informed mode has some more limitations when it comes to schemas. And since in these cases we work directly with EXI, you can't make the assumption that there is even an XML text mode foo. There may only be for example foo+json and foo+exi. 

> A quick look at 
> makes me think it is the latter, for SenML. It does not seem a very nice
> way to convey the schema information, SchemaId is meant to serve this 
> purpose, not the media type. Since you need to carry other EXI options,
> out-of-band or in the EXI header, why not using SchemaId?.

I don't find the SchemaId all that useful. First of all, you need to invoke your EXI parser to even get at that. It is more useful to immediately look at the content-type to decide which parser to throw a representation at. A strictly defined foo+exi registration would tell you that nicely. 

Anyways, I think it is worthwhile to write a short draft on what the registration requirements for +exi would be as Peter suggests. I am happy to help with that.


Zach Shelby, Chief Nerd, Sensinode Ltd.  - My blog "On the Internet of Things" - My book "6LoWPAN: The Wireless Embedded Internet"
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