Re: [apps-discuss] New Version Notification for draft-shelby-exi-registration-01.txt

Cullen Jennings <fluffy@iii.ca> Tue, 24 April 2012 21:15 UTC

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From: Cullen Jennings <fluffy@iii.ca>
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To: Ned Freed <ned.freed@mrochek.com>
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Subject: Re: [apps-discuss] New Version Notification for draft-shelby-exi-registration-01.txt
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On Apr 24, 2012, at 10:51 , Ned Freed wrote:

> 
>> On Apr 24, 2012, at 8:51 , Ned Freed wrote:
> 
>>> 
>>>> On Apr 23, 2012, at 18:14 , Ned Freed wrote:
>>> 
>>>>>>> application/senml+json
>>>>>>> application/senml+xml
>>>>>>> application/senml-exi
>>> 
>>>> I think the idea that first two are OK but the third one needs to have a "-"
>>>> instead of a "+" is simply baffling. Can someone explain the logic to me ?
>>> 
>>> +exi implies a syntax that can be processed generically by systems knowing
> 
>> Thanks - that answer does help. But what do you mean can be "processed
>> generically"? If we mean can check the syntax is valid, sure, all can do that.
> 
> Well, there are these things called XML editors and renderers... And probably
> ones for JSON too, although I'm not as familiar with that space.
> 
>> If we mean understand the semantic content of the data without the schema
>> information,  it seem pretty unlikely that senml should have the + for json or
>> xml.
> 
> No, it doesn't mean that. If it did there would basically be no use-case at all
> for +xml or +json.
> 
>> I will point out the senml mandates that data inside has to identify the
>> schema in use for that inside the exi data - now it's not a globally resolvable
>> URI for the schema or something but it does make sense in the context of senml.
>> You can process the senml exi without the schema at least in the context of
>> determining it might be valid exi.
> 
> First of all, it is by no means clear that even if the schema reference
> was mandatory, it would fulfill the requirements of +suffixes. The idea
> was that no external information would be needed to understand the syntax
> of such types. As best I can tell, there is no consensus to loosen this.
> 
> That said, a +exi suffix is necessarily a generic mechanism that needs to be
> able to apply to multiple types. If all such usage required explicit schema
> specification in the document, or better still, mandated that EXI be operated
> in schema-agnostic mode, then +exi might make sense. But it seems people using
> EXI aren't willing to make that tradeoff in order to use +exi. Which given the 
> target space I completely understand and agree with.
> 
>> But really the questions is what's is our definition of "generically
>> processable" ?
> 
> It's pretty simple: Processing at the syntactic but no the semantic level.

Ok, but it seem that is what EXI in this form allows - you can step over the elements, often find their types at the "string" "int" sort of level but can not expand what the actually tags names are without the schema but you tell there is a tag named something, you know if you encounter the same tag again, and so on. You can check it is valid.  I don't use EXI editors but they do exist and they should be able to load it and display it. It would look a lot like XML where all the tag names had been changed to tag1, tag2, tag3 etc but otherwise had the structure and many of the values. 

Cullen

I should mention one thing - I have only participated in this thread because I did not think it is was clear why some things use + and some use -. For the uses of senml-exi that I care about senml-exi will work just as well as senml+exi. But what happens here seem like it will impact other uses of EXI.