W3C home > Mailing lists > Public > public-exi@w3.org > March 2012

Re: Concise Format for EXI Grammar

From: Yusuke DOI <yusuke.doi@toshiba.co.jp>
Date: Fri, 09 Mar 2012 22:04:17 +0900
Message-ID: <4F59FFD1.8040809@toshiba.co.jp>
To: Takuki Kamiya <tkamiya@us.fujitsu.com>
CC: Carine Bournez <carine@w3.org>, "public-exi@w3.org" <public-exi@w3.org>
Hi Takuki,

Thank you for the clarification. I think the state machines should be 'equivalent' even if there are many algorithms. Anyway I understand the situation.

OpenEXI grammar serialization will be very helpful, though Nagasena implementation is not yet released.

Thank you very much.

Yusuke

(2012/03/09 14:51), Takuki Kamiya wrote:
> Hi Yosuke,
>
> The EXI specification specifies abstract grammar for EXI, and how it binds to
> XML Schema.
>
> Although section 8.5.4 specifies a normative way to generate grammars given
> a schema, it is normative only in the sense that an implementations needs to
> produce encodings *as if* it was using the exact grammars generated by the
> method described in the spec. The paragraph that explains this is exerpted
> below from section 8.5.4:
>
> "The algorithms expressed in this section provide a concise and formal
>   description of the EXI grammars for a given set of XML Schema definitions.
>   More efficient algorithms likely exist for generating these EXI grammars and
>   EXI implementations are free to use any algorithm that produces grammars and
>   event codes that generate EXI encodings that match those produced by the
>   grammars described here."
>
> In other words, "EXI grammar" is just a denomination, a designation,
> a conceptual term that merely *depends* on the example "method"
> described in the spec.
>
> For example, OpenEXI [1] contains two EXI implementations (Milinda and Nagasena)
> each using fundamentally different way to compute and deliver grammars.
> Milinda uses a novel technique to generate schema-informed EXI grammars from
> schemas whereby the number of grammar state objects generated is roughly the
> same as that of schema constructs such as elements, types and groups regardless
> of minOccurs/maxOccurs constraint numbers given to particles in the schemas.
> Nagasena, on the other hand, uses the algorithm specified in the EXI
> specification to generate schema-informed EXI grammars. Unlike Milinda, the
> number of grammar state objects is additionally affected by minOccurs/maxOccurs
> numbers given to particles.
>
> Milinda and Nagasena were implemented by the same developer. They both have
> grammar serialization format. Nevertheless, it is technically not feasible
> to feed one serialized grammar into the other implementation. They are just
> fundamentally very different.
>
> The good news is that Nagasena's grammar format is independent of programming
> languages. EXI implementors who seek direct access to grammar knowledge
> without dealing with grammar's binding to W3C XML Schema can tap into
> Nagasena's serialized grammars.
>
> Sincerely,
>
> [1] http://openexi.sourceforge.net/
>
> taki
>
>
>
> -----Original Message-----
> From: Yusuke DOI [mailto:yusuke.doi@toshiba.co.jp]
> Sent: Wednesday, March 07, 2012 6:50 PM
> To: Carine Bournez; public-exi@w3.org
> Subject: Re: Concise Format for EXI Grammar
>
> Carie,
>
> Thanks for clarification. I don't find apparent interoperability problems so far. My concern is the learning cost before make things work. EXI spec is good and clear I think, but still needs certain amount of effort to understand correctly.
>
> When someone just want to make it work in some field, it's far better for him/her if s/he can start from a pre-compiled grammar. It can be implementation specific, but I don't find a reason to avoid some 'non-normative' reference serialization model. And I believe if we want to make more use of EXI in the world (my concern is on embedded systems), make it easy to start is very effective strategy.
>
> Regards,
>
> Yusuke
>
> (2012/03/08 3:36), Carine Bournez wrote:
>> Hi,
>>
>> On Thu, Feb 09, 2012 at 04:49:12AM +0900, Yusuke DOI wrote:
>>> Dear EXI gurus,
>>>
>>> Is there any intermediate format to describe EXI grammar?
>>>
>>> As I'm working for several EXI-related projects including SEP2, I'm
>>> feeling it's very convenient if we can share EXI grammar in well-defined
>>> format. The format used in EXI spec is very descriptive, but I guess
>>> that grammar notation is for humans.
>>>
>>> If there's machine-readable (e.g. in plain text or XML) intermediate
>>> format for EXI grammars, I believe we can reduce troubles on
>>> spec-understanding stage by sharing a good grammar between
>>> implementations. Then people can focus on implementations for various
>>> devices of their own.
>>
>>
>> The EXI 1.0 specification does not define a format to exchange grammars
>> between processors. It specifies how to build the grammars in a non-ambiguous
>> way, so that a grammar exchange is not needed. The grammar notation used in the
>> specification is for implementers of EXI processors and it has no
>> machine-readable serialization. In some applications it may be interesting
>> to define a serialized format of the grammars in use, but such a format
>> would be specific to each use case to suit best the application needs.
>>
>> If you encounter particular interoperability issues about grammars, we
>> welcome your feedback and will do our best to clarify the specification
>> wording.
>>
>>
>
>
>
Received on Friday, 9 March 2012 13:04:52 UTC

This archive was generated by hypermail 2.3.1 : Tuesday, 6 January 2015 19:52:44 UTC