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Re: Device description structures and families

From: Rafael Casero <rcasero@satec.es>
Date: Thu, 22 Mar 2007 11:17:36 +0100
Message-ID: <460257C0.3030007@satec.es>
To: public-ddwg@w3.org
Hi all,

I think there was a somewhat similar problem at OGC (Open Geospatial 
Consortium) and maybe its solution can be useful for us too. In order to 
explain the similarities (and then the approach) let me first summarize 
a little bit our problem.

a) There are some 'static' device properties, for instance, screen width

b) There are, also, some other properties 'derived' from the 'static' 
ones: we can say that belonging to a particular family is the result of 
applying a 'formula', for instance,
(XHTML-MP = yes) AND (width > 128)  AND  (height > 160).

In such a view, the 'family' semantics is the result of applying a 
formula (or pseudocode) . The way in which that is implemented in a real 
DDR need not to be specified: it can be evaluated on demand or can be 
previously evaluated and stored (like any 'static' property), that will 
depend on the particular implementation.

The similar problem that OGC found is that they have 'features' that are 
'static' properties related to a particular location (i.e., there is a 
petrol station at location x, y). For that they defined the 'Web Feature 
Server' (WFS) that it is a minimum set of specifications that a server 
must comply. Also they have a specification for a 'Web Processing 
Server' (WPS) that allows for 'derived' properties or calculated results 
(i.e., give me the petrol stations inside the area defined by xMin, 
yMin, xMax, yMax). They separate both specifications because the 
processing required in the second case can be much demanding than in the 
WFS case.

Translating this specification to our case will be something like this:

a) Families can be defined as a formula or a pseudo-code

b) DDRs could have processing capabilities or not

c) DDRs, with processing capabilities, could store formulas (or code) as 
a way to define families. The way in which they are solved and processed 
(on demand, previously stored, etc.) depends on the particular 
implementation allowing for a quality of service differentiation between 

d) Different families can be defined for different companies using, for 
instance, name spaces. Then there can be also a business case for the 
families definition (effective terminal segmentation)

e) Privileged users could be able to define 'derived properties' (i.e. 
families) by defining the name (within a name space) and the formula (or 
pseudo code)

f) Developers could define the 'formula' to apply in the query or 
(depending on their privileges) store it as a 'derived property'

g) Effective terminal segmentation (families) can be offered by some 
providers by defining particular formulas.

h) Developers can query for a 'static' or 'derived' property in the same 
way transparently, only, maybe, they have to query to a different DDR 
depending on the property queried. (Also there is here a business case: 
the DDRs that can deliver 'derived' properties can offer to their 
customers processing capabilities and good semantics)

This figure is like to mimic the OGC way of doing. Of course we have to 
discuss if that model is of any use for us but I think is worth to think 
at it.

What do you think about it?

- Raf.Casero

-------- Mensaje Original --------
> Hi all,
> I have started with some use cases regarding device description 
> structures [1]. Two of them are envisaged but not yet written :).
> You are welcome to contribute with more use cases, like those that 
> Kevin and Andrea has mentioned these days in the list.
> Feedback from the public and group members is also needed
> Thanks and best regards
> [1] 
> http://www.w3.org/2005/MWI/DDWG/wiki/DeviceDescriptionStructuresUseCases
> Rotan Hanrahan escribió:
>>> This would assume a common syntax for representing the family rules.
>> And this is precisely where I think the work that José is leading will help us.
>> ---Rotan
>> -----Original Message-----
>> From: Smith, Kevin, VF-Group [mailto:Kevin.Smith@vodafone.com] 
>> Sent: 20 March 2007 15:48
>> To: Rotan Hanrahan; public-ddwg@w3.org
>> Subject: RE: Device description structures and families
>> Hi Rotan, 
>> Thanks for the clarification...
>> Another use case is content filtering, e.g. indicating that 'this family gets a movie, while this family gets an image'. Resolution of the expression would involve confirming the requesting device is of a given family. Then the appropriate link or object would be presented.
>> As both yourself and José say, there could be benefit in sharing some of these family classifications: for example, a games publisher could create a set of rules as to which devices can support their latest games for the best user experience (mature J2ME, good CPU, decent resolution etc.) and this could be represented as a family (possibly namespace bound, eg gamescorp.bestSupport). They could also provide minimum criteria for legacy games (gamescorp.justSupport). Maybe the provisioning of these family rules can be in a DDR extension, or it could be possible in the query to the DDR to ask for the family rules to be fetched from an external source (such as gamescorp themselves). This would assume a common syntax for representing the family rules.
>> Cheers
>> Kevin 
>> [...]
Received on Friday, 23 March 2007 11:53:34 UTC

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