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Subject: Re: RE: [xdi] Rationale and semantics for the 3rd markup model


Am I right in saying that:
(a) models one and two support the current use of XML, i.e. current web 
service standards and possibly the semantic web, more so than model 
(b) The Dataweb, as you envision it, will primarily use model three?

If so then IMHO a really good name for model three would be the DataWeb 
model. What do you think?


----- Original Message -----
From: "Drummond Reed" <drummond.reed@cordance.net>
Date: Tuesday, November 30, 2004 2:19 am
Subject: RE: [xdi] Rationale and semantics for the 3rd markup model

> I see your point, and I agree it means "logical" is probably not 
> the best
> name for the third XDI markup model, because "logical" could 
> equally applies
> to the abstract XDI model as a whole, not to any one markup model.
> In that case I believe the single most distinguishing 
> characteristic of the
> third model is that it is independent of any XML schema OTHER than 
> the XDI
> schema. This is the biggest contrast with the other two models, 
> which are
> both XML-schema-centric. In which case the most precise label for 
> the third
> model would appear to be either "the independent model" or "the 
> XDI schema
> model".
> =Drummond 
> -----Original Message-----
> From: Loren West [mailto:loren.west@epok.net] 
> Sent: Monday, November 29, 2004 12:44 PM
> To: 'Drummond Reed'; 'XDI TC'
> Subject: RE: [xdi] Rationale and semantics for the 3rd markup model
> I'm not a big fan of the terms logical, physical, and abstract
> because they don't communicate anything in and of themselves.
> Sort of like the word "low" - it only makes sense when compared
> to something "high".
> If one model is logical, what is it compared to?  Illogical?
> Physical?  And what is it that makes it more logical than the
> others?
> ALL 3 models allow you to identify, describe, and exchange data
> so none of them are any more or less XDI than the other.
> I think it would be a mistake to say that the inline and enveloped
> models are just a translation of a logical XDI model into XML
> because it places emphasis on the model itself vs. the virtues
> of identifying, describing, and exchanging data.
> It suggests that you should understand the model first, then 
> understand it's translations into XML if that's how you want
> to use XDI.  I fear we'll lose people if we try to get them 
> to understand the 3rd model in order to understand XDI.
> =Loren
> -----Original Message-----
> From: Drummond Reed [mailto:drummond.reed@cordance.net] 
> Sent: Monday, November 29, 2004 11:37 AM
> To: 'XDI TC'
> Subject: RE: [xdi] Rationale and semantics for the 3rd markup model
> Loren,
> I think I get what you're saying - that the two applications that 
> need to
> exchange data may need to first establish context, and that's what 
> this"meta-context" is for.
> But in that case, as you said on the last call, the application 
> *is* XDI.
> XDI is the context.
> That's why it strikes me that most natural name for the third 
> model is the
> term Ajay uses - "the logical model" - because the goal of XDI is 
> to provide
> an abstract, logical model for identifying, describing, and 
> exchanging data.
> All forms of XDI markup, including inline and enveloped, serve to 
> map data
> to and from this logical model. But the first two do so from the 
> context of
> existing XML schemas. The third one does so from the context of 
> the logical
> model itself.
> =Drummond 
> -----Original Message-----
> From: Loren West [mailto:loren.west@epok.net] 
> Sent: Monday, November 29, 2004 11:12 AM
> To: 'Drummond Reed'; 'XDI TC'
> Subject: RE: [xdi] Rationale and semantics for the 3rd markup model
> Hi Drummond,
> This is the best description of the 3rd model yet.  It's still
> a stretch of my imagination to think about an implementation of
> software that could take advantage of this format, because
> by the time I'm thinking about implementing software, I'm in
> context, and I don't know how to handle out-of-context data.
> I can imagine, however, a conversational application where
> context is communicated in real-time - much like human 
> conversation -
> and data is retrieved and delivered based on ever changing context.
> This would be a great way to communicate in that application.
> With this said, I'd like to suggest a few more names for it:
> Runtime model
> Real-time model
> Conversational model (I like this the best)
> =Loren
> -----Original Message-----
> From: Drummond Reed [mailto:drummond.reed@cordance.net] 
> Sent: Saturday, November 27, 2004 2:03 PM
> To: xdi@lists.oasis-open.org
> Subject: [xdi] Rationale and semantics for the 3rd markup model
> I had an action item from Wednesday's XDI TC call (for which Marc 
> is still
> working on the minutes) as follows:
> # Start a thread on the list to: a) solicit our collective 
> rationale for
> using each of the three XDI markup models, and b) out of this, develop
> consensus on the name we should use for the third model. 
> The three XDI markup models were summarized in
> http://lists.oasis-open.org/archives/xdi/200411/msg00041.html. The 
> first two
> models are both "XML-centric", i.e., in both cases XDI markup is 
> added to
> existing XML markup in order to gain the data sharing virtues of 
> XDI while
> still leveraging any existing investment in XML schema, tools, and
> applications.
> The only difference between first two models comes down to whether the
> existing XML schemas being marked up with XDI are extensible or not:
> be placed
> directly inline with the existing XML. Thus the consensus on the 
> call was to
> call this XDI markup model "Inline".
> must be
> added in an envelope wrapping the existing XML. The consensus on 
> the call
> was to call this XDI markup model "Enveloped". 
> Because these two models are so clear, most of the discussion on 
> Wednesday'scall focused on the third model, and when and why an 
> implementer would want
> to use it. Three rationales were put forth:
>  1) When richer resource description is needed than is available 
> using XML
> QNames (and thus is better provided by XRIs).
>  2) When the data being marked up does not yet have an XML schema.
>  3) When the data being aggregated in a single XDI document does 
> not lend
> itself to a particular XML schema because comes from many 
> different data
> sources and there is no single XML schema that makes sense for 
> aggregatingall of it.
> After the call, I realized the killer example of the third type of 
> data is
> when the resource being described is one as generalized as "person",
> "organization", or "topic". It would be all but impossible to 
> create a
> single XML schema that can describe all the data that might be 
> associatedwith a person, an organization, or a topic. The reason 
> is that these are
> simply very general concepts, that can be reused in thousands or 
> millions of
> data sharing applications.
> It dawned on me that this made perfect sense. The universe of XML 
> schemastoday exist mostly to describe data in particular contexts, 
> i.e., existing
> applications and data stores that already have their own schema. 
> Moving the
> data in XML in this case is the first step in being able to share 
> it with
> other applications, domains, and Web services.
> But the more generalized the data, the harder it becomes to completely
> satisfy this need with conventional XML, because the data is less 
> and less
> "schema-specific" and conventional XML is designed to put data in 
> a specific
> schema context.
> It is for these classes of applications, where data may be reused 
> acrossmany (i.e., hundreds or thousands) of different XML schemas, 
> that the real
> demand for XDI arises. Of course all 3 markup models supply the 
> solution:XDI markup can identify and describe the data in a schema-
> independentmanner, so the same logical data can be identified and 
> shared across many
> different physical XML schema instances. But if the distinguishing 
> criteriaof the first two models is that the data already exists 
> and makes sense to
> be used in the context of existing XML schemas, then the 
> distinguishingcriteria of the third model is that either:
> a) No XML schema currently exists to provide the data context, or 
> b) The context is so general that no single XML schema CAN exist 
> to provide
> sufficient context.
> Although in the first case it can be argued that the easiest route to
> establishing the context is to simply create a new conventional 
> XML schema,
> in the second case that's not an option. There is no such schema. 
> The only
> solution is a "generalized" or "universal" XML schema that exists to
> describe things independent of any one specific XML schema 
> context. That's
> the third model.
> Loren predicted that the right term for the third model would 
> emerge once
> the rationale for the third model was clear. I would summarize the
> rationaled for using the third model as "the schema to use when 
> you need
> express and reuse data in a generalized, universal, XML-schema-
> independentformat". This would suggest the following names:
> General model
> Universal model
> Independent model
> Schema-independent model
> Metaschema model
> Abstract model (Victor's suggestion on the call)
> Votes? Other suggestions?
> =Drummond 

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