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Re: RDFa vs RDF/XML and content negotiation

From: Kingsley Idehen <kidehen@openlinksw.com>
Date: Tue, 23 Jun 2009 11:41:57 -0400
Message-ID: <4A40F7C5.4080009@openlinksw.com>
To: bill.roberts@planet.nl
CC: public-lod@w3.org
bill.roberts@planet.nl wrote:
> I've been trying to weigh up the pros and cons of these two approaches 
> to understand more clearly when you might want to use each.  I hope 
> that the list members will be able to provide me with the benefit of 
> their experience and insight!
>  
> So the situation is that I have some information on a topic and I want 
> to make it available both in machine readable form and in human 
> readable form, for example a company wanting to publish information on 
> its products, or a government department wanting to publish some 
> statistics. 
>  
> I can either:
> 1) include 'human' and 'machine' representations in the same web page 
> using RDFa
> 2) have an HTML representation and a separate RDF/XML representation 
> (or N3 or whatever) and decide which to provide via HTTP content 
> negotiation.
>  
> So which should I use? I suppose it depends on how the information 
> will be produced, maintained and consumed.  Some generic 
> requirements/wishes:
Yes it does.

If you take the RDFa route you are making assumptions about the 
existence of RDFa processors (not many at the current time, but this 
will change in due course).
>  
> - I only want to have one place where the data is managed.
Is this a Triple or Quad store?
> - I want people to be able to browse around a nicely formatted 
> representation of the information, ie a regular web page, probably 
> incorporating all sorts of other stuff as well as the data itself.
You want user agents to negotiate representations of your data which 
brings you back to content negotiation.
> - I don't want to type lots of XHTML or XML.
> - I want the data to be found and used by search engines and aggregators.
Simply put RDFa in your HTML representations and via content negotiation 
this will be exposed to crawlers (which are user agents).


>  
>  
> The approach presented by Halb, Raimond and Hausenblas (
> http://events.linkeddata.org/ldow2008/papers/06-halb-raimond-building-linked-data.pdf) 
> seems attractive: to summarise crudely, auto-generate some RDFa from 
> your database, but provide an RDF/XML dump too.
You can auto-generate RDFa as part of your automated HTML generation 
pipeline, but you still have the subtle issue of implicit association of 
a given entity and its metadata (your choice of URI scheme will 
determine if content negotiation is required, assuming all of your data 
exists in an RDFa annotated HTML doc).
>  
> On the other hand I find that RDFa leads to rather messy markup - I 
> prefer the 'cleanliness' of the separate representations.
>  

Well back to Triple / Quad Stores and URL-rewrite rules.

> For any non-trivial amount of data, then we will need a templating 
> engine of some sort for either approach.  I suppose what may tip the 
> balance is that Yahoo and Google are starting to make use of RDFa, but 
> AFAIK they are not (yet) doing anything with "classic" 
> content-negotiated linked data.
They are, they just don't know it. The always request HTML so they get 
an HTML representation of the metadata :-)
>  
> Anyone care to argue for one approach or the other?  I suppose the 
> answer may well be "it depends" :-)  But if so, what does it depend on?
Yes, it really just depends.

RDFa and Content Negotiation work better together that apart (note: to 
Giovanni) .

Kingsley
>  
> Thanks in advance
>  
> Bill Roberts


-- 


Regards,

Kingsley Idehen	      Weblog: http://www.openlinksw.com/blog/~kidehen
President & CEO 
OpenLink Software     Web: http://www.openlinksw.com
Received on Tuesday, 23 June 2009 15:42:33 UTC

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