Re: comparing XML and RDF data models

Yes views are very interesting. Simon Schenk has developed a Sail for  
Sesame that uses SPARQL construct
queries to create views. I wrote up here:

http://blogs.sun.com/bblfish/entry/opening_sesame_with_networked_graphs

There is no need to remove namespaces for this to work btw. This is  
very very useful.

Henry


On 1 Jul 2008, at 15:33, <tim.glover@bt.com> wrote:

>
>
> I think it is also interesting to make a comparison with SQL and  
> RDBMS,
> which sets a pretty high bar for query languages.
>
> One of the great strengths of SQL/RDBMS is *views*. These shield users
> (SQL queries) from changes in the underlying schema. I think this  
> would
> have a particular application and relevance in the XML/RDF world,
> because views could shield users from the complexity and  
> immovability of
> namespaces. IMO there is a strong case for storing XML/RDF data with  
> no
> namespaces, and add namespace information in views.
>
> I expect this has already been thought of - are there any
> implementations out there?
>
> Tim.
>
>
>
>
> -----Original Message-----
> From: semantic-web-request@w3.org [mailto:semantic-web-request@w3.org]
> On Behalf Of Maciej Gawinecki
> Sent: 01 July 2008 11:21
> To: semantic-web@w3.org
> Subject: comparing XML and RDF data models
>
>
> In one of the article comparing two data models: XML and RDF I found a
> statement stating that (I'm loosely citing from my memory):
>
>   Searching XML with XPath query expression is easy if you know the
>   schema of the document being quiried. However, the same query will
> not
>   work any a document, which is differently structured, but contains
>   equivalent information. This can be solved by usage of RDF model,
>   which can be then queried with RDQL or SPARQL query.
>
> Is that really true, that XPath-based XML search is limited due to its
> structure? Yes, that's why there is a great research on keyword-based
> quering of XML documents (not knowing schema in advance). But is it  
> RDF
> really better for this issue ?
>
> I will try to give a few example what I exactly mean. [Of course, I'm
> ommiting here the problem of knowning the name a tag/property/ 
> resource,
> only the structure can be different.] Let's see two XML documents:
>
>   <Sensor>
>     <name>Sensor220</name>
>     <isLocatedNearBy>
>       <Road>
>         E330
>       </Road>
>     <isLocatedNearBy>
>   </Sensor>
>
> Here road value can be check through XPath expression:
> \\Sensor\isLocatedNearBy\Road
>
> And let's see differently structured document (road defined by name
> property)
>
>   <Sensor>
>     <name>Sensor220</name>
>     <isLocatedNearBy>
>       <Road>
>         <name>E330</name>
>       </Road>
>     <isLocatedNearBy>
>   </Sensor>
>
> With XPath expression: \\Sensor\isLocatedNearBy\Road\name
>
> Or yet another one (road is ancestor tag to the sensor tag, not the
> oposite)
>
>   <Road>
>     <name>E330</name>
>     <hasSensor>
>       <Sensor>
>         <name>Sensor 220</name>
>       </Sensor>
>     </hasSensor>
>   </Road>
>
> XPath: \\Road\name
>
> The same problem would be with RDF. Let see the first model
>
>   :Sensor220 :isLocatedNearBy :Road_E330 .
>
> WHERE clause of SPARQL query would be then like a
>
>   ?s :isLocatedNearBy :Road_E330 .
>
> For other version we define a road with a specific value of hasName
> property:
>
>   :Sensor220 :isLocatedNearBy :RoadXXX .
>   :RoadXXX :hasName "E330" .
>
> the SPARQL query part:
>
>   ?s :isLocatedNearBy ?r .
>   ?r :hasName "E330" .
>
> or by analogy to the third XML representation (road "has" a sensor,  
> not
> the opposite):
>
>   :RoadXXX :hasName "E330" .
>   :RoadXXX :hasSensor :Sensor220 .
>
> the SPARQL query part:
>
>   ?r :hasName "E330" .
>   ?r :hasSensor ?s .
>
> Can someone comment it ?
>
> Thanks,
> Maciej
>
>
>
>