RE: comparing XML and RDF data models

I think there is a valid observation to be made about XML and RDF or
relational representations. 

Take the simplest atom of information, "There is a Person named John"

In RDF, there is only one representation;

<Person name John>

In RDBMS there is only one representation

Person
|------|
| name |
|======|
| John |
|------|

In XML there are several possible representations, eg

<Person name="John"/>

<Person>
  <name>John</name>
</Person>

<Person>
  <name value="John">
</Person>
 

With more complicated data, the possible XML representations vary in
different ways, and increase exponentially w.r.t. the number of atoms of
information.  To extract the data from the XML we have to know the
detailed representation chosen. Saying we can UNION different queries
misses the point - we still have to write 3 queries. Saying we can use
transformations misses the point - we still have to write
transformations. 

The issue here is that XML fails to abstract the data from the
representation as effectively as RDF and RDBMS. In this sense, RDF and
RDBMS are better data representations than XML. 

Tim. 




-----Original Message-----
From: semantic-web-request@w3.org [mailto:semantic-web-request@w3.org]
On Behalf Of Bijan Parsia
Sent: 02 July 2008 10:29
To: Olivier Rossel
Cc: semantic-web@w3.org
Subject: Re: comparing XML and RDF data models


On 2 Jul 2008, at 08:43, Olivier Rossel wrote:

>> Any XML instance can be considered a compact, early-bound 
>> serialization of an infoset RDF graph.
>
> +1.
> XML is very powerful when it comes to presenting data (because it 
> details how data imbricate with each other). But XML is very unnatural

No, please no. Don't make such claims without backup. What's  
unnatural for you may be very natural to other people. And   
naturalness doesn't matter if *effectiveness* is at issue.

> when it comes to crawling the data in an unexpected and ever-changing 
> manner (because XML tree structure is chosen once for all,
[snip]

And this is just false. Google for "open content model". Look at XML
Schema's "lax" and "skip" validation modes. Consider transformations.  
(I.e., many XML people are perfectly comfortable treating the "input
tree" as just one step, not a fixed one)

RDF structure is similarly fixed in advanced (by and large).

This kind of talk, aside from being wrong, helps marginalize the
semantic web and related technologies.

In general, if you are inclined to make a general "betterness" claim
based on some abstract feature, don't. If you are going to anyway, make
sure you have every detail nailed with concrete, preferably real
examples ready to hand. Even then, one is better off just presenting the
goodness without contrast. If it's good enough, people will come.

Cheers,
Bijan.

 

-----Original Message-----
From: semantic-web-request@w3.org [mailto:semantic-web-request@w3.org]
On Behalf Of Bijan Parsia
Sent: 02 July 2008 10:29
To: Olivier Rossel
Cc: semantic-web@w3.org
Subject: Re: comparing XML and RDF data models


On 2 Jul 2008, at 08:43, Olivier Rossel wrote:

>> Any XML instance can be considered a compact, early-bound 
>> serialization of an infoset RDF graph.
>
> +1.
> XML is very powerful when it comes to presenting data (because it 
> details how data imbricate with each other). But XML is very unnatural

No, please no. Don't make such claims without backup. What's  
unnatural for you may be very natural to other people. And   
naturalness doesn't matter if *effectiveness* is at issue.

> when it comes to crawling the data in an unexpected and ever-changing 
> manner (because XML tree structure is chosen once for all,
[snip]

And this is just false. Google for "open content model". Look at XML
Schema's "lax" and "skip" validation modes. Consider transformations.  
(I.e., many XML people are perfectly comfortable treating the "input
tree" as just one step, not a fixed one)

RDF structure is similarly fixed in advanced (by and large).

This kind of talk, aside from being wrong, helps marginalize the
semantic web and related technologies.

In general, if you are inclined to make a general "betterness" claim
based on some abstract feature, don't. If you are going to anyway, make
sure you have every detail nailed with concrete, preferably real
examples ready to hand. Even then, one is better off just presenting the
goodness without contrast. If it's good enough, people will come.

Cheers,
Bijan.

Received on Wednesday, 2 July 2008 10:26:21 UTC