THE SQL Server Blog Spot on the Web

Welcome to SQLblog.com - The SQL Server blog spot on the web Sign in | |
in Search

Jamie Thomson

This is the blog of Jamie Thomson, a freelance data mangler in London

Explaining the difference between OData & RDF by way of analogy

A couple of months back I wrote a blog post entitled Microsoft, OData and RDF where I gave a high level view of the OData protocol and how it compares to RDF. I talked about linked data, triples and such like which may have been somewhat useful however jargon-heavy. Earlier today Dr Michael Hausenblas (blog | twitter) offered an analogy which I think is probably more useful and with Michael's permission I'm re-posting it here:

Imagine a Web (a Web of Documents, if you wish), which is not based on HTML and hyperlinks, but on MS Word documents. The documents are all available on the Internet, so you can download them and consume the content. But after you’re done with a certain document that talks about a book, how do you learn more about it? For example, reviews about the book or where you can purchase it? Maybe the original document mentions that there is some more related information on another server. So you’d need to go there and look for the related bit of information yourself. You see? That’s what the Web is great at – you just click on a hyperlink and it takes you to the document (or section) you’re interested in. All the legwork is taken care of for you through HTML, URIs and HTTP.

Hm, right, but how is this related to OData?

Well, OData feels a bit like the above mentioned scenario, just concerning data. Of course you – well actually rather a software program I guess – can consume it (a single source), but that’s it.

from Oh – it is data on the Web by Michael Hausenblas

I believe that OData has loads of use cases but its important to understand its limitations as well and I think Michael has done a good job of explaining those limitations.

@Jamiet

 

Published Wednesday, April 14, 2010 12:18 PM by jamiet

Comment Notification

If you would like to receive an email when updates are made to this post, please register here

Subscribe to this post's comments using RSS

Comments

 

Roger Jennings said:

Jamie,

IMO, Michael is incorrect when he concludes "Of course you – well actually rather a software program I guess – can consume it (a single source), but that’s it."

OData is not single-source, either for clients (consumers) or servers (providers). Microsoft has published open-source clients for various platforms and Microsoft and IBM have providers for .NET and WebSphere, respectively.

Cheers,

--rj

April 14, 2010 12:57 PM
 

jamiet said:

Hi Roger,

I suspect that's now what Michael meant. I think he meant that each OData service is a single source (i.e. disconnected from any other), not that an OData service can only provide information from a single source.

I stand to be corrected.

-Jamie

April 14, 2010 2:44 PM
 

Michael Hausenblas said:

Roger,

Re single-source - this is a simple misunderstanding ;)

What you seem to refer to is 'platforms' (and I agree, OData is available for multiple platforms, as you highlighted), however what I mean is that each OData source is a data silo, not connected with other OData sources.

Technically it would be possible to connect the OData sources (through Atom), though it seems that this is not the way OData is deployed. Contrast this with the Linked Data Web, where the data sources (datasets called there) link to each other, just like in the Web of Documents (with @href) in the Linked Data world RDF properties are used to link entities in the datasets and in Atom one would use @rel values. I suggest to read [1] which gives a nice overview and introduction into the Linked Data world.

Hope this clarifies the issue and happy to discuss in greater detail, if you want.

Cheers,

Michael

[1] http://tomheath.com/papers/bizer-heath-berners-lee-ijswis-linked-data.pdf

April 15, 2010 3:56 AM
 

tnafoo said:

Hi Jamie,

I just thought you'd be interested in this article at http://briancray.com/2010/09/08/html5-microdata/

HTML5 has already started enabling OData in the form of MicroData.

September 12, 2010 10:55 PM
 

jamiet said:

tnafoo,

Thank you very much, very interesting indeed and superbly timed because I have also just been reading this: http://www.webmonkey.com/2010/09/microdata-html5s-best-kept-secret/

Having said that I don't really understand this comment:

"HTML5 has already started enabling OData in the form of MicroData."

Please could you elaborate?

-Jamie

September 13, 2010 4:13 AM

Leave a Comment

(required) 
(required) 
Submit

This Blog

Syndication

Powered by Community Server (Commercial Edition), by Telligent Systems
  Privacy Statement