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Re: service description vocabulary

From: Gregory Williams <greg@evilfunhouse.com>
Date: Mon, 28 Sep 2009 12:06:34 -0400
Cc: "public-rdf-dawg@w3.org Group" <public-rdf-dawg@w3.org>
Message-Id: <BE21477D-D6A4-40A5-A83D-B5298D41EAFC@evilfunhouse.com>
To: Steve Harris <steve.harris@garlik.com>
On Sep 26, 2009, at 4:36 AM, Steve Harris wrote:

>> So, in a quad store, you will describe each graph separately using  
>> voiD ?
>> Won't it be too much information in the SD, e.g. if I have 1  
>> million RDF files in my store, will have 1 million of voiD  
>> descriptions in the SD.
> Right, the FOAF store that backs http://foaf.qdos.com/ for example  
> has around 2 million graphs in it, and we would obviously like to be  
> able to describe its contents in a standard manner.

We've talked about having both a way to embed the dataset description  
in the SD document and also a way to link to a URL where the dataset  
description can be retrieved. Would that satisfy your needs here?

> Also, at the risk of sounding like a broken record :) it's critical  
> that there be a way to talk about the endpoint using relative URIs  
> or some similar trick so that the software emitting the descriptions  
> is not required to know the endpoint URI that the client is  
> connected to.
> Descriptions using <> as a subject are fine, but other things will  
> be problematic.

I'm not sure what it is that you're referring to as I thought  
everything that's been proposed regarding the vocabulary so far is in  
line with your relative URI requirement.

>> So
>> <endpoint> sd:datasetDescription [
>> 	sd:defaultGraph [
>>               sd:graphName <graph-name> ;
>> 		sd:graphDescription <void-dataset-for-default-graph> ;
>>       ] .
>> 	sd:namedGraph [
>> 		sd:graphName <graph-name> ;
>> 		sd:graphDescription <void-dataset-for-named-graph> ;
>> 	] .
>> ] .
> Let's not bake Void into SPARQL. It's sufficient to say that it  
> should be an RDF description, the exact vocabulary can be left open.

Yeah, agreed. The idea was never to bake voiD into the spec, but to  
think of it as a possible best practice to use for describing the  
datasets (and it makes examples easier to discuss since we've already  
got a vocabulary that people know).

>> while I'd think a simple way would be
>> <endpoint> sd:datasetDescription <void-dataset-for-dataset> ;
>> 	sd:defaultGraph <graph-name> ;
>> 	sd:namedGraph <graph-name> .
> That would be more palatable, but if it's possible for the client to  
> request a description there needs to be some way for the client to  
> request the description of a specific graph.

How about the two variants (embedded and linked) like so:

sd:namedGraph [
	sd:graphName <graph-name> ;
	sd:graphDescription <void-dataset-for-named-graph> ;
] .

(this is example from before), and:

sd:namedGraph [
	sd:graphName <graph-name> ;
	sd:graphDescriptionURL <document-url-with-void-dataset-for-named- 
graph> ;
] .

It's not quite as simple as just "<> sd:namedGraph <graph-name>", but  
it keeps the actual dataset description out of service description  
document while giving you a place to go get it.

Received on Monday, 28 September 2009 16:07:15 UTC

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