Hi Frans,
Thanks for your feedback !! So, now let's iterate over your comments ;)
More comments in-line...
As for the details, I tried to form a better understanding of the SPARQL
1.1 Service Description
(http://www.w3.org/TR/sparql11-service-description/), since that is
vocabulary that is extended. But some things I did not get:
* I was wondering whether it would be good to know the version(s) of
the SPARQL Protocol that is supported by an endpoint. I have just
noticed that the Service Description vocabulary is for SPARQL 1.1
only, not for SPARQL in general (including past and future
versions). Does this mean that a user agent can infer that the
service supports version 1.1 of SPARQL if it is described by the
SPARQL 1.1 Service Description? And will it be probable that new
vocabularies will be published to describe future versions of SPARQL?
I am not sure to understand your point here. Did you look at sd:Language
definition at
http://www.w3.org/TR/sparql11-service-description/#sd-Language ?. At the
moment, this class defines 3 instances for the past and current version
of SPARQL query, namely sd:SPARQL10Query, sd:SPARQL11Query and
sd:SPARQL11Update. So, I guess you can always create an instance of
sd:Language for the future versions of SPARQL.
btw, if a service implements SPARQL1.1, does it mean it take into acount
the past versions of the language? I suspect the answer is yes but not
sure...I'll investigate later.
* In the abstract it says /"//These descriptions provide a mechanism
by which a client or end user can discover information about the
SPARQL service such as supported extension functions and details
about the available dataset//"/. Note the singular in the last word:
dataset. Does this mean that a 1:1 relationship between services and
datasets is assumed?
No, I don't think so... I prefer to look at the semantic in the owl spec
instead..
* I think I have always seen a SPARQL Service and a SPARQL endpoint as
being the same thing. But looking closely at the SD vocabulary, I
see they are modelled as different things. I think it is important
to understand the difference, but I could not find a description of
the difference between a SPARQL endpoint and a SPARQL service.
However, I do find web resources that seem to equate the two, like
this text from the SPARQL overview
(http://www.w3.org/TR/sparql11-overview/) : /"//Assuming the graph
data from above is loaded into a SPARQL service (i.e., an HTTP
service endpoint that can process SPARQL queries) ..//. "//. /I am
afraid I am confused...
As I can read from the Terminology section, A SPARQL Service could be
generally speaking "Virtuoso 6.0" and a SPARQL endpoint
<http://dbpedia.org/sparql>. A service seems to be more generic than
just a particular endpoint.
Maybe this small sample for lov endpoint using the SD vocab could help?
@prefix sd: <http://www.w3.org/ns/sparql-service-description#> .
@prefix void: <http://rdfs.org/ns/void#> .
[] a sd:Service ;
sd:endpoint <http://lov.okfn.org/endpoint/lov> ;
sd:supportedLanguage sd:SPARQL11Query ;
sd:resultFormat <http://www.w3.org/ns/formats/RDF_XML>,
<http://www.w3.org/ns/formats/Turtle>,
<http://www.w3.org/ns/formats/N3>,
<http://www.w3.org/ns/formats/SPARQL_Results_XML>;
sd:feature sd:DereferencesURIs ;
sd:defaultDataset [
a sd:Dataset ;
sd:defaultGraph [
a sd:Graph ;
void:triples 23985
] ;
] .
As for the proposal, here are some remarks:
* I was taught at school that it is good practice to always use whole
SI units. I notice you use milliseconds to denote the query timeout
value. Wouldn't it be better to use seconds (regardless of present
day common practice)?
+1. :
* Why is sdm:maxResultsPerRequest a property of sdm:SPARQLRequest?
Isn't the limit always the same across for all requests that can be
sent to the endpoint?
I see your point. But I define sdm:SPARQLRequest as subClassOf
http:Request to be able to have access to the httpVersion of the
protocol. That was actually one of your requirement.
* Shouldn't sdm:maxResultsPerRequest and sdm:remainingPerRequest be
of type xsd:integer?
Yes. I update it.
Regards,
Ghislain
--
Ghislain Atemezing
EURECOM, Multimedia Communications Department
Campus SophiaTech
450, route des Chappes, 06410 Biot, France.
e-mail: [email protected] & [email protected]
Tel: +33 (0)4 - 9300 8178
Fax: +33 (0)4 - 9000 8200
Web: http://www.eurecom.fr/~atemezin
