spatiotemporal capabilties of web data sources (was: ISSUE 14: temporal reasoning and relations)

Hello all,

I am branching off from the other thread, because this is about another
subject:

[snip]

>
>
> Note also that Hobbs and Pan refer to a ‘temporal reasoner’, since a
> generic OWL reasoner could not support all the required comparison
> operations, particularly where OWL-Time steps outside OWL datatypes.
> Similarly, GeoSPARQL implicitly defines a ‘spatial reasoner’, to manage all
> the functions http://www.opengis.net/def/function/geosparql/ .
>

This remark triggered a sleeping thought: How can a consumer know that a
SPARQL endpoint is spatially or temporally enabled, i.e. it supports some
set of functions and datatypes that are defined externally to the SPARQL
specification?

I think the proper way to describe the capabilities of a SPARQL service is
to use the SPARQL Service Vocabulary
<http://www.w3.org/TR/sparql11-service-description/> (namespace: sd). It
has a class sd:Function, which can be used to make it known that the
endpoint supports a certain function (e.g. geof:contains). At first glance,
this seems a good way of making the spatial or temporal capabilities of a
SPARQL service known. A user agent could request the service description
and check whether the extended SPARQL functions it intends to use are
supported by the endpoint. It allows SPARQL services to partially support a
specification like GeoSPARQL - not all GeoSPARQL functions need to be
implemented.

For datatypes, the SPARQL function datatype() could be used to find out if
a dataset uses special spatial or temporal data types. So that seems to be
covered too.

But I wonder if this covers all possible requirements a data consumer might
have with regard to finding out spatiotemporal capabilties of data sources
on the web. Could there be a requirement that we have not identified yet
somewhere?

Greetings,
Frans


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Frans Knibbe
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