- From: Robert Scanlon <rscanlon@revelytix.com>
- Date: Fri, 6 May 2011 12:50:23 -0500
- To: public-rdf-dawg-comments@w3.org
- Message-ID: <BANLkTi=mXk7iTqXn9TU9kjHRxu2WfLaUDg@mail.gmail.com>
Hi, Any thoughts on this? I modified the original text slightly below (from what I'd sent earlier). Bob On Sun, Mar 27, 2011 at 7:29 PM, Robert Scanlon <rscanlon@revelytix.com>wrote: > Hi, > Our company is implementing a SPARQL federator. We are planning on using > the Service Description<http://www.w3.org/TR/2010/WD-sparql11-service-description-20101014/>specification to describe all services, including the services exposed 'out > the top' by our federator ('federation services'), and the external services > that are federated together by any given federation service ('federated > services'). The latter are the services that can be referenced by the > SERVICE clause in a SPARQL query. > > There's a few issues we've found with respect to a service's name (IRI) and > endpoint URL: > > > - It appears to us that the Service Description spec assumes all > services are 'directly accessible', that is, that they all have a URL (the > 'endpoint' property, formerly the 'url' property). Federated services > will not (necessarily) be directly accessible by URL. > > > - In addition, it does not seem like the spec accommodates describing > services that are the references of the SERVICE clause in SPARQL, such as > federated services. Per the federation spec<http://www.w3.org/TR/2010/WD-sparql11-federated-query-20100601/#defn_service>, > the SERVICE graph pattern contains an IRI which is the 'service name', not a > URL; though it is not stated explicitly, one might infer from the > description of GRAPH graph pattern IRIs (in the query spec) that the service > IRI is meant to be 'interpreted by the query service' (in this case, our > federator) to resolve the service (that is, it's not a directly-resolvable > URL). > > > - The implication that a service is identified by URL (as opposed to > IRI) seems to tightly couple a service to a particular URL. This does not > allow for 'relocating' a (logically named) service, such as moving it to a > new machine, or migrating it through a development-testing-production > staging process, both typical of operations performed in enterprise > environments. > > - Currently a service MUST have a URL (sd:endpoint property), per 'Conformance' section. This does not allow for the used of a Service Description to describe a federated service, which is accessible through a federation query service (via SERVICE clause) but may not necessarily be directly accessible on its own (so will not have a URL). A URL is also unnecessary for services accessed through an embedded component (as opposed to a remote-accessible endpoint). > > > We would like to suggest that the spec be modified to allow the 'sd:name' > property to be optionally used with Services (domain sd:Service, range IRI, > cardinality 0..1, or maybe mandatory?). This would uniquely identify a > service (similar to and consistent with graph naming/identification); would > define exactly the IRI required for the SERVICE graph pattern in federated > queries; and would decouple the service's identity from its served-up > location (URL). In addition, the sd:url property should be optional, so > that for federated services, or for services exposed by an embedded > component, it could be excluded. > > Thanks, > Bob Scanlon > Revelytix <http://www.revelytix.com/> > > >
Received on Friday, 6 May 2011 17:51:11 UTC