Scott,
The Getting Started guide that I read didn't have this kind of
detail. Just for clarification, if I use drag an drop to import one
file, rdffile1.rdf into another rdfile2.rdf, is the statement
rdffile2.rdf owl:imports rdffile1.rdf
automatically added?
Secondly, if I click on the imports tab in the bottom center pane and
import from uri, does that automatically create an owl:imports triple?
Similarly, if I want to do queries against properties defined in a
vocabulary that is defined on the web, do I need store a local copy,
that is download the ontology, so that it can run queries that use
that vocabulary? I assume this must be required in order to have
those properties in memory to use for running queries. Is that right?
Thanks,
Bruce
On Feb 4, 1:14 pm, Scott Henninger <[email protected]> wrote:
> Hello Bruce; It may be a good idea to take a look at the Getting Started
> Guide for TopBraid Composer. The first few chapters will give you some good
> guidance on basic operations with files. You can find the guide, and other
> guides and tutorials, athttp://www.topquadrant.com/products/support.html.
> The basic principle is that data is brought into memory for computation, just
> as with any other application I can think of. You can't run a query on a
> remote piece of data. You could run a query against a service that wraps a
> piece of data. That's what a SPARQL Endpoint does.
> owl:imports just makes it easy to specify what data needs to be brought into
> memory as part of the definition of a file. If fileA imports fileB, e.g.
> {<fileA> owl:imports <fileB>}, then when fileA is opened, Composer will use
> the base URI of fileB to open it and merge the data in the in-memory storage.
> fileB could be a file on the Web. That means when opening fileA, Composer
> will use the base URI as a URL, download the data, and read it into memory.
> Depending on network latency and file size, this could take a while. If
> fileB changes frequently, you may need to keep it that way (i.e. leave the
> file on the Web). If it changes infrequently, then it may be best to create
> a copy and place it in Composer's workspace. This reduces the amount of time
> to open the file. In the case of FOAF, they use a versioning scheme so files
> are immutable - a change to the file will result in a new file name. Hence
> downloading to use a specific version is the anticipated use.
> Regardless of how the file is stored, loading into Composer involves
> converting the triples into a data structure (Jena RDF). The data structure
> implements an in-memory graph structure that optimizes access to triples.
> This in-memory model is what is used to display Composer's UI, fetch data,
> apply SPARQL queries, run inferences, etc. Merging an imported file is
> basically reading the file into this model.
> Namespaces have little to do with any of this - it's a separate concept taken
> from XML. A namespace is the syntactic part of the URL before the name. So
> forhttp://example.org/mydata#myitem, the namespace
> is"http://example.org/mydata#". That's it. The namespace can appear in any
> file to define a fully qualified URI (namespace + local name). It's a
> "space" in that one can say that there are a set of entities defined in the
> "space""http://example.org/mydata#";, one of which is "myitem" in this example.
> So, back to your specific questions. To use FOAF in Composer, it has to be
> downloaded and read into memory. Then you can apply queries, etc.
> <<if I import an RDF file into another file, that
> is rdffiel1.rdf into rdffile2.rdf and then save the second file, the
> next time I open this rdffile2.rdf should this file have saved the
> imported graph within the same file?>>
> No, the imported graph will not be saved *in* rdffile2.rdf. If you specify an
> owl:imports of rdffile1.rdf into rdffile2.rdf, i.e. {rdffile2.rdf owl:imports
> rdffile1.rdf}, the data fromrdffiel1.rdfstays in rdffile1.rdf. What the
> imports statement means is "Whenever rdffile2.rdf is opened (read into
> memory), also open rdffile1.rdf and merge into the same in-memory model."
> You can then perform browsing and query operations on the files as a single
> model.
> Be clear about separating the concepts of namespaces and imports. Imports
> are basically an "include statement". Namespace is a syntactic piece of the
> URI.
> Hopefully that helps some. I'd really encourage taking a look at the Getting
> Started Guide and/or looking into our training offerings.
> -- Scott
> Scott Henninger, PhD
> Platform Product Manager, Senior Product and Training EngineerTopQuadrant,
> Inc.,
> tel: 402-429-3751 / fax: 703 991-8192 / main: 703 299-9330
> Training:
> Introduction to Semantic Web Technologies - March. 5-8, 2012, Washington, DC
> TopBraid Advanced Products Training - April 9-12, 2012, Washington, DC
> Introduction to Semantic Web Technologies - April 24-26, 2012, New York, NY
> TQ Blog:Voyages of the Semantic Enterprise
> On 2/3/12 7:05 PM, Bruce Whealton wrote:I was a bit unclear about this
> concept. Let's assume that TBC didn't have a copy of FOAF included with the
> download. So, is it possible to run SPARQL queries against FOAF Classes and
> Properties using just the namespace for FOAF on the web? Or does TBC need to
> import the FOAF ontology into the open file? That leads to my second
> question, if I had an ontology file and a data file, as discussed in the
> Learning Sparql book, if I was going to query against the data using TBC, do
> I need to import the ontology into the data file? Or will TBC support SPARQL
> queries against files that are in the same project? Lastly, but relatedly, if
> I import an RDF file into another file, that is rdffiel1.rdf into
> rdffile2.rdf and then save the second file, the next time I open this
> rdffile2.rdf should this file have saved the imported graph within the same
> file? That doesn't seem to be the case for me. I have several namespaces that
> are defined in my foaf.rdf file. At one point I must have let TBC import the
> external namespaces because I have import statements, in the file. But each
> time I open that file, it takes a long time because it has to go get the
> files off the web. Thanks, Bruce
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