SemWeb.Sparql : SemWeb.Query Namespace
SparqlProtocolServerHandler Class

Implements a SPARQL Protocol server for ASP.NET.

public class SparqlProtocolServerHandler : System.Web.IHttpHandler

⊟ Remarks

This class implements the System.Web.IHttpHandler interface to provide a SPARQL Protocol query server over HTTP.

To activate the SPARQL server in your ASP.NET site, place the SemWeb.dll, SemWeb.Sparql.dll, and sparql-core.dll assemblies in the bin directory of your ASP.NET application. Then add the following to your web.config file. Note that you must specify a spec string to a data source to serve, as described in SemWeb.Store.CreateForInput(string).

Example 
<configuration>
     <configSections>
          <section name="sparqlSources" type="System.Configuration.NameValueSectionHandler,System"/>
     </configSections>

     <system.web>
          <httpHandlers>
               <!-- This line associates the SPARQL Protocol implementation with a path on your
                    website. With this, you get a SPARQL server at http://yourdomain.com/sparql.  -->
               <add verb="*" path="sparql" type="SemWeb.Query.SparqlProtocolServerHandler, SemWeb.Sparql" />
          </httpHandlers>
     </system.web>

     <sparqlSources>
          <!-- This line configures the data source associated with each SPARQL server added above.
                  This sets the server to query the RDF/XML file at the given path.  You can use any
                  spec string described in SemWeb.Store.CreateForInput(). -->
          <add key="/sparql" value="xml:/home/user/datafile.rdf"/>
     </sparqlSources>
</configuration>

Precede the data source specification string with "rdfs+" to wrap the data source with the SemWeb.Inference.RDFS reasoning engine. And precede that with "noreuse," to create a new instance of the data source on each request, which is good for SQL-backed stores to allow for concurrent queries, but bad for file-backed stores which would be read from disk on each request. For instance:

Example 
<add key="/sparql" value="noreuse,rdfs+mysql:rdftable:Database=databasename;Server=localhost;User Id=username"/>

Using Mono's XSP light-weight web server, you can create a standalone SPARQL Protocol server by:

  • Creating a new directory for your server.
  • Creating a bin directory within it, and placing the files mentioned above into the directory.
  • Creating a web.config file in the directory using the template above.
  • Running "xsp" from within the directory.

You may want to add this index.html file to create a form to experiment with SPARQL queries:

Example 
<html>
     <body>
          <form action="/sparql" method="get">
        <input type="hidden" name="outputMimeType" value="text/xml"/>
        <textarea name="query" rows="10" cols="80">
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX pol: <tag:govshare.info,2005:rdf/politico/>
SELECT * WHERE {
?s rdf:type pol:Politician .
?s foaf:gender "male" .
?s foaf:name ?name .
}
LIMIT 10
        </textarea>
        <p><input type="submit"/></p>
          </form>
     </body>
</html>

⊟ Requirements

Namespace: SemWeb.Query
Assembly: SemWeb.Sparql (in SemWeb.Sparql.dll)
Assembly Versions: 0.0.0.0

⊟ Members

See Also: Inherited members from object.

⊟ Public Constructors

Creates a new SPARQL Protocol implementation class.

⊟ Public Fields

MaximumLimit int . The maximum number of bindings to return for any query.

⊟ Public Methods

ProcessRequest (System.Web.HttpContext)
Processes an HTTP request from the ASP.NET subsystem.

⊟ Protected Methods

CreateQuery (string) : Query
Constructs a Query object for a SPARQL query.
GetDataSource (out bool) : SemWeb.SelectableSource
Gets the data source to query.
RunQuery (Query, SemWeb.SelectableSource, System.IO.TextWriter)
Runs a query.

⊟ Explicitly Implemented Interface Members

[read-only]
 System.Web.IHttpHandler.IsReusable bool . Documentation for this section has not yet been entered.

⊟ Member Details

⊟ SparqlProtocolServerHandler Constructor

Creates a new SPARQL Protocol implementation class.

public SparqlProtocolServerHandler ()

⊟ Remarks

This class does not listen on an HTTP port by itself. It is meant to be embedded in an ASP.NET site.

⊟ Requirements

Namespace: SemWeb.Query
Assembly: SemWeb.Sparql (in SemWeb.Sparql.dll)
Assembly Versions: 0.0.0.0

⊟ CreateQuery Method

Constructs a Query object for a SPARQL query.

protected virtual Query CreateQuery (string query)

⊟ Parameters

query
The SPARQL query as a string.

⊟ Returns

A Query object.

⊟ Remarks

The default implementation returns a new SPARQL query object based on the query. Override in subclasses to create a query in a different way, or to set limits on the query.

⊟ Requirements

Namespace: SemWeb.Query
Assembly: SemWeb.Sparql (in SemWeb.Sparql.dll)
Assembly Versions: 0.0.0.0

⊟ GetDataSource Method

Gets the data source to query.

protected virtual SemWeb.SelectableSource GetDataSource (out bool closeAfterQuery)

⊟ Parameters

closeAfterQuery
Set to true to indicate that the data source should be closed/disposed after the query is complete.

⊟ Returns

A data source to query.

⊟ Remarks

None.

⊟ Requirements

Namespace: SemWeb.Query
Assembly: SemWeb.Sparql (in SemWeb.Sparql.dll)
Assembly Versions: 0.0.0.0

⊟ MaximumLimit Field

The maximum number of bindings to return for any query.

public int MaximumLimit

⊟ Remarks

Set to -1, the default, to have no limit.

⊟ Requirements

Namespace: SemWeb.Query
Assembly: SemWeb.Sparql (in SemWeb.Sparql.dll)
Assembly Versions: 0.0.0.0

⊟ ProcessRequest Method

Processes an HTTP request from the ASP.NET subsystem.

public virtual void ProcessRequest (System.Web.HttpContext context)

⊟ Parameters

context
The request context.

⊟ Remarks

This method is not meant to be called from user code.

⊟ Requirements

Namespace: SemWeb.Query
Assembly: SemWeb.Sparql (in SemWeb.Sparql.dll)
Assembly Versions: 0.0.0.0

⊟ RunQuery Method

Runs a query.

protected virtual void RunQuery (Query query, SemWeb.SelectableSource source, System.IO.TextWriter output)

⊟ Parameters

query
The query to run.
source
The data source to query against.
output
The output stream.

⊟ Remarks

The default implementation runs the query on the data source and outputs the results in the SPARQL XML Results specification format. Override in subclasses to output the results in a different way, to run the query differently, or to set limits on the query or output.

⊟ Requirements

Namespace: SemWeb.Query
Assembly: SemWeb.Sparql (in SemWeb.Sparql.dll)
Assembly Versions: 0.0.0.0

⊟ System.Web.IHttpHandler.IsReusable Property

Documentation for this section has not yet been entered.

bool System.Web.IHttpHandler.IsReusable { get; }

⊟ Value

Documentation for this section has not yet been entered.

⊟ Remarks

Documentation for this section has not yet been entered.

⊟ Requirements

Namespace: SemWeb.Query
Assembly: SemWeb.Sparql (in SemWeb.Sparql.dll)
Assembly Versions: 0.0.0.0