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Contents
Preface

Installation Guide

Virtuoso for Windows
Virtuoso for Linux (Enterprise Edition)
Virtuoso for Unix (Enterprise Edition)
Virtuoso for Unix (Personal Edition)
Virtuoso for Mac OS X
Virtuoso ADO.Net Data Grid Form Application
Using Visual Studio 2008 to Build an Entity Frameworks based Windows Form Application
Using Visual Studio 2008 to Build an ADO.NET Data Services based Application
Windows Form Application for accessing Virtuoso RDF data via SPASQL using the Virtuoso ADO.Net Provider
Creating a Web Browser Application to Access RDF Data Using The Virtuoso ADO.Net Provider
Pre-requisites Creating the Web Service Creating the Browser Application Deploy With IIS
Creating a Silverlight Application to consume the service
Creating A Simple .NET RIA Services Application To Display Data From Virtuoso
Creating a .Net RIA Services Application That Will Update Virtuoso Data
Cluster Installation and Config

2.10. Creating a Web Browser Application to Access RDF Data Using The Virtuoso ADO.Net Provider

This section will guide you through creating first a Web Service that exposes RDF data from Virtuoso and then a simple web browser application that consumes the Web Service and allowing you to access and explore the RDF data by clicking on dereferenceable IRIs.

2.10.1. Pre-requisites

  1. The example assumes that you have a local Virtuoso server with the Northwind demo database installed. If the demo database is not already installed then download the demo database VAD package (demo_dav.vad) and install it. The VAD package will create a new database in Virtuoso called demo containing the familiar Northwind tables. It will also creates RDF views of the Northwind tables. In the example we assume the database is accessible on a hostname of "demo.openlinksw.com" on the default port 80, where an actually live instance of the Virtuoso Demo database is hosted. Users would use the appropriate hostname and port number of their Virtuoso installation to create the sample application, and would be would be localhost:8890 for a default installation or whatever the URIQA DefaultHost Virtuoso configuration parameter is set to when the demo database VAD package is installed.
  2. The Virtuoso ADO.Net provider for .Net 3.5 and the Entity Framework.
  3. Microsoft Visual Studio 2008
  4. The Virtuoso RDF Mappers VAD package.

2.10.2. Creating the Web Service

Step 1 - Create a view of the RDF data

To create a view of the customers in the Northwind first open the Virtuoso Conductor and log in as dba. Then open iSQL from the menu on the left and execute the following statement.

create view Demo.demo.sparqlview as
sparql
select distinct ?s  from <http://localhost:8890/Northwind>
where {?s a <http://demo.openlinksw.com/schemas/northwind#Customer>}

Note:

create a view
Figure: 2.10.2.1. create a view

Step 2 - Create the Visual Studio Project and Add the Model

  1. Open Visual Studio and create a new ASP .NET Web Application called RDFWebDemo.
    create new application
    Figure: 2.10.2.1. create new application
  2. Right click RDFWebDemo in the Solution Explorer and add a new ADO.NET Entity Data Model called Model1.edmx. This will open the Entity Data Model Wizard.
  3. Choose Generate From Database and click Next.
  4. Set up a connection to the Demo database on your local Virtuoso Server, select Yes, include the sensitive data in the connection string and set the name of the entities to DemoEntities. Click Next.
  5. On the Choose Your Database Objects page expand Views and select sparqlview. Check that the Model Namespace is DemoModel and click Finish.
    Model Namespace
    Figure: 2.10.2.1. Model Namespace

Step 3 - Add the Web Service

  1. Right click RDFWebDemo in the Solution Explorer and add a new ADO.NET Data Service called WebDataService1.svc. Click Add.
  2. In the class definition of WebDataService1 in the newly created file WebDataService1.svc.cs replace /* TODO: put your data source class name here */ with the name of our model, DemoEntities.
    public class WebDataService1 : DataService<DemoEntities>
    
  3. In the InitializeService method add the line:
    config.SetEntitySetAccessRule("*", EntitySetRights.All);
    

    The method should look like this:

     public static void InitializeService(IDataServiceConfiguration config)
       {
           // TODO: set rules to indicate which entity sets and service operations are visible, updatable, etc.
           // Examples:
           // config.SetEntitySetAccessRule("MyEntityset", EntitySetRights.AllRead);
           // config.SetServiceOperationAccessRule("MyServiceOperation", ServiceOperationRights.All);
    
           config.SetEntitySetAccessRule("*", EntitySetRights.All);
       }
    

Step 4 - Compile and Run

Hit F5 to compile and run the service. Select OK when prompted to enable debugging. The default browser will be launched showing a page like:

  <?xml version="1.0" encoding="utf-8" standalone="yes" ?>
- <service xml:base="http://localhost:1241/WebDataService1.svc/" xmlns:atom="http://www.w3.org/2005/Atom" xmlns:app="http://www.w3.org/2007/app" xmlns="http://www.w3.org/2007/app">
- <workspace>
  <atom:title>Default</atom:title>
- <collection href="sparqlview">
  <atom:title>sparqlview</atom:title>
  </collection>
  </workspace>
  </service>

The service is now running.

Note the address on which the service is made available. You will need to know this when creating the app to consume the service. Look in the Address Bar of the browser. It will be something like: http://localhost:1492/WebDataService1.svc/


2.10.3. Creating the Browser Application

Step 1 - Create the Visual Studio Project.

  1. Open Visual Studio and create a new ASP.NET Web Application called RDFWebApp.
    New Web Application
    Figure: 2.10.3.1. New Web Application
  2. Create client side entities with datasvcutil.exe
    • Open a command prompt.
    • Navigate to *C:\WINDOWS\Microsoft.NET\Framework\v3.5*.
    • Generate the client classes using the following command:
      datasvcutil.exe /uri:http://localhost:1492/WebDataService1.svc /out:DemoEntities.cs
      

      Note the address of the service - you may need to change the port number to match the one seen in the address at the end of Step 4 in Creating the Web Service.

  3. Add the classes to RDFWebApp.
    • Right click RDFWebApp
    • Choose to add an existing item and add c:\WINDOWS\Microsoft.NET\Framework\v3.5\DemoEntities.cs.
  4. Add a reference to System.Data.Services.Client to the project.

Step 2 - Display the contents of sparqlview as a table on the page

To display the RDF data on the web page we create a table with a row for each item in sparqlview. We then use each IRI from sparqlview to create a hyperlink. The hyperlinks are displayed in the table cells. To do this add the following block of code to the page_load method in Default.aspx.cs.

 DemoModel.DemoEntities svc = new DemoModel.DemoEntities(new Uri("http://localhost:1492/WebDataService1.svc"));

  var query = svc.sparqlview;
  Table iriTable = new Table();
  this.Controls.Add(iriTable);

  foreach (DemoModel.sparqlview sv in query)
  {
      TableRow tRow = new TableRow();
      iriTable.Rows.Add(tRow);
      TableCell tCell = new TableCell();
      tRow.Cells.Add(tCell);
      HyperLink h = new HyperLink();
      h.Text = sv.s;
      h.NavigateUrl = sv.s;
      tCell.Controls.Add(h);
  }

Note the address of the service in the first line - you may need to change the port number to match the one seen in the address at the end of Step 4 in Creating the Web Service.

Compile and run RDFWebApp (ensuring that the service created above is still running). This will launch a browser and display the IRIs from sparqlview as a list of hyperlinks.

list of hyperlinks
Figure: 2.10.3.1. list of hyperlinks

With the RDF Mappers VAD package installed in Virtuoso, clicking on these links will take you to a description page of the referenced resource. The description page is created using description.vsp.

Description page
Figure: 2.10.3.2. Description page

2.10.4. Deploy With IIS

To create and test this simple Web Service we have used the Visual Studio Development Server. This section describes how to deploy the service using IIS.

2.10.4.1. Web Service

To deploy the service using IIS:

The start page that you see when you test the service will look the same as before but the address in the browser bar will be something like http://localhost/RDFWebDemo1/WebDataService1.svc/. You can now access your service remotely using the hostname or IP address of your server.

If at this point you get an Access is denied error, 401.3, then you will need to add the Internet Guest Account (IUSR_XXX where XXX is your computer name) to the users allowed to access the folder containing the RDFWebDemo project.


2.10.4.2. Web Application

You will now need to modify RDFWebApp to access the service at the new address. At the same time we will also change RDFWebApp so that it too is deployed using IIS

The web application is accessible on http://localhost/RDFWebApp/Default.aspx and can also be accessed using the hostname or IP address of you server e.g. http://192.168.7.129/RDFWebApp/Default.aspx

Default.aspx
Figure: 2.10.4.2.1. Default.aspx

Next Steps

The next example shows you how to quickly create an ADO.Net Data Service that exposes RDF data in Virtuoso and how to create a basic Web application to consume that service. The next step is to create a Silverlight Application to consume the same service.