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---+ Creating a Web Browser Application to Access RDF Data Using The Virtuoso ADO.NET Provider

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---++ Introduction

This document 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 
[[http://docs.openlinksw.com/virtuoso/rdfdatarepresentation.html#rdfiriidtype][IRIs]].  

---++ Prerequisites

   1 Microsoft Visual Studio 2008
   1 The Virtuoso ADO.NET provider for .NET 3.5 and the Entity Framework
   1 The Virtuoso 
[[https://virtuoso.openlinksw.com/download/][Cartridges VAD package]]
   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 
[[https://virtuoso.openlinksw.com/download/][demo database VAD package]] 
(<code>demo_dav.vad</code>) and install it. The VAD package will create a new database in Virtuoso called demo 
containing the familiar Northwind tables. It will also create 
[[http://docs.openlinksw.com/virtuoso/rdfsparqlintegrationmiddleware.html#rdfviews][Linked Data Views]] 
of the Northwind tables.  In the example we assume the database is accessible on a hostname of 
"<code>demo.openlinksw.com</code>" on the default port <code>80</code>, 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 <code>localhost:8890</code> for a default 
installation or whatever the <code>URIQA <nowiki>DefaultHost</nowiki></code> Virtuoso configuration parameter 
is set to when the demo database VAD package is installed. 

---++ 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 <b><code>dba</code></b>.  Then open <b><nowiki>iSQL</nowiki></b> from the menu on the left 
and execute the following statement.
<verbatim>
CREATE VIEW Demo.demo.sparqlview AS 
  SPARQL
  PREFIX  nwind:  <http://demo.openlinksw.com/schemas/northwind#>
  SELECT DISTINCT  ?s  
    FROM <http://demo.openlinksw.com/Northwind>
    WHERE { ?s  a  nwind:Customer }
</verbatim>

*Note*: 
   * If the view is added to the Visual Studio project as user "<code>demo</code>" (or any other 
than "<code>dba</code>'), then it must be ensured that the "<code>SPARQL_SELECT</code>" and 
"<code>SPARQL_SPONGE</code>" roles are assigned to this user, which can be done via the Virtuoso 
Conductor in the <b>System Admin</b> -> <b>User Accounts</b> tab.
   * Execute permissions will also need to be granted to the RDF_MAKE_LONG_OF_SQLVAL procedure, 
with an iSQL statement similar to the following:
<verbatim>
GRANT  EXECUTE 
  ON  DB.DBA.RDF_MAKE_LONG_OF_SQLVAL 
  TO  "demo"
</verbatim>
%BR%%BR%<img src="%ATTACHURLPATH%/isql.png" style="wikiautogen"/>%BR%%BR%

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

   1 Open <b>Visual Studio</b> and create a new <b>ASP .NET Web Application</b> called 
<b><code>><nowiki>RDFWebDemo</nowiki></code></b>.
 %BR%%BR%<img src="%ATTACHURLPATH%/RDFWebDemo.png" style="wikiautogen"/>%BR%%BR%
   1 Right-click <b><nowiki>RDFWebDemo</nowiki></b> in the <b>Solution Explorer</b>, and add 
a new <b><nowiki>ADO.NET Entity Data Model</nowiki></b> called <b><code>Model1.edmx</code></b>.  
This will open the <b>Entity Data Model Wizard</b>.
   1 Choose <b>Generate From Database</b> and click <b>Next</b>.
   1 Set up a connection to the Demo database on your local Virtuoso Server, select <b>Yes, 
include the sensitive data in the connection string</b> and set the name of the entities to 
<b><code><nowiki>DemoEntities</nowiki></code></b>.  Click <b>Next</b>.
   1 On the <b>Choose Your Database Objects</b> page expand <b>Views</b> and select 
<b><code>sparqlview</code></b>.  Check that the <b>Model Namespace</b> is 
<b><nowiki>DemoModel</nowiki></b> and click <b>Finish</b>.
%BR%%BR%<img src="%ATTACHURLPATH%/sparqlview.png" style="wikiautogen"/>%BR%%BR%
 
---+++ Step 3 - Add the Web Service

   1 Right click <b><nowiki>RDFWebDemo</nowiki></b> in the <b>Solution Explorer</b> and add 
a new <b><nowiki>ADO.NET Data Service</nowiki></b> called <b><code>WebDataService1.svc</code></b>.  
Click <b>Add</b>.
   1 In the class definition of <b><nowiki>WebDataService1</nowiki></b> in the newly created 
file <b><code><nowiki>WebDataService1.svc.cs</nowiki></code></b> replace "<code>/* TODO: put 
your data source class name here */</code>" with the name of our model,
<b><code><nowiki>DemoEntities</nowiki></code></b>.
<verbatim>
public class WebDataService1 : DataService<DemoEntities>
</verbatim>
   1 In the <b><nowiki>InitializeService</nowiki></b> method, add the line:
<verbatim>
config.SetEntitySetAccessRule("*", EntitySetRights.All);
</verbatim>
The method should look like this
<verbatim>
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);
}
</verbatim>
 
---+++ Step 4 - Compile and Run
Hit <b>F5</b> to compile and run the service.  Click <b>OK</b> when prompted to enable debugging.  
The default browser will be launched showing a page like --
<verbatim>
  <?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>
</verbatim>
The service is now running.  

<i>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:</i> <b><code><nowiki>http://localhost:1492/WebDataService1.svc/</nowiki></code></b>



---++ Creating the Browser Application

---+++ Step 1 - Create the Visual Studio Project

   1 Open <b>Visual Studio</b> and create a new <b>ASP.NET Web Application</b> called 
<b><code><nowiki>RDFWebApp</nowiki></code></b>.
%BR%%BR%<img src="%ATTACHURLPATH%/RDFWebApp.png" style="wikiautogen"/>%BR%%BR%
   1 Create client side entities with <b><code>datasvcutil.exe</code></b>.
      1 Open a command prompt.
      1 Navigate to <b><code><nowiki>C:\WINDOWS\Microsoft.NET\Framework\v3.5</nowiki></code></b>.
      1 Generate the client classes using the following command:
<verbatim>
datasvcutil.exe /uri:http://localhost:1492/WebDataService1.svc /out:DemoEntities.cs
</verbatim>
<i>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</i>. 
   1 Add the classes to <b><nowiki>RDFWebApp</nowiki></b>. 
      1 Right click <b><nowiki>RDFWebApp</nowiki></b>.
      1 Choose to add an existing item and add 
<b><code><nowiki>c:\WINDOWS\Microsoft.NET\Framework\v3.5\DemoEntities.cs</nowiki></code></b>.
   1 Add a reference to <b><code>System.Data.Services.Client</code></b> 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 <b><code>page_load</code></b> 
method in <b><code>Default.aspx.cs</code></b>.
<verbatim>
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);
}
</verbatim>
<i>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</i>.

Compile and run <b><nowiki>RDFWebApp</nowiki></b> (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.  
%BR%%BR%<img src="%ATTACHURLPATH%/DefaultPage.png" style="wikiautogen"/>%BR%%BR%

With the 
[[https://virtuoso.openlinksw.com/download/][Cartridges 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 
<code>[[http://virtuoso.openlinksw.com/Whitepapers/html/vdld_html/VirtDeployingLinkedDataGuide_Glossary.html#mozTocId13075][description.vsp]]</code>.
%BR%%BR%<img src="%ATTACHURLPATH%/Description.png" style="wikiautogen"/>%BR%%BR%

---++ Deploy With IIS

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

---+++ Web Service

To deploy the service using IIS:
   1 Open the <b><nowiki>RDFWebDemo</nowiki></b> project in Visual Studio, go to the 
<b>Project</b> menu and select <nowiki>RDFWebDemo</nowiki> <b>Properties.</b>
   1 Select the <b>Web</b> tab and scroll down to the <b>Servers</b> section.  Select 
<b>Use local IIS Server</b>.  The project URL defaults to using localhost.  
   1 Click the <b>Create Virtual Directory</b> button then check that the Service works on localhost.  
   1 Build the project; then start without debugging (ctrl-F5).  

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 
<b><code><nowiki>http://localhost/RDFWebDemo1/WebDataService1.svc/</nowiki></code></b>.  You 
can now access your service remotely using the hostname or IP address of your server.

If at this point you get an <b>Access is denied</b> error, <b>401.3</b>, then you will need to 
add the Internet Guest Account (<code>IUSR_XXX</code> where <code>XXX</code> is your computer 
name) to the users allowed to access the folder containing the <nowiki>RDFWebDemo</nowiki> project.
 
---+++ Web Application

You will now need to modify <nowiki>RDFWebApp</nowiki> to access the service at the new address.  
At the same time we will also change <nowiki>RDFWebApp</nowiki> so that it too is deployed using IIS 
   1 Open The <nowiki>RDFWebApp</nowiki> project in Visual Studio.
   1 Go to the <b>Project</b> menu and select <nowiki>RDFWebApp</nowiki> <b>Properties.</b>
   1 Select the <b>Web</b> tab and scroll down to the <b>Servers</b> section.  Select <b>Use 
local IIS Server</b>.  The project URL defaults to using localhost.  
   1 Click the <b>Create Virtual Directory</b> button.  The web application will then run on 
the local IIS.
   1 To reference the web service running on IIS you will need to edit 
<b><code>Default.aspx.cs</code></b>.  Change
<verbatim>
DemoModel.DemoEntities svc = new DemoModel.DemoEntities(new Uri("http://localhost:1492/WebDataService1.svc"));
</verbatim>
to
<verbatim>
DemoModel.DemoEntities svc = new DemoModel.DemoEntities(new Uri("http://localhost/RDFWebDemo/WebDataService1.svc/"));
</verbatim>
   1 Build the project then start without debugging (ctrl-F5).

The web application is accessible on 
<b><code><nowiki>http://localhost/RDFWebApp/Default.aspx</nowiki></code></b> and can also be 
accessed using the hostname or IP address of your server, e.g., 
<b><code><nowiki>http://192.168.7.129/RDFWebApp/Default.aspx</nowiki></code></b>

%BR%%BR%<img src="%ATTACHURLPATH%/firefox.png" style="wikiautogen"/>%BR%%BR%

---++ Next Steps
This example showed 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.

   * [[VirtSPASQLSilverLightApp][Creating a Silverlight Application to consume the service]]