Creating a client¶

The BrightstarService class provides a number of static methods that can be used to create a new client. The most general one takes a connection string as a parameter and returns a client object. The client implements the BrightstarDB.IBrightstarService interface.

The following example shows how to create a new service client using a connection string:

var client = BrightstarService.GetClient(
                  "Type=http;endpoint=http://localhost:8090/brightstar;");

For more information about connection strings, please read the “Connection Strings” topic

Creating a Store¶

A new store can be creating using the following code:

string storeName = "Store_" + Guid.NewGuid();
client.CreateStore(storeName);

Deleting a Store¶

Deleting a store is also straight forward:

client.DeleteStore(storeName);

Adding data¶

Data is added to the store by sending the data to add in N-Triples format. Each triple must be on a single line with no line breaks, a good way to do this is to use a StringBuilder and then using AppendLine() for each triple:

var data = new StringBuilder();
data.AppendLine("<http://www.brightstardb.com/products/brightstar> <http://www.brightstardb.com/schemas/product/name> \\"BrightstarDB\\" .");
data.AppendLine("<http://www.brightstardb.com/products/brightstar> <http://www.brightstardb.com/schemas/product/category> <http://www.brightstardb.com/categories/nosql> .");
data.AppendLine("<http://www.brightstardb.com/products/brightstar> <http://www.brightstardb.com/schemas/product/category> <http://www.brightstardb.com/categories/.net> .");
data.AppendLine("<http://www.brightstardb.com/products/brightstar> <http://www.brightstardb.com/schemas/product/category> <http://www.brightstardb.com/categories/rdf> .");

The ExecuteTransaction() method is used to insert the N-Triples data into the store:

client.ExecuteTransaction(storeName,null, null, data.ToString());

Deleting data¶

Deletion is done by defining a pattern that should matching the triples to be deleted. The following example deletes all the category data about BrightstarDB, again we use the StringBuilder to create the delete pattern.

var deletePatternsData = new StringBuilder();
deletePatternsData.AppendLine("<http://www.brightstardb.com/products/brightstar> <http://www.brightstardb.com/schemas/product/category> <http://www.brightstardb.com/.well-known/model/wildcard> .");

The identifier http://www.brightstardb.com/.well-known/model/wildcard is a wildcard match for any value, so the above example deletes all triples that have a subject of http://www.brightstardb.com/products/brightstar and a predicate of http://www.brightstardb.com/schemas/product/category.

The ExecuteTransaction() method is used to delete the data from the store:

client.ExecuteTransaction(storeName, null, deletePatternsData.ToString(), null);

Conditional Updates¶

The execution of a transaction can be made conditional on certain triples existing in the store. The following example updates the productCode property of a resource only if its current value is 640.

var preconditions = new StringBuilder();
preconditions.AppendLine("<http://www.brightstardb.com/products/brightstar> <http://www.brightstardb.com/schemas/product/productCode> "640"^^<http://www.w3.org/2001/XMLSchema#integer> .");
var deletes = new StringBuilder();
deletes.AppendLine("<http://www.brightstardb.com/products/brightstar> <http://www.brightstardb.com/schemas/product/productCode> "640"^^<http://www.w3.org/2001/XMLSchema#integer> .");
var inserts = new StringBuilder();
inserts.AppendLine("<http://www.brightstardb.com/products/brightstar> <http://www.brightstardb.com/schemas/product/productCode> "973"^^<http://www.w3.org/2001/XMLSchema#integer> .");
client.ExecuteTransaction(storeName, preconditions.ToString(), deletes.ToString(), inserts.ToString());

When a transaction contains condition triples, every triple specified in the preconditions must exist in the store before the transaction is applied. If one or more triples specified in the preconditions are not matched, a BrightstarClientException will be raised.

Data Types¶

In the code above we used simple triples to add a string literal object to a subject, such as:

<http://www.brightstardb.com/products/brightstar> <http://www.brightstardb.com/schemas/product/name> "BrightstarDB"

Other data types can be specified for the object of a triple by using the ^^ syntax:

<http://www.brightstardb.com/products/brightstar> <http://www.brightstardb.com/schemas/product/productCode> "640"^^<http://www.w3.org/2001/XMLSchema#integer> .
<http://www.brightstardb.com/products/brightstar> <http://www.brightstardb.com/schemas/product/releaseDate> "2011-11-11 12:00"^^<http://www.w3.org/2001/XMLSchema#dateTime> .
<http://www.brightstardb.com/products/brightstar> <http://www.brightstardb.com/schemas/product/cost> "0.00"^^<http://www.w3.org/2001/XMLSchema#decimal> .

Updating Graphs¶

The ExecuteTransaction() method on the IBrightstarService interface accepts a parameter that defines the default graph URI. When this parameters is specified, all precondition triples are tested against that graph; all delete triple patterns are applied to that graph; and all addition triples are added to that graph:

// This code update the graph http://example.org/graph1
client.ExecuteTransaction(storeName, preconditions, deletePatterns, additions, "http://example.org/graph1");

In addition, the format that is parsed for preconditions, delete patterns and additions allows you to mix N-Triples and N-Quads formats together. N-Quads are simply N-Triples with a fourth URI identifier on the end that specifies the graph to be updated. When an N-Quad is encountered, its graph URI overrides that passed into the ExecuteTransaction() method. For example, in the following code, one triple is added to the graph “http://example.org/graphs/alice” and the other is added to the default graph (because no value is specified in the call to ExecuteTransaction():

var txn1Adds = new StringBuilder();
txn1Adds.AppendLine(
    @"<http://example.org/people/alice> <http://xmlns.com/foaf/0.1/name> ""Alice"" <http://example.org/graphs/alice> .");
txn1Adds.AppendLine(@"<http://example.org/people/bob> <http://xmlns.com/foaf/0.1/name> ""Bob"" .");
var result = client.ExecuteTransaction(storeName, null, null, txn1Adds.ToString());

Querying data using SPARQL¶

BrightstarDB supports SPARQL 1.1 for querying the data in the store. A simple query on the N-Triples above that returns all categories that the subject called “Brightstar DB” is connected to would look like this:

var query = "SELECT ?category WHERE { " +
        "<http://www.brightstardb.com/products/brightstar> <http://www.brightstardb.com/schemas/product/category> ?category " +
        "}";

This string query can then be used by the ExecuteQuery() method to create an XDocument from the SPARQL results (See SPARQL XML Query Results Format for format of the XML document returned).

var result = XDocument.Load(client.ExecuteQuery(storeName, query));

BrightstarDB also supports several different formats for SPARQL results. The default format is XML, but you can also add a BrightstarDB.SparqlResultsFormat parameter to the ExecuteQuery method to control the format and encoding of the results set. For example:

var jsonResult = client.ExecuteQuery(storeName, query, SparqlResultsFormat.Json);

By default results are returned using UTF-8 encoding; however you can override this default behaviour by using the WithEncoding() method on the SparqlResultsFormat class. The WithEncoding() method takes a System.Text.Encoding instance and returns a SparqlResultsFormat instance that will ask for that specific encoding:

var unicodeXmlResult = client.ExecuteQuery(
                         storeName, query,
                         SparqlResultsFormat.Xml.WithEncoding(Encoding.Unicode));

Querying Graphs¶

By default a SPARQL query will be executed against the default graph in the BrightstarDB store (that is, the graph in the store whose identifier is http://www.brightstardb.com/.well-known/model/defaultgraph). In SPARQL terms, this means that the default graph of the dataset consists of just the default graph in the store. You can override this default behaviour by passing the identifier of one or more graphs to the ExecuteQuery() method. There are two overrides of ExecuteQuery() that allow this. One accepts a single graph identifier as a string parameter, the other accepts multiple graph identifiers as an IEnumerable<string> parameter. The three different approaches are shown below:

// Execute query using the store's default graph as the default graph
var result = client.ExecuteQuery(storeName, query);

// Execute query using the graph http://example.org/graphs/1 as
// the default graph
var result = client.ExecuteQuery(storeName, query,
                                 "http://example.org/graphs/1");

// Execute query using the graphs http://example.org/graphs/1 and
// http://example.org/graphs/2 as the default graph
var result = client.ExecuteQuery(storeName, query,
                                 new string[] {
                                                                   "http://example.org/graphs/1",
                                                                       "http://example.org/graphs/2"});

Using extension methods¶

To make working with the resulting XDocument easier there exist a number of extensions methods. The method SparqlResultRows() returns an enumeration of XElement instances where each XElement represents a single result row in the SPARQL results.

The GetColumnValue() method takes the name of the SPARQL result column and returns the value as a string. There are also methods to test if the object is a literal, and to retrieve the data type and language code.

foreach (var sparqlResultRow in result.SparqlResultRows())
{
   var val = sparqlResultRow.GetColumnValue("category");
   Console.WriteLine("Category is " + val);
}

Update data using SPARQL¶

BrightstarDB supports SPARQL 1.1 Update for updating data in the store. An update operation is submitted to BrightstarDB as a job. By default the call to ExecuteUpdate() will block until the update job completes:

IJobInfo jobInfo = _client.ExecuteUpdate(storeName, updateExpression);

In this case, the resulting IJobInfo object will describe the final state of the update job. However, you can also run the job asynchronously by passing false for the optional waitForCompletion parameter:

IJobInfo jobInfo = _client.ExecuteUpdate(storeName, updateExpression, false);

In this case the resulting IJobInfo object will describe the current state of the update job and you can use calls to GetJobInfo() to poll the job for its current status.

Data Imports¶

To support the loading of large data sets BrightstarDB provides an import function. Before invoking the import function via the client API the data to be imported should be copied into a folder called ‘import’. The ‘import’ folder should be located in the folder containing the BrigtstarDB store data folders. After a default installation the stores folder is [INSTALLDIR]\Data, thus the import folder should be [INSTALLDIR]\Data\import. For information about the RDF syntaxes that BrightstarDB supports for import, please refer to Supported RDF Syntaxes.

With the data copied into the folder the following client method can be called. The parameter is the name of the file that was copied into the import folder:

client.StartImport("data.nt");

Introduction To N-Triples¶

N-Triples is a consistent and simple way to encode RDF triples. N-Triples is a line based format. Each N-Triples line encodes one RDF triple. Each line consists of the subject (a URI), followed  by whitespace, the predicate (a URI), more whitespace, and then the object (a URI or literal) followed by a dot and a new line. The encoding of the literal may include a datatype or language code as well as the value. URIs are enclosed in ‘<’ ‘>’ brackets. The formal definition of the N-Triples format can be found here.

The following are examples of N-Triples data:

# simple literal property
<http://www.brightstardb.com/products/brightstar> <http://www.brightstardb.com/schemas/product/name> "Brightstar DB" .


# relationship between two resources
<http://www.brightstardb.com/products/brightstar> <http://www.brightstardb.com/schemas/product/category> <http://www.brightstardb.com/categories/nosql> .


# A property with an integer value
<http://www.brightstardb.com/products/brightstar> <http://www.brightstardb.com/schemas/product/productCode> "640"^^<http://www.w3.org/2001/XMLSchema#integer> .

# A property with a date/time value
<http://www.brightstardb.com/products/brightstar> <http://www.brightstardb.com/schemas/product/releaseDate> "2011-11-11 12:00"^^<http://www.w3.org/2001/XMLSchema#dateTime> .

# A property with a decimal value
<http://www.brightstardb.com/products/brightstar> <http://www.brightstardb.com/schemas/product/cost> "0.00"^^<http://www.w3.org/2001/XMLSchema#decimal> .

Allowed Data Types

Data types are defined in terms of an identifier. Common data types use the XML Schema identifiers. The prefix of these is http://www.w3.org/2001/XMLSchema#. The common primitive datatypes are defined in the XML Schema specification.

Introduction To SPARQL¶

BrightstarDB is a triple store that implements the RDF and SPARQL standards. SPARQL, pronounced “sparkle”, is the query language developer by the W3C for querying RDF data. SPARQL primarily uses pattern matching as a query mechanism. A short example follows:

PREFIX ont: <http://www.brightstardb.com/schemas/>
SELECT ?name ?description WHERE {
  ?product a ont:Product .
  ?product ont:name ?name .
  ?product ont:description ?description .
}

This query is asking for all the names and descriptions of all products in the store.

SELECT is used to specify which bound variables should appear in the result set. The result of this query is a table with two columns, one called “name” and the other “description”.

The PREFIX notation is used so that the query itself is more readable. Full URIs can be used in the query. When included in the query directly URIs are enclosed by ‘<’ and ‘>’.

Variables are specified with the ‘?’ character in front of the variable name.

In the above example if a product did not have a description then it would not appear in the results even if it had a name. If the intended result was to retrieve all products with their name and the description if it existed then the OPTIONAL keyword can be used.

PREFIX ont: <http://www.brightstardb.com/schemas/>
SELECT ?name ?description WHERE {
  ?product a ont:Product .
  ?product ont:name ?name .

  OPTIONAL {
    ?product ont:description ?description .
  }
}

For more information on SPARQL 1.1 and more tutorials the following resources are worth reading.

1. SPARQL 1.1 Query Language
2. Introduction to RDF Query with SPARQL Tutorial

Data Storage And Connection Strings¶

When running on WP, BrightstarDB writes its data using the IsolatedStorage APIs. This means that a BrightstarDB store opened within an application will be written into the IsolatedStorage for that application. This keeps the stores used by different applications separate from each other. An application can also use multiple stores, as long as each store has a unique store name. As the BrightstarDB server is not running on the phone, the only access to the store is by using the embedded connection type. A typical connection string used in a WP application is shown in the code snippet below::

var connectionString = "type=embedded;storesdirectory=brightstar;storename=MyAppStore";

SDK Libraries¶

The BrightstarDB libraries for WP are all contained in [INSTALLDIR]\SDK\WP71. You need to add references to these libraries to your WP application project.

Development Considerations¶

For the most part, working with BrightstarDB on Windows Phone is the same as working with it on the full .NET Framework. However due to the platform and some .NET restrictions there are a few things that you need to keep in mind when building your application.

// Code to execute when the application is deactivated (sent to background)
// This code will not execute when the application is closing
private void Application_Deactivated(object sender, DeactivatedEventArgs e)
{
    BrightstarService.Shutdown(true);
}


// Code to execute when the application is closing (eg, user hit Back)
// This code will not execute when the application is deactivated
private void Application_Closing(object sender, ClosingEventArgs e)
{
    BrightstarService.Shutdown(true);
}

Deploying a Reference Store¶

As well as using BrightstarDB to store user-modifiable data, you can also ship reference data with your application. A BrightstarDB reference store can be embedded as part of your application content and deployed to the Isolated Storage on the mobile device. Once deployed, the store can be queried and/or updated through your code as normal. The basic steps to deploying a store in a mobile application are as follows:

1. Create the reference store
2. Add the reference store files to your application and compile it
3. Deploy the application to the device
4. At runtime, copy the reference store files from the application directory to Isolated Storage
5. Access the copied store from your code

IsolatedStorageFile Root
|
+-brightstar    <-- the storesDirectory value in the connection string, create a sub
  |                 create one sub-directory for each store you want to access
  |
  +-dining      <-- the storeName value in the connection string,
                    only the files for a single store should go in here

if (!BrightstarDbDeploymentHelper.StoreExists("brightstar", "dining"))
{
    BrightstarDbDeploymentHelper.CopyStore("data", "brightstar", "dining");
}

public static class BrightstarDbDeploymentHelper
{
    public static bool StoreExists(string storeDirectoryName, string storeName)
    {
        IsolatedStorageFile iso = IsolatedStorageFile.GetUserStoreForApplication();
        return iso.DirectoryExists(storeDirectoryName + "\\\\" + storeName) &&
               iso.FileExists(storeDirectoryName + "\\\\" + storeName + "\\\\master.bs") &&
               iso.FileExists(storeDirectoryName + "\\\\" + storeName + "\\\\resources.bs") &&
               iso.FileExists(storeDirectoryName + "\\\\" + storeName + "\\\\data.bs");
    }


    public static void CopyStore(string resourceFolderPath,
                                 string storeDirectoryName,
                                 string storeName)
    {
        IsolatedStorageFile iso = IsolatedStorageFile.GetUserStoreForApplication();
        CopyStoreFile(iso, "data.bs", resourceFolderPath, storeDirectoryName, storeName);
        CopyStoreFile(iso, "master.bs", resourceFolderPath, storeDirectoryName, storeName);
        CopyStoreFile(iso, "resources.bs", resourceFolderPath, storeDirectoryName, storeName);
    }


    private static void CopyStoreFile(IsolatedStorageFile iso, string fileName,
                                      string resourceFolderPath,
                                      string storeDirectoryName, string storeName)
    {
        if (!iso.DirectoryExists(storeDirectoryName))
        {
            iso.CreateDirectory(storeDirectoryName);
        }
        if (!iso.DirectoryExists(storeDirectoryName + "\\\\" + storeName))
        {
            iso.CreateDirectory(storeDirectoryName + "\\\\" + storeName);
        }


        // Create a stream for the file in the installation folder.
        var appResource =
            Application.GetResourceStream(
              new Uri(resourceFolderPath + "\\\\" + fileName, UriKind.Relative));
        if (appResource != null)
        {
            using (Stream input = appResource.Stream)
            {
                // Create a stream for the new file in isolated storage.
                using (
                    IsolatedStorageFileStream output =
                        iso.CreateFile(storeDirectoryName + "\\\\" + storeName + "\\\\" + fileName))
                {
                    // Initialize the buffer.
                    var readBuffer = new byte[4096];
                    int bytesRead = -1;
                    // Copy the file from the installation folder to isolated storage.
                    while ((bytesRead = input.Read(readBuffer, 0, readBuffer.Length)) > 0)
                    {
                        output.Write(readBuffer, 0, bytesRead);
                    }
                }
            }
        }
        else
        {
            // There is no application resource for this file, so create it as an empty file

            iso.CreateFile(storeDirectoryName + "\\\\" + storeName + "\\\\" + fileName).Close();
        }
    }
}

type=embedded;storesDirectory={path to directory containing store directories};storeName={name of store directory}

type=embedded;storesDirectory=brightstar;storeName=dining