Projects/Nepomuk/QueryingMethods - Revision history

AnneW: Marked this version for translation

2012-12-12T13:33:52Z

Marked this version for translation

AnneW: Prepare for translation

2012-12-12T13:33:40Z

Prepare for translation

Vishesh: /* Soprano::Model */

2012-08-24T08:33:36Z

‎Soprano::Model

Vishesh: /* QueryServiceClient */

2012-08-24T08:31:59Z

‎QueryServiceClient

Vishesh at 08:29, 24 August 2012

2012-08-24T08:29:10Z

Vishesh: /* Result Iterator */

2012-08-23T15:37:33Z

‎Result Iterator

Vishesh: /* Result Iterator */ Added info about it being a wrapper

2012-08-23T15:36:45Z

‎Result Iterator: Added info about it being a wrapper

Vishesh: /* Soprano::Model */

2012-08-23T12:15:42Z

‎Soprano::Model

Vishesh: /* QueryServiceClient */

2012-08-23T11:52:41Z

‎QueryServiceClient

Vishesh: Code examples

2012-08-23T11:43:49Z

Code examples

@@ Line 2: / Line 2: @@
 <translate>
-== Querying your Data ==
+== Querying your Data == <!--T:1-->
 There isn't much point of pushing all your data into Nepomuk, if you cannot query it. This article mentions the different ways you can query Nepomuk and the advantages and disadvantages of each.
-== QueryServiceClient ==
+== QueryServiceClient == <!--T:3-->
 The Nepomuk [http://api.kde.org/4.x-api/kdelibs-apidocs/nepomuk-core/html/classNepomuk2_1_1Query_1_1QueryServiceClient.html <tt>QueryServiceClient</tt>] is an asynchronous method of running queries in '''Nepomuk'''. It accepts both Nepomuk Queries and direct SPARQL queries. It provides convenient signal which your application can connect to in order to receive the results.
 Please note that the asynchronous nature of the [http://api.kde.org/4.x-api/kdelibs-apidocs/nepomuk-core/html/classNepomuk2_1_1Query_1_1QueryServiceClient.html QueryServiceClient] is achieved by transmitting the query over dbus to the storage service, where a new thread is spawned, the query is run on that thread, and the results are returned over dbus. This is fine for casual use, but when you care about high performance, it is recommended that you avoid the QueryServiceClient.
 Example -
 <syntaxhighlight lang="cpp-qt">
@@ Line 36: / Line 40: @@
 The [http://api.kde.org/4.x-api/kdelibs-apidocs/nepomuk-core/html/classNepomuk2_1_1Query_1_1QueryServiceClient.html QueryServiceClient] also offers ways of updating the results via [http://api.kde.org/4.x-api/kdelibs-apidocs/nepomuk-core/html/classNepomuk2_1_1Query_1_1QueryServiceClient.html#a1b843e5bf89ddb1a0d5c66eb0193375b entriesRemoved] and [http://api.kde.org/4.x-api/kdelibs-apidocs/nepomuk-core/html/classNepomuk2_1_1Query_1_1QueryServiceClient.html#a6ed2be5579a00e9b8de1f5f23faf1fb6  newEntries]. While these methods may seem very attractive, their implementation is not. They work by running the entire query when some data in the Nepomuk database changes.
 In the future the queries will only be re-run when data related to the query changes (heuristics), but until then '''the entire query is re-run every time ANY data changes'''. Therefore it is recommended that you delete the QueryServiceClient when it has finished execution as follows -
 <syntaxhighlight lang="cpp-qt">
      Nepomuk2::Query::QueryServiceClient* client = new Nepomuk2::Query::QueryServiceClient( this );
@@ Line 45: / Line 52: @@
 </syntaxhighlight>
-== Result Iterator ==
+== Result Iterator == <!--T:10-->
 The <tt>ResultIterator</tt>, which has been introduced in 4.10, can take either a Nepomuk or SPARQL query and provides an iterator which you can use to get the results. The iterator is obviously blocking, so you may want to put it another thread, depending on the kind of query.
 Example -
 <syntaxhighlight lang="cpp-qt">
@@ Line 58: / Line 67: @@
              QHashIterator<QUrl, Nepomuk2::Variant> it( prop );
-             while( it.hasNext() ) {
+             <!--T:13-->
                  it.next();
                  kDebug() << it.key() << " " << it.value();
@@ Line 68: / Line 78: @@
 The ResultIterator is just a light wrapper over the <tt>Soprano::QueryResultIterator</tt>. It converts the bindings returned by the <tt>QueryResultIterator</tt> into a <tt>Query::Result</tt>.
-== Soprano::Model ==
+== Soprano::Model == <!--T:15-->
 The underlying '''Soprano''' model can also be used to directly run the queries. You can only run [[Projects/Nepomuk/SparqlQueries|SPARQL queries]] on the model. Use this method when you're writing a custom query. The underlying Model also provides an iterator similar to that of the <tt>ResultIterator</tt>.
 Example -
 <syntaxhighlight lang="cpp-qt">
@@ Line 80: / Line 93: @@
      Soprano::QueryResultIterator it = model->executeQuery( query, Soprano::Query::QueryLanguageSparql );
-     while( it.next() ) {
+     <!--T:18-->
          kDebug() << it["r"].uri();
+     }
@@ Line 86: / Line 100: @@
 You might want to check out the [http://soprano.sourceforge.net/apidox/trunk/index.html Soprano API] for more information about the lower level details.
 [[Category:Documentation]]
 [[Category:Development]]
 [[Category:Tutorials]]
 </translate>

@@ Line 1: / Line 1: @@
 There isn't much point of pushing all your data into Nepomuk, if you cannot query it. This article mentions the different ways you can query Nepomuk and the advantages and disadvantages of each.
-= QueryServiceClient =
+== QueryServiceClient ==
-The Nepomuk [http://api.kde.org/4.x-api/kdelibs-apidocs/nepomuk-core/html/classNepomuk2_1_1Query_1_1QueryServiceClient.html <code>QueryServiceClient</code>] is an asynchronous method of running queries in Nepomuk. It accepts both Nepomuk Queries and direct SPARQL queries. It provides convenient signal which your application can connect to in order to receive the results.
+The Nepomuk [http://api.kde.org/4.x-api/kdelibs-apidocs/nepomuk-core/html/classNepomuk2_1_1Query_1_1QueryServiceClient.html <tt>QueryServiceClient</tt>] is an asynchronous method of running queries in '''Nepomuk'''. It accepts both Nepomuk Queries and direct SPARQL queries. It provides convenient signal which your application can connect to in order to receive the results.
 Please note that the asynchronous nature of the [http://api.kde.org/4.x-api/kdelibs-apidocs/nepomuk-core/html/classNepomuk2_1_1Query_1_1QueryServiceClient.html QueryServiceClient] is achieved by transmitting the query over dbus to the storage service, where a new thread is spawned, the query is run on that thread, and the results are returned over dbus. This is fine for casual use, but when you care about high performance, it is recommended that you avoid the QueryServiceClient.
@@ Line 33: / Line 38: @@
 The [http://api.kde.org/4.x-api/kdelibs-apidocs/nepomuk-core/html/classNepomuk2_1_1Query_1_1QueryServiceClient.html QueryServiceClient] also offers ways of updating the results via [http://api.kde.org/4.x-api/kdelibs-apidocs/nepomuk-core/html/classNepomuk2_1_1Query_1_1QueryServiceClient.html#a1b843e5bf89ddb1a0d5c66eb0193375b entriesRemoved] and [http://api.kde.org/4.x-api/kdelibs-apidocs/nepomuk-core/html/classNepomuk2_1_1Query_1_1QueryServiceClient.html#a6ed2be5579a00e9b8de1f5f23faf1fb6  newEntries]. While these methods may seem very attractive, their implementation is not. They work by running the entire query when some data in the Nepomuk database changes.
-In the future the queries will only be re-run when data related to the query changes (heuristics), but till then '''the entire query is re-run every time ANY data changes'''. Therefore it is recommended that you delete the QueryServiceClient when it has finished execution as follows -
+In the future the queries will only be re-run when data related to the query changes (heuristics), but until then '''the entire query is re-run every time ANY data changes'''. Therefore it is recommended that you delete the QueryServiceClient when it has finished execution as follows -
 <syntaxhighlight lang="cpp-qt">
@@ Line 40: / Line 45: @@
 </syntaxhighlight>
-= Result Iterator =
+== Result Iterator ==
-The <code>ResultIterator</code>, which has been introduced in 4.10, can take either a Nepomuk or SPARQL query and provides an iterator which you can use to get the results. The iterator is obviously blocking, so you may want to put it another thread, depending on the kind of query.
+The <tt>ResultIterator</tt>, which has been introduced in 4.10, can take either a Nepomuk or SPARQL query and provides an iterator which you can use to get the results. The iterator is obviously blocking, so you may want to put it another thread, depending on the kind of query.
 Example -
@@ Line 63: / Line 68: @@
-The ResultIterator is just a light wrapper over the <code>Soprano::QueryResultIterator</code>. It converts the bindings returned by the <code>QueryResultIterator</code> into a <code>Query::Result</code>.
+The ResultIterator is just a light wrapper over the <tt>Soprano::QueryResultIterator</tt>. It converts the bindings returned by the <tt>QueryResultIterator</tt> into a <tt>Query::Result</tt>.
-= Soprano::Model =
+== Soprano::Model ==
-The underlying Soprano model can also be used to directly run the queries. You can only run [[Projects/Nepomuk/SparqlQueries|SPARQL queries]] on the model. Use this method when you're writing a custom query. The underlying Model also provides an iterator similar to that of the <code>ResultIterator</code>.
+The underlying '''Soprano''' model can also be used to directly run the queries. You can only run [[Projects/Nepomuk/SparqlQueries|SPARQL queries]] on the model. Use this method when you're writing a custom query. The underlying Model also provides an iterator similar to that of the <tt>ResultIterator</tt>.
 Example -
@@ Line 82: / Line 87: @@
 You might want to check out the [http://soprano.sourceforge.net/apidox/trunk/index.html Soprano API] for more information about the lower level details.

@@ Line 67: / Line 67: @@
 = Soprano::Model =
-The underlying Soprano model can also be used to directly run the queries. You can only run SPARQL queries on the model. Use this method when you're writing a custom query. The underlying Model also provides an iterator similar to that of the <code>ResultIterator</code>.
+The underlying Soprano model can also be used to directly run the queries. You can only run [[Projects/Nepomuk/SparqlQueries|SPARQL queries]] on the model. Use this method when you're writing a custom query. The underlying Model also provides an iterator similar to that of the <code>ResultIterator</code>.
 Example -

@@ Line 33: / Line 33: @@
 The [http://api.kde.org/4.x-api/kdelibs-apidocs/nepomuk-core/html/classNepomuk2_1_1Query_1_1QueryServiceClient.html QueryServiceClient] also offers ways of updating the results via [http://api.kde.org/4.x-api/kdelibs-apidocs/nepomuk-core/html/classNepomuk2_1_1Query_1_1QueryServiceClient.html#a1b843e5bf89ddb1a0d5c66eb0193375b entriesRemoved] and [http://api.kde.org/4.x-api/kdelibs-apidocs/nepomuk-core/html/classNepomuk2_1_1Query_1_1QueryServiceClient.html#a6ed2be5579a00e9b8de1f5f23faf1fb6  newEntries]. While these methods may seem very attractive, their implementation is not. They work by running the entire query when some data in the Nepomuk database changes.
-In the future the queries will only be re-run when data related to the query changes (heuristics), but till then the entire query is re-run every time ANY data changes. Therefore it is recommended that you delete the QueryServiceClient when it has finished execution as follows -
+In the future the queries will only be re-run when data related to the query changes (heuristics), but till then '''the entire query is re-run every time ANY data changes'''. Therefore it is recommended that you delete the QueryServiceClient when it has finished execution as follows -
 <syntaxhighlight lang="cpp-qt">
@@ Line 39: / Line 39: @@
      connect( client, SIGNAL(finishedListing()), client, SLOT(deleteLater()) );
 </syntaxhighlight>
 = Result Iterator =

@@ Line 29: / Line 29: @@
+     }
 </syntaxhighlight>
 The [http://api.kde.org/4.x-api/kdelibs-apidocs/nepomuk-core/html/classNepomuk2_1_1Query_1_1QueryServiceClient.html QueryServiceClient] also offers ways of updating the results via [http://api.kde.org/4.x-api/kdelibs-apidocs/nepomuk-core/html/classNepomuk2_1_1Query_1_1QueryServiceClient.html#a1b843e5bf89ddb1a0d5c66eb0193375b entriesRemoved] and [http://api.kde.org/4.x-api/kdelibs-apidocs/nepomuk-core/html/classNepomuk2_1_1Query_1_1QueryServiceClient.html#a6ed2be5579a00e9b8de1f5f23faf1fb6  newEntries]. While these methods may seem very attractive, their implementation is not. They work by running the entire query when some data in the Nepomuk database changes.
@@ Line 38: / Line 39: @@
      connect( client, SIGNAL(finishedListing()), client, SLOT(deleteLater()) );
 </syntaxhighlight>
 = Result Iterator =
@@ Line 60: / Line 62: @@
+     }
 </syntaxhighlight>
 The ResultIterator is just a light wrapper over the <code>Soprano::QueryResultIterator</code>. It converts the bindings returned by the <code>QueryResultIterator</code> into a <code>Query::Result</code>.
@@ Line 77: / Line 80: @@
+     }
 </syntaxhighlight>
 You might want to check out the [http://soprano.sourceforge.net/apidox/trunk/index.html Soprano API] for more information about the lower level details.

← Older revision		Revision as of 12:15, 23 August 2012
Line 75:		Line 75:
	}		}
	</syntaxhighlight>		</syntaxhighlight>
		+
		+	You might want to check out the [http://soprano.sourceforge.net/apidox/trunk/index.html Soprano API] for more information about the lower level details.