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             <h1 class="title">Creating Jena models</h1>

 	<h2 id="introduction">Introduction</h2>
 <p>Jena is a moderately complicated system, with several
 different kinds of <code>Model</code> and ways of constructing them. This note
 describes the Jena <code>ModelFactory</code>, a one-stop shop for
 creating Jena models. <code>ModelFactory</code> lives in Java package
 <code>org.apache.jena.rdf.model</code>.</p>
 <p>This note is an introduction, not an exhaustive description. As
 usual consult the Javadoc for details of the methods and classes to
 use.</p>
 <h2 id="simple-model-creation">Simple model creation</h2>
 <p>The simplest way to create a model (if not the shortest) is to call
 <code>ModelFactory.createDefaultModel()</code>. This [by default] delivers a
 plain RDF model, stored in-memory, that does no inference and has
 no special ontology interface.</p>
 <h2 id="database-model-creation">Database model creation</h2>
 <p>For methods of creating models for <a href="/documentation/tdb/index.html">TDB</a>
 please see the relevant reference sections.</p>
 <h2 id="inference-model-creation">Inference model creation</h2>
 <p>An important feature of Jena is support for different kinds of
 inference over RDF-based models (used for RDFS and OWL).
 Inference models are constructed by applying <em>reasoners</em> to
 <em>base models</em> and optionally <em>schema</em>. The statements deduced by
 the reasoner from the base model then appear in the inferred model
 alongside the statements from the base model itself.
 RDFS reasoning is directly available:</p>
 <ul>
 <li>
 <p><code>createRDFSModel(Model base)</code> creates an inference model over the
 base model using the built-in RDFS inference rules and any RDFS
 statements in the base model.</p>
 </li>
 <li>
 <p><code>createRDFSModel(Model schema, Model base)</code> creates an RDFS
 inference model from the base model and the supplied schema model.
 The advantage of supplying the schema separately is that the
 reasoner may be able to compute useful information in advance on
 the assumption that the schema won&rsquo;t change, or at least not change
 as often as the base model.</p>
 </li>
 </ul>
 <p>It&rsquo;s possible to use other reasoning systems than RDFS. For these a
 Reasoner is required:</p>
 <ul>
 <li>
 <p><code>createInfModel(Reasoner reasoner, Model base)</code> creates an
 inference model using the rules of <code>reasoner</code> over the model
 <code>base</code>.</p>
 </li>
 <li>
 <p><code>createInfModel(Reasoner reasoner, Model schema, Model base)</code> Just
 as for the RDFS case, the schema may be supplied separately to
 allow the reasoner to digest them before working on the model.</p>
 </li>
 </ul>
 <p>From where do you fetch your reasoners? From the
 <em>reasoner registry</em>, the class
 <a href="/documentation/javadoc/jena/org/apache/jena/reasoner/ReasonerRegistry.html">ReasonerRegistry</a>.
 This allows reasoners to be looked up by name, but also provides
 some predefined access methods for well-know reasoners:</p>
 <ul>
 <li>
 <p><code>getOWLReasoner()</code>: the reasoner used for OWL inference</p>
 </li>
 <li>
 <p><code>getRDFSReasoner()</code>: the reasoner used for RDFS inference</p>
 </li>
 <li>
 <p><code>getTransitiveReasoner()</code>: a reasoner for doing subclass and
 sub-property closure.</p>
 </li>
 </ul>
 <h2 id="ontology-model-creation">Ontology model creation</h2>
 <p>An <em>ontology model</em> is one that presents RDF as an ontology -
 classes, individuals, different kinds of properties, and so forth.
 Jena supports RDFS and OWL ontologies through <em>profiles</em>.
 There is extensive documentation on
 <a href="../ontology/index.html">Jena&rsquo;s ontology support</a>, so all we&rsquo;ll do
 here is summarise the creation methods.</p>
 <ul>
 <li>
 <p><code>createOntologyModel()</code> Creates an ontology model which is
 in-memory and presents OWL ontologies.</p>
 </li>
 <li>
 <p><code>createOntologyModel(OntModelSpec spec, Model base)</code> Creates an
 ontology model according the
 <a href="/documentation/javadoc/jena/org/apache/jena/ontology/OntModelSpec.html">OntModelSpec</a>
 <code>spec</code> which presents the ontology of <code>base</code>.</p>
 </li>
 <li>
 <p><code>createOntologyModel(OntModelSpec spec, ModelMaker maker, Model base)</code>
 Creates an OWL ontology model according to the <code>spec</code> over the
 <code>base</code> model. If the ontology model needs to construct additional
 models (for OWL imports), use the <code>ModelMaker</code> to create them. [The
 previous method will construct a <code>MemModelMaker</code> for this.]</p>
 </li>
 </ul>
 <p>Where do <code>OntModelSpec</code>s come from? There&rsquo;s a cluster of
 constants in the class which provide for common uses; to name but
 three:</p>
 <ul>
 <li>
 <p><code>OntModelSpec.OWL_MEM_RDFS_INF</code> OWL ontologies, model stored in
 memory, using RDFS entailment only</p>
 </li>
 <li>
 <p><code>OntModelSpec.RDFS_MEM</code> RDFS ontologies, in memory, but doing no
 additional inferences</p>
 </li>
 <li>
 <p><code>OntModelSpec.OWL_DL_MEM_RULE_INF</code> OWL ontologies, in memory, with
 the full OWL Lite inference</p>
 </li>
 </ul>
 <h2 id="creating-models-from-assembler-descriptions">Creating models from Assembler descriptions</h2>
 <p>A model can be built from a description of the required model.
 This is documented in the
 <a href="../assembler/assembler-howto.html">assembler howto</a>.
 Access to the
 assembler system for model creation is provided by three
 ModelFactory methods:</p>
 <ul>
 <li>
 <p><code>assembleModelFrom( Model singleRoot )</code>: assemble a Model from the
 single Model description in <code>singleRoot</code>. If there is no such
 description, or more than one, an exception is thrown. If a
 description has to be selected from more than one available
 candidates, consider using the methods below.</p>
 </li>
 <li>
 <p><code>findAssemblerRoots( Model m )</code>: answer a Set of all the Resources
 in <code>m</code> which are of type <code>ja:Model</code>, ie descriptions of models to
 assemble. (Note that this will include sub-descriptions of embedded
 models if they are present.)</p>
 </li>
 <li>
 <p><code>assembleModelFrom( Resource root )</code>: answer a Model assembled
 according to the description hanging from <code>root</code>.
 Assemblers can construct other things as well as models, and the
 Assembler system is user-extensible: see the howto for details.</p>
 </li>
 </ul>
 <h3 id="file-based-models">File-based models</h3>
 <p>The method <code>ModelFactory.createFileModelMaker(String)</code> returns a
 <code>ModelMaker</code> which attaches models to filing-system files. The
 <code>String</code> argument is the <em>fileBase</em>. When a file-ModelMaker opens a
 file, it reads it from a file in the directory named by the
 fileBase; when the model is closed (and <em>only</em> then, in the current
 implementation), the contents of the model are written back to the
 file.</p>
 <p>Because the names of models in a modelMaker can be arbitrary
 character strings, in particular URIs, they are translated slightly
 to avoid confusion with significant characters of common filing
 systems. In the current implementation,</p>
 <ul>
 <li>colon : is converted to \_C</li>
 <li>slash / is converted to \_S</li>
 <li>underbar _ is converted to \_U</li>
 </ul>
 <h2 id="modelmakers">ModelMakers</h2>
 <p>Plain models can be given names which allows them to be &ldquo;saved&rdquo; and
 looked up by name later. This is handled by implementations of the
 interface <code>ModelMaker</code>; each <code>ModelMaker</code> produces Models of the
 same kind. The simplest kind of <code>ModelMaker</code> is a memory model
 maker, which you get by calling
 <code>ModelFactory.createMemModelMaker()</code>. The methods you&rsquo;d want to use
 to start with on a ModelMaker are:</p>
 <ul>
 <li>
 <p><code>createModel(String)</code>: create a model with the given name in the
 ModelMaker. If a model with that name already exists, then that
 model is used instead.</p>
 </li>
 <li>
 <p><code>openModel(String)</code>: open an existing model with the given name. If
 no such model exists, create a new empty one and give it that name.
 [createModel(String) and openModel(String) behave in the same way,
 but each has a two-argument form for which the behaviour is
 different. Use whichever one best fits your intention.]</p>
 </li>
 <li>
 <p><code>createModel()</code>: create a fresh anonymous model.</p>
 </li>
 <li>
 <p><code>getModel()</code>: each <code>ModelMaker</code> has a <em>default model</em>; this method
 returns that model.</p>
 </li>
 </ul>
 <p>There are other methods, for removing models, additional control
 over create <em>vs</em> open, closing the maker, and looking names up; for
 those consult the
 <a href="/documentation/javadoc/jena/org/apache/jena/rdf/model/ModelMaker.html">ModelMaker JavaDoc</a>.</p>
 <h2 id="miscellany">Miscellany</h2>
 <p>Finally, <code>ModelFactory</code> contains a collection of methods for some
 special cases not conveniently dealt with elsewhere.</p>
 <p><code>createModelForGraph(Graph g)</code> is used when an advanced user with
 access to the Jena SPI has constructed or obtained a <code>Graph</code> and
 wishes to present it as a model. This method wraps the graph up as
 a plain model. Alterations to the graph are visible in the model,
 and <em>vice versa</em>.</p>


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	<h1 class="title">Creating Jena models</h1>

	<h2 id="introduction">Introduction</h2>
	<p>Jena is a moderately complicated system, with several
	different kinds of <code>Model</code> and ways of constructing them. This note
	describes the Jena <code>ModelFactory</code>, a one-stop shop for
	creating Jena models. <code>ModelFactory</code> lives in Java package
	<code>org.apache.jena.rdf.model</code>.</p>
	<p>This note is an introduction, not an exhaustive description. As
	usual consult the Javadoc for details of the methods and classes to
	use.</p>
	<h2 id="simple-model-creation">Simple model creation</h2>
	<p>The simplest way to create a model (if not the shortest) is to call
	<code>ModelFactory.createDefaultModel()</code>. This [by default] delivers a
	plain RDF model, stored in-memory, that does no inference and has
	no special ontology interface.</p>
	<h2 id="database-model-creation">Database model creation</h2>
	<p>For methods of creating models for <a href="/documentation/tdb/index.html">TDB</a>
	please see the relevant reference sections.</p>
	<h2 id="inference-model-creation">Inference model creation</h2>
	<p>An important feature of Jena is support for different kinds of
	inference over RDF-based models (used for RDFS and OWL).
	Inference models are constructed by applying <em>reasoners</em> to
	<em>base models</em> and optionally <em>schema</em>. The statements deduced by
	the reasoner from the base model then appear in the inferred model
	alongside the statements from the base model itself.
	RDFS reasoning is directly available:</p>
	<ul>
	<li>
	<p><code>createRDFSModel(Model base)</code> creates an inference model over the
	base model using the built-in RDFS inference rules and any RDFS
	statements in the base model.</p>
	</li>
	<li>
	<p><code>createRDFSModel(Model schema, Model base)</code> creates an RDFS
	inference model from the base model and the supplied schema model.
	The advantage of supplying the schema separately is that the
	reasoner may be able to compute useful information in advance on
	the assumption that the schema won’t change, or at least not change
	as often as the base model.</p>
	</li>
	</ul>
	<p>It’s possible to use other reasoning systems than RDFS. For these a
	Reasoner is required:</p>
	<ul>
	<li>
	<p><code>createInfModel(Reasoner reasoner, Model base)</code> creates an
	inference model using the rules of <code>reasoner</code> over the model
	<code>base</code>.</p>
	</li>
	<li>
	<p><code>createInfModel(Reasoner reasoner, Model schema, Model base)</code> Just
	as for the RDFS case, the schema may be supplied separately to
	allow the reasoner to digest them before working on the model.</p>
	</li>
	</ul>
	<p>From where do you fetch your reasoners? From the
	<em>reasoner registry</em>, the class
	<a href="/documentation/javadoc/jena/org/apache/jena/reasoner/ReasonerRegistry.html">ReasonerRegistry</a>.
	This allows reasoners to be looked up by name, but also provides
	some predefined access methods for well-know reasoners:</p>
	<ul>
	<li>
	<p><code>getOWLReasoner()</code>: the reasoner used for OWL inference</p>
	</li>
	<li>
	<p><code>getRDFSReasoner()</code>: the reasoner used for RDFS inference</p>
	</li>
	<li>
	<p><code>getTransitiveReasoner()</code>: a reasoner for doing subclass and
	sub-property closure.</p>
	</li>
	</ul>
	<h2 id="ontology-model-creation">Ontology model creation</h2>
	<p>An <em>ontology model</em> is one that presents RDF as an ontology -
	classes, individuals, different kinds of properties, and so forth.
	Jena supports RDFS and OWL ontologies through <em>profiles</em>.
	There is extensive documentation on
	<a href="../ontology/index.html">Jena’s ontology support</a>, so all we’ll do
	here is summarise the creation methods.</p>
	<ul>
	<li>
	<p><code>createOntologyModel()</code> Creates an ontology model which is
	in-memory and presents OWL ontologies.</p>
	</li>
	<li>
	<p><code>createOntologyModel(OntModelSpec spec, Model base)</code> Creates an
	ontology model according the
	<a href="/documentation/javadoc/jena/org/apache/jena/ontology/OntModelSpec.html">OntModelSpec</a>
	<code>spec</code> which presents the ontology of <code>base</code>.</p>
	</li>
	<li>
	<p><code>createOntologyModel(OntModelSpec spec, ModelMaker maker, Model base)</code>
	Creates an OWL ontology model according to the <code>spec</code> over the
	<code>base</code> model. If the ontology model needs to construct additional
	models (for OWL imports), use the <code>ModelMaker</code> to create them. [The
	previous method will construct a <code>MemModelMaker</code> for this.]</p>
	</li>
	</ul>
	<p>Where do <code>OntModelSpec</code>s come from? There’s a cluster of
	constants in the class which provide for common uses; to name but
	three:</p>
	<ul>
	<li>
	<p><code>OntModelSpec.OWL_MEM_RDFS_INF</code> OWL ontologies, model stored in
	memory, using RDFS entailment only</p>
	</li>
	<li>
	<p><code>OntModelSpec.RDFS_MEM</code> RDFS ontologies, in memory, but doing no
	additional inferences</p>
	</li>
	<li>
	<p><code>OntModelSpec.OWL_DL_MEM_RULE_INF</code> OWL ontologies, in memory, with
	the full OWL Lite inference</p>
	</li>
	</ul>
	<h2 id="creating-models-from-assembler-descriptions">Creating models from Assembler descriptions</h2>
	<p>A model can be built from a description of the required model.
	This is documented in the
	<a href="../assembler/assembler-howto.html">assembler howto</a>.
	Access to the
	assembler system for model creation is provided by three
	ModelFactory methods:</p>
	<ul>
	<li>
	<p><code>assembleModelFrom( Model singleRoot )</code>: assemble a Model from the
	single Model description in <code>singleRoot</code>. If there is no such
	description, or more than one, an exception is thrown. If a
	description has to be selected from more than one available
	candidates, consider using the methods below.</p>
	</li>
	<li>
	<p><code>findAssemblerRoots( Model m )</code>: answer a Set of all the Resources
	in <code>m</code> which are of type <code>ja:Model</code>, ie descriptions of models to
	assemble. (Note that this will include sub-descriptions of embedded
	models if they are present.)</p>
	</li>
	<li>
	<p><code>assembleModelFrom( Resource root )</code>: answer a Model assembled
	according to the description hanging from <code>root</code>.
	Assemblers can construct other things as well as models, and the
	Assembler system is user-extensible: see the howto for details.</p>
	</li>
	</ul>
	<h3 id="file-based-models">File-based models</h3>
	<p>The method <code>ModelFactory.createFileModelMaker(String)</code> returns a
	<code>ModelMaker</code> which attaches models to filing-system files. The
	<code>String</code> argument is the <em>fileBase</em>. When a file-ModelMaker opens a
	file, it reads it from a file in the directory named by the
	fileBase; when the model is closed (and <em>only</em> then, in the current
	implementation), the contents of the model are written back to the
	file.</p>
	<p>Because the names of models in a modelMaker can be arbitrary
	character strings, in particular URIs, they are translated slightly
	to avoid confusion with significant characters of common filing
	systems. In the current implementation,</p>
	<ul>
	<li>colon : is converted to \_C</li>
	<li>slash / is converted to \_S</li>
	<li>underbar _ is converted to \_U</li>
	</ul>
	<h2 id="modelmakers">ModelMakers</h2>
	<p>Plain models can be given names which allows them to be “saved” and
	looked up by name later. This is handled by implementations of the
	interface <code>ModelMaker</code>; each <code>ModelMaker</code> produces Models of the
	same kind. The simplest kind of <code>ModelMaker</code> is a memory model
	maker, which you get by calling
	<code>ModelFactory.createMemModelMaker()</code>. The methods you’d want to use
	to start with on a ModelMaker are:</p>
	<ul>
	<li>
	<p><code>createModel(String)</code>: create a model with the given name in the
	ModelMaker. If a model with that name already exists, then that
	model is used instead.</p>
	</li>
	<li>
	<p><code>openModel(String)</code>: open an existing model with the given name. If
	no such model exists, create a new empty one and give it that name.
	[createModel(String) and openModel(String) behave in the same way,
	but each has a two-argument form for which the behaviour is
	different. Use whichever one best fits your intention.]</p>
	</li>
	<li>
	<p><code>createModel()</code>: create a fresh anonymous model.</p>
	</li>
	<li>
	<p><code>getModel()</code>: each <code>ModelMaker</code> has a <em>default model</em>; this method
	returns that model.</p>
	</li>
	</ul>
	<p>There are other methods, for removing models, additional control
	over create <em>vs</em> open, closing the maker, and looking names up; for
	those consult the
	<a href="/documentation/javadoc/jena/org/apache/jena/rdf/model/ModelMaker.html">ModelMaker JavaDoc</a>.</p>
	<h2 id="miscellany">Miscellany</h2>
	<p>Finally, <code>ModelFactory</code> contains a collection of methods for some
	special cases not conveniently dealt with elsewhere.</p>
	<p><code>createModelForGraph(Graph g)</code> is used when an advanced user with
	access to the Jena SPI has constructed or obtained a <code>Graph</code> and
	wishes to present it as a model. This method wraps the graph up as
	a plain model. Alterations to the graph are visible in the model,
	and <em>vice versa</em>.</p>


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