Node Class Reference

from PyKDE4.soprano import *

Namespace: Soprano

Detailed Description

\class Node node.h Soprano/Node

A Node represents one RDF resource.

Nodes are the cornerstone of RDF data in %Soprano. Four Nodes form one Statement and a Model is essentially a set of Statements.

A Node can have one of four types: EmptyNode, ResourceNode, LiteralNode, and BlankNode. Resource nodes are identified through their URI (uri()), literal nodes have a LiteralValue (literal()), and blank nodes have a string identifier.

Empty nodes can be used as wildcards in methods such as Model.listStatements.

Author:: Daniele Galdi <daniele.galdi@gmail.com>
Sebastian Trueg <trueg@kde.org>

Enumerations
N3ParserFlag	{ NoFlags, StrictLiteralTypes, StrictUris, IgnorePrefixes }
Type	{ EmptyNode, ResourceNode, LiteralNode, BlankNode }
Methods
	__init__ (self)
	__init__ (self, QUrl uri)
	__init__ (self, QString id)
	__init__ (self, Soprano.LiteralValue value)
	__init__ (self, Soprano.LiteralValue value, QString language)
	__init__ (self, Soprano.Node other)
QUrl	dataType (self)
QString	identifier (self)
bool	isBlank (self)
bool	isEmpty (self)
bool	isLiteral (self)
bool	isResource (self)
bool	isValid (self)
QString	language (self)
Soprano.LiteralValue	literal (self)
bool	matches (self, Soprano.Node other)
bool	operator != (self, Soprano.Node other)
bool	operator == (self, Soprano.Node other)
bool	operator == (self, QUrl uri)
bool	operator == (self, Soprano.LiteralValue other)
QString	toN3 (self)
QString	toString (self)
Soprano.Node.Type	type (self)
QUrl	uri (self)
Static Methods
QString	blankToN3 (QString blank)
Soprano.Node	createBlankNode (QString id)
Soprano.Node	createEmptyNode ()
Soprano.Node	createLiteralNode (Soprano.LiteralValue value)
Soprano.Node	createLiteralNode (Soprano.LiteralValue value, QString language)
Soprano.Node	createResourceNode (QUrl uri)
Soprano.Node	fromN3 (QString n3, Soprano.Node.N3ParserFlags flags=Soprano.Node.NoFlags)
Soprano.Node	fromN3Stream (QTextStream stream, Soprano.Node.N3ParserFlags flags=Soprano.Node.NoFlags)
QString	literalToN3 (Soprano.LiteralValue literal)
QString	resourceToN3 (QUrl resource)

Method Documentation

__init__ ( self )

Default costructor. Creates an empty node.

\sa createEmptyNode()

__init__	(	self,
		QUrl	uri
	)

Creates a resource node.

Parameters:

uri

The URI of the node. If empty the type will be ignored and an empty node will be created.

\sa createResourceNode()

__init__	(	self,
		QString	id
	)

Creates a blank node.

Parameters:

An identifier for the blank node.

\sa createBlankNode()

__init__	(	self,
		Soprano.LiteralValue	value
	)

Creates a literal node.

Parameters:

value

The value of a node. If empty the node will become an empty node.

\sa createLiteralNode()

Since:: 2.3

__init__	(	self,
		Soprano.LiteralValue	value,
		QString	language
	)

__init__	(	self,
		Soprano.Node	other
	)

Copy constructor.

QUrl dataType ( self )

Returns:: The datatype URI of a literal node, i.e. the XML schema type or an empty value if the node is not a LiteralNode.

\sa LiteralValue.dataTypeUri

QString identifier ( self )

Retrieve a blank node's identifier.

Returns:: The node's identifier if it is a BlankNode, a null string otherwise.

bool isBlank ( self )

Returns:: true if the node is a BlankNode (anonymous).

bool isEmpty ( self )

Returns:: true if the node is empty.

bool isLiteral ( self )

Returns:: true if the node is a LiteralNode.

bool isResource ( self )

Returns:: true if the node is a ResourceNode.

bool isValid ( self )

Returns:: true if the node is a ResourceNode, LiteralNode or BlankNode.

QString language ( self )

Each literal value can have an associated language, thus each property can be stored for different languages. An empty language refers to the default language.

Returns:: A string representing the language of the literal value or an empty string if the node is not a literal.

Deprecated:: Language exists on the Soprano.LiteralValue. Use Soprano.Node.literal() and Soprano.LiteralValue.language().

Soprano.LiteralValue literal ( self )

Returns:: The literal value if the node is a LiteralNode. An null QString otherwise.

bool matches	(	self,
		Soprano.Node	other
	)

Match this node against template node other. The only difference to operator== is that empty nodes are matched as wildcards, i.e. they match any other node.

Be aware that the following is NOT always true since only other is treated a a wildcard:

 // NOT always true:
 a.matches(b) == b.matches(a)

Returns:: true if this node matches other, false if not.

\sa Statement.matches

bool operator !=	(	self,
		Soprano.Node	other
	)

Comparision operator.

Returns:: true if this node and other differ.

bool operator ==	(	self,
		Soprano.Node	other
	)

Comparision operator.

Returns:: true if this node is a LiteralNode and has literal value other.

bool operator ==	(	self,
		QUrl	uri
	)

Comparision operator.

Returns:: true if this node is a LiteralNode and has literal value other.

bool operator ==	(	self,
		Soprano.LiteralValue	other
	)

Comparision operator.

Returns:: true if this node is a LiteralNode and has literal value other.

QString toN3 ( self )

Convert a Node into N3 notation to be used in SPARQL graph patterns.

Examples:

 <http://soprano.sourceforce.net/>
 "Hello World"^^<http://www.w3.org/2001/XMLSchema#string>
 "09-08-1977T17:42.234Z"^^<http://www.w3.org/2001/XMLSchema#dateTime>
 _:blankNode

Returns:: A string representing the node in N3 encoding or an empty string for invalid nodes.

\sa resourceToN3(), literalToN3(), blankToN3(), fromN3(), toString()

Since:: 2.2

QString toString ( self )

Converts the Node to a string.

Returns:: A String representation of the Node, suitable for storage, not really suitable for user readable strings.

\sa LiteralValue.toString(), QUrl.toString(), toN3()

Soprano.Node.Type type ( self )

Returns:: The node type.

QUrl uri ( self )

Returns:: The URI if the node is a ResourceNode. An null QUrl otherwise.

Static Method Documentation

QString blankToN3	(	QString	blank
	)

Format a blank node identifier as N3 string to be used in SPARQL queries.

Returns:: A string representing the blank identifier in N3 encoding or an empty string for invalid/empty ids.

Example:

 _:blankNode

\sa toN3(), fromN3()

Since:: 2.3

Soprano.Node createBlankNode	(	QString	id
	)

Convenience method to create a blank node. Using this method instead of the constructor may result in better readable code.

If you need to create a new blank node which is not used in the model yet and, thus, has a unique identifier see Model.createBlankNode().

Parameters:

An identifier for the blank node.

Returns:: A blank node or an empty Node if the specified identifier was empty.

Soprano.Node createEmptyNode ( )

Convenience method to create an empty node. Using this method instead of the default constructor may result in better readable code.

Returns:: An empty Node.

Soprano.Node createLiteralNode	(	Soprano.LiteralValue	value
	)

Convenience method to create a literal node. Using this method instead of the constructor may result in better readable code.

Parameters:

value

The value of a node. If empty the node will become an empty node.

Parameters:

language

The language of the literal value.

Returns:: A literal node or an empty node if the specified value was empty.

Deprecated:: Use Soprano.Node.createLiteralNode( const LiteralValue& ) and Soprano.LiteralValue.createPlainLiteral( const QString&, const LanguageTag& )

Soprano.Node createLiteralNode	(	Soprano.LiteralValue	value,
		QString	language
	)

Convenience method to create a literal node. Using this method instead of the constructor may result in better readable code.

Parameters:

value

The value of a node. If empty the node will become an empty node.

Parameters:

language

The language of the literal value.

Returns:: A literal node or an empty node if the specified value was empty.

Deprecated:: Use Soprano.Node.createLiteralNode( const LiteralValue& ) and Soprano.LiteralValue.createPlainLiteral( const QString&, const LanguageTag& )

Soprano.Node createResourceNode	(	QUrl	uri
	)

Convenience method to create a resource node. Using this method instead of the constructor may result in better readable code.

Parameters:

uri

The URI of the node. If empty the type will be ignored and an empty node will be created.

Returns:: A resource Node or an empty Node if the specified URI is empty.

Soprano.Node fromN3	(	QString	n3,
		Soprano.Node.N3ParserFlags	flags=Soprano.Node.NoFlags
	)

Convert a node from its N3 representation.

Parameters:

The N3 representation of the node.

Returns:: A %Node representing the parsed version of n3 or an invalid %Node in case parsing failed.

\sa resourceToN3(), literalToN3(), blankToN3(), toN3()

Since:: 2.5

Soprano.Node fromN3Stream	(	QTextStream	stream,
		Soprano.Node.N3ParserFlags	flags=Soprano.Node.NoFlags
	)

Read a node from its N3 representation on a stream.

Parameters:

stream

The stream from which the N3 representation of the node will be read.

Returns:: A %Node representing the parsed version of n3 or an invalid %Node in case parsing failed.

\sa resourceToN3(), literalToN3(), blankToN3(), toN3()

Since:: 2.5

QString literalToN3	(	Soprano.LiteralValue	literal
	)

Format a literal value as N3 string to be used in SPARQL queries.

Returns:: A string representing the literal in N3 encoding or an empty string for invalid literals.

Examples:

 "Hello World"^^<http://www.w3.org/2001/XMLSchema#string>
 "09-08-1977T17:42.234Z"^^<http://www.w3.org/2001/XMLSchema#dateTime>

\sa toN3(), fromN3()

Since:: 2.3

QString resourceToN3	(	QUrl	resource
	)

Format a resource URI as N3 string to be used in SPARQL queries.

Returns:: A string representing the resource in N3 encoding or an empty string for invalid URIs.

Example:

 <http://soprano.sourceforce.net/>

\sa toN3(), fromN3()

Since:: 2.3

Enumeration Documentation

N3ParserFlag

Parsing flags to infuence the behaviour of the parser in fromN3() and fromN3Stream().

Since:: 2.5

Enumerator:

NoFlags = 0x0
StrictLiteralTypes = 0x1
StrictUris = 0x2
IgnorePrefixes = 0x4

Type

Enumerator:

EmptyNode = 0
ResourceNode = 1
LiteralNode = 2
BlankNode = 3

Node Class Reference

Detailed Description

Enumerations

Methods

Static Methods

Method Documentation

Static Method Documentation

Enumeration Documentation

Modules