KDE 4.9 PyKDE API Reference

- KDE's Python API

# 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:

  | id | 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:

  | id | 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:

  | n3 | 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 |