LiteralInterface
extends
TermInterface, TermCompareInterface
in
Description of RdfTerm
Tags
Table of Contents
- CAST_DATATYPE = 2
- CAST_LEXICAL_FORM = 1
- __construct() : mixed
- Creates a new literal.
- __toString() : string
- equals() : bool
- getDatatype() : string
- Returns literal's datatype.
- getLang() : string|null
- Returns literal's language tag.
- getValue() : mixed
- Returns literal's value.
- withDatatype() : LiteralInterface
- Returns a new literal being a copy with this one with datatype set to a given value.
- withLang() : LiteralInterface
- Returns a new literal being a copy of this one with a lang tag set to a given value.
- withValue() : LiteralInterface
- Returns a new literal being a copy of this one with a given value.
Constants
CAST_DATATYPE
public
mixed
CAST_DATATYPE
= 2
Tags
CAST_LEXICAL_FORM
public
mixed
CAST_LEXICAL_FORM
= 1
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Methods
__construct()
Creates a new literal.
public
__construct(int|float|string|bool|Stringable $value[, string|null $lang = null ][, string|null $datatype = RDF::XSD_STRING ]) : mixed
If the $datatype is null or empty, it must be set according to the $value and $lang parameter values:
- if $lang is not empty, the $datatype must be set to
http://www.w3.org/1999/02/22-rdf-syntax-ns#langString - if $lang is empty or null, the $datatype depends on the PHP type of the
$value parameter:
- bool -
http://www.w3.org/2001/XMLSchema#boolean - int -
http://www.w3.org/2001/XMLSchema#integer - float -
http://www.w3.org/2001/XMLSchema#decimal - string -
http://www.w3.org/2001/XMLSchema#string - Stringable object -
http://www.w3.org/2001/XMLSchema#stringor any other more precise XSD datatype if the implementation is able to derive it from the object class
- bool -
The created literal must have valid combination of datatype and lang tag (meaning the datatype is rdf:langString if and only if the literal has a lang tag). It's up to the implementation how to assure it. Both throwing an exception and one of $lang/$datatype taking precedense over the other are considered valid solutions. Of course the implementation behavior should be documented.
See https://www.w3.org/TR/rdf11-concepts/#section-Graph-Literal for a reference.
Parameters
- $value : int|float|string|bool|Stringable
-
Literal's value. Only values which can be casted to a string are allowed so it's clear how to obtain literal's value lexical form (see the RDF specification mentioned above). The lexical forms of scalar values must be created (returned by the getValue() method) in a way that back-casting them to the scalar type gives an equal value (probably the only tricky case here is boolean
false). - $lang : string|null = null
-
Literal's lang tag. If null or empty string, the literal is assumed not to have a lang tag (as an empty lang tag is not allowed in RDF).
- $datatype : string|null = RDF::XSD_STRING
-
Literal's datatype. If it's null, the datatype must be assigned according to the $lang and $value parameter values. The detailed procedure is described above.
Tags
Return values
mixed —__toString()
public
__toString() : string
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Return values
string —equals()
public
equals(TermInterface $term) : bool
Parameters
- $term : TermInterface
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Return values
bool —getDatatype()
Returns literal's datatype.
public
getDatatype() : string
The method must return the actual datatype even if it's implicit. It
means http://www.w3.org/1999/02/22-rdf-syntax-ns#langString must be
returned for literals with a lang tag and
http://www.w3.org/2001/XMLSchema#string must be returned for literals
without lang tag and without datatype specified explicitely.
Tags
Return values
string —getLang()
Returns literal's language tag.
public
getLang() : string|null
If a literal lacks a language tag, null should be returned. It means this method can't return an empty string.
Tags
Return values
string|null —getValue()
Returns literal's value.
public
getValue([int $cast = self::CAST_LEXICAL_FORM ]) : mixed
Separate cast options are needed as the RDF specification defines a few kinds of literal values. See https://www.w3.org/TR/rdf11-concepts/#section-Graph-Literal for details.
Parameters
- $cast : int = self::CAST_LEXICAL_FORM
-
Determines the kind of value being returned:
- \rdfInterface\CAST_LEXICAL_FORM - a string with literal's lexical form. All implementations must handle this kind of cast.
- \rdfInterface\CAST_DATATYPE - value mapped to the datatype's domain. Implementations may handle this kind of cast. It's up to the implementation which datatypes are supported and how the mapping is being done. Implementations may provide additional types of cast.
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Return values
mixed —withDatatype()
Returns a new literal being a copy with this one with datatype set to a given value.
public
withDatatype(string $datatype) : LiteralInterface
Be aware it's impossibe to set the datatype to rdf::langString that way as it would require setting a non-empty lang tag. The withLang() method should be used in such a case as it changes the datatype implicitly.
As this method by definition doesn't allow to set a datatype allowing a literal to have a lang tag, it must set returned literal's lang tag to null.
This method must throw a \BadMethodCallException when called with a wrong
datatype (http://www.w3.org/1999/02/22-rdf-syntax-ns#langString or an
empty one).
Parameters
- $datatype : string
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Return values
LiteralInterface —withLang()
Returns a new literal being a copy of this one with a lang tag set to a given value.
public
withLang(string|null $lang) : LiteralInterface
Be aware setting a lang tag on a literal without one as well as dropping a lang tag from a literal having it implicitly changes literal's datatype. Setting a lang on a literal without one enforces setting its datatype to rdf:langString while dropping a lang from a literal having it changes literal's datatype to xsd:string (see https://www.w3.org/TR/rdf11-concepts/#section-Graph-Literal for details).
Parameters
- $lang : string|null
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Return values
LiteralInterface —withValue()
Returns a new literal being a copy of this one with a given value.
public
withValue(int|float|string|bool|Stringable $value) : LiteralInterface
If the $value type is int/float/bool, the lang tag of the returned literal is set to null and the datatype is set to a corresponding XSD type (see the constructor documentation). If the $value is string/Stringable, the lang tag and datatype are preserved.
Parameters
- $value : int|float|string|bool|Stringable