Help:Special properties

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This page describes the 32 special properties that are built-in to Semantic MediaWiki (SMW). They are needed to make the system work. They appear in a page's factbox, on special page "Properties" and on special page "Browse" in italic. Since Semantic MediaWiki 1.4.0, special properties can be used in browsing interfaces and inline queries just like all other properties. Also see the help page Properties and types for more information.

Special properties may also be provided by extensions to Semantic MediaWiki like, e.g. Semantic Extra Special Properties or Sematic Cite, etc. These however are currently not being documented here.

The names and aliases of special properties are reserved and cannot be used for other properties. Additionally special properties should only be used according to their documented purpose! It is not necessary to create pages for special properties. They will perform their special behaviour even if your wiki does not have a property page for it.

The pages listed in the table below provide an overview and link to documentation pages for 32 special properties:

NameAliasDescriptionHelp pageComponentSinceOptionalLabel
Allows valuehas no aliasLists one permissible value for a propertySpecial property Allows valueSemantic MediaWiki1.0falsenot specified
Corresponds tohas no aliasGives the conversion factor for some unit of a physical quantity and the possible names for that unitSpecial property Corresponds toSemantic MediaWiki1.0falsenot specified
Display unitsDisplay unitSpecifies the a comma-separated list of units or formats that a property should use in displaySpecial property Display unitsSemantic MediaWiki1.0falsenot specified
Equivalent URIhas no aliasMarks a page in the wiki as having a well-known meaning beyond this wiki, in an external URISpecial property Equivalent URISemantic MediaWiki1.0falsenot specified
Has typehas no aliasAssigns a type to a propertySpecial property Has typeSemantic MediaWiki1.0falsenot specified
Imported fromhas no aliasAllows users to reuse elements of external vocabularies directly within the wikiSpecial property Imported fromSemantic MediaWiki1.0falsenot specified
Provides servicehas no aliasAdds service links to propertiesSpecial property Provides serviceSemantic MediaWiki1.0falsenot specified
Subproperty ofhas no aliasLets you indicate that one property is a subproperty of anotherSpecial property Subproperty ofSemantic MediaWiki1.0falsenot specified
Modification datehas no aliasIt has a fixed value that corresponds to the date of the last modification of each pageSpecial property Modification dateSemantic MediaWiki1.4.0true_MDAT
Has improper value forhas no aliasAlerts in case the assigned value to a property is invalidSpecial property Has improper value forSemantic MediaWiki1.4.2falsenot specified
Has fieldshas no aliasDefines a short list of fields with a fixed type and order for datatype RecordSpecial property Has fieldsSemantic MediaWiki1.5.0falsenot specified
Subcategory ofhas no aliasLets you explicitly indicate that one category is a subcategory of anotherSpecial property Subcategory ofSemantic MediaWiki1.5.0falsenot specified
Creation datehas no aliasIt has a fixed value that corresponds to the date of the first revision of each pageSpecial property Creation dateSemantic MediaWiki1.7.0true_CDAT
Has subobjecthas no aliasHolds the subobjects set on a pageSpecial property Has subobjectSemantic MediaWiki1.7.0falsenot specified
Is a new pagehas no aliasMarks a page as being new or notSpecial property Is a new pageSemantic MediaWiki1.7.1true_NEWP
Last editor ishas no aliasHolds the page name of the user who created the last page revisionSpecial property Last editor isSemantic MediaWiki1.7.1true_LEDT
Has queryhas no aliasLinks a page to the subobject created by a querySpecial property Has querySemantic MediaWiki1.8.0falsenot specified
Query depthhas no aliasHolds the value of the property depth of a querySpecial property Query depthSemantic MediaWiki1.8.0falsenot specified
Query formathas no aliasHolds the name of the result format used in a querySpecial property Query formatSemantic MediaWiki1.8.0falsenot specified
Query sizehas no aliasHolds the value of the number of conditions in a querySpecial property Query sizeSemantic MediaWiki1.8.0falsenot specified
Query stringhas no aliasHolds the conditions of the query as a stringSpecial property Query stringSemantic MediaWiki1.8.0falsenot specified
Query durationhas no aliasHolds the value of the duration a query took to executeSpecial property Query durationSemantic MediaWiki1.9.0truenot specified
MIME typehas no aliasHolds the MIME type of an uploaded fileSpecial property MIME typeSemantic MediaWiki1.9.1true_MIME
Media typehas no aliasHolds the Media type of an uploaded fileSpecial property Media typeSemantic MediaWiki1.9.1true_MEDIA
Allows patternhas no aliasPattern to match a permissible valueSpecial property Allows patternSemantic MediaWiki2.4.0trueSMW_DV_PVAP
Display precision ofhas no aliasPrecision in digitsSpecial property Display precision ofSemantic MediaWiki2.4.0falsenot specified
Display title ofhas no aliasDisplay an specific denote title for an entitySpecial property Display title ofSemantic MediaWiki2.4.0true_DTITLE
Has processing errorhas no aliasHolds a "container" with further information about a problem and allows to explore it.Special property Has processing errorSemantic MediaWiki2.4.0false
Has processing error texthas no aliasContains a textual description of an error which occurred during the processing of a page.Special property Has processing error textSemantic MediaWiki2.4.0false
Has property descriptionhas no aliasAdd localizable context help to propertiesSpecial property Has property descriptionSemantic MediaWiki2.4.0falsenot specified
Has uniqueness constrainthas no aliasRestrict value annotation to be uniqueSpecial property "Has uniqueness constraint"Semantic MediaWiki2.4.0trueSMW_DV_PVUC
Language codehas no aliasHandles BCP47 conform language codes specifying the language of the annotated textSpecial property Language codeSemantic MediaWiki2.4.0trueSMW_DV_MLTV_LCODE

NoteNote:  Of the page related special properties, i.e. the ones that are marked as optional with "true" in the above list only special property "Modification date" is enabled by default. See the help page on the $smwgPageSpecialProperties configuration parameter for how to activate all or just a specific set of them.

You can create your own special properties in an extension using the smwInitProperties hook. See, for example, the usage in the Semantic Extra Special Properties extension, which provides extra special properties.

In case you would like to make special properties easier to be identified in the factbox, on special pages "Properties" and "Browse" just add, e.g. the following CSS code to the MediaWiki:Common.css page.

.smwbuiltin a,
.smwbuiltin {
    color: #ff8000;

NoteNote:  Special properties are are already printed in italics prior to the extra formatting mentioned here.

This documentation page applies to all SMW versions from 1.4.0 to the most current version.
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Help:Special properties en 1.4.0