Help:Special properties

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This page describes the 34 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 34 special properties:

NameDescriptionHelp pageComponentSinceOptionalLabel
Allows valueLists one permissible value for a propertySpecial property Allows valueSemantic MediaWiki1.0falsenot specified
Corresponds toGives the conversion factor for some unit of a physical quantity and the possible names for that unitHelp:Special property "Corresponds to"Semantic MediaWiki1.0falsenot specified
Display unitsSpecifies the a comma-separated list of units or formats that a property should use in displaySpecial property Display unitsSemantic MediaWiki1.0falsenot specified
Equivalent URIMarks 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 typeAssigns a type to a propertySpecial property Has typeSemantic MediaWiki1.0falsenot specified
Imported fromAllows users to reuse elements of external vocabularies directly within the wikiSpecial property Imported fromSemantic MediaWiki1.0falsenot specified
Provides serviceAdds service links to propertiesHelp:Special property "Provides service"Semantic MediaWiki1.0falsenot specified
Subproperty ofLets you indicate that one property is a subproperty of anotherSpecial property Subproperty ofSemantic MediaWiki1.0falsenot specified
Modification dateIt 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 forAlerts in case the assigned value to a property is invalidSpecial property Has improper value forSemantic MediaWiki1.4.2falsenot specified
Has fieldsDefines a short list of fields with a fixed type and order for datatype RecordSpecial property Has fieldsSemantic MediaWiki1.5.0falsenot specified
Subcategory ofLets you explicitly indicate that one category is a subcategory of anotherSpecial property Subcategory ofSemantic MediaWiki1.5.0falsenot specified
Creation dateIt has a fixed value that corresponds to the date of the first revision of each pageHelp:Special property "Creation date"Semantic MediaWiki1.7.0true_CDAT
Has subobjectHolds the subobjects set on a pageSpecial property Has subobjectSemantic MediaWiki1.7.0falsenot specified
Is a new pageMarks a page as being new or notHelp:Special property "Is a new page"Semantic MediaWiki1.7.1true_NEWP
Last editor isHolds the page name of the user who created the last page revisionHelp:Special property "Last editor is"Semantic MediaWiki1.7.1true_LEDT
Has queryLinks a page to the subobject created by a queryHelp:Special property "Has query"Semantic MediaWiki1.8.0falsenot specified
Query depthHolds the value of the property depth of a querySpecial property Query depthSemantic MediaWiki1.8.0falsenot specified
Query formatHolds the name of the result format used in a queryHelp:Special property "Query format"Semantic MediaWiki1.8.0falsenot specified
Query sizeHolds the value of the number of conditions in a queryHelp:Special property "Query size"Semantic MediaWiki1.8.0falsenot specified
Query stringHolds the conditions of the query as a stringHelp:Special property "Query string"Semantic MediaWiki1.8.0falsenot specified
Query durationHolds the value of the duration a query took to executeHelp:Special property "Query duration"Semantic MediaWiki1.9.0truenot specified
MIME typeHolds the MIME type of an uploaded fileHelp:Special property "MIME type"Semantic MediaWiki1.9.1true_MIME
Media typeHolds the Media type of an uploaded fileHelp:Special property "Media type"Semantic MediaWiki1.9.1true_MEDIA
Allows patternPattern to match a permissible valueSpecial property Allows patternSemantic MediaWiki2.4.0trueSMW_DV_PVAP
Display precision ofPrecision in digitsSpecial property Display precision ofSemantic MediaWiki2.4.0falsenot specified
Display title ofDisplay an specific denote title for an entityHelp:Special property "Display title of"Semantic MediaWiki2.4.0true_DTITLE
Has processing errorHolds a "container" with further information about a problem and allows to explore it.Special property Has processing errorSemantic MediaWiki2.4.0falsenot specified
Has processing error textContains a textual description of an error which occurred during the processing of a page.Special property Has processing error textSemantic MediaWiki2.4.0falsenot specified
Has property descriptionAdds localizable context help to propertiesHelp:Special property "Has property description"Semantic MediaWiki2.4.0falsenot specified
Has uniqueness constraintAllows to restrict value annotation to be uniqueHelp:Special property "Has uniqueness constraint"Semantic MediaWiki2.4.0trueSMW_DV_PVUC
Language codeHandles BCP47 conform language codes specifying the language of the annotated textHelp:Special property "Language code"Semantic MediaWiki2.4.0trueSMW_DV_MLTV_LCODE
Has preferred property labelAdds localizable labels to a propertyHelp:Special property "Has preferred property label"Semantic MediaWiki2.5.0false_PPLB
Is edit protectedStores the status of an edit restriction of a pageHelp:Special property "Is edit protected"Semantic MediaWiki2.5.0falsenot specified

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