Special properties

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This page describes the 38 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"Lists properties and displays their usage and on special page "Browse"Shows all properties and their values annotated to a page in italic. Since Semantic MediaWiki 1.4.0Released on 21 November 2008 and compatible with MW 1.13.x - 1.16.x., 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. extension "Semantic Extra Special Properties"Adds some extra special properties to all pages or extension "Semantic Cite"Provides a simple way of organizing citation resources with the help of semantic annotations., 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 behavior 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 38 special properties:

NameDescriptionHelp pageComponentSinceOptionalLabel
Allows valueLists one permissible value for a propertyHelp:Special property "Allows value"Semantic 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 displayHelp:Special property "Display units"Semantic MediaWiki1.0falsenot specified
Equivalent URIMarks a page in the wiki as having a well-known meaning beyond this wiki, in an external URIHelp:Special property "Equivalent URI"Semantic MediaWiki1.0falsenot specified
Has typeAssigns a datatype to a propertyHelp:Special property "Has type"Semantic MediaWiki1.0falsenot specified
Imported fromAllows users to reuse elements of external vocabularies directly within the wikiHelp:Special property "Imported from"Semantic 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 anotherHelp:Special property "Subproperty of"Semantic MediaWiki1.0falsenot specified
Modification dateHolds a fixed value that corresponds to the date of the last modification of each pageHelp:Special property "Modification date"Semantic MediaWiki1.4.0true_MDAT
Has improper value forAlerts in case the assigned value to a property is invalidHelp:Special property "Has improper value for"Semantic MediaWiki1.4.2falsenot specified
Has fieldsDefines a short list of fields with a fixed type and order for datatype RecordHelp:Special property "Has fields"Semantic MediaWiki1.5.0falsenot specified
Subcategory ofLets you explicitly indicate that one category is a subcategory of anotherHelp:Special property "Subcategory of"Semantic MediaWiki1.5.0falsenot specified
Creation dateHolds 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 pageHelp:Special property "Has subobject"Semantic MediaWiki1.7.0falsenot specified
Is a new pageHolds a value marking 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 query recording its profileHelp:Special property "Has query"Semantic MediaWiki1.8.0falsenot specified
Query depthHolds the value of the property depth of a queryHelp:Special property "Query depth"Semantic 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 valueHelp:Special property "Allows pattern"Semantic MediaWiki2.4.0trueSMW_DV_PVAP
Display precision ofPrecision in digitsHelp:Special property "Display precision of"Semantic MediaWiki2.4.0falsenot specified
Display title ofHolds a 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.Help:Special property "Has processing error"Semantic MediaWiki2.4.0falsenot specified
Has processing error textContains a textual description of an error which occurred during the processing of a page.Help:Special property "Has processing error text"Semantic 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
Allows value listAdds a reference to a list of permissible values for a propertyHelp:Special property "Allows value list"Semantic MediaWiki2.5.0truenot specified
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
Query parametersHolds the parameters a query used to select its outputHelp:Special property "Query parameters"Semantic MediaWiki2.5.0truenot specified
Change propagationHolds the new property specification of a property or category pageHelp:Special property "Change propagation"Semantic MediaWiki3.0.0falsenot specified
Query scodeHolds the status code a query uses to define its internal stateHelp:Special property "Query scode"Semantic MediaWiki3.0.0falsenot 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 special property "Modification date"Holds a fixed value that corresponds to the date of the last modification of each page is enabled by default. See the help page on configuration parameter $smwgPageSpecialPropertiesSets the page related special properties to be used 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 extension "Semantic Extra Special Properties"Adds some extra special properties to all pages, which provides extra special properties.

In case you would like to make special properties easier to be identified in the factbox, on special page "Properties"Lists properties and displays their usage and on special page "Browse"Shows all properties and their values annotated to a page just add, e.g. the following CSS code to the MediaWiki:Common.css page.

.smwbuiltin a,
.smwbuiltin a.new {
    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