Help:Special properties
This page describes the 24 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:Browse and on Special:Properties in italic. Since SMW 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 Semantic Forms. 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 special properties.
| Name | Alias | Description | Help page | Component | Since | Optional | Label |
|---|---|---|---|---|---|---|---|
| Allows value | has no alias | Lists one permissible value for a property | Special property Allows value | Semantic MediaWiki | 1.0 | false | not specified |
| Corresponds to | has no alias | Gives the conversion factor for some unit of a physical quantity and the possible names for that unit | Special property Corresponds to | Semantic MediaWiki | 1.0 | false | not specified |
| Display units | Display unit | Specifies the a comma-separated list of units or formats that a property should use in display | Special property Display units | Semantic MediaWiki | 1.0 | false | not specified |
| Equivalent URI | has no alias | Marks a page in the wiki as having a well-known meaning beyond this wiki, in an external URI | Special property Equivalent URI | Semantic MediaWiki | 1.0 | false | not specified |
| Has type | has no alias | Assigns a type to a property | Special property Has type | Semantic MediaWiki | 1.0 | false | not specified |
| Imported from | has no alias | Allows users to reuse elements of external vocabularies directly within the wiki | Special property Imported from | Semantic MediaWiki | 1.0 | false | not specified |
| Provides service | has no alias | Adds service links to properties | Special property Provides service | Semantic MediaWiki | 1.0 | false | not specified |
| Subproperty of | has no alias | Lets you indicate that one property is a subproperty of another | Special property Subproperty of | Semantic MediaWiki | 1.0 | false | not specified |
| Modification date | has no alias | It has a fixed value that corresponds to the date of the last modification of each page | Special property Modification date | Semantic MediaWiki | 1.4.0 | true | _MDAT |
| Has improper value for | has no alias | Alerts in case the assigned value to a property is invalid | Special property Has improper value for | Semantic MediaWiki | 1.4.2 | false | not specified |
| Has fields | has no alias | Defines a short list of fields with a fixed type and order for datatype Record | Special property Has fields | Semantic MediaWiki | 1.5.0 | false | not specified |
| Subcategory of | has no alias | Lets you explicitly indicate that one category is a subcategory of another | Special property Subcategory of | Semantic MediaWiki | 1.5.0 | false | not specified |
| Creation date | has no alias | It has a fixed value that corresponds to the date of the first revision of each page | Special property Creation date | Semantic MediaWiki | 1.7.0 | true | _CDAT |
| Has subobject | has no alias | Holds the subobjects set on a page | Special property Has subobject | Semantic MediaWiki | 1.7.0 | false | not specified |
| Is a new page | has no alias | Marks a page as being new or not | Special property Is a new page | Semantic MediaWiki | 1.7.1 | true | _NEWP |
| Last editor is | has no alias | Holds the page name of the user who created the last page revision | Special property Last editor is | Semantic MediaWiki | 1.7.1 | true | _LEDT |
| Has query | has no alias | Links a page to the subobject created by a query | Special property Has query | Semantic MediaWiki | 1.8.0 | false | not specified |
| Query depth | has no alias | Holds the value of the property depth of a query | Special property Query depth | Semantic MediaWiki | 1.8.0 | false | not specified |
| Query format | has no alias | Holds the name of the result format used in a query | Special property Query format | Semantic MediaWiki | 1.8.0 | false | not specified |
| Query size | has no alias | Holds the value of the number of conditions in a query | Special property Query size | Semantic MediaWiki | 1.8.0 | false | not specified |
| Query string | has no alias | Holds the conditions of the query as a string | Special property Query string | Semantic MediaWiki | 1.8.0 | false | not specified |
| Query duration | has no alias | Holds the value of the duration a query took to execute | Special property Query duration | Semantic MediaWiki | 1.9.0 | true | not specified |
| MIME type | has no alias | Holds the MIMI type of an uploaded file | Special property MIME type | Semantic MediaWiki | 1.9.1 | true | _MIME |
| Media type | has no alias | Holds the Media type of an uploaded file | Special property Media type | Semantic MediaWiki | 1.9.1 | true | _MEDIA |
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:Properties and Special:Browse just add, e.g.
.smwbuiltin a, .smwbuiltin a.new { color: #FF8000; }
to the MediaWiki:Common.css page. Note that they are already printed in italics prior to the extra formatting mentioned here.
