Inverse properties


Since Semantic MediaWiki 1.5.0, it is possible to invert the direction of a property with datatype "Page" in Semantic search (Inline queries, Concepts) and on Browsing interfaces (special page "Ask", special page "Browse").

In order to achieve this, simply write "-" in front of property name anywhere in Semantic MediaWiki to refer to the inverse direction of a property. Thus the property relates to the same pages but with annotated page and property value exchanged. For example, the inverse of "parent of" is "-parent of". This intuitively means "child of". Because of this a property with that name does not have to be created and annotated explicitly. However, note that "-father of" corresponds to "has male parent", not to "son of"!

Semantic MediaWiki does not support naming of inverses nor is it possible to assign a value to an inverse property (e.g. [[-Parent of::Michael]] will not work). Semantic MediaWiki allows inverses to be used for retrieving data. This works in browsing interfaces, queries, and query output directives. In queries it works only for properties of datatype Page.

Starting with Semantic MediaWiki 2.4.0 it is to use inverse properties in printout statements.1. The sandbox wiki provides an example demonstrating this.2

Simple Example

To convert inverse property syntax to English, you can read [[-Has mother::Michael]] as get value of "has mother" from page "Michael".

For example, let's say the page "Michael" has the following wikitext:

Michael's mother is [[Has mother::Carol]].

Then on another page you could do:

{{#ask: [[-Has mother::Michael]] }}

Since get value of property "Has mother" from page "Michael" equates to "Carol", the output of this "#ask" inline query would be just:


Remember that the value for property "Has mother" must be a page. Inverse properties do not work on properties of type number, date, etc. Moreover it only works within inline queries using the "#ask" parser function. It does not work using the "#show" parser function since it only takes pages as selection criterion.3

See also

This documentation page applies to all SMW versions from 1.5.0 to the most current version.
      Other languages: deru

Inverse properties en 1.5.0


  1. ^  Semantic MediaWiki: GitHub pull request gh:smw:1270
  2. ^  Semantic MediaWiki: Sandbox example sb:smw:1270
  3. ^  Semantic MediaWiki: GitHub issue gh:smw:2548