Help:Special property Allows pattern

The Allows pattern property is a special property in Semantic MediaWiki with a built-in meaning: it provides the possibility to specify a regular expression pattern to match permissible values. It is similar in it functionality to. It was introduced starting with .CiteRef::gh:smw:1417 It is enabled by default. See the help page on for details on configuring Semantic MediaWiki for special data value features including "Allows pattern" with the   option.



Features and limitations

 * This special property can only be assigned via a reference.
 * This can only validly be assigned once to a property. If more than one assignment is made the last one assigned takes precedence.CiteRef::gh:smw:1417:240831598
 * The references together with their regular expressions available for this special property are provided on system message page "Smw allows pattern" as a list.
 * Only users with user right " " can edit system message page "Smw allows pattern".
 * The regular expression modifier  is not permitted and removed from any expression.

Example
System message "Smw allows pattern" can contain something like:
 * - Allows matching a ISBN-10CiteRef::regexlib:isbn.
 * " " is the reference to be added to a property page like e.g.  " " after the pipe is the assigned regular expression.
 * - Allows whitelisting certain terms.
 * " " is the reference to be added to a property page like e.g. . " " after the pipe is the assigned regular expression.

See  for further examples.

Error Handling
When  is used to set a property to a value that is not allowed, the property will not be set, and a warning sign will be shown. When using  to set the property, the error will be silently ignored. To find all pages that use a value that is not allowed, can be used.