Property:Has improper value for
From AcaWiki
"Has improper value for" is a predefined property that tracks input errors for irregular value annotations and is provided by Semantic MediaWiki. In most cases it is caused by a type mismatch or a value restriction. This property is pre-deployed (also known as special property) and comes with additional administrative privileges but can be used just like any other user-defined property.
Has improper value for is a special property in SMW with a built-in meaning: it helps to keep track of input errors in a wiki when values that are assigned to some property are invalid. This special property is available since SMW 1.4.2.
See http://semantic-mediawiki.org/wiki/Property:Has_improper_value_for