Definition of Constraints

The combination of Functional Roles and Instance Properties defines the Instance Metadata Schema. You could think of it as the cross product between the two. On this schema you can define fine-grained constraints, which are then checked on the instance metadata you upload or edit in MetaKraftwerk. The constraint is only checked, when a instance metadata record has the related Functional Role of the constraint and only for the related Instance Property (column). For a constraint you can set similar properties like on a Instance Property:

▪ Occurrence: The value could either be required, optional or disallowed

▪ Regular Expression: Defines a regular expression which is used to check the values

▪ Enumeration: A list of allowed values

▪ Unique: If true, the property-value/role combination must be unique within an instance

▪ Fixed Value: A fixed value for this property

▪ Description: Optional description of the constraint used by the developer for the documentation