When the source attribute is dragged over a target attribute to which a mapping is not possible, the target attribute will not be highlighted at all. If the user releases the cursor, the attribute trailing the cursor and the extending mapping line will disappear.
There are a number of reasons why a mapping may be invalid:
- An evidence attribute can only have one datastore attribute mapped to it.
- A mapping cannot be made between attributes with different underlying data types. For example a mapping cannot be made from an integer data type to a string data type.
- A mapping cannot be made between attributes of the same data type if the datastore entity attribute type is larger than the evidence entity attribute type. For example, a mapping cannot be created from a 32 bit integer to a 16 bit integer.
- It is not possible to create mappings that originate from evidence entity attributes, i.e. all mappings must originate from datastore entities.
- It is not possible to drag a datastore entity attribute onto another datastore entity attribute.