The Constant transformation has a feature to enter the type of value used for the constant. The default type is a Guid type field, and I am allowed to enter anything I want for its value. I am able to start an adapter with a constant value therefore populating a Guid field "newguid" with the string value "something". I was also able to do this with a date field. Depending on the type of field that gets mapped in FIM, I'm not entirely sure what would happen on an attempt to import this field - I imagine it would result in every entry failing with unexpected data, or possibly when committing the value to the adapter context.
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