1. A method comprising: obtaining an indication of a first Unified Modeling Language (UML) model element of a first model element type which is to be migrated to a second UML model element of a second model element type; and automatically migrating the first UML model element of the first model element type to the second UML model element of the second model element type, wherein the automatically migrating migrates a relationship between the first UML model element of the first model element type and a related UML model element, of a third model element type, to a relationship between the second UML model element of the second model element type and the related UML model element, and wherein the automatically migrating comprises: obtaining indications of relationship types that are deemed valid or invalid as between model element types, including as between the second model element type and the third model element type, the relationship types being for relationships between UML model elements, the relationships having at least one directional property associated therewith; checking the relationship between the first UML model element and the related UML model element to identify a relationship type of the relationship between the first UML model element and the related UML model element; checking the obtained indications to determine whether the identified relationship type of the relationship between the first UML model element and the related UML model element is indicated to be a valid relationship type that may exist as between the second UML model element of the second model element type and the related UML model element of the third model element type, wherein the checking the obtained indications checks one or more data structures comprising the indications and determines that the identified relationship type is an invalid type of relationship as between the second model element type and the third model element type; based on determining that the identified relationship type is an invalid type of relationship as between the second model element type and the third model element type, identifying a replacement relationship type that is indicated to be a valid type of relationship that may exist as between the second model element type and the third model element type; obtaining the identified replacement relationship type; and automatically creating, with the identified replacement relationship type, the relationship between the second UML model element of the second model element type and the related UML model element to apply the identified replacement relationship type to the relationship between the second UML model element of the second model element type and the related UML model element.