ODM12 — Issues in Annex G

Annex G (MOF QVT: A Brief Tutorial) contains some statements that are incorrect or incomplete:

• Section G.2, paragraph 3, sentence 2 states: "No work is done via a when clause". This is misleading. Relations invoked in a when clause can create instances.
• Section G.2, paragraph 3, sentence 4: The sentence states that predicates can be connected by an or operator. Individual predicates can contain or operators, but the QVT specification doesn't say or connects predicates.
• Section G.2, paragraph 4: The paragraph reads "OCL functions can be used." This is true, but incomplete. QVT permits a transformation to define functions, and to access externally-defined functions written in a language such as Java. The paragraph should be amended to describe these types of functions.
• Section G.2, paragraph 5, sentence 1:
  • The sentence references OCL statements. The OCL specification describes a statement as something along the lines of an invariant (including the keyword inv) or a default attribute value. The correct term is "OCL expressions".
  • The sentence neglects to state that an OCL let expression can define a variable.
• Section G.2, paragraph 7, sentence 2 reads "A top relation is executed by the system." A top relation may also be called in a where clause.
• Section G.3, paragraph 6, sentence 2 reads "A process in a repository can link from one object to another via any property ..." The paragraph does not explain what "process" means.
• Section G.3, paragraph 2, last sentence: the second clause should begin with "it".