predicate - Modelling Relation in Event-B -


i have question follows:

a primary school class contains number of children , variety of books. write model keeps track of books children have read. should maintain relation hasread between children , books.

so have context so

context       bookscontext sets     students     books  constants     student     book axioms     axm1: partition(students, {student})     axm2: partition(books,{book})

and machine follows:

machine     books sees     bookscontext variables     students     readbooks invariants     students ⊆ students     readbooks ⊆ books     readbooks ∈ students → ℕ

readbooks ∈ students → ℕ trowing error. modelling wrong. can body me this? new event b , don't know do

readbooks variable can't both subset of books , total function because books isn't total function students ℕ.

the fixed model can found in this question.

it looks this:

machine     books sees     bookscontext variables     students     books     readbooks invariants     students ⊆ students     books ⊆ books     readbooks ∈ students → books

where readbooks total function set of students set of books these students have read.


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