1. CS551 Behavior Models: Object Types and Operations (Chap. 3 of UML)
Yugi Lee
STB #555
(816)
CS551 - Lecture 6-2

2. Subtypes and Type Extension
Class
an object-oriented programming (OOP) construct (implementation of some objects)
Type
a specification of a set of objects
Subclassing
inheriting implementation with certain forms of overriding of implementation:
Subtyping
no overriding of specifications, only extension.
CS551 - Lecture 6-2

3. Classes & Types
CS551 - Lecture 6-2

4. Type Expression Subtype: Multiple Supertypes Type Exclusion
Cow Mammal
Multiple Supertypes
Bat Mammal * Flier
Type Exclusion
TA1 * TA2 =
Type Partitioning:
TA = TA1+TA2
CS551 - Lecture 6-2

5. State Type A set of objects defined by a predicate
Objects are classified based on a condition and define resultant properties they will have
An employee is a person with an employer; employees have a salary and can get fired.
CS551 - Lecture 6-2

6. State Chart Each state is a Boolean attribute
The structure of states defines invariants across these attributes.
States are
mutually exclusive.
can be nested inside a state.
can be divided into concurrent sections
CS551 - Lecture 6-2

7. CS551 - Lecture 6-2

8. State Transitions as Actions
CS551 - Lecture 6-2

9. Translating State Transitions to Actions
action Type::a1
pre: s1 & precond
post: s2 & postcond
action Pump::hangup
pre: ready
post: idle
action Pump::pickup
pre: idle
post: ready
CS551 - Lecture 6-2

10. State Charts of Specification Types
CS551 - Lecture 6-2

11. State Charts of Specification Types
action Drawing_Editor::select (shape:Shape)
post:
current_doc_contents ->
forAll ( s |
((s.selected &
==> s.unselected)
&
((s.unselected &
==> s.selected))
CS551 - Lecture 6-2

12. Sequence Expression S1 ; S2 S1 always precedes S2 S1 | S2 S1 or S2
Any number of repetitions
of S1
S1 || S2
S1 concurrent with S2
CS551 - Lecture 6-2

13. The Meaning of Containment
Containment represents a localized view, which is
a state type of the common usage.
CS551 - Lecture 6-2

14. Type Specifications: Summary
An object’s behavior (or part of it) can be described with a type specification.
A type specification is a set of action specifications
A postcondition: a relationship between the states before and after any of its occurrences takes place.
A precondition: when the associated postcondition is applicable.
CS551 - Lecture 6-2