Génie Logiciel Avancé

Transcription

1 L3 Mention Informatique Parcours Informatique et MIAGE Génie Logiciel Avancé UML/OCL III + StateMachines Burkhart Wolff wolff@lri.fr

2 State Machines " State-Machines offer another view on a system: the dynamique behaviour of an object instance # In which state of an object a method is applicable? # In which state this method call will lead? # Which is the sequence of method calls necessary to bring an object into a particular state? This allows to check if object transitions have been forgotten! B. Wolff - GL A - UML/OCL 2

3 State Machines " State machines = Refined Automaton: # (explicit) states, # transitions + «guards» (conditions for state transitions) # actions B. Wolff - GL A - UML/OCL 3

4 State Machines (2) " Notion State: Abstraction of a stage in the life-cycle of an object in which it satisfies a condition, executing certain activities and responding at external events in a certain manner. # Notion: Compound State (structured state) # Internal activities within a state # Activities when entering and leaving a state B. Wolff - GL A - UML/OCL 4

5 State Machines (3) " Notion Transition: relation ( bridge ) between 2 states, reflecting generally a change of bnehaviour. Described by :! initial and final state! event ( l évènement déclencheur )! guard ( condition de franchissement, garde )! action(s) associated with a transition B. Wolff - GL A - UML/OCL 5

6 State Machines (4) " There are two ways to implement state machines: # States can remain implicite in each method # or in contrary, there is an explicit enumeration class «state» allowing to program via switch (à la Java/C) code for an automata, organised around a variable which represents the current state " State-Machines are half-way between analysis and design! B. Wolff - GL A - UML/OCL 6

7 State Machines (5) " Actions are associated to a transition. This may be: # A method call to the object instance # An assignment to an attribute # Sending of a signal (an own enumeration type, can be linked with the enumeration type for events) # Creation or destruction of an object instance # " Possibility of «internal transitions» B. Wolff - GL A - UML/OCL 7

8 State Machines (6) " Compound states can be: # Orthogonal States (États orthogonaux) (modelling parallel/concurrent execution) # Non orthogonal states (just a sequence of sub-states) # Transitions possible from a global state to a sub-state and vice versa...! Complex Sémantics which is difficult to master! B. Wolff - GL A - UML/OCL 8

9 State Machines : extended syntax «UML 2.0, Guide de référence» Rumbaugh & alli, CampusPress, B. Wolff - GL A - UML/OCL 9

10 State Machines : A Telephone Key Interface Numbering Start digit(n)/ nb='' Partial when nb.size=10 entry/strttonality() exit/endtonality() entry/nb.append(n) digit(n)[nb.size<10] [not nb.valid()] Invalid hangup() [nb.valid()] Valid Exercise: modify the state machine to accept short numbers! B. Wolff - GL A - UML/OCL 10

11 State Machines and OCL We implement states as enumeration type, and add an internal protected attribute to the Clock class <<énumération>> Clock-State DisplayHour ModifyHour ModifyMinute We implement a cornerstone method: O.oclInState (s) : which returns true if the internal protected attribute is equal to s B. Wolff - GL A - UML/OCL 11

12 State Machines and OCL Example: if M1 is an instance of Clock we write : M1.oclInState(DisplayHour) or M1.oclInState(Set{ModifyHour,ModifyMinute}) in the case of a state superposition (in different «regions» at the same time) M1.oclInState(e) returns true iff M1 is in state e B. Wolff - GL A - UML/OCL 12

13 Contraints of the clock (1) context Clock inv : Minutes >= 0 and Minutes <= 59 and Hours >= 0 and Hours <= 23 context Clock :: appuyerb () pre: true post : self.oclinstate (ModifyHour) implies Minutes = Minutes@pre and Hours = Hours@pre + 1 mod 24 and self.oclinstate (ModifyMinute) implies Minutes = Minutes@pre + 1 mod 60 and Hours = Hours@pre and self.oclinstate (DisplayHour) implies Minutes = Minutes@pre and Hours = Hours@pre B. Wolff - GL A - UML/OCL 13

14 Contraints of the clock (2) context Clock :: appuyera () pre: true post: (DisplayHour) implies self.oclinstate(modifyhour) and (ModifyHour) implies self.oclinstate(modificationminutes) and (ModifyMinutes) implies self.oclinstate(displayhour) B. Wolff - GL A - UML/OCL 14