Software Design, Modelling and Analysis in UML

Transcription

1 Software Design, Modelling and Analysis in UML Lecture 03: Object Constraint Language (OCL) main Prof. Dr. Andreas Podelski, Dr. Bernd Westphal Albert-Ludwigs-Universität Freiburg, Germany Contents & Goals Sprelim Last Lecture: Basic Object System Signature Ë and Structure System State σ Σ Ë (Smells like they re related to class/object diagrams, officially we don t know yet...) This Lecture: Educational Objectives: Capabilities for these tasks/questions: Please explain this OCL constraint. Please formalise this constraint in OCL. Does this OCL constraint hold in this system state? Can you think of a system state satisfying this constraint? Please un-abbreviate all abbreviations in this OCL expression. In what sense is OCL a three-valued logic? For what purpose? How are (C) and τ C related? Content: OCL Syntax, OCL Semantics over system states 2/36

2 What is OCL? And What is It Good For? main 3/36 What is OCL? How Does it Look Like? OCL: Object Constraint Logic Swhatis OCL/Beispiel TeamMember age : Integer 2.. meetings participants Meeting title : String numparticipants : Integer start : Date duration: Time move(newstart : Date) context TeamMember inv: age => 18 context Meeting inv: duration > 0 Location 1 ((C) Prof. Dr. P. Thiemann, 4/36

3 What s It Good For? Most prominent: write down requirements supposed to be satisfied by all system states. Often targeting all alive objects of a certain class Swhatis 5/36 What s It Good For? Most prominent: write down requirements supposed to be satisfied by all system states. Often targeting all alive objects of a certain class. Not unknown: write down pre/post-conditions of methods (Behavioural Features). Then evaluated over two system states Swhatis 5/36

4 What s It Good For? Most prominent: write down requirements supposed to be satisfied by all system states. Often targeting all alive objects of a certain class. Not unknown: write down pre/post-conditions of methods (Behavioural Features). Then evaluated over two system states. Common with State Machines: guards in transitions Swhatis 5/36 What s It Good For? Most prominent: write down requirements supposed to be satisfied by all system states. Often targeting all alive objects of a certain class Swhatis Not unknown: write down pre/post-conditions of methods (Behavioural Features). Then evaluated over two system states. Common with State Machines: guards in transitions. Lesser known: provide operation bodies. Metamodeling: the UML standard is a MOF-Model of UML. OCL expressions define well-formedness of UML models (cf. Lecture 21). 5/36

5 Plan. Today: The set OCLExpressions(Ë ) of OCL expressions over Ë. Given an OCL expression expr, a system state σ Σ, and a valuation of Ë logical variables β, define IÂexpr Ã(σ, β) {true, false, }. Later: use I to define = Σ Ë OCLExpressions(Ë ). UML W N E OCL CD, SM ϕ OCL CD, SD S Swhatis Model Instances Ë = (Ì,, V,atr), SM expr Ë,SD M = (Σ, A Ë Ë, SM) B = (QSD, q0, A Ë, SD, FSD) π = (σ0, ε0) (cons0,snd0) (σ1, ε1) u0 G = (N, E, f) wπ = ((σi,consi,sndi)) i N Mathematics Structure Component Object Class Composite Deployment Structure Package Activity Interacti Sequence 6/36 (Core) OCL Syntax [OMG, 2006] main 7/36

6 OCL Syntax 1/4: Expressions expr ::= w : τ(w) expr 1 = τ expr 2 : τ τ Bool oclisundefined τ (expr 1 ) : τ Bool {expr 1,...,expr n } : τ τ Set(τ) isempty(expr 1 ) : Set(τ) Bool size(expr 1 ) : Set(τ) Int allinstances C : Set(τ C ) v(expr 1 ) : τ C τ(v) r 1 (expr 1 ) : τ C τ D r 2 (expr 1 ) : τ C Set(τ D ) Where, given Ë = (Ì,, V,atr), W {self C C } is a set of typed logical variables, w has type τ(w) τ is any type from Ì T B T {Set(τ 0 ) τ 0 T B T } T B is a set of basic types, in the following we use T B = {Bool,Int,String} T = {τ C C } is the set of object types, Set(τ 0 ) denotes the set-of-τ 0 type for τ 0 T B T (sufficient because of flattening (cf. standard)) v : τ(v) atr(c), τ(v) Ì, r 1 : D 0,1 atr(c), r 2 : D atr(c), C, D. 8/36 (Core) OCL Syntax [OMG, 2006] main 7/36

7 OCL Syntax: Notational Conventions for Expressions Each expression ω(expr 1,expr 2,...,expr n ) : τ 1 τ n τ may alternatively be written ( abbreviated as ) expr 1. ω(expr 2,...,expr n ) if τ 1 is an object type, i.e. if τ 1 T. expr 1 -> ω(expr 2,...,expr n ) if τ 1 is a collection type (here: only sets), i.e. if τ 1 = Set(τ 0 ) for some τ 0 T B T. Examples: (self : τ C W; v,w : Int V ; r 1 : D 0,1, r 2 : D V ) self. v self. r 1. w self. r 2 -> isempty 9/36 OCL Syntax 2/4: Constants, Arithmetical Operators For example: expr ::=... true, false : Bool expr 1 {and, or, implies} expr 2 : Bool Bool Bool not expr 1 : Bool Bool 0, 1, 1, 2, 2,... : Int OclUndefined : τ expr 1 {+,,... } expr 2 : Int Int Int expr 1 {<,,... } expr 2 : Int Int Bool Generalised notation: expr ::= ω(expr 1,...,expr n ) with ω {+,,... } : τ 1 τ n τ 10/36

8 OCL Syntax 3/4: Iterate expr ::= expr 1 ->iterate(w 1 : τ 1 ; w 2 : τ 2 = expr 2 expr 3 ) or, with a little renaming, expr ::= expr 1 ->iterate(iter : τ 1 ; result : τ 2 = expr 2 expr 3 ) where expr 1 is of a collection type (here: a set Set(τ 0 ) for some τ 0 ), iter W is called iterator, gets type τ 1 (if τ 1 is omitted, τ 0 is assumed as type of iter) result W is called result variable, gets type τ 2, expr 2 in an expression of type τ 2 giving the initial value for result, ( OclUndefined if omitted) expr 3 is an expression of type τ 2 in which in particular iter and result may appear. 11/36 Iterate: Intuitive Semantics (Formally: later) expr ::= expr 1 ->iterate(iter : τ 1 ; result : τ 2 = expr 2 expr 3 ) Set(τ 0 ) hlp = expr 1 ; τ 1 iter; τ 2 result = expr 2 ; while (!hlp.empty()) do od iter = hlp.pop(); result = expr 3 ; Note: In our (simplified) setting, we always have expr 1 : Set(τ 1 ) and τ 0 = τ 1. In the type hierarchy of full OCL with inheritance and oclany, they may be different and still type consistent. 12/36

9 Abbreviations on Top of Iterate expr ::= expr 1 ->iterate(w 1 : τ 1 ; w 2 : τ 2 = expr 2 expr 3 ) expr 1 ->forall(w : τ 1 expr 3 ) is an abbreviation for expr 1 ->iterate(w: τ 1 ; w 1 : Bool = true w 1 andexpr 3 ). (To ensure confusion, we may again omit all kinds of things, cf. [OMG, 2006]). Similar: expr 1 ->Exists(w : τ 1 expr 3 ) 13/36 OCL Syntax 4/4: Context context ::= context w 1 : τ 1,...,w n : τ n inv : expr where w W and τ i T, 1 i n, n 0. context w 1 : C 1,...,w n : C n inv : expr is an abbreviation for allinstances C1 ->forall(w 1 : C 1... allinstances Cn -> forall(w n : C n expr )... ) 14/36

10 Context: More Notational Conventions For context self : τ C inv : expr we may alternatively write ( abbreviate as ) context τ C inv : expr Within the latter abbreviation, we may omit the self in expr, i.e. for self.v and self.r we may alternatively write ( abbreviate as ) v and r 15/36 Examples (from lecture Softwaretechnik TeamMember 2008 ) Meeting age : Integer 2.. meetings participants title : String numparticipants : Integer start : Date duration: Time move(newstart : Date) context TeamMember inv: age => 18 context Meeting inv: duration > 0 Location 1 ((C) Prof. Dr. P. Thiemann, 16/36

11 Examples (from lecture Softwaretechnik 2008 ) OCL/Mehr Navigation/Beispiele TeamMember age : Integer 2.. meetings participants Meeting title : String numparticipants : Integer start : Date duration: Time move(newstart : Date) context Meeting inv: self.participants->size() = numparticipants context Location inv: name="lobby" implies meeting->isempty() Location 1 ((C) Prof. Dr. P. Thiemann, 17/36 Example (from lecture Softwaretechnik 2008 ) TeamMember age : Integer 2.. meetings participants Meeting title : String numparticipants : Integer start : Date duration: Time move(newstart : Date) Location 1 context Meeting inv : participants -> iterate(i : TeamMember; n : Int = 0 n + i. age) /participants -> size() > 25 18/36

12 Not Interesting Among others: Enumeration types Type hierarchy Complete list of arithmetical operators The two other collection types Bag and Sequence Casting Runtime type information Pre/post conditions (maybe later, when we officially know what an operation is)... 19/36 References main 35/36

13 References [OMG, 2006] OMG (2006). Object Constraint Language, version 2.0. Technical Report formal/ [OMG, 2007a] OMG (2007a). Unified modeling language: Infrastructure, version Technical Report formal/ [OMG, 2007b] OMG (2007b). Unified modeling language: Superstructure, version Technical Report formal/ [Warmer and Kleppe, 1999] Warmer, J. and Kleppe, A. (1999). The Object Constraint Language. Addison-Wesley main 36/36