Time Exceptions in Sequence Diagrams

Transcription

1 in Sequence Diagrams Oddleif Halvorsen, Ragnhild Kobro Runde, Øystein Haugen 02-Oct-2006 MARTES 2006 at MoDELS

2 Summary Introducing time exceptions improve the completeness of sequence diagram descriptions without obscuring the readability of the specification. A concrete syntax is suggested and motivated Formal semantics are given showing compositionality associativity of time exceptions that adding a time exception is a refinement that refinement is monotonic wrt. time exceptions meaning that the main part and the exceptional parts can be refined separately 02-Oct-2006 MARTES 2006 at MoDELS

3 Time constraints in proper UML 2 02-Oct-2006 MARTES 2006 at MoDELS

4 Why exceptions? Focus on the entering of the PIN sd Withdrawal :Bank Cardid(cid) ref EnterPin Code(cid, pin) msg( Select amount ) Amount(selectedAmount) OK Withdraw(selectedAmount) Money(selectedAmount) card 02-Oct-2006 MARTES 2006 at MoDELS

5 The PIN was not entered properly sd EnterPin The PIN is not fully received by the ATM msg( Enter PIN ) loop(4) Digit {0..5} Exception UserLeftCard sd UserLeftCard... but we want to specify what should happen then msg( Service canceled. ) terminate 02-Oct-2006 MARTES 2006 at MoDELS

6 Returning from recovery sd Withdrawal catch Cardid(cid) :Bank sd ATMPinValidationTimeout ref EnterPin msg( Select amount ) Amount(selectedAmount) Money(selectedAmount) Card The ATM does not receive the OK in time Code(cid, pin) {0..3} OK(maxAmount) Withdraw(selectedAmount) Exception ATMPinValidationTimeout sd ATMCancel Exception ATMCancel Code(cid, pin) {0..3} OK(maxAmount) return :Bank returning to the exception caller... Msg( Bank timeout ) card terminate... unless it fails again and no OK comes 02-Oct-2006 MARTES 2006 at MoDELS

7 Exception semantics sd Withdrawal catch The ATM has not received the OK in time, and cannot proceed until this has been handled Cardid(cid) :Bank sd ATMPinValidationTimeout ref EnterPin msg( Select amount ) Amount(selectedAmount) Money(selectedAmount) Card... But butthe thebank and and the the User does not know about the exception. Code(cid, pin) {0..3} OK(maxAmount) Withdraw(selectedAmount) Exception ATMPinValidationTimeout sd ATMCancel Msg( Bank timeout ) card Exception ATMCancel Code(cid, pin) {0..3} OK(maxAmount) return :Bank terminate 02-Oct-2006 MARTES 2006 at MoDELS

8 TimedSTAIRS Defines denotational trace semantics for timed sequence diagrams. An event is a triple (kind, message, timestamp tag) where kind is either sending, reception or consumption message is a triple (signal, transmitter, receiver) timestamp tag is a placeholder for real timestamp values The semantics of a sequence diagram d is a pair (p,n) p is a set of positive, i.e. valid traces n is a set of negative, i.e. invalid traces traces that are neither positive nor negative are inconclusive If a time constraint is broken, the described traces are negative. 02-Oct-2006 MARTES 2006 at MoDELS

9 Refinement in TimedSTAIRS Positive Supplementing Inconclusive Narrowing A sequence diagram d with semantics (p',n') is a refinement of a sequence diagram d with semantics (p,n) iff n n' p p n' Negative 02-Oct-2006 MARTES 2006 at MoDELS

10 STAIRS semantics for q: the event that may never arrive C: the time constraint on q Textual syntax: e: the exception handling when C is violated The semantics of such a diagram is the combination of The semantics without the exception, i.e. the semantics of The semantics of d 1 and d 2 in parallel with the exception e, such that the exception handling does not start too early (this is negative). for the lifeline of q, the exception handling comes strictly after d 1 and strictly before d 2. Also: formal semantics for return, terminate and catch 02-Oct-2006 MARTES 2006 at MoDELS

11 Results: Associativity We have associativity with respect to exceptions, i.e. = 02-Oct-2006 MARTES 2006 at MoDELS

12 Results: Refinement Adding a time constraint with an exception is a valid refinement: Refinement is monotonic with respect to exceptions, meaning that the main diagram and the exception can be refined separately: 02-Oct-2006 MARTES 2006 at MoDELS

13 Summary Introducing time exceptions improve the completeness of sequence diagram descriptions without obscuring the readability of the specification. A concrete syntax is suggested and motivated Formal semantics are given showing compositionality associativity of time exceptions that adding a time exception is a refinement that refinement is monotonic wrt. time exceptions meaning that the main part and the exceptional parts can be refined separately 02-Oct-2006 MARTES 2006 at MoDELS