Aspect-Oriented Software Development (AOSD) Tutorial #9 Modular Verification of Aspects

Aspect-Oriented Software Development (236608) 2 Today: Aspects Verification Pointcut-ready models Weaving the aspect into the tableau MAVEN tool Examples

Aspect-Oriented Software Development (236608) 3 Example: Theft Protection Aspect General description: Can be used in a system with remote authorized access. Most useful for systems in which each user can have only one open session at a time. Prevents identity-theft: If a wrong password is provided in several consequent attempts of logging in, the aspect guarantees that the user is blocked.

Aspect-Oriented Software Development (236608) 4 Theft Protection Aspect – contd. Example system: ATM system of a bank: several ATM machines and a server. ATM usage: (in a cycle) –insert card –enter code (repeat until the correct code or “cancel” is entered) –if permission is granted (i.e, the code was correct), enter a request for the bank operation (money withdrawal, account balance check, …) –the request is then processed by the system Point of view of the aspect: the card serves as a user-login, and code - as a password.

Aspect-Oriented Software Development (236608) 5 Pointcut-ready Base Sys. Model Base system model: q t ¬pp q t p Pointcut-ready model: Pointcut (example): wrong passw. entered 3 times consequently p ≡ correct passw. enter psw. perform ATM operations cancel enter psw. pointcut

Aspect-Oriented Software Development (236608) 6 Weaving Example q t ¬p, r p ¬p Pointcut-ready base model: ¬p, r … p … … … Advice model: ¬p, r r – new predicate, to mark the pointcut

Aspect-Oriented Software Development (236608) 7 Weaving– Stage1 q t ¬p, r p ¬p Pointcut-ready base model: ¬p, r … p … … … Advice model: ¬p, r base → aspect connections

Aspect-Oriented Software Development (236608) 8 Weaving– Stage2 q t ¬p, r p ¬p Pointcut-ready base model: ¬p, r … p … … … Advice model: ¬p, r aspect → base connections

Aspect-Oriented Software Development (236608) 9 Weaving– Stage3 q t ¬p, r p ¬p Pointcut-ready base model: ¬p, r … p … … … Advice model: ¬p, r remove unnecessary base edges

Aspect-Oriented Software Development (236608) 10 Pointcut-ready Base Sys. Model Base system model: q t ¬pp q t p Pointcut-ready model: Pointcut (example2): wrong passw. has been entered 3 times q t p q t p q t p ¬p pointcut

Aspect-Oriented Software Development (236608) 11 Theft Protection Aspect Assumption For each card and for each ATM: There is a state predicate telling that the card is stolen (st), and a state predicate telling the card is in the ATM (in) Whenever a card is stolen, it remains stolen forever Formally: G (st → G (st))

Aspect-Oriented Software Development (236608) 12 Theft Protection Aspect Pointcut Some stolen card is inserted into an ATM Formally: (st ∧ in)

Aspect-Oriented Software Development (236608) 13 Assumption Tableau ¬in ¬st ¬q ¬r ¬in ¬st ¬q r in ¬st ¬q ¬r in st ¬q ¬r in ¬st ¬q r ¬in st ¬q ¬r pointcut - ready? st – card stolen; in – card in ATM; r,q – aux. vars; pointcut: st ∧ in pointcut Yes! Here: all the states are fair

Aspect-Oriented Software Development (236608) 14 Simple Advice Model in st ¬q ¬r

Aspect-Oriented Software Development (236608) 15 Weaving into the Tableau – Stage1 ¬in ¬st ¬q ¬r ¬in ¬st ¬q r in ¬st ¬q ¬r in st ¬q ¬r in ¬st ¬q r ¬in st ¬q ¬r in st ¬q ¬r

Aspect-Oriented Software Development (236608) 16 Weaving into the Tableau – Stage2 ¬in ¬st ¬q ¬r ¬in ¬st ¬q r in ¬st ¬q ¬r in st ¬q ¬r in ¬st ¬q r ¬in st ¬q ¬r in st ¬q ¬r

Aspect-Oriented Software Development (236608) 17 Weaving into the Tableau – Stage3 ¬in ¬st ¬q ¬r ¬in ¬st ¬q r in ¬st ¬q ¬r in st ¬q ¬r in ¬st ¬q r ¬in st ¬q ¬r in st ¬q ¬r Is the guarantee satisfied?

Aspect-Oriented Software Development (236608) 18 Card Theft Protection - Model VAR --BASE card_in : boolean ; card_stolen : boolean ; VAR --ASPECT pcT : 1..2 ; POINTCUT card_stolen & card_in ; … TRANS pcT = 1 -> next(pcT = 2) & next(card_in) & next(card_stolen); RETURN pcT = 2 ; … LTLSPEC --BASE G (card_stolen -> G (card_stolen)) ; LTLSPEC --AUGMENTED G ((card_in & card_stolen) -> G (card_in)) ; Variables that should be calculated from the base system state – those used in the assumption, pointcut and advice Aspect variables Pointcut description (state predicate!) Advice Assumption Guarantee