Slides Part 2 (OOA, pages 1-128, pdf, 4 slides per page)
Slides Part 2 (OOA, pages 1-128, pdf, 4 slides per page)
Slides Part 2 (OOA, pages 1-128, pdf, 4 slides per page)
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APPLICATION OF THE DESIGN-BY-CONTRACT-PRINCIPLE<br />
➠ Fusion <strong>OOA</strong>: Specifies system o<strong>per</strong>ations by means of preconditions and<br />
postconditions.<br />
➠ Fusion OOD: Specifies all added o<strong>per</strong>ations by means of preconditions<br />
and postconditions.<br />
➠ OOI: Give preconditions and postconditions as documentation in the<br />
source code.<br />
➠ There are programming languages (e. g. Eiffel) which allow for dynamic<br />
checking of preconditions and postconditions.<br />
CLASS MODEL FOR BANK<br />
Schufa<br />
Bank<br />
81<br />
Queries<br />
Owns<br />
Customer Account<br />
Checking<br />
Keeps<br />
Works_for<br />
Savings Credit<br />
83<br />
BankClerk<br />
LoanEx<strong>per</strong>t<br />
EXAMPLE: WITHDRAW MONEY FROM BANK ACCOUNT<br />
sd WithdrawN<br />
sd<br />
: Bank<br />
WithdrawE<br />
BankClerk BankClerk<br />
withdraw_money<br />
withdraw_money<br />
give_money no_cover<br />
OPERATION SCHEMA<br />
82<br />
O<strong>per</strong>ation = withdraw money<br />
Description = Money should be withdrawn from an account. This is possible<br />
only if the account is not overdrawn.<br />
Reads = supplied accountnr : Accountnr<br />
supplied amount : N<br />
: Bank<br />
Changes = account : Account with account.number = accountnr<br />
with: Predicate which uniquely determines an object.<br />
number must be introduced as attribute of the class Account<br />
(=⇒ system class model)<br />
84
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