Slides Part 2 (OOA, pages 1-128, pdf, 4 slides per page)

Sends = BankClerk: {give money(amount), no cover}
Pre = accountnr is a valid account number, account.balance ≥ 0
Post = If account.balance − amount ≥ 0:
account.balance ′ = account.balance − amount
is sent{give money(amount)}
If account.balance − amount < 0:
account.balance ′ = account.balance
is sent{no cover}
account.balance ′ ≥ 0
=⇒ The class Account has the attribute balance.
account.balance ≥ 0: Invariant. Contained in pre- and in postcondition.
Note: the output event give money gets a parameter (These are not contained
in the scenarios ).
MORE EXAMPLES
sd OpenAccountS1
: Bank
BankClerk Schufa
open_new_customer_account
alt
[ClientKnown]
customer_already_known
[else]
alt
[queryOK]
account_opened
[else]
account_not_opened
ref
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SchufaQuery
REMARK
The precondition of the operation must be consistent with the scenarios.
If it cannot be taken for granted that only valid account numbers can be given
as a parameter of the operation withdraw money, then a scenario must be
added that states how to treat the case of an invalid account number.
Once such a scenario is added, the precondition “accountnr is a valid account
number” may be dropped.
Assumption: cd is sufficient to distinguish different customers
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Operation = open new customer account
Description = A new customer wants to open an account. A query is sent to
the Schufa before the account can be opened.
Reads = supplied cd : Customer data
Changes = —
Sends = BankClerk: {customer already known},
Schufa: {schufa query(cd))}
Pre = —
Post = If exists account : Account with account.customer data = cd:
is sent{customer already known}
Otherwise: is sent{schufa query(cd)}
=⇒ The class Account has the attribute customer data.
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