Requirements as Goals and Commitments Too - Intentional Perspectives on Information Systems Engineering - page 147

Fig. 5 Visual representation of Fly's travel agency -bound specification
and they have been paid. Fly is capable of goal ticketsPaid . There are two ways to
deliver tickets: either electronic tickets are e-mailed or tickets are posted. In order
to send tickets via mail, Fly has to ship the tickets and pay for the shipping. Fly is
capable of eticketsEmailed . E-mailing tickets contributes positively (++S) [ 18] to
softgoal costsKeptLow , whereas sending via shipping contributes negatively (-S)
to such softgoal.
We present now some queries concerning goal and commitment support that can
be run against the specification of Fig. 5.
Query 1. Can Fly support goal ticketsSold ?
The answer to this query is yes. Fly can support ticketsObtained by using its
capability for ticketsPaid and getting C 4 from some airline. Fly supports tickets-
Delivered via its capability for eticketsEmailed. Fly can support servicePaid by
making C 2 to some customer.
An alternative solution involves sending tickets via shipping. Fly could support
ticketsShipped and shippingPaid if it makes C 3 to a customer (which sup-
ports servicePaid and shippingPaid ) and get C 1 from some shipper (to support
ticketsShipped ).
Another solution includes supporting both eticketsEmailed and ticketsSent :
both C 2 and C 3 are made to the customer.
Query 2. Can Fly support goals ticketsSold and costsKeptLow ?
This query adds an additional constraint to Query 1: supporting softgoal
costsKeptLow . The only solution is when tickets are e-mailed: eticketsEmailed
contributes positively to costsKeptLow and the softgoal gets no negative con-
tribution. Posting tickets does not work: ticketsSent contributes negatively to
costsKeptLow .