Our modeling of goals, operations and their relationships
is influenced by the TROPOS agent-oriented software development
methodology [4], which is evolved from the i*
framework [24] for modeling and reasoning about organizational
environments and their information system requirements.
In TROPOS, Goals can be hard or soft: unlike hard
goals, a softgoal has neither clear cut definition nor criteria
to decide whether it is satisfied, and is usually used to model
non-functional requirements. Three basic qualitative goal
reasoning techniques are available: (i) AND/OR-goal decomposition
for refining high-level abstract goals into lowlevel
operational ones; (ii) means-end analysis for identifying
operations (modeled as plans) to fulfill the refined goals;
and (iii) contribution analysis for detecting lateral influence
on goal fulfillment. The result of a goal analysis is a goal
model [10], which is a forest of goal/plan AND-OR trees
with contribution edges between nodes of different trees and
means-end edges connecting goal and plan nodes. Thanks
to the presence of OR-decomposition and means-end edges,
there are subsets of leaves in the tree that define alternative
ways, i.e., design alternatives, to fulfill the aggregate toplevel
goals.