=Paper=
{{Paper
|id=Vol-57/paper-8
|storemode=property
|title=Applying Tropos to requirement analysis for a Tropos tool
|pdfUrl=https://ceur-ws.org/Vol-57/id-9.pdf
|volume=Vol-57
|authors=Paolo Bresciani and Fabrizio Sannicolò
|dblpUrl=https://dblp.org/rec/conf/aois/BrescianiS02
}}
==Applying Tropos to requirement analysis for a Tropos tool==
https://ceur-ws.org/Vol-57/id-9.pdf
Applying Tropos Early Requirements Analysis
for defining a Tropos tool
Paolo Bresciani and Fabrizio Sannicolò
ITC-irst
Via Sommarive, 18, I-38050 Trento-Povo, Italy
bresciani,sannico @irst.itc.it
1 Introduction
Tropos [8, 6] is a novel agent-oriented software engineering methodology characterized
by three key aspects [7]. First, it pays attention to the activities that precede the spec-
ification of the prescriptive requirements, like understanding how the intended system
would meet the organizational goals. Second, it deals with all the phases of system re-
quirement analysis and all the phases of system design and implementation in a uniform
and homogeneous way, based on common mentalistic notions as those of actors, goals,
softgoals, plans, resources and intentional dependencies. Third, the methodology rests
on the idea of building a model of the system-to-be that is incrementally refined and
extended from a conceptual level to executable artifacts, by means of a sequence of
transformational steps [1].
One of the main advantages of the Tropos methodology is that it allows to capture
not only the what or the how, but also the why a piece of software is developed. This, in
turn, allows for a more refined analysis of the system dependencies and, in particular,
for a much better and uniform treatment not only of the system functional requirements,
but also of the non-functional requirements. Tropos, although not exclusively, addresses
particularly well the Agent Oriented Programming. In fact, the decision of using men-
talistic notions in all the analysis phases has important consequences. Agent oriented
specifications and programs use the same notions and abstractions used to describe the
behavior of the human agents and the processes involving them; thus, the conceptual
gap between users’ specification (in terms of why and what) and system realization (in
terms of what and how), is reduced to a minimum.
Tropos supports five phases of software development: early requirements, late re-
quirements, architectural design, detailed design and implementation [5, 6].
The present short paper concentrates on the analysis of the early requirement phase
for the definition of a support tool for the Tropos methodology itself, called, since now
on, the Tropos tool. In particular, the task of encoding initial informal requirement into
the diagrammatic format used in the methodology, as well as the incremental transfor-
mational process that is at the basis of the construction of the complete model, will be
addressed.
artifacts understand Legend
easily customer
understandable feasibility req.
study Goal Softgoal
delivered
PRG
manager Analyst Goal
requirements dependency
modeled
manage
versions organization
and doc. described Actor
Fig. 1. An actor diagram specifying the stakeholders of the Tropos tool project.
2 Early Requirement Analysis
The early requirements analysis concerns with the understanding of a problem by study-
ing an existing organizational setting. The intentions of the stakeholders are modeled
as goals and goal dependencies among actors, and analyzed by means some form of
goal analysis [3, 4]. The output of this phase is an organizational model including the
relevant actors and their respective dependencies for the achievement of the goals and
the softgoals, and for performing or obtaining resources. The model is visualized by
means of actor diagrams, describing the network of social dependencies among actors,
and goal diagrams, analyzing the goal fulfillments.
An awful lot of high level requirements has been identified, listed and justified
in [2]; due to lack of space, only a short subset of these requirements are intro-
duced here. For example, the actor diagram of Figure 1 shows the actor PRG manager
who depends on the Analyst for two goals: feasibility study delivered and
requirements modeled.
A further step concerns the decomposition of each goal from the point of view of the
actor who committed for its fulfillment. Goals are analyzed by using three basic analysis
techniques: means-ends analysis, contribution analysis and AND-OR decomposition [3,
9]. Means-ends analysis proceeds by refining a goal into subgoals in order to identify
goals, plans, resources and softgoals that provide means for achieving the goal (the end).
Contribution analysis allows the designer to point out goals, softgoals and plans that can
contribute positively or negatively at reaching the goal. AND-OR decomposition allows
for a combination of AND and OR decompositions of a root goal into subgoals.
In Figure 2, the goal requirements modeled is the “end” in a means-ends analysis
where the “mean” is the goal build a requirements Tropos model. This last is
AND-decomposed into the four subgoals: learn Tropos language, model managed,
model documented and model reasoned.
An instance of contribution analysis is provided, in the figure, between the soft-
goal exhaustive guide and the goal learn Tropos language. Of course, subgoals
deriving from an AND-OR analysis can be further AND-OR analyzed. For example,
model managed is decomposed into the retrotraceability managed, multiple
views visualized, diagrams edited and syntax of model checked. The sub-
goals automatic documentation generated and version managed contribute pos-
itively at the achievement of the goal model documented. The first subgoal concerns
with the automatic generation of the documentation about the conceptual model and/or
PRG requirements
manager modeled Analyst
exhaustive
guide
+ build a
requirements
Legend Tropos model model
reasoned
learn Tropos
language
+ model model
managed documented NFR
+ made
retrotra-
Contribution OR decomposition ceability +
version
managed managed
sintax
multiple of model
views checked automatic
visualized documentation
diagrams generated
edited
AND decomposition
Fig. 2. Goal analysis from the perspective of the Analyst.
some views on it, while the second regards the management of different versions for
each analyst.
The final setting of each Tropos phase may be reached after possibly several re-
finements, in each one of which not only new details may be added, but, also, already
present elements and dependencies can be revised or even deleted [1].
It is obvious that the diagram of Figure 2 (and other developed during a first loop [2])
may be not sufficiently detailed. For this reason, iterative steps of incremental refine-
ment of the model have to be performed. As already mentioned in the introduction,
this way of proceeding is a typical feature of the Tropos methodology. The iterative
process not only may require intra-phase refinements, but, possibly, also revisions of
artifacts produced during early phases (inter-phases refinements). The importance of
retrotraceability is, here, evident.
PRG requirements
manager modeled
understand
organization customer
exhaustive described req.
guide + + Analyst
build a
requirements
Tropos model
+
learn Tropos
language
model
reasoned
model
managed model design
views on documented case tests
the model
visualized
+
NFR
made
retrotra- automatic
ceability documentation graphic
managed generated documented
diagrams
edited
sintax text
feasibility of model documented
study checked
delivered
+
record
interview
Fig. 3. Revising Goal analysis from the point of view of the Analyst.
Just as an example of the intra-phase refinement activity, the revision of the
goal diagram in Figure 2 is presented in Figure 3. The contributions from build
a requirements Tropos model to organization described and understand
customer requirements are here introduced. These were initially considered as orig-
inal Analyst’s goal (see Figure 1), but then not further analyzed in Figure 2. The
revision proposed in Figure 3 is necessary to complete the analysis of the require-
ments of Figure 2, according to what was initially introduced in Figure 1. Among
others elements introduced in the revision, let’s list: design case tests, text
documented, graphic documented and feasibility study delivered (see Fig-
ure 1), that became the end in a means-ends analysis where the “mean” is the goal
record interview. For more details, see [2].
3 Conclusion
In the present paper the early analysis for a Tropos tool has been used as a case study
for presenting some features of the Tropos methodology itself.
One point that deserves a note here is that the management of traceability has been
raised as a crucial point for correctly dealing with the revision (specially the inter-phase
revision) process. In future works, we aim at further developing this issue with other
specifically focused case studies and examples.
References
1. P. Bresciani, A. Perini, P. Giorgini, F. Giunchiglia, and J. Mylopoulos. Modelling early re-
quirements in Tropos: a transformation based approach. In P.Ciancarini M.J. Wooldridge,
G. Weiß, editor, Agent-Oriented Software Engineering II, LNCS 2222, pages 151–168.
Springer-Verlag, Montreal, Second International Workshop, AOSE2001 edition, May 2002.
2. P. Bresciani and F. Sannicolò. Applying Tropos to requirement analysis for a Tropos tool.
Technical Report 0204-01, ITC-IRST, via Sommarive, Trento, April 2002.
3. L. Chung, S. Liao, W. Huaiqing, E. Yu, and J. Mylopoulos. Exploring alternatives during
requirements analysis. IEEE Software, 18(1), jan, feb 2001.
4. A. Dardenne, A. van Lamsweerde, and S. Fickas. Goal-directed requirements acquisition.
Science of Computer Programming, 20(1-2):3–50, 1993.
5. P. Giorgini, A. Perini, J. Mylopoulos, F. Giunchiglia, and P. Bresciani. Agent-oriented soft-
ware development: A case study. In S. Sen J.P. Müller, E. Andre and C. Frassen, editors,
Proceedings of the Thirteenth International Conference on Software Engineering - Knowl-
edge Engineering (SEKE01), Buenos Aires, June 2001.
6. F. Giunchiglia, A. Perini, and F. Sannicolò. Knowledge level software engineering. In Springer
Verlag, editor, In Proceedings of ATAL 2001, Seattle, December 2001. Also IRST TR 0112-
22, Istituto Trentino di Cultura, Trento, Italy.
7. A. Perini, P. Bresciani, P. Giorgini, F. Giunchiglia, and J. Mylopoulos. Towards an Agent
Oriented approach to Software Engineering. In Proceedings of the Workshop, dagli oggetti
agli agenti: tendenze evolutive dei sistemi software, Modena, Sep 2001.
8. A. Perini, P. Bresciani, F. Giunchiglia, P. Giorgini, and J. Mylopoulos. A Knowledge Level
Software Engineering Methodology for Agent Oriented Programming. In Proceedings of the
Fifth International Conference on Autonomous Agents, Montreal CA, 28 May - 1 June 2001.
9. F. Sannicolò, A. Perini, and F. Giunchiglia. The Tropos modeling language. A User Guide.
Technical Report 0202-12, ITC-IRST, Jan 2002.