This document discusses two methods for evaluating software architectures: the ATAM and CBAM. It provides details on: 1. The ATAM evaluates architectures through stakeholder participation to identify business goals, quality attributes, and tradeoffs. It produces outputs like quality scenarios and architectural risk areas. 2. The CBAM builds on the ATAM to model the costs and benefits of architectural decisions. It aims to maximize the difference between system benefits and implementation costs. 3. Both methods rely on artifacts from earlier phases, like business goals and quality attributes. The CBAM then evaluates architectural strategies based on their return on investment calculated from utility benefits versus implementation costs.

1. UNIT2-1

2. 1.The ATAM
(A Comprehensive method for Architecture
Evaluation)
2.The CBAM
(A Quantitative Approach to Architecture
Design Decision Making)

3. 1.1 Participants in the ATAM
1.2 Outputs of the ATAM
1.3 Phases of the ATAM

4.  The ATAM( Architecture Tradeoff Analysis
Method) a thorough and comprehensive way
to evaluate a s/w architecture.
 The ATAM is designed to elicit the business
goals for the system as well as for the
architecture.
 It is also designed to use those goals and
stakeholder participation to focus the
attention of the evaluators on the portion of
the architecture that is central to the
achievement of the goals.

5.  The ATAM requires the participation and mutual
cooperation of three groups:
1. The Evaluation team- this group is external to
the project whose architecture is being
evaluated.
2. Project decision makers- these people are
empowered to speak for the development
project or have the authority to mandate
changes to it.
3. Architecture stakeholders- stakeholders have a
vested interest in the architecture performing as
advertised.

9.  An ATAM-based evaluation will produce at
least the following outputs:
- A concise presentation of the architecture
- Articulation of the business goals
- Quality requirements in terms of a collection
of scenarios
- Mapping of architectural decisions to quality
requirements

10. - A set of identified sensitivity and tradeoff
points
- A set of risks and nonrisks
- A set of risk themes

11.  Activities in an ATAM-based evaluation are
spread out over four phases.

12. STEPS OF THE EVALUATION PHASES
 The ATAM analysis phases(phase 1 and phase
2) consists of nine steps.
 Steps1 through 6 are carried out in phase 1.
 In phase 2 with all stakeholders present those
steps are summarized and steps 7 through 9
are carried out.

13. 1. Present the ATAM
2. Present Business Drivers
3. Present Architecture
4. Identify Architectural Approaches
5. Generate Quality Attribute Utility Tree
6. Analyze Architectural Approaches
7. Brainstorm and Prioritize Scenarios
8. Analyze Architectural Approaches
9. Present Results

14. USING THE LIMITED TIME OF AN EVALUATION
EFFECTIVELY
 We identified limited time as one of the main
problem in conducting an architectural
evaluation
 The business goals are used as motivations
for the collection of scenarios that represent
the utility tree

15. 2.1 Decision-Making Context
2.2 The Basis for the CBAM
2.3 Implementing the CBAM

16.  CBAM(Cost Benefit Analysis Method), it builds
on the ATAM to model the costs and the
benefits of architectural design decisions and
is a means of optimizing such decisions.
 The CBAM provides an assessment of the
technical and economic issues and
architectural decisions.

17.  The s/w architect or decision makers wishes
to maximize the difference b/w the benefit
derived from the system and the cost of
implementing the design.
 The CBAM begins where the ATAM concludes
and in fact, depends upon the artifacts that
the ATAM produces as output.
 Fig depicts the context for the CBAM

19.  Recall that when an ATAM has been applied
to a s/w system, we have as a result a set of
artifacts documents on completion. They are:
- A description of the business goals
- A set of architectural views
- A utility tree
- A set of risks
- A set of sensitivity points
- A set of tradeoff points

20.  The idea behind the CBAM is that
architectural strategies(a collection of
architectural tactics) after the quality
attributes of the system and these in turn
provide system stakeholders with some
benefit
 We refer to this benefit as utility
 Each architectural strategy provides a specific
level of utility to the stakeholders

21.  Each also has cost and takes time to
implement
 Given this info, the CBAM can aid the
stakeholders in choosing architectural
strategies based on their return on
investment(ROI)- the ration of benefit to cost.

22.  Our goal is here is to develop the theory
underpinning a measure of ROI for various
architectural strategies in light of scenarios
chosen by the stake holders.
 Utility
-Variations of scenarios
-Utility-response curves
-Priorities of scenarios
- Architectural strategies
 Calculating ROI

24. STEPS
 A process flow diagram for the CBAM is given
in fig.
 The first 4 steps are annotated with the
relative no.of scenarios they consider.
 That number steadily decreases, ensuring
that the method concentrates the
stakeholders time on the scenarios believed
to be of the greatest potential in terms of
ROI.