Architecture Tradeoff Analysis

ARCHITECTURE TRADEOFF ANALYSIS

Developers and acquirers of complex software systems need their systems to be modifiable and to perform predictably. They may also need them to be secure, interoperable, portable, usable, and reliable. These quality attributes depend more on the software architecture than on code-level practices, such as language choice. Moreover, these qualities do not exist in isolation. Performance affects modifiability, interoperability affects security, and everything affects cost.

An architecture either explicitly or implicitly makes tradeoffs among these qualities, often with undesirable consequences. The SEI has developed a high-payoff method for identifying the relationships and tradeoffs among such quality attributes. The Architecture Tradeoff Analysis MethodSM (ATAMSM) enables software developers and acquirers to evaluate an architecture for required quality attributes and business goals before the system is actually developed. Because architectural decisions are difficult and expensive to change later, an early evaluation with a proven method makes sense.

Purpose

The SEI's work in software architectures

> ensures that architectural errors in software-intensive systems can be detected early in development or evolution, when the cost to fix them is minimal and the reduction in total cost of system ownership is the greatest

> provides acquirers and developers with a high-level capability for evaluating software architectures: the ATAM and its variants. By conducting architecture evaluations on existing and proposed software, acquirers and developers exert significantly greater control over key software qualities, such as affordability, reliability, security, modifiability, and performance. Conducting ATAM evaluations also helps to mitigate the risks involved in making the necessary tradeoffs among these software qualities.

> provides acquirers and developers with effective architectural practices based on best commercial practices in leading software organizations

2002 Accomplishments

New Book, Documenting Software Architectures, Published
Documenting Software Architectures, published this year in the SEI Series in Software Engineering, was written by SEI staff members to help practicing architects produce a comprehensive documentation package for a software architecture that will be useful to its many stakeholders. The approach is view based; the fundamental principle is that documenting an architecture consists of documenting the relevant views of that architecture and then documenting the information that applies to more than one view.

Documenting Software
Architectures is of immense value. The description and communication of software architecture is quite crucial to its many stakeholders, and this handbook should save you months of trials and errors, lots of undeserved hassle, and many costly mistakes that could potentially jeopardize the whole endeavor. It will become an important reference on the shelf of the software architect.
Philippe Kruchten
Director of Process Development, Rational Software Canada

Architecture Training Courses Developed
The SEI has developed new courses to help software practitioners and acquirers better understand architectural principles and best practices. The Software Architecture Familiarization course, based on the book Software Architecture in Practice, Second Edition, provides the fundamentals. The ATAM Evaluators Training course prepares qualified practitioners to perform ATAM evaluations. The tutorial titled "Integrating Software Architecture Analysis and Evaluation in DoD System Acquisitions" presents architecture evaluation practices in an acquisition context and provides guidelines for their use. These courses were piloted in FY2002 and will be among the SEI's public courses in FY2003.

Architecture Tradeoff Analysis Method Stabilized; Adoption Program to Begin
The SEI has been developing and piloting the ATAM and associated architecture tradeoff technology for several years. The method has been technically validated in both commercial and DoD applications and has now stabilized. The SEI is preparing to offer adoption packages to outside organizations to perform SEI-authorized ATAM evaluations. The adoption package includes SEI training and coaching to prepare individuals from those organizations.

FBCB2 software will give future soldiers, such as the LandWarrier, much greater knowledge of their positions relative to the enemy and their fellow soldiers. The SEI is working with the Army on the architecture for FBCB2 software.

Army Uses Analysis of Software Architecture
Force XXI Battle Command Brigade and Below (FBCB2) is the principal tactical digital command-and-control system for the U.S. Army from the brigade level down to the soldier. This system consists of rugged computer hardware running FBCB2 software, installed on a variety of weapons platforms and linked through a radio network. The situational awareness services of FBCB2 software provide answers to three questions that are critical for soldiers during battle:

1
Where am I?

2 Where are my fellow soldiers?

3 Where is the enemy?

FBCB2’s command-and-control services provide leaders with
the ability to rapidly assess and control the battle space even
under adverse conditions.

At the request of the office of the Assistant Secretary of the Army (Acquisition, Logistics and Technology) and program executive officers for the various users of FBCB2, the SEI performed an extensive study of the FBCB2 software architecture to determine the architectural changes to consider for near-term and long-term improvement and increased efficiency. The SEI is now working closely with the FBCB2 program office and its supporting contractors to build on the program’s successes and implement the study’s architectural recommendations to provide a solid foundation for future success.


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