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The ATAM A Method for Architecture Evaluation

• RiSEs Seminars
• Clementss book Chapters 3
• Frederico Durão

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Summary

• Steps of ATAM
• Step 1- 9
• The Phases of ATAM
• Phases 0 - 3

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ATAM Steps Chapter 3
Summary of ATAM Steps

• Presentation
• Present the ATAM
• Present the business drivers
• Present the architecture
• Investigation and Analysis
• Identify the architecture approaches
• Generate the quality attributes utility tree
• Analyze the architectural approaches
• Testing
• Brainstorming and prioritize scenarios
• Analyze the architectural approaches
• Reporting
• Present the results

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ATAM Steps Chapter 3

• Step 1 Present the ATAM
• The evaluation leader presents the ATAMs steps
  to the stakeholders, besides techniques and the
  outputs of the evaluation

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ATAM Steps Chapter 3

• Step 2 Present the Business Drivers
• A project decision maker presents a overview from
  a business perspective
• Business Context/Drivers Presentation (12 slides
  / 45 minutes)
• Description of the business environment,
  history(3-4 slides)
• Description of the business constraints (1-3
  slides)
• Description of the technical constraints (1-3
  slides)
• Quality attributes requirements and from what
  business needs these are derived (2-3 slides)
• Glossary(1 slide)

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ATAM Steps Chapter 3

• Step 3 Present the Architecture
• A lead architect or a architecture team presents
  the architecture in the appropriated level of
  detail
• In this presentation the architect should cover
• Technical constraints such as operating system,
  hardware, or middleware prescribed for use
• Other systems with which the system must
  interact
• Architectural approaches used to meet quality
  attribute requirements
• Architectural Views
• Functional, concurrency, code and physical views
• Architectural Presentation (20 slides60 minutes)

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ATAM Steps Chapter 3

• Step 4 Identify the Architectural Approaches
• The architect identify the architectural
  approaches and styles
• Architectural styles define important structures
  of the system and describe how the system can
  grow, respond to changes, withstand attacks,
  integrate with other system
• Example Concurrent Pipeline Style
• Sequence of data transformation
• Each component can be replaced or modified
• Elements can be reused elsewhere
• Evaluators can reason this style in terms of
  performance implications

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ATAM Steps Chapter 3

• Step 5 Generate the Quality Attribute Utility
  Tree
• The evaluation team works with the project
  decision maker to identify, prioritize, and
  refine the system most important quality
  attribute goals.
• Utility trees translate the business drivers of a
  system into concrete quality attribute scenarios
• Utility
• Performance
• Data Latency
• (M,L) Minimize storage latency
• (H,M) Deliver video in real time
• Transaction Throughput
• (M,M) Maximize average throughput to the
  authentication server

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ATAM Steps Chapter 3

• Step 5 Generate the Quality Attribute Utility
  Tree 2
• Scenarios
• A short statement describing an interaction of
  one of the stakeholders with the system
• User, maintainer, developer, product line manager
• Useful in understanding run time qualities such
  as performance or availability
• Structures
• Stimulus the user interaction
• Environment the system state
• Response how the system should respond to the
  system
• Types
• Use Case Scenarios
• Growth Scenarios
• Exploratory Scenarios

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ATAM Steps Chapter 3

• Step 5 Generate the Quality Attribute Utility
  Tree 3
• Use Case Scenarios
• Describes a users intended interaction with the
  completed running system
• The user wants to examine budgetary and actual
  data under different fiscal years without
  reentering project data (usability)
• Growth Scenarios
• Represent typical anticipated changes to a system
• Double the maximum number of tracks to be
  handled by the system and keep to 200 ms the
  maximum latency of track data to the screen
  (Performance consequences)

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ATAM Steps Chapter 3

• Step 5 Generate the Quality Attribute Utility
  Tree 4
• Exploratory Scenarios
• To expose the limits or boundary conditions of
  the current design
• Improve the systems availability from 98 to
  99,999

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ATAM Steps Chapter 3

• Step 6 Analyze the Architectural Approaches
• At this point there is
• A set of concrete quality requirements a set of
  architectural approaches gt Size up how well
  suited they are to each other
• Now the evaluation team can probe the
  architectural approaches that realize the
  important quality attributes.
• Outputs of this Phase
• The architectural approaches or decisions
  relevant to each priority utility tree scenario
• The analyst questions associated with each
  approach
• The architects response to the questions
• The risks, nonriks, sensitivity points and
  tradeoff points identified
• At the end of this steps, the evaluation team
  should have a clear picture of the most important
  aspects of the entire architecture

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ATAM Steps Chapter 3

• Step 7 Brainstorm and Prioritize Scenarios
• Use of Scenarios to
• Represent stakeholders interests
• Understand quality attribute requirements
• The evaluation team ask the stakeholders to
  brainstorm
• Use Case Scenarios
• In this case stakeholder is an end user
• Growth Scenarios
• Modifications, changes in performance or
  availability
• Exploratory Scenarios
• Limits, dramatic new performance attributes

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ATAM Steps Chapter 3

• Step 7 Brainstorm and Prioritize Scenarios 2
• Once the Scenarios are collected
• The stakeholders merge the similar scenarios
• Then they vote for the most important scenarios
  (30 of total scenarios)
• Each stakeholders casts his votes publicity
• The evaluation leader orders the scenarios
• The scenario above the line are selected to the
  subsequent steps
• The result is compared with the utility tree
  result
• Three things will happen after these steps
• The scenario will match essentially duplicated an
  already-existing leaf node
• The scenario will go into a new leaf of an
  existing branch
• The scenario will fit in no branch of the tree
  because it expresses a quality attribute no
  previously accounted for

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ATAM Steps Chapter 3

• Step 7 Producers of system stakeholders

Stakeholder Definition Interest
SW Architect Person responsible for the architecture of the system and responsible for making tradeoffs among competing quality pressures Moderation and mediation all of the quality concerns of the other stakeholder
Developer Code or designer Clarity of architecture description, high cohesion of parts, limited coupling of parts, clear interconnection mechanisms
Standard Expert Developer responsible for knowing the details of standards (current and future) to which the software must conform Separation of concerns, modifiability, interoperability
Project Manager Person who allocates resources to teams, is responsible for meeting schedule and budget, interfaces with customer Clear structuring architecture to drive team formation, work breakdown structure, milestones and deadlines, etc
Product Line manager or reuse czar Person who has a vision for how this architecture and related assets can be reused further by the organization Reusability, Flexibility
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ATAM Steps Chapter 3

• Step 7 Consumers of the system

Stakeholder Definition Interest
Customer Purchaser on the system Schedule of completion, over all budget, usefulness of the system, meeting customers expectations
End User Use of the implemented system Functionality, usability

• Step 7 Servicers of the system

Stakeholder Definition Interest
System Administrator Person running the system Ease in finding the location that may arise
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ATAM Steps Chapter 3

• Step 8 Analyze the Architectural Approaches
• The architect carry out the highest-ranked
  scenarios from step 7
• The evaluation team performs the same activities
  as in Step 6
• This Step is a testing activity it is to be
  hopped that little new information will be
  uncovered

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ATAM Steps Chapter 3

• Step 9 Present the Results
• The collected information from the ATAM needs to
  be summarized and presented back to the
  stakeholders
• Verbal report slides more complete document
  written report including
• The architectural approaches documented
• A set of scenarios and their prioritization
• The set of attribute-based questions
• The utility tree
• The risk discovered
• The nonrisks documented
• The sensitivity points and tradeoff points found

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ATAM Steps Chapter 3

• The Phases of the ATAM
• Consist of 4 phases
• Phase 0
• Partnership
• Preparation
• Phase 1
• Phase 2
• Phase 3

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ATAM Steps Chapter 3

• The Phases of the ATAM PHASE 0
• Partnership
• Involves the communication with the client, the
  sponsor of the evaluation
• For that
• The client should have a basic understanding of
  the evaluation method
• The client should describe the system and
  architecture being evaluated
• A contracted or statement of work should be
  negotiated and signed
• Issues of proprietary information should be
  resolved
• Its a good time to talk about cost and benefits
  of architecture evaluation

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ATAM Steps Chapter 3

• The Phases of the ATAM PHASE 0
• Preparation
• Forming the evaluation team
• Holding an evaluation team kickoff meeting
• Making the necessary preparations for Phase 1
• Set the roles for each member

Role Responsibilities Desirable Characteristics
Team Leader Sets up the evaluation coordinates with client Well-organized, with managerial skills
Evaluation Leader Runs evaluation Comfortable in front of an audience.
Questioner Raises issues of architectural interest that perhaps the stakeholders have not considered Good architectural insights Experience with systems in similar domain.
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ATAM Steps Chapter 3

• The Phases of the ATAM PHASE 1
• Concentrates on Steps 1 through 6
• Besides this steps the team needs to determine
• Whether the remainder of the evaluation is
  feasible and should proceed
• Whether more architectural documentation is
  required
• Which stakeholders should be present for Phase 2

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ATAM Steps Chapter 3

• The Phases of the ATAM PHASE 2
• New stakeholders add the group that has
  participated of Phase 1
• Steps 1 to 6 are encored for the new stakeholders
  and
• Steps 7 to 9 are carried out.

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ATAM Steps Chapter 3

• The Phases of the ATAM PHASE 3
• The following tasks must be accomplished
• Produce the final report
• Cataloging what you did, found, concluded
• Use of the template
• Collect data for measurement and process
  improvement
• Improve ideas about what worked particularly well
  and what could stand to be improved
• Data comes evaluation team and client
• Generation of surveys
• Update the artifact repositories
• Record the cost and benefit information
• Stored scenarios produced
• Store a list of the analysis questions used

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ATAM Steps Chapter 3
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References

• CLEMENTS, P. Software Product Line.
  Springer-Verlag, 2005.