Software Architecture Assessment of Usability Eelke Folmer, Jan Bosch IPA lentedagen, Made.

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Software Architecture Assessment of Usability
Eelke Folmer, Jan BoschIPA lentedagen, Made.
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STATUS project

• European Research Project STATUS (Software
  Architecture that supports Usability)
• Duration 12/01-12/04
• Partners
• Technical University of Madrid (Spain)
• University of Groningen (Netherlands)
• Imperial College (England)
• IHG (Spain)
• LogicDIS (Greece)

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Overview of my presentation

• Introduction
• Relationship between usability SA
• SALUTA steps
• Case studies
• Research questions Future work

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Introduction

• Usability ? Software Quality
• Tradeoffs (Cost, Quality, Time)
• Practice ? Ensuring Usability is expensive
• Result ? systems with less than optimal usability
  
• need cost effectively engineer usable software

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What Causes these high costs?

• Majority of usability costs are spent during
  maintenance.
• Some requirements are detected late
• Requirements are often weakly specified.
• Requirements engineering techniques have only
  limited ability to capture all req.
• requirements change during development.

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Role of the SA

• Hard and expensive to change a running system to
  Improve its usability
• Causes
• The impact of software architecture on usability.
  
• The impact of usability on software architecture
  design.

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Usability ? SA

• The retrofit problem

Architectural assessment
Get rid of the hard to change
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SA ? Usability

• Usability depends on
• Information architecture
• Interaction architecture
• System quality attributes

SA design
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Investigating the relationship between Usability
and SA

• Need to know the solutions that are hard to
  retrofit.
• Investigate rel. SA usability
• Result SAU SA-Usability-Framework
• Elements
• Usability attributes
• Usability properties
• Architecture sensitive usability patterns

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Usability attributes

• Learnability
• Efficiency of use
• Reliability in use
• Satisfaction
• Attributes tell you how to
• measure usability!

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Usability Properties

• Based on heuristics/ design principles
• Likely have architectural implications
• Architecture sensitive usability Patterns can be
  used to fulfill these properties
• Some examples
• Error management
• Error prevention
• Error correction
• Consistency
• Visual consistency
• Functional consistency
• Properties tell you how to design for usability!

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Architecture sensitive usability patterns

• Consider patterns
• that should be addressed during architectural
  design (architecture sensitive)
• Patterns obtained from
• Existing (usability) pattern collections
• Inductive process from different practical cases
  ( systems developed by industrial partners in
  STATUS project)

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Undo (1/2)

• Problem Users do actions they later want reverse
  
• Solution Maintain a list of user actions and
  allow users to reverse selected actions.
• Properties affected
• Error management providing the ability to
  undo an action helps the user to correct errors
  if the user makes a mistake. Explicit user
  control allowing the user to undo actions helps
  the user feel that they are in control of the
  interaction.

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Undo (2/2)

• Architectural Implications record the sequence
  of actions carried out by the user and the
  system.
• capture the entire state of the system after each
  user action.
• capture only relative changes.
• Implementation Most implementations of
  multi-level undo are based on the COMMAND
  pattern.

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Relationships in the SAU framework
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SALUTA steps

• SALUTA Scenario based Architecture Level
  UsabiliTy Assessment
• Describe required usability create usage
  profile.
• Describe provided usability analyze the software
  architecture.
• Evaluate scenarios determine the support for the
  usage scenarios.
• Interpret the results draw conclusions from the
  analysis results.

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1. Create usage profile 1/3

• Req. Rather weakly specified
• Traditional specification techniques Rather
  metric/abstract
• Solution Use scenario profiles!
• Scenarios express meaning of requirement
• More specific fine grained.

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1.Create usage profile 2/3

• ISO 9241 usability depends on users, tasks,
  contexts of use.

Req.
Efficiency reliability satisfaction
learnability

• learnability
• satisfaction
• reliability,
• efficiency,

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1. Create usage profile 3/3

• Identify the users
• Identify the tasks
• Identify contexts of use
• Determine attribute values
• Scenario Selection weighing

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2. Analyze architecture
framework
Software architecture
Design decisions
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3. Evaluate scenarios
Usability patterns
Usability patterns
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User Modes
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User Modes
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Undo
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Undo
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Multiple views
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Multiple views
Usability properties
Usability properties
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Consistency
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Consistency
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Provide feedback
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Provide feedback
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Guidance
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Guidance
Software architecture
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Error prevention
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Error prevention
framework
framework
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4.Interpret results

• Interpretation
• Goal of the analysis
• Selection
• Design/ use results of the assessment.
• Requirements

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Case studies
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Case study
Web-platform analysis

• CMS for managing WebPages within the university
  of Groningen.
• Allows creating, editing managing and publish a
  variety of content (text, graphics, video etc).
• Consists of 200000 different web pages 15.000
  users
• Usability an explicit design goal

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Inputs to the analysis

• Usage profile creation ? functional requirements
  specification
• Architecture analysis ? software architecture
  description
• Interviews with usability engineer software
  architect

Web-platform analysis
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Selected users tasks
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Create APT table 1/2
Web-platform analysis
Navigating should be intuitive and self
explanatory
Always let the user know where he is
Students are not familiar with the system
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Create APT table 2/2
Web-platform analysis
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Architecture description
Web-platform analysis
History logging
Multi channeling
User profiles
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Architecture description 1/2
Web-platform analysis
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Architecture description 2/2
Web-platform analysis
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Scenario evaluation
Web-platform analysis
Visual consistency
System feedback
Multipleviews
Contextsensitive help
Visual consistency





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Interpretation
SA provides sufficient support
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Validation / research questions

• Usage profile representative?
• Webplatform Usability tests
• No SA related usability issues were discovered
  (yet)
• usability tests show learnability for content
  admins is not supported very well (cannot be
  traced back to insufficient support of the SA)

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SALUTA experiences

• 1. Usage profile creation
• Difficult to transform requirements to scenarios
• Specification of certain quality attributes is
  difficult during initial design
• Cost benefit tradeoffs
• Representativeness of the usage profile
• 2. Architecture analysis
• Non-explicit nature of architecture design
• Validation of the SAU framework
• Qualitative nature of SAU framework

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SALUTA experiences

• 3. Scenario evaluation
• Evaluation is guided by tacit knowledge
• 4. Interpretation
• Initially Lacked a frame of reference

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General experiences

• Lack of integration of SE and HCI processes
• Technology driven design
• Impact of software architecture design on
  usability
• Accuracy of the analysis is unclear
• Design rather than evaluate

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Future work

• Tool support for Usage profile creation
  scenario evaluation
• Reworking the set of patterns provide specific
  implementation details
• Specialization of framework to particular domains
  extension to other qualities (usability,
  security safety)
• Future case studies
• Expand our frame of reference
• Measure decrease in usability related maintenance
  costs

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Concluding

• Main benefits of using SALUTA
• Be able to predict the SA support of usability
  (which could not be done before)
• Allow for more usability tuning
• Save on maintenance costs.
• Systems with higher usability.

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The last slide!

• Questions???
• More on www.designforquality.com