CS5714 Usability Engineering An Iterative, Evaluation- Centered Life Cycle For Interaction Development Copyright 2004 H. Rex Hartson Deborah Hix Topics Connections of user interaction development to engineering Development activities in the usability engineering life cycle Usability management development team 2 System development Mobius System feasibility Typical Engineering plans requirements Product The Waterfall Model Detailed Code Integration Implementation 3 Operations maintenance 1
The Process of Interaction Development Connections of user interaction development to engineering All these figures depict communication paths, not temporal ordering of activities Distinction between implementation Start with basic engineering concept: 4 Spec'ns implementation Con The Process of Interaction Development Adding systems analysis, testing, problem (application) domain Test plan, criteria Systems analysis Req'ts Req'ts Spec'ns Pgms Problem domain implementation Errors, bugs Main feedback: flaws, errors, modifications testing 5 Major reconsiderations The Process of Interaction Development Analogous activities for user development Test plan, usability Systems analysis Interface req'ts, usability interaction Con requirements Con implementation implemen- Contatio Pgms Errors, bugs based evaluation of 6 Main feedback is due to low usability: flaws, errors, modifications Major reconsiderations 2
The Process of Interaction Development Connecting the processes together adding rapid prototyping 7 Test plan, criteria Systems analysis Req'ts Req'ts Spec'ns Applica- Pgms Applica- Problem tion tion domain implemen- Contation Errors, Contraints bugs Main feedback: flaws, errors, modifications Major reconsiderations Interface req'ts, imple- usability requirementation ments Pgms interaction implemen- Contation Errors, bugs based testing evaluation of non Usability Main feedback is due to low usability: flaws, errors, modifications Test plan, usability 8 Rapid prototyping Formative userbased evaluation The Process of Interaction Development The rest of this course is about just this part: Systems analysis Interface req'ts, usability interaction Con Usability 9 Rapid prototyping Formative userbased evaluation 3
Iterative, evaluation-centered process model for interaction development Why iterative? Because it s not possible to get it right the first time (in any complex domain) Need: Ready, Fire, Aim! 10 New life cycle concept comes from: The waterfall model movement toward completion Star (Hartson & Hix, 1989) evaluation centered LUCID (Cognetics, Inc.) development activities Boehm s Spiral Model iteration New work by Helms & Hartson (2001) put it together 11 Star (Hartson & Hix, 1989) Evaluation centered 12 4
Boehm s spiral model-evolution through iteration 13 Cumulative Cost Boehm s spiral model abstracted Determine objectives, alternatives, con Evaluate alternatives, identify, resolve risks Commitment Review 14 Devt methodology Plan next phases Develop, verify nextlevel product Spiral model adapted 15 5
Spiral unwound 16 Spiral unwound stretched out 17 Waterfall with whirlpools 18 6
Direction of evolutionary advancement Wheel /task model Usage scenarios Screen s Connecting into Wheel, for intercycle iteration Product concept Global evaluation hub Lo-fi prototype Close down Hi-fi prototype 19 Operational system Deployment Integration 20 Life cycle=iterative configuration of cycles (each associated with a stage/form of the product) Example: System analysis model, scenarios screen s, lo-fi prototype, hi-fi prototype, production & integration Cycle is a sequence of four development activity types: Analyze Design Build Evaluate Cycle as sequence of four types of development activities Design Product form in Analyze Cycle of activities Implement Evaluate 21 Product form out 7
Technique Technique Project role Zoom in on details of a generic cycle activity Technique selection criteria Product form in Activity role Activity type/ instance Product form out Work products Tools/templates Relationships with other activities Work products 22 Common database of documentation Choose a technique for each activity type in each cycle 23 Shows how each activity type is assigned a technique, the role of the person doing the activity, support tools, documentation Example: In scenario screen cycles, walkthrough is used as evaluation technique Basic Principles Process is product oriented Products evolve through cycles (cycles named for product forms) 24 8
Each cycle is iterative Each cycle contains same activity types Each cycle is evaluation-centered Work products (documentation) evolve over cycles Process can be viewed at different levels Process, cycle, activity, documentation 25 Any part of the process is an instance of what is possible Pick choose cycles, activities, iterations to meet schedule, budget, management style Integrate with engineering development process Validated by Helms & Hartson (2001) in e- commerce start-up company 26 Any part of process is instance of what is possible Developers include their favorite UE methods techniques Omit activities, cycles, iterations indicated by management, budget, schedule, project scope, team composition Can be different every time 27 9
Usability Management The control mechanism for the iteration Control involves: Establishing usability specifications Evaluating against usability specifications Performing impact cost/benefit analyses 28 Usability Management Deciding on changes to make to interaction Deciding when to stop iterating Same process can be applied to develop user documentation or training course 29 Meet the Interface Development Team 30 Roles on user development team Note: Different roles, but not necessarily different people interaction er (or usability engineer or usability specialist) Evaluator (or facilitator) (/or user representative) engineer /or programmer Technical writer Graphic er Application domain expert (also called subject matter expert) Engineers 10