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Software engg. pressman_ch-12


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Software engg. pressman_ch-12

  1. 1. Chapt er 12 User I nt er f ace Design Software Engineering: A Practitioner’s Approach, 6th edition by Roger S. Pressman 1
  2. 2. Interface Design Easy to learn? Easy to use? Easy to understand? 2
  3. 3. Interface Design  Interface design focuses on three areas of concern: 1) The design of interface between software components 2) The design of interfaces between the software and other nonhuman producers and consumers of information. 3) The design of the interface between a human (ie the user) and the computer.  Focus on the third interface design category – User Interface Design. 3
  4. 4. Golden Rules  Place the user in control  Reduce the user’s memory load  Make the interface consistent 4
  5. 5. Place the User in Control 1. Define interaction modes in a way that does not force a user into unnecessary or undesired actions. 2. Provide for flexible interaction. 3. Allow user interaction to be interruptible and undoable. 4. Streamline interaction as skill levels advance and allow the interaction to be customized. 5. Hide technical internals from the casual user. 6. Design for direct interaction with objects that appear 5
  6. 6. Reduce the User’s Memory Load 1. Reduce demand on short-term memory. 2. Establish meaningful defaults. 3. Define shortcuts that are intuitive. 4. The visual layout of the interface should be based on a real world metaphor. 5. Disclose information in a progressive fashion. 6
  7. 7. Make the Interface Consistent 1. Allow the user to put the current task into a meaningful context. 2. Maintain consistency across a family of applications. 3. If past interactive models have created user expectations, do not make changes unless there is a compelling reason to do so. 7
  8. 8. User Interface Design Models Four models come into existence when a user interface is to be analyzed and designed. 1.Human engineer (or software engineer) establishes a user model. 2.Software engineer creates a design model. 3.End-users develops a mental image that is often called the user’s mental model or the system perception. 4.Implementers of the system create a implementation mode. 8
  9. 9. User Interface Design Models  User model — a profile of all end users of the system  Design model — a design realization of the user model  Mental model (system perception) — the user’s mental image of what the interface is  Implementation model — the interface “look and feel” coupled with supporting information that describe interface syntax and semantics 9
  10. 10. User Interface Design Process 10
  11. 11. Interface Analysis  Interface analysis means understanding 1. the people (end-users) who will interact with the system through the interface; 2. The tasks that end-users must perform to do their work, 3. The content that is presented as part of the interface 4. The environment in which these tasks will 11 be conducted.
  12. 12. User Analysis 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. Are users trained professionals, technician, clerical, or manufacturing workers? What level of formal education does the average user have? Are the users capable of learning from written materials or have they expressed a desire for classroom training? Are users expert typists or keyboard phobic? What is the age range of the user community? Will the users be represented predominately by one gender? How are users compensated for the work they perform? Do users work normal office hours or do they work until the job is done? Is the software to be an integral part of the work users do or will it be used only occasionally? What is the primary spoken language among users? What are the consequences if a user makes a mistake using the system? Are users experts in the subject matter that is addressed by the system? Do users want to know about the technology the sits behind the interface? 12
  13. 13. Task Analysis and Modeling       Task Analysis answers the following questions …  What work will the user perform in specific circumstances?  What tasks and subtasks will be performed as the user does the work?  What specific problem domain objects will the user manipulate as work is performed?  What is the sequence of work tasks—the workflow?  What is the hierarchy of tasks? Use-cases define basic interaction Task elaboration refines interactive tasks Object elaboration identifies interface objects (classes) Workflow analysis defines how a work process is completed when several people (and roles) are involved Hierarchical representation the hierarchy is derived by a stepwise elaboration of each task identified for the user 13
  14. 14. Swimlane Diagram p at ien t p h armacist r e q u e st s t h at a p r e scr ip t io n b e r e f ille d d e t e r m in e s st at u s o f p r e scr ip t io n no ref ills remaining ref ills remaining ch e cks in v e n t o r y f o r r e f ill o r alt e r n at iv e r e ce iv e s o u t o f st o ck n o t if icat io n out of st ock p h ysician ch e cks p at ie n t r e co r d s approv es ref ill ref ill not allowed e v alu at e s alt e r n at iv e m e d icat io n alt ernat iv e av ailable in st ock r e ce iv e s t im e / d at e t o p ick u p p icks u p p r e scr ip t io n none f ills p r e scr ip t io n r e ce iv e s r e q u e st t o co n t act p h y sician Fig u re 1 2 .2 Sw imlan e d iag ram fo r p rescrip t io n refill fu n ct io n 14
  15. 15. Analysis of Display Content 1. 2. 3. 4. 5. 6. 7. 8. Are different types of data assigned to consistent geographic locations on the screen (e.g., photos always appear in the upper right hand corner)? Can the user customize the screen location for content? Is proper on-screen identification assigned to all content? If a large report is to be presented, how should it be partitioned for ease of understanding? Will mechanisms be available for moving directly to summary information for large collections of data. Will graphical output be scaled to fit within the bounds of the display device that is used? How will color to be used to enhance understanding? How will error messages and warning be presented to the user? 15
  16. 16. I nt er f ace Design St eps  Using information developed during interface analysis, define interface objects and actions (operations).  Define events (user actions) that will cause the state of the user interface to change. Model this behavior.  Depict each interface state as it will actually look to the end-user.  Indicate how the user interprets the state of the system from information provided through the interface. 16
  17. 17. I nt er f ace Design Pat t er ns  Patterns are available for  The complete UI  Page layout  Forms and input  Tables  Direct data manipulation  Navigation  Searching  Page elements  e-Commerce 17
  18. 18. Design I ssues       Response time Help facilities Error handling Menu and command labeling Application accessibility Internationalization 18
  19. 19. Design Evaluation Cycle preliminary design build prototype #1 interface build prototype #n interface user evaluate's interface design modifications are made evaluation is studied by designer Interface design is complete 19