User Interface Design The Golden Rules: Place the user in control. 2. Reduce the user’s memory load. 3. Make the interface consistent. These golden rules actually form the basis for a set of user interface design principles that guide this important aspect of software design.

1. Place the User in Control Define interaction modes in a way that does not force a user into unnecessary or undesired actions. Provide for flexible interaction. Allow user interaction to be interruptible and undoable. Streamline interaction as skill levels advance and allow the interaction to be customized. Hide technical internals from the casual user. Design for direct interaction with objects that appear on the screen.

2. Reduce the User’s Memory Load Reduce demand on short-term memory. Establish meaningful defaults. Define shortcuts that are intuitive. The visual layout of the interface should be based on a real-world metaphor. Disclose information in a progressive fashion.

3.Make the Interface Consistent Allow the user to put the current task into a meaningful context. Maintain consistency across a family of applications. If past interactive models have created user expectations, do not make changes unless there is a compelling reason to do so.

User Interface Analysis and Design 1.Interface Analysis and Design Models To build an effective user interface, “all design should begin with an understanding of the intended users, including profiles of their age, gender, physical abilities, education, cultural or ethnic background, motivation, goals and personality” users can be categorized as: Novices Knowledgeable, intermittent users. Knowledgeable, frequent users.

2. The Interface design Process

Interface Analysis User analysis User Interviews. Sales input. Marketing input. Support input.

2. Task Analysis and Modeling The goal of task analysis is to answer 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?

3. Analysis of Display Content 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 be used to enhance understanding? How will error messages and warnings be presented to the user? The answers to these (and other) questions will help you to establish requirements for content presentation.

Interface Design Steps 1. Using information developed during interface analysis, define interface objects and actions (operations). 2. Define events (user actions) that will cause the state of the user interface to change. Model this behavior. 3. Depict each interface state as it will actually look to the end user. 4. Indicate how the user interprets the state of the system from information provided through the interface.

Applying Interface Design Steps the following homeowner tasks, objects, and data items are identified: • accesses the SafeHome system • enters an ID and password to allow remote access • checks system status • arms or disarms SafeHome system • displays floor plan and sensor locations • displays zones on floor plan • changes zones on floor plan • displays video camera locations on floor plan • selects video camera for viewing • views video images (four frames per second) • pans or zooms the video camera

User Interface Design Patterns

User Interface Design Issues Response time. Help facilities. Error handling. Menu and command labeling. Application accessibility. Internationalization.

Interface design principles and guidelines Anticipation Communication , Consistency Controlled memory Efficiency , Flexibility Focus Fitt’s law Human interface objects Latency reduction Learnability Metaphors Maintain work product integrity Readability Track state, visible navigation

Design Evaluation

Implementation Issues Executable version of the software from the initial requirements of the systems High –or - low level programming languages or tailoring and adapting generic, off-the-shelf systems to meet the specific requirements of organization Aspects Reuse Configuration management – keep track of versions Host-target development- develop ( in host) & execute ( in target)

Reuse Initially functions and objects in programming language libraries were reused Now software reuse is possible at different levels Abstraction level- design & architectural patterns Object level- objects from appropriate libraries (objects and methods offer needed functionality) eg. JavaMail library Component level- components are collections of objects and object classes that operate together to provide related functions and services eg. User interface using a framework

System level- reuse entire applications with some kind of configuration eg. COTS Costs associated with reuse Cost of time spent in looking for software to reuse and assessing whether or not it meets your needs Cost of buying the reusable software Costs of adapting and configuring the reusable software components or systems Cost of integrating reusable software components from different sources with the new code developed

Configuration management General process of managing a changing software system Aim is to support the system integration process for all developers to access the project code and documents in a controlled way, to find the changes been made, compile and link components in a system Fundamental configuration management activities Version management – development by several programmers System configuration- what versions of components to create each version Problem tracking- report bugs and other problems

Tools Version management- Subversion (multi site, multi team devp) System integration- GNU build system Bug tracking- Bugzilla Host target development (based on Host-target model) Development and execution platforms (platforms can be hardware, OS, dbms-interactive platforms) Development and execution platforms same- Simulators (Embedded Systems)- Simulators are costly so only for popular hardware architectures

Middleware also possible Tools Integrated compiler and syntax- directed editing systems Language debugging system Graphical editing tools eg. UML models Testing tools eg. Junit Project support tools Specialized tools eg. Static analyzers IDE (Integrated Development Environment)- set of software tools that supports different aspects with common framework and user interface eg. Eclipse

Issues Hardware and software components Availability requirements of the systems- platform failure Component communication- same /physically close platform implementation to reduce communication latency, delay between sending and receiving message Document hardware and software deployment using UML deployment diagrams across hardware platforms Embedded systems – above components + physical size, power capabilities , real time responses in sensor events, real time operating systems