Term Test Set
Design Principles - Learnability Barrier
If the interface is comprehensible it will be learnable, there is a direct relationship. Effective use generally requires that the way of working through the interface become natural to the user (that they 'learn' it)
Design Principles - Comprehensibility Barrier
If the presentation is comprehensible, the comprehensibility barrier will be superseded. This depends on the degree of efficiency/usability in the interface design. The user needs to understand how they access the functionality
Design Principles - Effectiveness / Usefulness
If the user can learn the interface s/he can take advantage of the functionality and the interface will, therefore, be useful.
State transition network (STN)
Provides a description what actions/events are available at what point and want state the system will be in after each action
Conceptual Design - Card Sort Disadvantages
Disadvantages of card sorting sessions: They only involve the elements that you have written on the cards. They suggest solutions that imply structures. They become difficult to navigate / interpret with more categories.
Conceptual Design - Semantic Network Disadvantages
Disadvantages of semantic networks: They require knowledge of the problem space. They can lead beyond the problem space. There is no formal semantics for defining symbol meaning Could get formal by using UML, but would tend to stifle the process
Fitt's Law
Fitts' Law is the classic performance measure. Time to target depends on target width (W) and distance to move pointer (D) (see tutorial exercise) It is a very valuable measure for designing Control size and location Its also fun to play with!
Hierarchical task analysis (HTA)
HTA provides a top-down, structured approach to documenting processes. Goals - top-level goal of the task being analysed Plans - the order and conditions for proceeding with the sub-tasks Information - all the information needed to undertake the task Objects - all the physical objects involved Methods - the various ways of doing the sub-tasks
Heuristic Evaluation
Heuristic evaluations are performed by usability experts using a predetermined set of criteria designed to measure the usability of a proposed design.
Usability Factors - Ease of LEarning
How fast can a user who has never seen the user interface before learn it sufficiently well to accomplish basic tasks?
Usability Factors - Subjective Satisfaction
How much does the user like using the system?
Usability Factors - Error Frequency and Severity
How often do users make errors while using the system, how serious are these errors, and how do users recover from these errors?
Usability Factors - Memorability
If a user has used the system before, can he or she remember enough to use it effectively the next time or does the user have to start over again learning everything?
Usability
Usability is the measure of the quality of a user's experience when interacting with a product or system (www.usability.gov 2006) Usability is a quality attribute that assesses how easy user interfaces are to use (Nielsen 2003)
Use Case
Use cases represent a formal, structured approach to interpreting work flows and processes Designed to describe a particular goal and explore the interaction between users and the actual system components. Actors: similar to stakeholders, but can also include other systems, networks, or software that interacts with the proposed system. Use Cases: Each actor has a unique use case, which involves a task or goal the actor is engaged in. Describe discrete goals that are accomplished in a short time period Describe the various ways the system will be used and cover all of the potential functionality being built into the design
Principles of Interaction Design - Effectiveness / Usefulness
Utility Safety Flexibility Stability
Shneiderman's 8 Golden Rules
1. Strive for consistency E.g. exact same terms for objects, same command syntax throughout 2. Enable frequent users to use shortcuts 3. Offer informative feedback 4. Design dialogs to yield closure 5. Offer error prevention and simple error handling 6. Permit easy reversal of actions 7. Support internal locus of control Make users initiators rather than responders (e.g. direct manipulation!) 8. Reduce short-term memory load What the user needs to know should be readily visible
Conceptual Design - Card Sort Advantages
Advantages of card sorting sessions: They are quick and easy to perform. They can be done before any preliminary designs have been made. They will let you know how people organize information. They will expose underlying structures.
Conceptual Design - Personals Advantages and Disadvantages
Advantages of personas: They are quick and easy to create. They provide a consistent model for all team members. They are easy to use with other design methods. They make the user "real" in the mind of the designer. i.e. a basis for our 'empathy' as designers Disadvantages of personas: They can be difficult to create if the target audience is international (or just diverse in whatever way) Having too many personas will make the work difficult. 6-8 is usual There is a risk of incorporating unsupported designer assumptions.
Conceptual Design - Semantic Network Advantages
Advantages of semantic networks: They allow an easy way to explore the problem space. They provide a way to create clusters of related elements. They provide a graphical view of the problem space. They resonate with the ways in which people process information. Can transform your card sort into a semantic network by using post-its, sticking them to a large piece of paper and drawing lines.
Conceptual Design - Iteration
By running the scenario we discover Weaknesses in the flowchart (or more advanced prototype) for accomplishing the scenario This implies where and how something has to change We may change the flowchart / prototype We may adjust the scenario (and/or persona) We may change the functional requirements Expand, contract or otherwise adjust the scope of the entire system development effort (if we have the freedom to do so)
Usability Factors - Fit for use
Can the system support the tasks that the user wants to perform
Conceptual Design - Card Sort
Card Sorting can be used to discover user-centered groupings Card sorting can be used to organize the information collected in the discovery phase Used to define groupings for menus, controls and Web page content Used to generate labels for menus, buttons and navigation links
Conceptual Design
Conceptual design involves Structuring the information space Creating alternative solutions Determining which design concept to pursue
Usability Factors - Efficiency of Use
Once an experienced user has learned to use the system, how fast can he or she accomplish tasks?
Conceptual Design - Personas
Personas are archetypes of actual users, defined by the user's goals and attributes.
Conceptual Design - Scenarios
Scenarios A description in 'plain English' of a typical task It describes The basic goal The conditions that exist at the beginning of the task The activities in which the persona will engage The outcomes of those activities Scenarios afford a rich picture of the user's tasks
Principles of Interaction Design - Efficiency / Usability
Simplicity Memorability Predictability Visibility
Storyboarding
Storyboarding involves using a series of pictures that describes a particular process or work flow Can be used to study existing work flows or generate requirements. Can facilitate the process of task decomposition Used to brainstorm alternative ways of completing tasks.
Conceptual Design - Brainstorming
Team activity Get out possible ideas Minimize critical thinking at this stage Any idea is 'good enough' to write down May use storyboarding Making a comic strip of the interaction concept Or any sort of diagramming that denotes the idea Can work in parallel by breaking into subgroups or individually to scribble ideas on butcher paper or post-its Brainstorming sessions generate a lot of material that must then be filtered and organized
Design Principles - Presentation Filter
The functionality must be made accessible through the presentation filter (interface). The user has to be able to access the functionality (that's what the 'user interface' is for!)
Secondary Stakeholder
The person who either supplies input or receives output from the design
Indirect Stakeholder
The person who is affected by the use of the design but has no contact with it, such as the user's superior or coworkers and the client who is paying for the project (the client may or may not also be the primary stakeholder)
Facilitator Stakeholder
The person who maintains or develops the design
Primary Stakeholder
The person who uses the design directly
Design Principles - Functionality
The system must have adequate functionality for a particular task.
Hick-Hyman Law
The time it takes for a person to make a decision as a result of the possible choices Particularly important for menus Although log2 only holds if menu is sorted in a logical order (e.g. alphabetical) - otherwise search time is linear! Other factors Recognition time: for icon or word Consistency is good: spatial memory is very powerful - Knowing it's at the left/right side, top/bottom
Nielsen's Heuristics
Visibility of System Status Match between System and the Real World User Control and Freedom Consistency and Standards Error Prevention Recognition Rather Than Recall Flexibility and Efficiency of Use Aesthetic and Minimalist Design Help Users to Recognise, Diagnose, and Recover from Errors Help and Documentation
