In discussing the usability of a computer system, it is easy to focus on the design of the interface between the user and the computer, but usability is a property of the total system. All the components must work together smoothly to create an effective and convenient digital library, for both the patrons, and for the librarians and systems administrators.
In any computer system, the user interface is built on a conceptual model that describes the manner in which the system is used.
The introduction of browsers, notably Mosaic in 1993, provided a stimulus to the quality of user interfaces for networked applications.
Mobile code gives the designer of a web site the ability to create web pages that incorporate computer programs
Interface design is partly an art, but a number of general principles have emerged from recent research. Consistency is important to users, in appearance, controls, and function. Users need feedback; they need to understand what the computer system is doing and why they see certain results. They should be able to interrupt or reverse actions. Error handling should be simple and easy to comprehend. Skilled users should be offered shortcuts, while beginners have simple, well-defined options. Above all the user should feel in control.
Research into functional design provides designers with choices about what functions belong on which of the various computers and the relationships between them.
A presentation profile is an interesting concept which has recently emerged. Managers of a digital library associate guidelines with stored information. The guidelines suggest how the objects might be presented to the user. For example, the profile might recommend two ways to render an object, offering a choice of a small file size or the full detail.
Few computer systems are completely reliable and digital libraries depend upon many subsystems scattered across the Internet
Kling and Elliott
"Systems usability" refers to how well people can exploit a computer system's intended functionality. Usability can characterize any aspect of the ways that people interact with a system, even its installation and maintenance.
wo key forms of DL usability - interface and organizational. The interface dimensions are centered around an individual's effective acclimation to a user interface, while the organizational dimensions are concerned with how computer systems can be effectively integrated into work practices of specific organizations.
interface usability dimensions:
1. Learnability - Ease of learning such that the user can quickly begin using it.
2. Efficiency - Ability of user to use the system with high level of productivity.
3. Memorability - Capability of user to easily remember how to use the system after not using it for some period.
4. Errors - System should have low error rate with few user errors and easy recovery from them. Also no catastrophic errors.
organizational usability dimensions include:
1. Accessibility - Ease with which people can locate specific computer systems, gain physical access and electronic access to their electronic corpuses. This dimension refers to both physical proximity and administrative/social restrictions on using specific systems.
2. Compatibility - Level of compatibility of file transfers from system to system.
3. Integrability into work practices - How smoothly the system fits into a person or group's work practices.
4. Social-organizational expertise - The extent to which people can obtain training and consulting to learn to use systems and can find help with problems in usage.
A great deal of people's satisfaction is influenced by the size and content of the corpus of a DL service"Design for usability" is a new term that refers to the design of computer systems so that they can be effectively integrated into the work practices of specific organizations.
The usability engineering life cycle model includes these stages proposed as a paradigm for companies to follow:
1. Know the user - Study intended users and use of the product. At a minimum, visit customer site to study user's current and desired tasks, and to understand the evolution of the user and the job.
2. Competitive analysis - Analyze existing products according to usability guidelines and perform user tests with products.
3. Setting usability goals - Establish minimal acceptable level of usability and estimate the financial impact on cost of users' time.
4. Parallel design - Use several designers to explore different design alternatives before deciding on one final design.
5. Participatory design - Include end-users throughout design phase.
6. Coordinated design of the total interface - Maintain consistency across screen layouts, documentation, on-line help systems, and tutorials.
7. Apply guidelines and heuristic analysis - Select user interface guideline appropriate for situation.
8. Prototyping - Build prototype to pretest on end-users.
9. Empirical testing - Test end-users on specific usability attributes.
10. Iterative design - Capture design rationale through iterative testing and design.
11. Collect feedback from field use - Gather usability work from field studies for future design.
The organizationally sensitive model of "design for usability" is a new model. It refers to the design of computer systems so that they can be effectively integrated into the work practices of specific organizations. It goes beyond the focus on user interfaces. "Design for usability" includes the infrastructure of computing resources which are necessary for supporting and accommodating people as they learn to maintain and use systems. "Design for usability" encourages system designers either to accommodate to end-users' mix of skills, work practices, and resources or to try to alter them
Saracevic:
Usability has been used widely in digital library evaluation, but there is no uniform definition of
what does it cover in digital library context. Usability is a very general criterion that covers a lot
of ground and includes many specific criteria – it is a meta term. ISO defines usability “as the
extent to which a product can be used by specified users to achieve specified goals with
effectiveness, efficiency and satisfaction in a specified context of use"
users have many difficulties with digital libraries, such as:
– they usually do not fully understand them
– they hold different conception of a digital library from operators or designers
– they lack familiarity with the range of capabilities, content and interactions
provided by a digital library.
– they often engage in blind alley interactions
in use, more often than not, digital library users and digital libraries are in an
adversarial position
The ultimate evaluation of digital libraries will revolve around assessing transformation of their
context – determining possible enhancing changes in institutions, learning, scholarly publishing,
disciplines, small worlds and ultimately society due to digital libraries.
Sheiderman and Plaisant
Human-Computer Interaction
Requirements analysis:
1- ascertain user needs
2- ensure proper readability
3-context of use & appropriate standardization, integration, consistency, portability
evaluation:
1- time to learn
2- speed of performance
3- rate of errors by user
4- retention over time
5- subjective satisfaction
motivations:
1- life-critical systems
2- industrial/commercial
3- office/home/entertainment
4- exploratory/creative/collaborative
5- sociotechnical
Universal Usability:
1- Variations in physical abilities & physical workplaces
2- diverse cognitive & perceptual abilities
3- personality differences
4- cultural & international diversity
5- users with disabilities
6- older adult users
7- designing for/with children
8- hardware and software diversity
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