Interface Design Metrics
19.4.3 Interface Design Metrics
Although there is significant literature on the design of human/computer interfaces (see Chapter 15), relatively little information has been published on metrics that would provide insight into the quality and usability of the interface.
Sears [SEA93] suggests that layout appropriateness (LA) is a worthwhile design metric for human/computer interfaces. A typical GUI uses layout entities—graphic icons, text, menus, windows, and the like—to assist the user in completing tasks. To accomplish a given task using a GUI, the user must move from one layout entity to the next. The absolute and relative position of each layout entity, the frequency with which it is used, and the “cost” of the transition from one layout entity to the next all contribute to the appropriateness of the interface.
For a specific layout (i.e., a specific GUI design), cost can be assigned to each “Beauty—the
sequence of actions according to the following relationship: adjustment of all
parts proportionately (19-7) so that one cannot add or subtract or
where k is a specific transition from one layout entity to the next as a specific task is change without
accomplished. The summation occurs across all transitions for a particular task or impairing the
set of tasks required to accomplish some application function. Cost may be charac- harmony of the
terized in terms of time, processing delay, or any other reasonable value, such as the whole.” distance that a mouse must travel between layout entities. Layout appropriateness
Leon Alberti (1404–1472)
is defined as (19-8) where LA = 100 for an optimal layout.
To compute the optimal layout for a GUI, interface real estate (the area of the screen) is divided into a grid. Each square of the grid represents a possible position for a layout entity. For a grid with N possible positions and K different layout entities to place, the number of possible layouts is represented in the following manner [SEA93]:
(19-9) As the number of layout positions increases, the number of possible layouts grows
Interface design very large. To find the optimal (lowest cost) layout, Sears [SEA93] proposes a tree metrics are fine, but
searching algorithm. above all else, be
LA is used to assess different proposed GUI layouts and the sensitivity of a particular absolutely sure that
your end-users like the layout to changes in task descriptions (i.e., changes in the sequence and/or frequency interface and are
of transitions). The interface designer can use the change in layout appropriateness, comfortable with the
∆LA, as a guide in choosing the best GUI layout for a particular application. interactions required.
It is important to note that the selection of a GUI design can be guided with met- rics such as LA, but the final arbiter should be user input based on GUI prototypes. Nielsen and Levy [NIE94] report that “one has a reasonably large chance of suc- It is important to note that the selection of a GUI design can be guided with met- rics such as LA, but the final arbiter should be user input based on GUI prototypes. Nielsen and Levy [NIE94] report that “one has a reasonably large chance of suc-
Parts
» The Concurrent Development Model
» SUMMARY Software engineering is a discipline that integrates process, methods, and tools for
» PEOPLE In a study published by the IEEE [CUR88], the engineering vice presidents of three
» THE PROCESS The generic phases that characterize the software process—definition, development,
» THE PROJECT In order to manage a successful software project, we must understand what can go
» METRICS IN THE PROCESS AND PROJECT DOMAINS
» Extended Function Point Metrics
» METRICS FOR SOFTWARE QUALITY
» INTEGRATING METRICS WITHIN THE SOFTWARE PROCESS
» METRICS FOR SMALL ORGANIZATIONS
» ESTABLISHING A SOFTWARE METRICS PROGRAM
» Obtaining Information Necessary for Scope
» An Example of LOC-Based Estimation
» QUALITY CONCEPTS 1 It has been said that no two snowflakes are alike. Certainly when we watch snow
» SUMMARY Software quality assurance is an umbrella activity that is applied at each step in the
» R diagram 1.4 <part-of> data model; data model <part-of> design specification;
» SYSTEM MODELING Every computer-based system can be modeled as an information transform using an
» Facilitated Application Specification Techniques
» Data Objects, Attributes, and Relationships
» Entity/Relationship Diagrams
» Hatley and Pirbhai Extensions
» Creating an Entity/Relationship Diagram
» SUMMARY Design is the technical kernel of software engineering. During design, progressive
» Data Modeling, Data Structures, Databases, and the Data Warehouse
» Data Design at the Component Level
» A Brief Taxonomy of Styles and Patterns
» Quantitative Guidance for Architectural Design
» Isolate the transform center by specifying incoming and outgoing
» SUMMARY Software architecture provides a holistic view of the system to be built. It depicts the
» The User Interface Design Process
» Defining Interface Objects and Actions
» D E S I G N E VA L U AT I O N
» Testing for Real-Time Systems
» Organizing for Software Testing
» Criteria for Completion of Testing
» The Transition to a Quantitative View
» The Attributes of Effective Software Metrics
» Architectural Design Metrics
» Component-Level Design Metrics
» SUMMARY Software metrics provide a quantitative way to assess the quality of internal product
» Encapsulation, Inheritance, and Polymorphism
» Identifying Classes and Objects
» The Common Process Framework for OO
» OO Project Metrics and Estimation
» Event Identification with Use-Cases
» SUMMARY Object-oriented analysis methods enable a software engineer to model a problem by
» Partitioning the Analysis Model
» Designing Algorithms and Data Structures
» Program Components and Interfaces
» SUMMARY Object-oriented design translates the OOA model of the real world into an
» Testing Surface Structure and Deep Structure
» Deficiencies of Less Formal Approaches 1
» What Makes Cleanroom Different?
» Design Refinement and Verification
» SUMMARY Cleanroom software engineering is a formal approach to software development that
» Structural Modeling and Structure Points
» Describing Reusable Components
» SUMMARY Component-based software engineering offers inherent benefits in software quality,
» Guidelines for Distributing Application Subsystems
» Middleware and Object Request Broker Architectures
» An Overview of a Design Approach
» Consider expert Web developer will create a complete design, but time and cost can be appropriate
» A Software Reengineering Process Model
» Reverse Engineering to Understand Data
» Forward Engineering for Client/Server Architectures
» SUMMARY Reengineering occurs at two different levels of abstraction. At the business level,
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