Cognitive dimensions or cognitive dimensions of notations are design principles for notations,

user interface In the industrial design field of human–computer interaction, a user interface (UI) is the space where interactions between humans and machines occur. The goal of this interaction is to allow effective operation and control of the machine f ...

s and programming languages, described by researcher

Thomas R.G. Green Thomas R. G. Green (born 1941) is a British cognitive scientist, and Visiting Professor at the University of York, known for his contribution to cognitive modelling and the development of the concept of cognitive dimensions of notations. In the ...

and further researched with Marian Petre. The dimensions can be used to evaluate the

usability Usability can be described as the capacity of a system to provide a condition for its users to perform the tasks safely, effectively, and efficiently while enjoying the experience. In software engineering, usability is the degree to which a soft ...

of an existing ''information artifact'', or as heuristics to guide the design of a new one, and are useful in Human-Computer Interaction design. Cognitive dimensions are designed to provide a lightweight approach to analyse the quality of a design, rather than an in-depth, detailed description. They provide a common vocabulary for discussing many factors in notation, UI or programming language design. Also, cognitive dimensions help in exploring the space of possible designs through ''design maneuvers'', changes intended to improve the design along one dimension.

List of the cognitive dimensions

Thomas Green originally defined 14 cognitive dimensions: ; Abstraction gradient : What are the minimum and maximum

levels of abstraction {{Multiple issues, {{context, date=March 2018 {{unreferenced, date=August 2009 The principle of abstraction is a grouping principle, whereby a hierarchy is adhered to with higher levels of abstraction placed near the top with more specific concep ...

exposed by the notation? Can details be encapsulated? ; Closeness of mapping : How closely does the notation correspond to the

problem Problem solving is the process of achieving a goal by overcoming obstacles, a frequent part of most activities. Problems in need of solutions range from simple personal tasks (e.g. how to turn on an appliance) to complex issues in business an ...

world? ; Consistency : After part of the notation has been

learned Learning is the process of acquiring new understanding, knowledge, behaviors, skills, values, attitudes, and preferences. The ability to learn is possessed by humans, animals, and some machines; there is also evidence for some kind of ...

, how much of the rest can be successfully guessed? ; Diffuseness / terseness : How many

symbol A symbol is a mark, sign, or word that indicates, signifies, or is understood as representing an idea, object, or relationship. Symbols allow people to go beyond what is known or seen by creating linkages between otherwise very different conc ...

s or how much space does the notation require to produce a certain result or express a

meaning Meaning most commonly refers to: * Meaning (linguistics), meaning which is communicated through the use of language * Meaning (philosophy), definition, elements, and types of meaning discussed in philosophy * Meaning (non-linguistic), a general te ...

? ; Error-proneness : To what extent does the notation influence the likelihood of the user making a mistake? ; Hard mental operations : How much hard mental processing lies at the notational level, rather than at the

semantic Semantics (from grc, σημαντικός ''sēmantikós'', "significant") is the study of reference, meaning, or truth. The term can be used to refer to subfields of several distinct disciplines, including philosophy, linguistics and comput ...

level? Are there places where the user needs to resort to fingers or penciled annotation to keep track of what's happening? ; Hidden dependencies : Are dependencies between entities in the notation visible or hidden? Is every dependency indicated in both directions? Does a change in one area of the notation lead to unexpected consequences? ; Juxtaposability : Can different parts of the notation be compared side by side at the same time? ; Premature commitment : Are there strong constraints on the order in which the user must complete the tasks to use the system? :Are there decisions that must be made before all the necessary information is available? Can those decisions be reversed or corrected later? ; Progressive evaluation : How easy is it to evaluate and obtain feedback on an incomplete solution? ; Role-expressiveness : How obvious is the role of each component of the notation in the solution as a whole? ; Secondary notation and escape from formalism : Can the notation carry extra information by means not related to syntax, such as layout, color, or other cues? ; Viscosity : Are there any inherent barriers to change in the notation? How much effort is required to make a change to a program expressed in the notation? : This dimension can be further classified into the following types: :* 'Knock-on viscosity' : a change in the code violates internal constraints in the program, whose resolution may violate further internal constraints. :* 'Repetition viscosity' : a single action within the user’s conceptual model requires many, repetitive device actions. :* 'Scope viscosity' : a change in the size of the input data set requires changes to the program structure itself. ; Visibility : How readily can required parts of the notation be identified, accessed and made visible?

Other dimensions

In addition to the above, new dimensions are sometimes proposed in the HCI research field, with different levels of adoption and refinement. Such candidate dimensions include creative ambiguity (does the notation encourage interpreting several meanings of the same element?), indexing (are there elements to guide finding a specific part?), synopsis (" Gestalt view" of the whole annotated structure) or unevenness (some creation paths are easier than others, which bias the expressed ideas in a developed artifact).

User activities

The authors identify four main user activities with interactive artifacts: ''incrementation'' reation ''transcription'', ''modification'' and ''exploratory design''. Each activity is best served by a different trade-off in the usability on each dimension. For example, a high viscosity (resistance to change) is harmful for modification and exploration activities, but less severe for the one-off tasks performed in transcription and incrementation.

Design maneuvers

A design maneuver is a change made by the designer in the notation design, to alter its position within a particular dimension. Dimensions are created to be pairwise independent, so that the design can be altered in one dimension while keeping a second one constant. But this usually results in a trade-off between dimensions. A modification increasing the usability of the notation in one dimension (while keeping a second one constant) will typically reduce its usability in a third dimension. This reflects an assumption in the framework that there is no perfect interface and that trade-offs are a fundamental part of usability design. An example of a design maneuver is reducing the viscosity of a notation by adding abstraction mechanisms. This can be done by incorporating style sheets, an abstraction that represent the common styling attributes of items in a document, to a notation where each item in a document has defined its own individual style. After this design maneuver is made, an editor that changes the style sheet will modify all items at once, eliminating the ''repetition viscosity'' present in the need to change the style of each individual item.

References

{{Reflist, 30em

External links

Cognitive Dimensions of Notation Resource Site

Cognitive dimensions
at usabilityfirst.com glossary
Cognitive Dimensions of Information Artefacts: a tutorial
by Thomas Green and Alan Blackwell
A Usable Guide to Cognitive Dimensions
and intuitive explanation of Cognitive Dimensions Usability Human–computer interaction Programming language topics Notation User interface techniques Usability inspection