Understanding Design Rationale and Usability

Design Rationale (DR) is an express process of documenting the factors or reasons behind decisions made on arriving on a particular design of a system or an artifact for that matter. It is the information which gives further details, explanations, clarity and justifies as to why an artifact or a system is structured in a specific manner. A proper design rationale must include the following: the reasons which led into a particular design decision; justification for the design decision; argumentations which helped in arriving on the decision; tradeoff evaluations and other alternatives which may have been considered.

Basic Concepts in DR

Design Rationale can be characterized in a number of ways and in each of these there are key features which make each system or artifact stand out. They include the following:-

Rationale capture

This is a process whereby rationale details are acquired and extended into the rationale management server. This may take different procedures including the following:

Reconstruction; this is where raw rationales are captured through videos and then worked on to produce more understandable structured forms. This method is advantageous as the rationales can be captured carefully and the whole process of capturing may not interfere with the designer. However, this method is costly and bias is possible on the one concerned with rationale production.

Record and replay; the rationales are captured as they happen or unfold. In this, the rationales are captured synchronously for example in video conferencing. On the hand, the rationales can be captured asynchronously on chat based or email based platforms. Record and play caters for the needs of both informal representations and semi formal representations.

Argumentation approach: This type of approach takes into consideration the arguments which are used in defining a design. It includes the issues raised, alternatives to the issues and the arguments raised for and against the alternatives.

Historian; as the name suggests, the approach records the actions of the designer without making any comment or suggestions. In this, a computer or a person may be used in recording the actions of the designer and this takes place during the design stage of a system or an artifact.

Other approaches may include; automatic generation and knowledge base among others.

Rationale representation

Representation of rationales must be carefully chosen as this will ensure that what is captured in rationales is what is communicated and used. Representation may include; formal, informal and semi formal representations. Informal includes use of videos, video records and the media. Formal representations include use of computers and semi informal use both the formal and informal methods.

Design Rationale applications

This process is highly applicable in mechanical designing, software Engineering, civil Engineering and artificial intelligence among other areas. DR helps in the verification of a designs; evaluating a design; reuse of a design; maintenance of a design; design teaching ; documentation of a design and communication of a design among other areas. On the other hand, Design Rationale is used by project managers in planning and keeping them in the know on the progress of their work.


Jessica is the Lead Author & Editor of UsabilityLab Blog. Jessica writes for the UsabilityLab blog to create a source for news and discussion about some of the issues, challenges, news, and ideas relating to usability.