Information System Development Life Cycle Models - High Level Models and Methodologies for Information Systems - page 34

2.9 Usability Engineering Life Cycle

Usability engineering is a concept of software engineering that places usability
characteristics at the center of the development process and implies that constant
measurements and analysis of usability should be undertaken as the development
proceeds. It is primarily related to user interface design. As a model for SDLC, it
was originally proposed by Deborah Mayhew in the late 1990s.
The main objective of usability engineering is to apply structured iterative design
and evaluation to all stages of the SDLC, thus ensuring constant involvement of the
user within the process. The life cycle is segmented in three parts

analysis/design,
development, and evaluation. Across the three sections, the successive activities are
performed, in a waterfall-like process, but re

—

ecting the existence of various iter-

ations before the final product is released (Gabbard et al. 2003 ).

Crucial to this process is determining who will constitute the product s user base

and what will they be doing with the product. User task analysis is the central
activity at the beginning of the process and can be achieved through surveys,
interviews, observation, etc. The product of such analysis consists of scenarios,
potentialities, and requirements that will be taken into account for the next stages of
the process. After establishing the requirements and de

'

ning them through user-
centered metrics, an initial design is outlined and swiftly prototyped, so that it can
be followed by extensive usability evaluation and testing (Gabbard et al. 2003 ).
This life cycle model is evidently user-centric, as it intends to create a system
that is

financially effective but also presents very high usability. The fact that it
helps the development of systems that are extremely user-friendly prevents errors
that derive from human misuse of the interface. Consequently, it promotes high
productivity.
When considering the entirety of the life of the interface, this development life
cycle, because it diminishes the need for the addition of features at a stage of the
development when they have an increased cost, has the potential to decrease

expenses (Gabbard et al. 2003 )

2.10 The Star Life Cycle Model

The star life cycle model was proposed by Harton and Hix in the late 1980s, as the
result of extensive observation of developers in real-time environments (Helms
2001 ). It is a particular variant of usability engineering, a user-centric set of soft-
ware development guidelines, and thus rejects the rigid, step-by-step nature of
waterfall-like models.
The most innovative premise is that each step in development does not neces-
sarily fall in a fixed process. Instead, it is assumed that there

are a number of essential stages of development, but they can be processed in
various orders and various time frames, according to the speci

fixed position within a

c needs of the