A lifecycle model is a representation of “a model that captures a set of activities and how they are related” (Rogers et al., 2007, p. 444). Three of the lifecycle models used in HCI are the Star lifecycle; the Usability Engineering lifecycle; and the ISO 13407 Human-centered design processes for interactive systems.
The Star lifecycle model has its origins in empirical work that aimed to understand how designers dealt with HCI design problems. It has evaluation at its core and represents a process that’s flexible. This model was developed by Hatson and Hix who identified 2 activity modes in HCI, namely the synthetic mode and the analytic mode (Rogers et al.). The synthetic mode is described by notions such as ad hoc, creative, free-thinking, and bottom-up – all of which work “from the user’s view towards the systems view” (Rogers et al., p. 458). The analytic mode, on the other hand, is described by notions such as formal, judicial, organizing, and top-down -- all of which work “from the systems view towards the user’s view” (Rogers et al., p. 58).
The Star lifecycle doesn’t provide specification for any sequence of activities. The activities are very much interconnected where an activity can be moved from one phase to another as long as it undergoes the evaluation phase first. With evaluation being a focus of this lifecycle model, every activity should be evaluated upon completion. As such, a project can begin with any phase – be it the analysis of existing tasks, the evaluation of a present situation, the requirements and specification gathering, or others.
An advantage of this lifecycle model is that with every activity being evaluated after it is completed, it becomes easier to make changes and corrections as compared to waiting for the entire project to be completed before performing an evaluation. However, its disadvantage is that it is too flexible, which can prevent developers and managers from getting an overall view of the entire development effort, which in turn prevents them from setting targets, allocating resources, specifying deliverables, and tracking progress. With too much flexibility, the stakeholders are unable to control the problems that may arise without making changes to the model.
The Usability Engineering lifecycle model makes use of a more structured approach and is derived from the tradition of usability engineering. It provides “a holistic view of usability engineering” (Rogers et al., p. 460) and provides detailed descriptions of the manner by which usability tasks are performed, as well as a specification of the integration of usability tasks into “traditional software development lifecycles” (Rogers et al., p. 460).
The Usability Engineering lifecycle model involves three tasks, namely 1.) requirements analysis; 2.) design, testing, and development; and 3.) installation. The first phase is where a set of usability goals are identified and the second phase is the largest where a lot of subtasks are involved.
An advantage of this lifecycle model is that it is most helpful for those who lack a background knowledge on usability, as this lifecycle model enables them “to see how the tasks may be performed alongside more traditional software engineering activities” (Rogers et al., p. 460). It also includes details about each stage of the lifecycle such as the identification of requirements, design, evaluation, and the building of prototypes. In addition, it includes a style guide for the capture and dissemination of the project’s usability goals.
A disadvantage of this lifecycle model, however, is that it is too structured and too sequential that the requirements are not revisited on the subsequent phases of the lifecycle. As such, changes to the needs of users aren’t readily captured and adjustments to the design are not made until the latter part of the lifecycle. The same results from the lack of constant evaluation, which prevents the developers and designers from identifying design errors at the earlier stages.
The ISO 13407 Human-centered design process for interactive systems lifecycle is developed from an international standard and resulted from international agreement and collaboration. In particular, ISO 13407 provides “guidance on human-centered design activities throughout the lifecycle of an interactive product” (Rogers et al., p. 462). It is concerned with both software and hardware components and addresses the management and planning of human-centered design. It does not provide the details of any design approach, which is covered by another standard, ISO 9241.
The four human-centered design principles covered by ISO 13407 include a clear understanding of task and user requirements and an active involvement of users; an appropriate allocation of function between technology and users; the “iteration of design solutions” (Rogers et al., p. 462); and a multi-disciplinary design. It also includes the following activities: understanding and specification of the context of use; specification of the organizational and user requirements; production of design solutions; and evaluation of designs against requirements.
The advantage of this lifecycle model is that it allows for iteration from the start to the completion of the project when all the product requirements are met. It also allows for the integration of the design activities into the other system development activities. However, its disadvantage is that strict compliance to this standard is quite difficult to implement, especially for organizations that don’t have well-structured processes. In addition, its agile quality poses the risk that not enough time may be spent on the data gathering phase before product development starts.
References
Rogers, Y., Sharp, H., & Preece, J. (2007). Chapter 9: The process of interaction design. In
Interaction design: Beyond human-computer interaction (2nd ed.) (412-470). Hoboken,
NJ: John Wiley & Sons
