11.1 Lifecycle Models for Interactive Design and HCI

Lifecycle models for interactive design and HCI are used as a tool that manages the design process in terms of linking the various activities that structure the interactive product.

Various models are used for interactive design and HCI such as the traditional waterfall model, the spiral model as well as the star model.

These lifecycle models are described below.

Lifecycle modeling, similar to any design process is an iterative process which means that designers need to have the ability to design and re-design the interactive products according to the users' needs as well as the evaluation that takes place in the design process.

As shown below, all lifecycle models take into account the requirements of the user as well as highlighting the importance of evaluating the interactive product in addition to it being an iterative process.

11.1 Lifecycle Models for Interactive Design and HCI

11.1.1 Waterfall Model (Software Engineering)

The traditional and oldest lifecycle model which was and still is widely used by designers is the 'waterfall' model (see Figure 11.1).

Generally, this model is used in software engineering where it is considered being a rather basic model.

It consists of five phases (requirement analysis, design, code, test, and maintenance).

These five phases or steps are rigid in structure and order as one phase cannot be completed if the phase prior to it is not complete.

Some consider this rigidity as a disadvantage of the waterfall model as designers cannot work on different aspects of the design process at the same time using this model.

All their resources are put into a specific phase and once this phase is complete their resources are transferred to the next phase.

The ability to work on different phases at the same time can prove to be time saving.

This model however does not facilitate this.

This said being a rigid model makes it very easy to follow and manage.

11.1 Lifecycle Models for Interactive Design and HCI

Working on more than one phase at a time may cause confusion and a lack of management may arise, this model prevents this.

Along with its rigidity, one of the waterfall model's key strengths is the documentation that occurs after every phase; documentation recording the various activities that took place during that specific stage of the model ranging from designers' interactions with one another to various code details that are used.

This documentation acts as a detailed record of the accomplishments of each and every stage of the model which prevents confusion and misunderstandings.

Finally, a major weakness of this model is the lack of or inability to go back a phase once a designer has moved on to the next phase.

The considerable amount of documentation that is carried out after every phase makes the process of going back a phase very time consuming and un-efficient.

This lack of iterative procedures means a lack of ability to react to the ever changing needs and wants of the final user as the final user only gets his hands on the final product after the final phase of the model has been completed.

11.1 Lifecycle Models for Interactive Design and HCI

11.1.2 Interactive Design Model

Moving away from software engineering and looking at interaction design modeling, one can instantly recognize the differences in regards to flexibility and the iteration process which the waterfall model lacks.

A simple interactive design model is shown in Figure 11.2 where the design process is user focused where the evaluation of the prototype is taken place and if the requirements are not met then a re-design is produced.

The next model (spiral model) further discusses the interactive design model.

In addition to this, the star model is also discussed which is a more HCI orientated lifecycle model.

Figure 11.2: Simple Interactive Design Model

11.1 Lifecycle Models for Interactive Design and HCI

11.1.3 Spiral Model (Interactive Design)

The spiral model, created by Barry Boehm in 1986 is a more flexible lifecycle model that focuses on key elements which the traditional waterfall model lacks.

These elements are the emphasis on risk analysis and management, prototyping and iteration.

The spiral model, unlike the waterfall model is a flexible cycle that places iteration and re-looping in the centre of its focus.

The model is divided up into four sections (determining objectives, identifying and resolving risks, development and testing, and planning).

Once the requirements or objectives of the interactive product are determined, the risks are then identified, resolved and the first prototype is developed.

This is followed by the development and testing of this prototype.

Finally, the final stage of the planning for the next loop that will be followed which take into account the changing user requirements and a second prototype is built accordingly and so on (see Figure 11.3).

11.1 Lifecycle Models for Interactive Design and HCI

This looping/repeating of the same procedures minimizes risk of failure as with every loop new requirements are identified and new prototypes are created for the user to use and offer feedback on which will go towards another loop and another prototype.

This approach involves the user more with the design process, unlike the traditional waterfall model.

Although such advantages of constant iteration is beneficial, drawbacks of the spiral model do exist as this type of lifecycle model is only suited for large projects with a considerable budget as many iterations will take place where the complexity level of the project/interactive product will be extremely high.

The issue of constantly identifying and managing risk is a beneficial but very costly procedure as it needs personnel with the right skills and techniques to correctly and efficiently carry out their work.

Finally, due to a certain lack of rigidity, procedures carried out at the different sections of the model need to be controlled by routine or system that guarantees the smooth running of the overall iterative process.

11.1 Lifecycle Models for Interactive Design and HCI

11.1.4 Star Model (HCI)

The star lifecycle model, created by Hartson and Hick in 1993 is a lifecycle model that puts all its focus on the evaluation process of the model.

Different activities such as requirements analysis, conceptual design, task analysis, prototyping, and implementation all feed into the evaluation process (see Figure 11.4).

The star model is considered by many as the most HCI orientated lifecycle model available to designers, unlike the waterfall model which is software engineering orientated.

Compared to the waterfall model, the star model is not rigid in any way, in fact, it is rather the opposite.

The various activates involved in the model can be carried out independently at any time as no order is needed.

Independent work by designers is carried out at each part of the model and then the work is combined together and evaluated.

This keeps repeating itself until the final interactive product is finalized.

This model provides designers of interactive products high flexibility.

11.1 Lifecycle Models for Interactive Design and HCI

This however does have its drawbacks as a lack of communication between the different team members for example working on different activities can result in confusion and mix ups.

On the other hand, the extensive evaluation that is carried out ensures the changing requirements are constantly being met which in turn minimizes the risk of failure.

Figure 11.4: Star Model