Process Models in Design and Development

Model scope dimension

The first dimension of the framework considers the scope, i.e., breadth of coverage of a model. This dimension is important because the framework organises models that range from an individual's mental activities during design through to complex development programs that may involve thousands of participants and multiple tiers of suppliers. These situations have quite different characteristics, which are reflected in the models.

Considering the relationship between these situations, Hall proposed a two-dimensional perspective of development projects in which the stage-based structure of a project's lifecycle is orthogonal to an iterative problem-solving process that occurs within each stage. Asimow similarly described the essentially linear, chronological structure of a project as its morphological dimension, and the highly cyclical, iterative activities characteristic of designers' day-to-day activities as the problem-solving dimension. Blessing refers to models concerned with Asimow's morphological and problem-solving dimensions as stage-based and activity-based, respectively. She also notes the existence of combined models which prescribe well-structured, iterative activities within each stage. Other models such as the Task DSM represent individual tasks and their interrelationships. Their focus is in between the iterative problem-solving process and the overall structure of the DDP.

Combining these ideas, the model scope dimension of the framework comprises three categories:

• Micro-level models focus on individual process steps and their immediate contexts.
• Meso-level models focus on end-to-end flows of tasks as the design is progressed.
• Macro-level models focus on project structures and/or the design process in context. This can include the overall form of a project or program, organisational and managerial issues relating to a DDP situation, and/or the interaction between the DDP and the context into which a design is delivered.