The Project Basis of Design

All changes commonly share a set of characteristics: a starting point, a journey and an end point.

Projects have starting points, journeys and end points, and exist solely as a means of bringing about change. The ultimate objective is to deliver something which, firstly, closes the gap between an operational need and delivered capability, and which, secondly, didn't previously exist. There is always a point of departure, a period of transition and a resulting product.

Like a journey which requires a map, changes require a plan. A design project's version of a plan is the basis of design.

The project Basis of Design (BoD) or “design basis” is a baseline project document which establishes the framework for all decisions related to engineering design by outlining the founding principles and necessary assumptions. As a compendium of instructions, information, and data, it ascribes design references, describes the past design decisions already taken, proscribes potential choices that could be made, and prescribes future decisions that must be made. While not exhaustive, the BoD is generally a starting point for preparing other project-specific documents such as discipline design criteria, equipment specifications, technical specifications, and design drawings. 

The basis of design could be arranged as three groups of elements roughly associated with the stage of development, namely:

- What we have and do not have at the beginning of the design development process?
- What is allowed and not allowed during the design development process?
- What we want to achieve by the end of the design development process?

These broad groups are in turn made up of at least 9 factors, namely:

- Design concepts
- Design commissions
- Design challenges
- Design criteria
- Design customs
- Design classes
- Design compliance
- Design capabilities
- Design compatibilities

An essential aspect of the BoD is describing what finished looks like, i.e. what "done" means. This description is deceptively nuanced.

Design and development for large, complex systems never follow a complete, uninterrupted gestation from embryo to birth. Approval gates and project milestones punctuate the process, dividing the endeavour into conceptual, feasibility, and detailed design. If we had to embark on a road trip, the final destination is the finish point. However, we plan to take breaks along the journey and revisit the GPS and map. These are interim destinations which similarly occur throughout design development.

The basis of design has to consider the final goal and the interim objectives, two different but related versions of "finished". For example, when the feasibility stage is completed, the delivered design is not fully mature at this point. It is only advanced enough for the current phase of evaluation. The basis of design is, therefore, a live document that must balance the project with the stage and get updated throughout the development process.