What is Inception? - UML

Most projects require a short initial step in which the following kinds of questions are explored:

  • What is the vision and business case for this project?
  • Feasible?
  • Buy and / or build?
  • Rough unreliable range of cost: Is it $10K - 100K or in the millions?
  • Should we proceed or stop?

Defining the vision and obtaining an order - of - magnitude (unreliable) estimate requires doing some requirements exploration. However, the purpose of the inception phase is not to define all the requirements, or generate a believable estimate or project plan.

At the risk of over - simplification, the idea is to do just enough investigation to form a rational, justifiable opinion of the overall purpose and feasibility of the potential new system, and decide if it is worthwhile to invest in deeper exploration (the purpose of the elaboration phase).

Most requirements analysis occurs during the elaboration phase, in parallel with early production - quality programming and testing.

Thus, the inception phase should be relatively short for most projects, such as one or a few weeks long. Indeed, on many projects, if it is more than a week long, then the point of inception has been missed: It is to decide if the project is worth a serious investigation (during elaboration), not to do that investigation.

Does this Analogy Help?

In the oil business, when a new field is being considered, some of the steps include:

  1. Decide if there is enough evidence or a business case to even justify exploratory drilling.
  2. If so, do measurements and exploratory drilling.
  3. Provide scope and estimate information.
  4. Further steps...

The inception phase is like step one in this analogy. In step one people do not predict how much oil there is, or how much cost or effort is needed to extract it. Although it would be nice to be able to answer "how much" and "when" questions without the cost and effort of the exploration, in the oil business it is understood to not be realistic.

In UP terms, the realistic exploration step is the elaboration phase. The preceding inception phase is akin to a feasibility study to decide if it is even worth investing in exploratory drilling. Only after serious exploration (elaboration) do we have the data and insight to make somewhat believable estimates and plans. Therefore, in iterative development and the UP, plans and estimates are not to be considered reliable in the inception phase. They merely provide an order - of - magnitude sense of the level of effort, to aid the decision to continue or not.

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