Once you have written the WBS, the next step consists in estimating the effort required to perform the described tasks. This is often done in two steps since it is not easy to determine directly the effort (or the cost) from the task. The first step aims defining possible measures that will help in performing estimations during the second step. Typical measures often concern size
. In the example initiated in a previous post
, the major part of the work is to write a specification from a requirement document. The first measure that comes to mind is the number of pages. This is a possible measure but not enough detailed in our case.Requirement documents are organized in requirements that have to be well defined, with an equivalent granularity level. Moreover, requirements are interesting because they lead the work. Once all requirements are treated , the work is finished. In consequence, requirements will be our main measure unit of the work to do.Usually, requirements are easily identifiable since they have an ID compliant to a convention. For example requirements ID can be put between brackets, in this case a simple regexp tool can be used to count them (I’m writing a reminder to work on a post concerning requirement analysis). This measure is a first level of measurement, it may be sufficient in most of the cases, however, the model can be refined by providing additional information like the complexity level of a requirement (simple, medium or complex). This additional information will permit to estimate more accurately the workload required to treat a requirement. A simple requirement will require less effort than a complex.For other tasks of the WBS, measures have also to be defined. For all activities requiring meetings, the number of meeting is a good measure. Some activities directly linked to the writing can be deduced from the main task. For example, reviewing a document will be directly linked to the size of the document, itself being linked to the number of requirements. Finally, the cost of some tasks is equal whatever the amount of work produced. This is the case for deliveries. For these tasks, measure is not required if you already know the time it takes to deliver a document.
When defining measure, it is important to write not only the result obtained but the definition of the measure. The definition of the measure will be used as the base of the estimation hypothesis (my estimation is based on the number of requirements) and it will permit to analyze and refine estimations for next works. Establishing measures is an activity described in the Measurement and Analysis (MA) process of CMMI for Development.
Here is the result of a WBS sheet with measure definition:
The second step of the estimation process (using measures to deduce workload) will be treated in a next post.