Control Accounts and Work Packages
The design of any earned value system must focus on the points at which a piece of work is defined, scheduled, budgeted, and tracked. These represent natural control points for cost and schedule planning. Throughout Cobra, these control points are referred to as control accounts and, at a lower level, work packages.
Although common to the EVMS environment, this terminology is not mandatory in Cobra. In fact you may label these control points using any descriptions appropriate to your organization. Nonetheless, we will use these terms here for the sake of convenience.
A control account is usually defined as the intersection of the project WBS and OBS. In effect, each control account defines the work that is to be performed and who will perform it.
In the EVMS environment, the control account is usually the lowest level at which information is reported to the client and the highest level at which actual costs can be entered.
Control Account Keys
How you choose to identify your control accounts in Cobra is, in many respects, the key to developing a successful reporting system. Each control account in a project must be assigned a unique ID or “key” that can consist of up to three different fields. Any key field can be associated with a code file, in which case Cobra validates the key at the time that the cost account is created. Typically, control account keys are created by combining a WBS code and an OBS code, but this approach is not required by Cobra.
Basing the control account keys on one or more user-defined code files allows for tremendous reporting flexibility and power. Provided that at least one key field is associated with a code file, control account information can be rolled up to any level in that structure. Thus, the use of WBS codes as control account keys allows you to summarize project information to any level of your WBS. If you want to be able to report in multiple dimensions (for example, according to both work content and organizational responsibilities), you must make sure that multiple control account keys are set up that allow you access to the appropriate code file.
Associating code files with control account keys allows Cobra to validate entries against existing code files. It is possible, for example, to use this validation feature to assure that a control account has been set up with a valid charge number.
It is also possible to use a third field (which may or may not be associated with a code file) as part of the control account key. This approach has the advantage of allowing for more compact control account identifiers as well as permitting the creation of multiple control accounts at any WBS/OBS intersection.
Work Packages
Although a control account can serve as a suitable control point for the purpose of reporting to clients, it is too broad to be used effectively as a means of measuring performance. For this we need access to a lower level of detail — the work package. There are no limits to the number of work packages that can be assigned to a single control account.
Although you can plan and budget work at both the control account and work package levels (budgeted control accounts are usually referred to as “planning accounts”), Cobra calculates earned value at the level of the work package only.
A work package is defined as a brief, discrete amount of work. In practice, the duration of the work package should depend on the level of detail you plan to maintain in Cobra. In planning the duration of a work package, it is important to maintain a balance between two extremes:
- If the work package is too short, the value gained from the extra detail does not outweigh the time it takes to maintain the data. For example, you would not want to enter a work package that is shorter in duration than the time it takes you to enter, status, and report on the work package.
- If the work package is very long and needs to be statused over multiple periods, errors can be introduced in the calculation of earned value.
Milestones
You can also define multiple milestones for each work package as a means of measuring progress.
Unlike control account and work package keys, however, milestone key fields cannot be associated with a code file for reporting purposes.
Collecting Actual Costs
Cobra allows you to enter actual costs at either the control account or the work package level. However, most project managers prefer to enter actual costs at the control account level. This reduces the number of charge numbers in the accounting system, making it easier to ensure that the correct charge number is used. The goal of a Cobra implementation is to create an environment that is easy to maintain while still providing the information required to properly manage projects.
In a typical implementation, control accounts may have durations that vary from about six months to a year; the work packages within these control accounts may have durations of about four to six weeks. Storing costs at the cost account level makes it easy to perform the detailed budget planning that is need to calculate earned value accurately while minimizing the number of required charge numbers.
This does not mean that you cannot report to the customer at a higher level. The flexibility built into Cobra allows you to report costs at any level you choose.