Costing assumptions

TIBCO Nimbus®  makes certain assumptions when calculating process costs.

•If multiple resources are attached to a single activity, all resource costs will be calculated (unless a resource is specifically set not to be included in any costing calculations). For example, if 3 resources are attached to an activity that takes 4 hours to complete, the total work hours for the activity is 12 hours.

•If no resources are associated with a map, TIBCO Nimbus®  will assume that one resource is associated with each activity, thereby allowing durations and volumes to be calculated in order to obtain the FTEs.

•If probabilities are introduced, TIBCO Nimbus®  will assume that multiple paths are exclusive. For example, if two paths exist, A and B, it is assumed that the process will take either path but not both paths. Therefore probabilities may need to be adjusted to account for this.

For example, the probability that the process will take path A is 20% and path B is 40%.

The probability of the process taking path A OR path B is 20% + 40% = 60%.

The probability of the process taking path A AND path B is 20% x 40% = 8%.

To account for this you can split the extra probability of the process taking path A AND path B, i.e. the 8%, between the probability between path A and path B. Therefore, the probabilities of the process taking path A then becomes 24% and path B 44%.

Note: If you are working out the probabilities from a study of volumes of transactions along different paths, these volumes will account for any possible effect of passing along both or all of the various paths at the same time.

TIBCO Nimbus®  also allows the probabilities of a path to be more than 100% to reflect manual interpretations of the AND possibilities; however the probability of any given activity occurring is capped at 100%.

•TIBCO Nimbus® uses predefinable working periods to translate a working day into hours, a working week into days and a working year into weeks. The defaults are set at a 8 hour day, 5 days per week and 48 weeks per year. For instructions on modifying these values see Setting costing defaults.

•If feedback loops are implemented, TIBCO Nimbus®  requires users to identify the feedback loop probabilities. Multiple feedback loops that terminate at a single activity cannot be calculated as TIBCO Nimbus®  does not know which feedback loop to calculate first. This requires a business understanding of the diagram in order to make the decision. Therefore, feedback loops need to be broken up by feedback breaks, which is achieved by creating 2 activities (an input and an output) and manually updating the volume of the output activity based on the calculated volume of the input activity. The output value will need to be adjusted as this will affect the value in the input box.

The rules for tuning multiple feedback breaks in a diagram are as follows:

•Ensure the Perform Calculations flag is set on the Basic Costing panel.

•Ensure both pairs of activities in all feedback breaks are approximately equal (+/1 100).

•Identify the largest feedback break (or the one that has the most impact on the map) and set them to within +/- 10. Then look at the other feedback breaks and get them within +/- 10. Once this is done, modify the feedback breaks to get them exactly correct.

See Probability feedback loops for more information.