Summary
Project networks describe the interrelated tasks that make up a project. The purpose of representing tasks as a network is to clarify the precedence relationships among tasks, and allow for critical path analysis which determines early and late start and finish times for each task.
Tasks may compete for resources, introducing another source for delay in task and project completion.
In addition, multiple projects may take place within the same network. Now, rather than representing a project, the network represents the capability to execute projects. Simulation is an effective tool for analysis of work flow through such networks.
Key Model Issues
The key concept in representing task networks in SC Builder is the milestone. Each precedence relationship between tasks is represented by a milestone. Each milestone has a prior task and a following task. When a task is complete it generates one token for each precedence milestone for which it is the prior task. In order for a task to start, all prior milestones must be available. When they are, the task removes one token for each prior milestone. Once they have started, there are many alternatives for modeling task durations. If tasks require resources, they must grab them before their duration clock begins to tick.
Major issues may revolve around resources that are required for task groups. For example, in order to repair a car, a garage and a lift may be required. These resources are not grabbed by individual tasks but rather by the group. This suggests the ability to define a task hierarchy. An alternative approach to multi task resource assignments is to allow a task to grab but not release a resource. The resource would be released by a downstream task. This approach is fraught with the peril that a resource might never be released if it is not released by the task that grabbed it.
Strategic Assessment
The following provides links to articles within this document that address strategic assessment issues related to this case study:
- Network capacity
This model captures the rate of execution of tasks with precedence relationships. Task execution is constrained not only be completion of prior tasks by y availability of assigned resources.