Activity Definition: Inputs Activity Definition

.2 Arrow Diagramming Method ADM ADM is a method of constructing a project schedule network diagram that uses arrows to represent activities and connects them at nodes to show their dependencies. Figure 6-6 shows a simple network logic diagram drawn using ADM. This technique is also called activity-on-arrow AOA and, although less prevalent than PDM, it is still used in teaching schedule network theory and in some application areas. ADM uses only finish-to-start dependencies and can require the use of “dummy” relationships called dummy activities, which are shown as dashed lines, to define all logical relationships correctly. Since dummy activities are not actual schedule activities they have no work content, they are given a zero value duration for schedule network analysis purposes. For example, in Figure 6-6 schedule activity “F” is dependent upon the completion of schedule activities “A” and “K,” in addition to the completion of schedule activity “H.” 6 .3 Schedule Network Templates Standardized project schedule network diagram templates can be used to expedite the preparation of networks of project schedule activities. They can include an entire project or only a portion of it. Portions of a project schedule network diagram are often referred to as a subnetwork or a fragment network. Subnetwork templates are especially useful when a project includes several identical or nearly identical deliverables, such as floors on a high-rise office building, clinical trials on a pharmaceutical research project, coding program modules on a software project, or the start-up phase of a development project. .4 Dependency Determination Three types of dependencies are used to define the sequence among the activities. • Mandatory dependencies. The project management team determines which dependencies are mandatory during the process of establishing the sequence of activities. Mandatory dependencies are those that are inherent in the nature of the work being done. Mandatory dependencies often involve physical limitations, such as on a construction project, where it is impossible to erect the superstructure until after the foundation has been built, or on an electronics project, where a prototype must be built before it can be tested. Mandatory dependencies are also sometimes referred to as hard logic. A Guide to the Project Management Body of Knowledge PMBOK ® Guide Third Edition 2004 Project Management Institute, Four Campus Boulevard, Newtown Square, PA 19073-3299 USA 133 • Discretionary dependencies. The project management team determines which dependencies are discretionary during the process of establishing the sequence of activities. Discretionary dependencies are fully documented since they can create arbitrary total float values and can limit later scheduling options. Discretionary dependencies are sometimes referred to as preferred logic, preferential logic or soft logic. Discretionary dependencies are usually established based on knowledge of best practices within a particular application area or some unusual aspect of the project where a specific sequence is desired, even though there are other acceptable sequences. Some discretionary dependencies include preferred schedule activity sequences based upon previous experience on a successful project performing the same type of work. • External dependencies. The project management team identifies external dependencies during the process of establishing the sequence of activities. External dependencies are those that involve a relationship between project activities and non-project activities. For example, the testing schedule activity in a software project can be dependent on delivery of hardware from an external source, or governmental environmental hearings may need to be held before site preparation can begin on a construction project. This input can be based on historical information Section 4.1.1.4 from previous projects of a similar nature or from seller contracts or proposals Section 12.4.3.2. .5 Applying Leads and Lags The project management team determines the dependencies Section 6.2.2.4 that may require a lead or a lag to accurately define the logical relationship. The use of leads and lags and their related assumptions are documented. A lead allows an acceleration of the successor activity. For example, a technical writing team can begin writing the second draft of a large document the successor activity fifteen days before they finish writing the entire first draft the predecessor activity. This could be accomplished by a finish-to-start relationship with a fifteen-day lead time. A lag directs a delay in the successor activity. For example, to account for a ten-day curing period for concrete, a ten-day lag on a finish-to-start relationship could be used, which means the successor activity cannot start until ten days after the predecessor is completed. A Guide to the Project Management Body of Knowledge PMBOK ® Guide Third Edition 134 2004 Project Management Institute, Four Campus Boulevard, Newtown Square, PA 19073-3299 USA