network analysis

Activity constraints can be imposed when there is a need to control the start or finish of an activity in a project schedule. In this article, three types of commonly used activity constraints will be discussed along the following dimensions:

A project network consists of a set of nodes and arcs. A project contains activities and precedence relations to model technological relations between pairs of activities. A project network can be represented in two formats, which is the topic of this article, as follows:

A project network consists of a set of activities, represented as nodes in a network between which links are drawn to represent the technological precedence relations between these project activities (see “Activity links: How to add precedence relations between activities?”). 

These precedence relations can be one out of four types (start-start (SS), start-finish (SF), finish-start (FS) and finish-finish (FF)), with a positive, zero or negative time-lag to express a minimal or a maximal time window between two activities.

A project network consists of a set of activities, represented as nodes in a network between which links are drawn to represent the technological precedence relations between these project activities. In figure 1, a finish-start precedence relation between activities 1 and 2 is used to imply that activity 2 can not start earlier than the finish of activity 1.