Event chain methodology is a network analysis technique that is focused on identifying and managing events and relationship between them (event chains) that affect project schedules. It is an uncertainty modeling schedule technique. Event chain methodology is an extension of quantitative project risk analysis with Monte Carlo simulations. It is the next advance beyond critical path method and critical chain project management. Event chain methodology tries to mitigate the effect of motivational and cognitive biases in estimating and scheduling. It improves accuracy of risk assessment and helps to generate more realistic risk adjusted project schedules.
History
Event chain methodology is an extension of traditional Monte Carlo simulation of project schedules where uncertainties in task duration and costs are defined by statistical distribution. For example, task duration can be defined by three point estimates: low, base, and high. The results of analysis is a risk adjusted project schedule, crucial tasks, and probabilities that project will be completed on time and on budget. Defining uncertainties using statistical distribution provide accurate results if there is a reliable historical data about duration and cost of similar tasks in previous projects. Another approach is to define uncertainties using risk events or risk drivers, which can be assigned to different tasks or resources. Information about probabilities and impact of such events is easier to elicit, which improves accuracy of analysis. Risks can be recorded in the Risk register. Event chain methodology was first proposed in the period of 2002–2004. It is fully or partially implemented in a number of software application. Event Chain Methodology is based on six principles and has a number of outcomes.
Principles
Moment of risk and state of activity
Activities (tasks) are not a continuous uniform procedure. Tasks are affected by external events, which transform an activity from one state to another. One of the important properties of an event is the moment when an event occurs during the course of an activity. This moment, when an event occurs, in most cases is probabilistic and can be defined using statistical distribution. The original state is called a ground state, other states are called excited states. For example, if the team completes their job on activity, they can move to other activities. The notion of an activity's state is important because certain events can or cannot occur when activity is in certain state. It means that the state of an activity is subscribed to the events. Events can be local, affecting particular tasks or resources, or global affecting all tasks or resources.
Event chains
Events can be related to other events, which will create event chains. These event chains can significantly affect the course of the project. For example, requirement changes can cause an activity to be delayed. To accelerate the activity, the project manager allocates a resource from another activity, which then leads to a missed deadline. Eventually, this can lead to the failure of the project. It could be different relationship between events. One event can trigger one or multiple events.
Events can be correlated with each other without one triggering another one. In this case if one risk has occurred, another one will occur and vice versa. One event assigned in one activity can execute another activity or group of activities. In many cases it the execution of risk response plans. For example, event “structural defect is discovered” can cause one or many activities “Repair”. Events can cause other events to occur either immediately or with a delay. The delay is a property of the event subscription. The delay can be deterministic, but in most cases, it is probabilistic. Also risks can be transferred from one activity to another. To define event chains, we need to identify a "sender", the event that initiates the chain of events. The sender event can cause one or more events that effect multiple activities. These are called "receiver" events. In turn, the receiver events can also act as sender events.
Event chain diagrams
Event chain diagram is a visualization that shows the relationships between events and tasks and how the events affect each other. The simplest way to represent these chains is to depict them as arrows associated with certain tasks or time intervals on the Gantt chart. Here are a few important rules: