Linked Activities in Planning and Scheduling Optimization

Linked Activities in PSO

Activities in Planning and Scheduling Optimization (PSO) can be setup with links to each other. This can be used to setup the order in which the activities have to be conducted. There are two forms of activity links that are handled in the scheduling engine.

Pre-Requisites: Pre-Requisite linking is defined by that a certain activity needs to be performed before the next activity can start. When two, or more, activities have pre-requisite dependencies to each other the scheduling engine will schedule the activities in the order accordingly to the dependencies. This so that the activities needed to be finished before others can start will be scheduled first in the scheduled.
Co-Requisites: Co-Requisite linking is defined by that certain activities needs to be performed at the same time. When two, or more, activities have co-requisite dependencies to each other the scheduling engine will schedule the activities so that they will start at the same time.

Pre-requisite linking between Work Tasks

Work Tasks that are set as dependent to each other (through a Finish-to-Start relationship) is the base for setting the pre-requisites for the activities sent to PSO. It is possible to define on each work task if it is dependent on that one, or more, work tasks are to be finished before it can be started. The dependencies can only be set up between work tasks that belongs to the same work order.

When dependencies are defined between work tasks each activity for the work tasks will be linked accordingly when the information is sent to the scheduling engine. An example is a work order with two work tasks. Work task 1 must be finished before work task 2 according to the dependency set up between them in IFS. Each of these two work tasks has one resource demand defined for one resource (one PSO activity per work task). When the work tasks are sent to PSO a link will be created between the two activities according to the work task dependency. The activity for work task 2 must then be scheduled after the activity for work task 1.

Co-requisite linking within a Work Task

The basic concept for a work task is that all the work to be done within the work task is to be done at the same time. If there are multiple resource demands (multiple PSO activities) defined within one work task it means that these resources would do the work task at the same time. An example is one work task that has a two resource demands, one electrician and one mechanic needs to attend the work. These two resource demands corresponds to two activities in PSO. Because of that they are to perform the work at the same time the activities will be set with a co-requisite link when sent to the scheduling engine. In scheduling these two activities will then be scheduled to start at the same time.

Co-requisite linking will only be set up when more than one resource is demanded for a work task. It is not possible to set up co-requisite linking between activities if they do not belong to the same work task.

Sending linked activities to PSO

If a dependency is defined between two work tasks (with one activity each) and one of the work tasks are set to the status defined in the scheduling dataset for when to send work task activities to PSO, both work task activities will be sent to scheduling. Even if one of the work tasks is not in the status for it to be sent to PSO the activity will anyway be sent when it is linked to another work task that has the status to be sent do scheduling. This is done to always keep the linking of the activities in the scheduling engine. If one of the activities in a linked chain would not be sent, the scheduling engine cannot create the correct linking between the activities.

The activity that belongs to the work task that is not in the "Schedule from Work Task Status" is sent as "do not schedule". First when all the work tasks is in the correct status according to "Schedule from Work Task Status" it will be possible for the activities to be scheduled by PSO, according to the linking.

Linked activities in Scheduling Workbench

In the Scheduling Workbench on the Activities page the links between activities are displayed with a grey line. Both Pre-Requisite and Co-Requisite links will be displayed.

In addition to that there is the possibility to analyze which other activities that are linked to one activity. If opening the activity details for an activity in the Scheduling Workbench and there is other activities linked the menu option Linked Activities is enabled. In the detail page for the linked activities both Pre-Requisite and Co-Requisite activities will be listed.

Linked activities with Appointment Booking

Booking appointments for a work task will also consider the activity links. For a work task that is dependent to another work task with a pre-requisite link, this link will be considered in the appointment booking process. Sending an appointment request for a work task to the Appointment Booking Engine will also include all the activities that are linked to the activities for the work task to be booked. An example would be having two work tasks on a work order, each with one resource demanded (one PSO activity). Work task 1 needs to be completed before work task 2 can be started, defined through a finish-to -start dependency between the work tasks. An appointment is to be booked for work task 1. When sending the appointment request to the Appointment Booking Engine for the activity of work task 1 the linked activity for work task 2 is then also sent in the process. This is done to get a correct result for when there are available appointment slots to book. As an appointment is performed on the work task level this means that also co-requisite links will apply in the appointment booking process if there are multiple resources demanded for the work task.