Scheduling of Activities

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Scheduling follows estimates of the time for each activity and is a very crucial step in the Planning Phase since a plan can only show the feasibility of achieving its objectives when the activities are put together in a schedule that defines when each activity will be carried out.


In order to proceed with scheduling you need the following inputs:

The Activities sequence and dependencies (refer to
Activity duration estimates (refer to
Resource requirements and resource availability (refer to 7.4.2). The number of people who will be available to do the work should be established. Any specific information like names, percentage availability, and availability in certain periods starting from …and ending at…. should also be noted. For preliminary schedule you may only need to know that X senior consultants will be available in a certain time period, whereas in the final schedule you need to know exactly who these senior consultants will be.
Constraints. There are two major categories of time constraints that you should consider during schedule development. First, imposed dates on activity starts or finishes which can be used to restrict the start or finish to occur either no earlier than a certain date or no later than a specified date (e.g in case of projects co-funded by the EU (target 2) for the present programming period must be completed before the next programming period starts). Second, the project owner or the project stakeholders may request that a certain deliverable be completed by a specified date
Milestones. Milestones are key events that provide the basis by which the project implementation will be monitored and managed. The simplest milestones are the dates estimated for completion of each Activity, for submission of deliverables, or for getting approval by the client (acceptance of the product produced).
Time leads and lags: There are cases that a dependency between two activities may require specification of a lead or lag to accurately define the relationship. (e.g. the compilation of Chapter 3 of the Public Procurement Best Practice Guide concerning the preparation of the tender documents may start 10 days before the completion of Chapter 2 dealing with the procurement strategy. Accordingly, a two week delay (lag) may be necessary between the completion of the training material and the training delivery).

There are many different approaches to scheduling. The steps can either be done manually or a computer tool (software) can be used. Project Management Software (like Microsoft Project, Primavera etc) is widely used to assist with schedule development.

The project schedule includes at least the start and finish dates of each activity and their duration (in days, weeks, months, etc). It can also include information concerning the responsible for the implementation of each action. It may be presented in summary form or in detail; graphically or in a tabular form. More specifically, the following formats are the ones most commonly in use:

Bar charts, also called Gantt Charts5 [ The Gantt chart was first developed by Charles Gantt in 1917. ]., A Gantt chart focuses on the sequence of tasks necessary for the completion of a certain project. Each activity/task is represented as a horizontal bar on an X-Y chart. The horizontal axis (X axis) is the time scale over which the project will be implemented. Therefore, the length of each activity/task bar corresponds to the duration of the activity/task or the time necessary for its completion.

Arrows connecting the activities/tasks represent the relationship between the activities/ tasks they connect.

The Gantt chart is an excellent tool for quickly assessing the status of a project, therefore is suitable for management presentations, for status reports and for communicating information regarding the progress of a project to all stakeholders.

The Gantt chart can be developed using Software Packages like MS Project, Primavera Project Planner (P3), Project Scheduler (PS8), etc.

Project Network Diagrams with dates. This format shows the activities’ sequence and dependencies as well as the start and finish date of each activity.  A project network diagram is often referred to as a PERT chart.

PERT6 [ PERT was developed in the late 1950’s for the U.S Navy’s Polaris project having thousands of contractors. ] chart, is a network-based aid for planning and scheduling the many interrelated tasks in a large and complex project. Common Software Packages like MS Project, Primavera Project Planner (P3), and Project Scheduler (PS8) can create a PERT chart from a Gantt chart.

PERT charts are more complicated than the Cantt charts and should be avoided in management presentations.

Milestone charts. This type normally presents the defined milestones, that is the start and completion dates of the production of the deliverables.


Example 7-7: Gantt and PERT charts for the Project “Improving the Implementing capacity of the Cypriot Authorities”

Project: “Improving the implementing capacity of the Cypriot Authorities”.

Using MS Project to prepare the Time Schedule for the above mentioned project (and especially for the Activities 2 “Compilation of an Action Plan for PPD”, 3 “Compilation of the Public Procurement Best Practice Guide” and 4 “Training design and execution”), we can have the following types of charts.

Gantt chart.

As mentioned above, this chart shows the activities and tasks to be performed, the prerequisites and dependencies between them, the start and finish date as well as the duration of each task. The time scale on the top can be easily changed and therefore in case of projects having a duration of a few months the units of the major time scale could be months while the unit of the minor scale could be weeks or days.

PERT chart

In this chart each activity is being presented as a non-rectangular parallelogram, whereas the tasks are presented as rectangular parallelograms. Each task presents its duration, start and ending date.

The tasks shown in red line indicate which the critical path is and therefore these are the tasks that must be completed in time for the project to finish on schedule. Definition of the critical path and guidance related to its use and importance is given in the following paragraph.




In case that instead of using a Software Package to produce the charts, you decide to do it manually, you will end to a graph similar to the following:









In Annex 7-1/ Sheet "Activities Schedule" a tool for preparing a project schedule in excel format is presented. In addition a completed example (for the Project “Improving the implementing capacity of the Cypriot Authorities) is also presented in the Sheet “Activities Schedule Example”. This tool is used for developing a “baseline schedule”, as well as for tracking the activities’ progress during the project implementation period (refer to 7.5.1).

Critical Path

The critical path is the series of tasks that dictates the calculated finish date of the project. That is, when the last task in the critical path is completed, the project is completed. If it is important for a project to finish on schedule, special attention should be given to the tasks on the critical path and the resources assigned to them.

Each task on the critical path is a critical task. In a typical project many tasks have some slack and can therefore be delayed a little without affecting the project finish date. Those tasks that cannot be delayed without affecting the project finish date are the critical tasks.

A task becomes critical when it meets any one of the following conditions:

There is zero slack on the task
It has a Must Start on or Must Finish on date constraint
It has a finish date that is the same or beyond its deadline date.

Because of the important relationship between critical tasks and the project end date, the Project Manager must always be cognizant of the critical path and understand how it is affected when tasks are being modified to resolve over allocations, costs are being adjusted, the scope is being revised or changes are made to the Project Schedule.  

Microsoft Project defines a task as critical if it has zero days of slack, but the user of the Software Package (the Project Manager) can change the definition of a critical task. For example he can define a task as critical if it has one or two days slack. This can be helpful if the Project Manager wants to be alerted to tasks becoming critical when there are still one or two days of buffer. The critical path is shown in both Gantt and PERT charts produced by Software Packages. In case of MS Project, the critical path is being highlighted when using the Detail Gantt view or the Network Diagram view (PERT).

If the Project Manager wishes to bring in the project finish date, he needs to bring in the dates of the critical path tasks. This is also known as “crashing”. In order to do this, the Project Manager can:

Shorten the duration of a task on the critical path
Change a task constraint to allow for more scheduling flexibility
Break a critical task into smaller tasks the implementation of which can be assigned to different resources
Revise the dependencies between the tasks to allow more flexibility in scheduling
Schedule overtime
Assign additional resources to work on critical paths.

However, the Project Manager has to be aware that if he brings in the dates of the primarily critical path, a different series of tasks could become the new critical path. In this case this new series must be tracked and monitored very closely to ensure the expected/desired finish date.

In Annex 7-2 guidance7 [ Part of Chapter 11: PERT for Project Planning and Scheduling from Practical Optimization: a Gentle Introduction written by Professor John W. Chinneck, Carleton University, Canada’s Capital University. ] on how to find the critical path of a project without using a Software Package is being provided.

© 2007 Republic of Cyprus, Treasury of the Republic, Public Procurement Directorate
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