Dependency in project management

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Developed by Behzad Sanie



Dependency in project management means that one activity is depended to another.[1] The purpose of dependency determination is indicating the type of dependency that makes a logical relationships between predecessor and successor activities in project time managing. Four types of dependency defined as: Finish-to-start (FS), Finish-to-finish (FF), Start-to-start (SS), Start-to-finish (SF).[2] The precedence diagramming method (PDM), as an example of the application of dependency, includes the four types of independencies or logical relationships. Dependency and activity sequence have also significant application in project planning that is known as product-based planning. The activities and dependency between them need to be identified to illustrate a complex picture of what a project manager has ahead. The two type of dependency in planning procedure is internal and external. [1]


Figure 1: Sequence of activities in project time management. Inspired by PMBOK[3]

In project time managing, defining the sequence and dependency of the activities is essential for documenting and recognising the relationship between each activities. The point is defining a logical sequence between tasks to do and increase efficiency during the project limitations. The sequence activity process includes inputs, tools and techniques, and output. (Figure 1) The input will be plan of scheduling management, list of activity, attribution of activity, milestone, scope and definition, environmental factors and organisation assets. The application tools and techniques are precedence diagramming method (PDM), dependency determination and leads & lags. The expected outputs are diagram of project schedule network and update of project documents.[3]

Figure 2: requirement step in Product-based planning. Inspired by Prince2[1]

Identifying the activities and dependency between them has a significant role in product-based planning. The procedure is finding first the final products requirements and then relevant activities, dependencies and the resource required for ending the project.[1] For producing product-based planning, few sequence steps required which first some need to accomplish then starting the next step.(Figure 2) Design the plan is the prerequisite step in Product-based planning procedure. Define and analyse the products, identifying activities and dependencies, prepare estimates and prepare the schedule are the following steps that run parallel with analysing the risks. Consolidation of the plan is the final step and accomplished by documenting it. [1]

Sequence Activities

The relationships between the activities of a project can be detected and documented in a process known as Sequence Activities, which are capable of considering the rational sequence of work and all project limitations to achieve the highest efficiency. At least a predecessor having a logical relationship of finish-to-start or start-to-start as well as minimum one successor having a logical relationship of finish-to-start or finish-to- finish in every activity and milestone, except for the first and last ones. A realistic and achievable project schedule should be considered in the design of logical relationships, which might be essentially supported using lead or lag time between the activities. In this context, project management software or manual or automated approaches can be beneficial in sequencing.

Inputs required in sequence activities

1. Schedule Management Plan (SMP): The SMP is a pre-project preventive thinking to identify several points, including the scheduling process involved in the project, thus helping the sequence activities.

2. Activity List : The activity list contains a critical pathway and basically a detailed documentation of all schedule activities required and sequenced for a particular project. The sequence activities can be affected by the dependencies and limitations that exist on the path to these activities.

3. Activity Attributes : Activity attributes generally refer to active components associated with an activity, which may be pivotal for sequencing for details like events, predecessors or successor.

4. Milestone List : The milestone list as a project management document may schedule all specific project milestones influencing sequence activities.

5. Project Scope Statement: The project scope statement is a good mean to describe the key deliverables of a project, including product properties involved in sequence activities like physical lineament of a project being implemented or the nature of a software project. Other scope statements of project can detail constraints and assumptions associated with sequence activities. Although these are mostly recorded in the activity list, their accuracy is explored as product scope description.

6. Enterprise Environmental Factors: The success of sequence activities is depended on either internal or external enterprise environmental factors (EEFs), including government regulations, industry conditions, 
project management information system (PMIS), scheduling tool, or work authorisation system (WAS).

7. Organizational Process Assets : Another factor contributing to the sequence activities is the organizational process assets (OPAs), including project plans of the corporate, formal or informal policies, procedures, processes, scheduling methods to developing logical relationships, and templates required for providing networks of project activities. Sequence activities can benefit from additional descriptive data provided by information related to activity characteristics in templates.

Tools and methods used in sequence activities

1. Precedence Diagramming Method (PDM)

The PDM is a common visual tool to draw a diagram of project schedule network, which depicts graphical rectangles known as nodes, connected by one or more logical relationships to represent activities in these boxes. A precedence diagram is shown with the aid of activity-on-node (AON) strategy that is applied frequently within project management software. There are four logical relationships or dependencies in the package of PDM, including finish-to-start (FS), finish-to-finish (FF), start-to-start (SS), and start-to-finish (SF), containing a predecessor activity depicted logically prior to a dependent activity of a schedule, and a successor activity as a dependent activity depicted logically after another activity of a schedule.

Figure 3: Four types of dependency in PDM. Inspired by PMBOK[2]
  • In a logical relationship of FS, a successor activity can be advanced when the predecessor activity has finished; for instance, the ceremony of awards (the successor activity) can be advanced when the competition (the predecessor activity) has elapsed.
  • In a logical relationship of FF, a successor activity can finish when a predecessor activity has finished; for instance, a document editing (the successor activity) can end when a document writing (the predecessor activity) has finished.
  • In a logical relationship of SS, a successor activity can be advanced when a predecessor activity has advanced; for instance, Level concrete (the successor activity) can be advanced when a pour foundation (the predecessor activity) has advanced.
  • In a logical relationship of SF, a successor activity can be ended when a predecessor activity begins; for instance, the first shift of security guard (the successor activity) can be ended when the second shift of security guard (the predecessor activity) begins.

The most and the least commonly used logical relationships in the PDM are FS and SF, respectively. However, all of these logical relationships are present in a complete list of the PDM.

2. Dependency determination

The characterizations considered in determining the dependencies included mandatory or discretionary and internal or external properties. Four dual attributes have been defined for the dependencies, consisting of a) mandatory external dependencies, b) mandatory internal dependencies, c) discretionary external dependencies, and d) discretionary internal dependencies.

  • Mandatory dependency refers to legal or contractual activities that must be happen inherently in the tasks, mostly including physical limitations. For example, it is mandatory to build a foundation in a construction project to continue to erect the superstructure; or a prototype in an electronics project cannot be tested until it must be produced. Another classification for the mandatory dependencies is hard logic or dependencies. Technical activities may not be placed in mandatory dependencies. Determination of mandatory dependencies in the process of sequence activities is undertaken by the project management team. The program's limitations in the scheduling tool should not be mistaken with mandatory dependencies.
  • Discretionary dependencies may be known as preferred logic, preferential logic, or soft logic. The behind principle of discretionary dependency is to understand the best strategies in certain or unusual domains of a project to reach targeted sequence in spite of other satisfactory sequences. It is essential to document all aspects of discretionary dependencies due to the presence of any total float value and limited later scheduling options. The modification or deletion of the discretionary dependencies should be taken while using fast tracking strategies. Determination of discretionary dependencies in the process of sequence activities is undertaken by the project management team.
  • External dependencies that are typically out of the control of the project team refer to a relationship between activities of project and out of project. For instance, an external source is required to deliver hardware to test a software project or the initiation of preparing a site in a construction project depends on governmental environmental hearings. Determination of external dependencies in the process of sequence activities is undertaken by the project management team.
  • Internal dependencies that are typically under the control of the project team refer to a precedence relationship between project activities. For instance, an internal mandatory dependency can be mentioned to inability of a team to test a machine until assembling. Determination of internal dependencies in the process of sequence activities is undertaken by the project management team.

3. Leads and Lags

Figure 4: Lead and lag in sequence activity. Inspired by PMBOK[3]

The time required for starting a successor activity regarding a predecessor activity is called as a lead. For example, scheduling a landscaping in a construction project of office building can begin two weeks before the completion of the scheduled punch list. Lead is often planned as a negative amount for lag in scheduling. The time required for delaying a successor activity regarding a predecessor activity is called as lag. For instance, a technical writing team has a 15-day delay time to edit a draft of a large document after writing, meaning a 15-day lag plus SS relationship (SS+10). Lag can be appeared in diagrams of project schedule network plotted for the relationship between H and I activities in spite of unclear offset relative to a timescale. Determination of the need for a lead or a lag in the dependencies is undertaken by the project management team in the exact process of defining the logical relationship. The schedule logic should not be changed following the use of leads and lags. it is essential to document the activities and corresponding assumptions. [2]

Outputs of sequence activities

1. Project Schedule network diagrams: The logical relationships are graphically drawn called as project schedule network diagram, also referred to as dependencies among the project schedule activities, which is prepared by manual manner or project management software. The diagram can represent full details or summarized activities of the project. A summary narrative can be illustrated with a diagram to show the used fundamental strategy in sequencing the activities, and to describe any abnormal sequence of activity on the network.[2]

2. Updates of project documents: There are needs to update the project documents, such as activity lists, activity attributes, milestone list and risk register. 

  • Only, the project product description should be prepared for a small project.
  • Careful thinking is necessary to achieve quality criteria in order to distinguish whether a product is acceptable or not. A way to test quality criteria is to scrutinise the distinction between completed or stopped working on this product.

Product-based planning

Product-based planning is a method for identifying first a product requirements and second all activities, dependencies and necessary resources to deliver that product. This method has different applications such as Project planning, Stage planning and Team planning. [1] The sequence involved in the development of products of the plan will be developed and the identification of their dependencies should be detected and defined, which is possible using a product flow diagram (PFD). The dependencies on any non-project products can be detected through this diagram, thereby providing the required activities and data for other planning approaches like estimating and scheduling.

Some essential items should be considered to draw the PFD:

  • The PFD is generated by the Project or Team Manager. However, the people responsible for developing or helping the plan products can be involved rationally.
  • When the product breakdown structure (PBS) has been drawn, some planners will decide to generate the PFD along with the PBS.
  • There is need for very few symbols in drawing the PFD. It is essential to detect any developed product (for instance, enclosure in a rectangle), and to exhibit any required sequence (for instance, interconnection of rectangles by arrows) in the plan. Moreover, the external products should be clear as any existing or non-project ongoing products (for instance, enclosure in a different shape like ellipse).
  • The PFD may be added with a starting point attached from all entry points. Although an exit is always available in the PFD, when many entrances exist, this position indicator prevents any of them from being ignored. The symbol of predecessor is there for all points of entry and is the only symbol in PFD not in PBS.

Detection of activities and dependencies in product-based planning

  • Activities:

It is inadequate to merely identify products for scheduling and controlling the objectives. To completely illustrate the workload of a plan, it is necessary to detect all the activities needed to establish or modify any of the planned products. The identification of activities can be achieved through multiple approaches, as follows:

  • A separate list of the activities can be provided in spite of the use of PFD as the information source.
  • The required activities can be detected by using the products from the PBS or the work breakdown structure (WBS).

The activities involve management and quality-checking activities, and those required for developing the specialist products or for interacting with external parties like those that a product obtained from an outside source or for transforming external products into targeted ones. It is needed to shield the spread of activities unnecessary for the plan. Things should be kept simple if there is any doubt.

  • Dependencies:

It is necessary to identify any internal and external dependencies of activities and products. For example, Activity C cannot start unless activities A and B are completed (as an internal dependency). Dependency of a delivery of a product needed for a project by another project, suggestion of a purchase order by the user and decision-making by the program manager are examples of the external dependencies.

  • Activity sequence:

In the wake of detecting the activities, and estimating related dependencies, duration and effort, the subsequent step is to approximate the optimal sequence required. This is an iterative step because the estimated effort and duration may be influenced by actual resource allocation.

Float or slack refers to the amount of time by which a given task in a project network can be delayed with no influence on the deadline for the project, which can be considered as both provision within the plan and spare time. Zero float means a condition with no excess time between activities, which defines a critical activity through the diagram (critical path). In fact, it can be claimed that any delay in the completion of an activity in the critical path (s) will result in delayed completion of the entire project.

The project manager will be able to monitor the plan’s activities by detecting the critical path (s) of the plan. Such activities should be timely completed in order to complete the whole plan in accordance with scheduling. Delay can occur for these activities for a period if resources are re-allocated to compensate for lost activities.

Annotated Bibliography

  • MURRAY, A., BENNETT, N., & BENTLEY, C. (2009). Managing successful projects with PRINCE2, 2009 edition manual. London, TSO (The Stationary Office).

“PRINCE2 is the world’s most widely-adopted project management method, used by people and organisations from wide-ranging industries and sectors. It is a flexible method that guides you through the essentials for managing successful projects, regardless of type or scale. Built upon seven principles, themes and processes, PRINCE2 can be tailored to meet your specific requirements.[4] For an organisation or individuals, to deliver successfully a project within time, cost and right quality, this book presents universal project management methods, techniques, principles, and processes based on experience extracted from many different projects. The book also defines a framework of processes and instructions which has verified over many years as solution to prevent failure in projects.

  • Project Management Institute. (2013). A guide to the project management body of knowledge (PMBOK® Guide). 5th ed. Pennsylvania: Project Management Institut).

The book contains the body of knowledge for project management. The body of knowledge defines a set of standers, terminology, methods, and guidelines which need to develop over time. Project Management Institute (PMI) is documenting and publishing the Guide over the seen works and results. The PMBOK includes also some unique tools and concepts e.g. critical path method and work breakdown structure (WBS) to guide project managers in planning, organising, staffing, executing and controlling.


  1. 1.0 1.1 1.2 1.3 1.4 1.5 MURRAY, A., BENNETT, N., & BENTLEY, C. (2009). Managing successful projects with PRINCE2, 2009 edition manual. London, TSO (The Stationary Office), pp. 63-69
  2. 2.0 2.1 2.2 2.3 Project Management Institute. (2013). A guide to the project management body of knowledge (PMBOK® Guide). 5th ed. Pennsylvania: Project Management Institute, pp. 156-159.
  3. 3.0 3.1 3.2 Project Management Institute. (2013). A guide to the project management body of knowledge (PMBOK® Guide). 5th ed. Pennsylvania: Project Management Institute, pp. 153.
  4. 2019. What is PRINCE2®?. [ONLINE] Available at: [Accessed 4 March 2019].
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