PMGT3623 Scheduling Lecture Plan (Week 3) PDF

PMGT3623 Scheduling Week 03: Project Network Diagram (Discrete Approach) Dr Shahadat Uddin The University of Sydney Page 1 Acknowledgement of Country I would like to acknowledge the Traditional Owners of Australia and recognise their continuing connection to land, water...

PMGT3623 Scheduling Week 03: Project Network Diagram (Discrete Approach) Dr Shahadat Uddin The University of Sydney Page 1 Acknowledgement of Country I would like to acknowledge the Traditional Owners of Australia and recognise their continuing connection to land, water and culture. I am currently on the land of the Gadigal people of the Eora Nation and pay my respects to their Elders, past, present and emerging. PMGT3623 Scheduling 2 PMGT3623 Overview Week Topic Week 01 Introduction to Scheduling, Course Resources and Assessment Components Week 02 Define and Sequence Project Tasks Week 03 Project Network Diagram (Discrete Approach) Week 04 Probabilistic Approach to Project Network Diagram – Part I Week 05 Probabilistic Approach to Project Network Diagram – Part II Week 06 Confidence Analysis of Project Network Diagram Week 07 Knowledge Test Week 08 Implementation of Project Network Diagram using Microsoft Project Week 09 Simple Task Allocation Approach Mid-Semester Break Week 10 Complex Task Allocation Approach Week 11 Progress Reporting and Earned Value Analysis Week 12 Group Assignment Presentation Week 13 Review PMGT3623: Scheduling 3 PMGT3623 Assessments No Assessment Name Weight Due date Comment 1 Weekly Participation 10% W2-W6; W9-W10 Best 6 (out of 7) 2 Knowledge Test 20% W7 3 Group Assignment Presentation (Part A) 10% W12 and W13 4 Group Assignment Report Submission (Part B) 20% Friday of W13 By 11:59 pm 5 Final Exam 40% Exam Week PMGT3623 Scheduling 4 Week 03: Project Network Diagram (Discrete Approach) Topics Covered - What is a Project Network Diagram? - Different approaches to the Project Network Diagram o Precedence Diagramming Method o Other Approaches - Project Duration, Critical Path and Near-Critical Path - Limitation of Discrete Approach to Project Network Diagram 5 Network Diagram Building Gate and Fence Project The first task is to ‘dig holes’ to accomplish this project. Only after finishing this task, the tasks of ‘buy wood’ and ‘buy gate’ can be started. You can only begin the ‘erect fence’ task if you finish the ‘buy wood’ task. Similarly, you can start the ‘buy paint’ task only if you finish the ‘buy gate’ task. Then, you can start the ‘erect gate’ task. But to start this task, you must finish the ‘erect fence’ and ‘buy paint’ tasks first. You can only start the ‘paint fence’ task if you finish the ‘erect gate’ task. Finally, you can start the ‘paint gate’ task after you finish the ‘paint fence’ task. Now consider these questions… o How many tasks are in this project? o What is the sequence of all tasks of this project? o What are the interdependencies between tasks? o And many more questions like these ones Is it easy to answer these questions and similar ones from the above textual description of the project (Yes/No)? No 6 Network Diagram (cont.…) What is a network diagram? ❖ A Network Diagram is a visual representation of a project’s schedule. ❖ It illustrates a logical stream of events that will lead to the completion of the project. ❖ A network diagram in project management helps plan and track the project from beginning to finish. ❖ It represents a project’s critical path as well as the scope of the project. ❖ It is widely used because it is easy to read and not only depicts the sequence of activities in the project but also shows parallel activities and the links between each activity. 7 Network Diagram (cont.…) Rule of Thumb for a Network Diagram ❖ There is a starting point ❖ There is an endpoint ❖ There are predecessors for all activities (except the start point) ❖ There are successors for all activities (except the endpoint) ❖ There are no loops or hangers 8 Network Diagram (cont.…) Rule of Thumb for a Network Diagram (cont.…) Activity A Activity C Start Finish Activity B Activity D A network diagram Loop must not have a loop Are there any loops in the above network diagram? Activity A Activity C Start Finish Activity B Activity D Tasks B, C and D make a loop 9 Network Diagram (cont.…) ❖ Precedence Diagramming Method (PDM) Node represents activity Also known as the activity on the node (AON) Start 1.1.1 1.1.2 1.2.2 Finish 1.2.1 1.3.1 1.3.2 AON → Activity-on-Node diagram 10 Network Diagram (cont.…) ❖ Precedence Diagramming Method (PDM) (cont.…) Another example of PDM Activity A Activity B Activity C Start Finish Activity D Activity E Activity F 11 Network Diagram (cont.…) Other Approaches for Network Diagram 1. Arrow Diagramming Method 2. Critical Chain Approach 3. Line of Balance Approach Figure: Arrow Diagramming Method 4. Advanced Work Package Approach 5. Beeline Diagramming Method 6. Chronographic Modelling Approach 7. Timeboxing 8. Kanban Figure: Line of Balance Approach Figure: Beeline Diagramming Method 12 1. Exercise on ‘Network Diagram’ Consider the same ‘Building Gate and Fence’ project The first task is to ‘dig holes’ to accomplish this project. Only after finishing this task, the tasks of ‘buy wood’ and ‘buy gate’ can be started. You can only begin the ‘erect fence’ task if you finish the ‘buy wood’ task. Similarly, you can start the ‘buy paint’ task only if you finish the ‘buy gate’ task. Then, you can start the ‘erect gate’ task. But to start this task, you must finish the ‘erect fence’ and ‘buy paint’ tasks first. You can only start the ‘paint fence’ task if you finish the ‘erect gate’ task. Finally, you can start the ‘paint gate’ task after you finish the ‘paint fence’ task. Now find all activities of this project, their predecessors and the corresponding network diagram Solution: Network Diagram List of activities Predecessors 13 Critical Path Network Diagram The first task is to ‘dig holes’ to accomplish this project. Only after finishing this task, the tasks of ‘buy wood’ and ‘buy gate’ can be started. You can only begin the ‘erect fence’ task if you finish the ‘buy wood’ task. Similarly, you can start the ‘buy paint’ task only if you finish the ‘buy gate’ task. Then, you can start the ‘erect gate’ task. But to start this task, you must finish the ‘erect fence’ and ‘buy paint’ tasks first. You can only start the ‘paint fence’ task if you finish the ‘erect gate’ task. Finally, you can start the ‘paint gate’ task after you finish the ‘paint fence’ task. It can now answer these questions o How many tasks are in this project? o What is the sequence of all tasks of this project? o What are the interdependencies between tasks? These are questions we put in a previous slide to justify the need for a Network Diagram However, there are crucial questions that this diagram can still not answer, such as o What is the total duration of the project? o What are the critical tasks within this network diagram? o For what tasks could we have a delay or pause? o And many more questions like these ones For this, we need to learn Critical path and how to find it from a network diagram using Forward pass and Backward pass 14 Critical Path (cont.…) Critical Path is… “Generally, but not always, the sequence of schedule activities that determines the duration of the project. It is the longest path through the project.” (from PMBOK 4th Edition) Use the logical network to calculate ❖ Forward pass that identifies early start (ES) and early finish (EF) dates ❖ Backward pass that identifies the late start (LS) and late finish (LF) dates To calculate the critical path, we first need to find the forward pass and backward pass of a network diagram These two calculations will tell what delay or opportunity you (being a project Manager) could afford each task of the project. 15 Critical Path (cont.…) Early Start (ES) Early Finish (EF) Task name and Duration Late Start (LS) Late Finish (LF) 16 Critical Path (cont.…) Forward pass (go along from the start to the end) Use the formulas (ES + duration = Set the early start date Begin at left, work EF) and (EF + lag = ES, EF – lead for the first activity left-to-right =ES) for successors When a successor has multiple predecessors, use the latest EF date Continue to the end of those predecessors as the ES date for the successor 17 Critical Path (cont.…) Forward pass (go along from the start to the end) – cont.… When a successor has multiple predecessors, use the latest EF ES + duration = EF date of those predecessors 4 7 7 9 9 12 C (3) F (2) G (3) 0 4 A (4) 6 9 12 H (3) 5 6 Start End D (1) 6 11 I (5) 0 5 B (5) 5 9 9 11 ES EF E (4) J (2) D LS LF 18 Critical Path (cont.…) Backward pass (go along from the end to the start) Set the LF of the last Use the formulas (LF - duration = Begin at right, work task equal to the EF of LS) and (LS - lag = LF, LS + lead right-to-left the last task =LF) for predecessors When a predecessor has multiple successors, Continue to the use the earliest LS date of those successors as beginning of the the LF date for the predecessor network 19 Critical Path (cont.…) Backward pass (go along from the end to the start) – cont.… When a predecessor has multiple successors, use the earliest LS date of those successors C (3) F (2) G/3 4 7 7 9 9 12 A (4) 12 0 4 H (3) Start 9 12 End D (1) 6 7 I (5) 7 12 B (5) 1 6 E (4) J (2) 6 10 10 12 ES EF D LS LF LF - duration = LS 20 Critical Path (cont.…) Merging Forward pass and Backward pass to Calculate Critical path 4 7 7 9 9 12 C (3) F (2) G (3) 0 4 4 7 7 9 9 12 A (4) 6 9 12 0 4 H (3) 5 6 9 12 Start End D (1) 6 11 6 7 I (5) 0 5 7 12 B (5) 5 9 9 11 1 6 E (4) J (2) 6 10 10 12 ES EF D LS LF 21 Critical Path (cont.…) The critical path is shown in bold and shaded Merging Forward pass and Backward pass to Early start (ES) = Late Start (LS) Calculate Critical path (cont.…) Early Finish (EF) = Late Finish (LF) 4 7 7 9 9 12 C (3) F (2) G (3) 0 4 4 7 7 9 9 12 A (4) 6 9 12 0 4 H (3) 5 6 9 12 Start End D (1) 6 11 6 7 I (5) 0 5 7 12 B (5) 5 9 9 11 1 6 E (4) J (2) 6 10 10 12 ES EF D LS LF 22 Critical Path (cont.…) Network diagram without any critical path This network has tasks that do not connect all the way through; the critical path is indeterminate Start End 23 Critical Path (cont.…) Slack Time (Float Time) Also known as float time, it refers to the amount of time that a task in a project schedule can be delayed without causing a delay to - (a) Project overall completion time, and (b) The start date of the subsequent task. 𝑇𝑜𝑡𝑎𝑙 𝑆𝑙𝑎𝑐𝑘 = 𝐿𝑎𝑡𝑒 𝐹𝑖𝑛𝑖𝑠ℎ − 𝐸𝑎𝑟𝑙𝑦 𝐹𝑖𝑛𝑖𝑠ℎ 𝑂𝑟, 𝑇𝑜𝑡𝑎𝑙 𝑆𝑙𝑎𝑐𝑘 = 𝐿𝑎𝑡𝑒 𝑆𝑡𝑎𝑟𝑡 − 𝐸𝑎𝑟𝑙𝑦 𝑆𝑡𝑎𝑟𝑡 Importance of Slack Time - Critical Path Identification: All tasks on the critical path has a slack or float time of 0. This means that any delay in these tasks will delay the entire project - Resource Allocation: Understanding slack time allows project managers to allocate resources more effectively, prioritising critical tasks while possibly reassigning resources from non-critical tasks. - Risk Management: Knowing the slack time helps in identifying potential risks and developing mitigation strategies. Tasks with little or no slack are riskier, as they can impact the project's schedule. - Project Flexibility: Slack time provides flexibility in scheduling, allowing for adjustments without affecting the project's overall timeline. 24 Critical Path (cont.…) Slack Time Or Float Time (cont.…) Float (A) = 4 - 4 = 0 Float (H) = ? 4 7 7 9 9 12 Float (H) = 12 – 9 = 3 C (3) F (2) G (3) 0 4 4 7 7 9 9 12 A (4) 6 9 12 0 4 H (3) 5 6 9 12 Start End D (1) 6 11 6 7 I (5) 0 5 7 12 B (5) 5 9 9 11 1 6 E (4) J (2) 6 10 10 12 25 Critical Path (cont.…) Near-Critical Path A ‘near-critical path’ is one or more paths that are not critical at the outset of the project under consideration but could become critical due to reasons such as: ❖ The ‘Probabilistic outcome’ of the duration of one of these (i.e., near-critical path) paths becomes longer than the identified critical path. ❖ Or, the previously identified ‘critical path’ becomes shorter because of the improved performance of its task, which could eventually promote one of the ‘near critical paths’ to being the ‘critical path’. 26 Critical Path (cont.…) Near-Critical Path (cont.…) 4 7 7 9 9 12 C (3) F (2) G (3) 0 4 4 7 7 9 9 12 A (4) 6 9 12 0 4 H (3) 5 6 9 12 Start End D (1) 6 11 6 7 I (5) 0 5 7 12 B (5) 5 9 9 11 1 6 E (4) J (2) 6 10 10 12 All paths? Critical path (s)? Hence, Near-critical paths are? 1. A→C→F→G 1. A→C→F→G 2. A→D→H 2. A→D→H 3. A→D→I 3. A→D→I 4. B→D→H 4. B→D→H 5. B→D→I 5. B→D→I 6. B→E→J 6. B→E→J 𝑭𝒐𝒓 𝒂𝒏𝒚 𝒏𝒆𝒕𝒘𝒐𝒓𝒌 𝒅𝒊𝒂𝒈𝒓𝒂𝒎, 𝑻𝒐𝒕𝒂𝒍 𝒑𝒂𝒕𝒉 = 𝑪𝒓𝒊𝒕𝒊𝒂𝒍 𝒑𝒂𝒕𝒉 𝒔 + 𝑵𝒆𝒂𝒓 𝒄𝒓𝒊𝒕𝒊𝒄𝒂𝒍 𝒑𝒂𝒕𝒉(𝒔) 27 Critical Path (cont.…) Another simpler way to find the Critical Path (No need to find Forward and Backward Pass) C (3) F (2) G (3) A (4) H (3) Start End D (1) I (5) B (5) E (4) J (2) All paths and their durations: Hence, the critical or longest possible 1. A → C → F → G (4 + 3 + 2 + 3 = 12) path is the one with the highest 2. A → D → H (4 + 1 + 3 = 8) 3. A → D → I (4 + 1 + 5 =10) duration 1. A → C → F → G (4 + 3 + 2 + 3 = 12) 4. B → D → H (5 + 1 + 3 = 9) 5. B → D → I (5 + 1 + 5 = 11) 6. B → E → J (5 + 4 + 2 = 11) 28 Critical Path (cont.…) Another simpler way to find the Critical Path (cont.…) (No need to find Forward and Backward Pass) Limitations of this approach: - This approach does not show the slack or float time of each task - This approach will become very complex if the number of project tasks is very high with a large volume of interdependencies among them. 29 2. Exercise on ‘Critical Path’ Given the network diagram below, find (a) all paths, (b) critical path(s) and (c) all near-critical paths. 30 2. Exercise on ‘Critical Path’ (cont.…) Given the network diagram below, find (a) all paths, (b) critical path(s) and (c) all near-critical paths. Solution: All paths: 1. A→C→J 2. A→D→G→J 3. A→D→H 4. A→D→I→K 5. B→E→G→J 6. B→E→H 7. B→E→I→K Critical path 7. B→E→I→K All Near-critical paths 1. A→C→J 2. A→D→G→J 3. A→D→H 4. A→D→I→K 5. B→E→G→J 6. B→E→H 31  Act.. Pre.. Dur.(M) Critical Path, Discrete Approach and A (None) 4 B (None) 5 Probabilistic Outcome C A 3 D A, B 1 E B 4 F C 2 G F 3 H D 3 I D 5 J E 2 4 7 7 9 9 12 C (3) F (2) G (3) 0 4 4 7 7 9 9 12 A (4) 6 9 12 0 4 H (3) 5 6 9 12 Start End D (1) 6 11 6 7 I (5) 0 5 7 12 B (5) 5 9 9 11 1 6 E (4) J (2) 6 10 10 12 Critical path: A → C → F → G (Duration 12 months) 32  Act.. Pre.. Dur.(M) Critical Path, Discrete Approach and A (None) 4 B (None) 5 Probabilistic Outcome (cont.…) C A 3 D A, B 1 (11) E B 4 F C 2 What will happen if D’s duration is 11 months? G F 3 H D 3 I D 5 J E 2 4 7 7 9 9 12 C (3) F (2) G (3) 0 4 13 16 16 18 18 21 A (4) 16 19 21 0 4 H (3) 5 16 18 21 Start End D (1 11) 16 21 5 16 I (5) 0 5 16 21 B (5) 5 9 9 11 0 5 E (4) J (2) 15 19 19 21 Critical path: B → D → I (Duration 21 months) 33 Critical Path, Discrete Approach and Probabilistic Outcome (cont.…) 4 7 7 9 9 12 C (3) F (2) G (3) 0 4 4 7 7 9 9 12 A (4) 6 9 12 0 4 H (3) 5 6 9 12 Start End D (1) 6 11 6 7 I (5) 0 5 7 12 B (5) 5 9 9 11 1 6 E (4) J (2) 6 10 10 12 Initial Critical path: A → C → F → G (Duration 12 months) When D’s duration is 11 months, then Critical path: B → D → I (Duration 21 months) Thus, B → D → I is the possible candidate for critical paths. Another possible candidate is B → E → I. They are known as near-critical paths. Thus, a discrete or deterministic approach to task duration allocation would lead to the wrong estimation during the project execution phase due to, for example, performance variance. 34 Critical Path, Discrete Approach and Probabilistic Outcome (cont.…) 4 7 7 9 9 12 C (3) F (2) G (3) 0 4 4 7 7 9 9 12 A (4) 6 9 12 0 4 H (3) 5 6 9 12 Start End D (1) 6 11 6 7 I (5) 0 5 7 12 B (5) 5 9 9 11 1 6 E (4) J (2) 6 10 10 12 ❖ A near-critical path could become a critical path during the project execution phase ❖ So far, in each example, we considered a discrete approach in allocating task duration ❖ For a simple project, it would be okay. However, for complex mega projects, such allocation would lead to wrong or biased estimations regarding project duration and cost. 35 Critical Path, Discrete Approach and Probabilistic Outcome (cont.…) Probabilistic Outcome ❖ In the discussion (as well as in all given examples) of the ‘critical path’, a specific duration for each task has been given. ❖ However, it does not work in this way in real-life life projects. ❖ Instead, it is said that it is highly probable (say 99% or 0.99) that a specific task could be finished in a given specific time period. ❖ No one can guarantee that any task can be done within a specific time period. ❖ For this reason, we need to learn the probability and probabilistic approach to project duration estimation. ❖ We learn them in the coming two weeks. 36 Review Questions a) What are the differences between critical path and near critical path? b) Can a network diagram have zero near critical path? Give an example. c) Can a network diagram have zero critical path? d) How to calculate the slack time of a task? What are the importance of slack time for project managers? e) Which tasks have a zero slack or float time? f) What is a loop? Can a network diagram have a loop? Explain g) What are the rule of thumps for drawing a network diagram? 37