Constructing a network diagram
- 1. Constructing a Network Diagram BUSINESS DECISION ANALYSIS Constructing a Network Diagram Click function key F5 to run this lecture as a Slide Show
- 2. Constructing a Network Diagram Are there any pre-requisites for this topic? NO. You may have come across terms like “ critical path ” but no knowledge is pre-supposed.
- 3. Constructing a Network Diagram Project management is also referred to as: network analysis critical path analysis PERT - program evaluation & review technique
- 4. Constructing a Network Diagram OK, so what’s a project? Well any managerial activity can be represented as a project. For example: developing a new product or service marketing a new product or service breaking into a new market building a new plant installing a new computer system planning a training programme re-locating head office.
- 5. Constructing a Network Diagram What do your example projects have in common? Each can be decomposed into its constituent parts, called ACTIVITIES . We can then define a project as a collection of related activities. Three things are important: each activity takes time each activity uses up resources activities are structured.
- 6. Constructing a Network Diagram What gives activities structure? But that’s too vague. A roof cannot be erected unless the foundations have been dug. Obviously true! So digging foundations must precede erecting the roof! But what about the walls? So we refer to the immediately preceding activities . Precedence : some activities have to be completed before others can be started.
- 7. Constructing a Network Diagram The first step for any project is to: list the constituent activities arrange them into a Precedence Table . The project is to build an extension to the Recreation Centre. The table lists the activities and their immediate predecessors – up to the point of starting construction.
- 8. Constructing a Network Diagram And here’s another project …………. “ purchase of a new car” . Activity Description Preceding Activity Duration (days) A Decide feasibility of purchase - 3 B Find buyer for existing car A 14 C Decide on possible models A 1 D Investigate models decided upon C 3 E Discuss with knowledgeable friends C 1 F Get information from dealers C 2 G Put all information together D,E,F 1 H Narrow down to three options G 1 I Test drive all three H 3 J Get warranty & finance information H 2 K Choose one car 1,J 2 L Compare dealers & choose one K 2 M Decide upon colour etc L 4 N Test drive chosen model L 1 O Buy new car B,M,N 3
- 9. Constructing a Network Diagram Is activity B a pre-condition for starting activity I? NO Activity Description Preceding Activity Duration (days) A Decide feasibility of purchase - 3 B Find buyer for existing car A 14 C Decide on possible models A 1 D Investigate models decided upon C 3 E Discuss with knowledgeable friends C 1 F Get information from dealers C 2 G Put all information together D,E,F 1 H Narrow down to three options G 1 I Test drive all three H 3 J Get warranty & finance information H 2 K Choose one car 1,J 2 L Compare dealers & choose one K 2 M Decide upon colour etc L 4 N Test drive chosen model L 1 O Buy new car B,M,N 3
- 10. Constructing a Network Diagram Is activity A a pre-condition for starting activity K? YES Activity Description Preceding Activity Duration (days) A Decide feasibility of purchase - 3 B Find buyer for existing car A 14 C Decide on possible models A 1 D Investigate models decided upon C 3 E Discuss with knowledgeable friends C 1 F Get information from dealers C 2 G Put all information together D,E,F 1 H Narrow down to three options G 1 I Test drive all three H 3 J Get warranty & finance information H 2 K Choose one car 1,J 2 L Compare dealers & choose one K 2 M Decide upon colour etc L 4 N Test drive chosen model L 1 O Buy new car B,M,N 3
- 11. Constructing a Network Diagram Can activities E and F take place at the same time? YES Activity Description Preceding Activity Duration (days) A Decide feasibility of purchase - 3 B Find buyer for existing car A 14 C Decide on possible models A 1 D Investigate models decided upon C 3 E Discuss with knowledgeable friends C 1 F Get information from dealers C 2 G Put all information together D,E,F 1 H Narrow down to three options G 1 I Test drive all three H 3 J Get warranty & finance information H 2 K Choose one car 1,J 2 L Compare dealers & choose one K 2 M Decide upon colour etc L 4 N Test drive chosen model L 1 O Buy new car B,M,N 3
- 12. Constructing a Network Diagram Precedence tables aren’t that easy to use. Is there some other way of representing a project? Y E S A useful visual representation of a project is obtained by drawing a network diagram.
- 13. Constructing a Network Diagram This is how we represent an activity. activity event of starting an activity event of ending an activity get out of bed So somewhere in the project “ Get to University Monday Morning ” will be:
- 14. Constructing a Network Diagram Err .. but we’ll need to link activities together, won’t we. That’s correct. Sometimes we might want to show: A B C
- 15. Constructing a Network Diagram Err .. but we’ll need to link activities together, won’t we. That’s correct. Sometimes we might want to show: M K L
- 16. Constructing a Network Diagram Err .. but we’ll need to link activities together, won’t we. That’s correct. Sometimes we might want to show: A B C
- 17. Constructing a Network Diagram Are there any rules to follow when drawing network diagrams? YES Must be drawn from left to right. 2. Must have a single starting point. 3. Also a single ending point. 4. One arrow (only) per activity. 5. Must correctly reflect the precedence table.
- 18. Constructing a Network Diagram There is one complication that we need to allow for. A dummy activity may be needed: to prevent 2 or more activities sharing the same starting and ending events. to maintain network logic – i.e. to ensure that the network abides by the precedence table. OK, tell me the worst!! Sometimes we have to use Dummy activities. We use a dashed arrow to record these.
- 19. Constructing a Network Diagram OK. Let’s have a go at drawing a network. We’ll draw the one for the extension to the recreation centre.
- 20. Constructing a Network Diagram Where do I start? Once the project has started which activities can be begun? Well, a network must have a single starting point – a circle or node. A Survey site B Develop initial proposal
- 21. Constructing a Network Diagram A B So we draw arrows for activities A & B running from the starting event. Make sure that you label the activities as you include them in the network. Activity Preceding Activity C A,B What comes next?
- 22. Constructing a Network Diagram Well is this correct. Does it abide by the rules for drawing network diagrams? That’s no problem. Just do this. Activity Preceding Activity C A,B A B C NO Two or more activities may not share the same starting and ending event.
- 23. Constructing a Network Diagram Use a dummy activity. Here’s one way in which it can be done. It prevents A & B from sharing the same starting and ending event. So how do I remedy this error? A B C
- 24. Constructing a Network Diagram So we’ll add these to the network. A B C Activities D & E can start when C is finished. E D
- 25. Constructing a Network Diagram The table says that F can start when D & E are completed. So can we do this? A B C E D F
- 26. Constructing a Network Diagram No. We’ve broken the rules again. So another dummy activity is needed. A B C E D F
- 27. Constructing a Network Diagram This will work. A B C E D F
- 28. Constructing a Network Diagram Now we can add activity G. G can be started once E is completed. A B C E D F G
- 29. Constructing a Network Diagram That leaves activity H. The start of H requires the completion of F and G. A B C E D F G
- 30. Constructing a Network Diagram So we bring the arrows for F & G into the starting event for activity H. And this is the finished network. A B C E D F G H
- 31. Constructing a Network Diagram Always check the network against the precedence table before continuing. A B C E D F G H
- 32. Constructing a Network Diagram Right, now we’ll draw the network for the project of buying a new car. For this project there’s only one starting activity, namely A
- 33. Constructing a Network Diagram A Activities B & C can be started once A is completed. B C
- 34. Constructing a Network Diagram A And D, E & F can be started when C is completed. B C D E F
- 35. Constructing a Network Diagram Activity G requires completion of D, E & F. So two dummy activities are needed to prevent D, E & F having the same starting and ending events. A B C D E F G
- 36. Constructing a Network Diagram Activity H can now be added to the network. A B C D E F G H
- 37. Constructing a Network Diagram I & J can now start. A B C D E F G H I J
- 38. Constructing a Network Diagram Since the start of K needs completion of I & J we need another dummy activity. A B C D E F G H I J K
- 39. Constructing a Network Diagram Now we add activity L A B C D E F G H I J K L
- 40. Constructing a Network Diagram Activities M & N can now be started. A B C D E F G H I J K L M N
- 41. Constructing a Network Diagram That leaves activity O. It can be started when activities B, M & N are completed. A B C D E F G H I J K L M N
- 42. Constructing a Network Diagram That leaves activity O. A dummy activity will be needed to separate activities M and N. A B C D E F G H I J K L M N
- 43. Constructing a Network Diagram C But remember to check it against the precedence table. A D E F G H I J K L M N The network is now completed. O B
- 44. Constructing a Network Diagram What should I now be able to do? Given the precedence table for a project, you should be able to draw its network diagram.
- 45. Constructing a Network Diagram That’s the end of this lecture. You should now explore the problems, on drawing networks, that are available within Blackboard.