 Hi, I'm Rui Rizzo and in this session we will talk about time planning and particularly about the project network diagram. Let's make a wrap up of what we have learned in previous sessions. First, we talk about the scope planning and about the work breakdown structure and the way we decompose the work that has to be done in the project into fill, into phases, modules or components until we reach the work packages that are the lowest level tasks. With these work packages it is possible to make an estimation about effort of each work package in person month, in person day or person hour and using the effort to obtain the duration in calendar month. Using the effort we can calculate the project cost that we will see in a different video and with the duration we can calculate the network diagram and the critical path and the total duration of the project is what we will start seeing in this video. Let's start with some few concepts about what is a Gantt chart and the network diagram. This is a Gantt chart. As you can see we have the tasks and then we have an estimation for tasks and some connection between those tasks and we can see the time of it. This is a Gantt chart but what is a network diagram? A network diagram is more complete than a Gantt chart because Gantt chart does not contain all the detailed information. It does not indicate whether the schedule resulting from the graph completes the project in the shortest possible time, nor whether the resources that are used in the most effective way. It is recommended to use a network diagram. Actually in softwares to that support project management such as Microsoft Project they use both network diagram and a Gantt diagram. Network diagram provides an image of the sequence in which the project workflows includes detailed information and it serves as analytical tool for project schedule and resource management issues as they arise over the life of the project. They can be used for detailed project planning and during implementation as a tool for analyzing alternative schedules and a control tool. So we start first of all from the activity list. The activity list is a table where we have all the lifts of the work breakdown structure. Which means the hand nodes, the lifts and with these nodes which are work packages we already made an estimation for the effort and the first derivation of the duration. As you can see in the previous video we make a first estimation of the duration based on effort plus effort times dot 35. Considering 35% of unused time. Then this is the first approach for duration. Of course we have to put this on schedule. But first let's build the activity sequence. How can you do this? Activity sequencing consists of identifying and documenting the logical interactions relationship between the project activity. And what this means? This means that there are relations between the activities and the tasks. Which means that sometimes you cannot do something before doing something else. You cannot drink water from the glass if you don't put water in the glass. So there is a presence in these tasks. And so you have to build the activity on error diagram method, for instance. The activity on error diagram method uses errors to represent activities and connects them by nodes representing dependencies. The typical type of dependency is and principle, which means that once you have a node after another node, it means that that node represents a work package or a task or activity. And it must end that work package and that activity before it starts the next one. Sometimes, as we can see, we have to use some dummy activities in order to define our logical relationships correctly. And as we will see shortly. So let's look at representation. As you can see here, we have nodes and we have errors. Each error represents an activity, a work package, a task. And as you can see here, node 1 connects node 2 to its task A. And after task A, you can have in parallel three tasks B, D and C. Which means that start from node 2 to 3, activity B, from node 2 to 5, activity D and from node 2 to 4, activity C. And so on. Which means that activity G can only be performed after A and B and F can be performed only after A and D and H only after A, C and D and N. This is the meaning of the diagram. There are some logical errors that can occur and must be represented in the activity on error diagram. And last one occurs when sequential dependence of the activity is circular. Which means that you cannot have circular activities which means that you have to correct the sequence of the tasks. That is something wrong when you have circular activities. And hanging activities occur when an activity has no sequence. When an activity has no sequence, sometimes we have to create in these types of diagrams fictitious identity activities. To connect both nodes in order to make logical sequences of the diagram. For instance in this example, you have activity A and activity B that they don't have precedence activities. But to make the diagram in a logical way, you have to connect fictitious activity that is dashed between node 1 and node 2. These fictitious activities don't have, don't represent time and don't have resources associated. What type of relationships can we have between these nodes? And that represents the diagram. We have to consider in this example in activity A. We can consider the earliest start time, which is the earliest start date that the activity can start. The earliest finish time, the earliest finish date that A can finish. The latest start time and the latest finish time. And we will consider T as time, the activity duration and A of course the activity. It is this way how you can understand this picture. And this will be important in the next few slides. A final activity on a root diagram which will look like this. Don't worry if you don't understand so far what is EST and how we calculate them EFT, LST and LFT. We will handle this in a further video. So far concentrate on the idea that you have to build the activity diagram with the precedence of the activities. And if you have to define an algorithm about this, how it will work. Well, it's easy. The idea is to identify all activities starting at node 1, draw the end nodes of those activities and draw the corresponding errors. Continue building the diagram from left to right, representing all the bifurcations and fusions. Continue building the diagram until all activities are represented. And in the end you will have your final activity in the error diagram. You can see it here, the full algorithm and the full steps that you can use to calculate the activity and error diagram with the calculation of times. Don't worry, we will see shortly how we can calculate those kinds of times. The precedence diagram method uses nodes to represent activities and connects them with errors representing dependency. The activity and error method uses errors to define activities. Here in this kind of diagram we use the nodes to represent the activities. What kind of dependencies can we have? The end beginning as usual, once an activity finishes, the other can start. But we can consider other types of dependencies between the activities. The start start, when an activity starts, the other can start. The end start finish, when one starts, the other finish. And finish finish, once one finish, the other can also finish. Here we have an example of the precedence diagram. As you can see here, we have the relationship between the tasks and the tasks are in the nodes. And as you can see here, you can represent dependency relationships. Start finish, start start, finish start and finish finish. We can consider two types of dependencies, mandatory and optional. Mandatory are those that are inherent to the nature of the work to be developed. That means that it is physically impossible to do, to unbreak this kind of dependency. Otherwise, on the other hand, you will have optional dependencies. That are decisions and options imposed by management restrictions. When you have optional dependencies, you can use those options, those dependencies to change it if you have to speed up the project. We will see that later. Finally, we will have external dependencies. They are usually imposed by interproject restrictions. And those involve relationships between project activities and activities outside the project. So to wrap up in this video, talk about the network diagram, activity on error and the precedence diagram. And we learn how to build it. We will talk how to use it to calculate the critical path and the slack in the next video.