 I am Priyanka Bidla and today we are going to see about behavioral model. At the end of this session, students will be able to explain behavioral model and differentiate between data-driven and event-driven modeling. These are the contents of this video lecture. Basically, we will concentrate on these points. Let us see first about behavioral model. This is one of the types of system model. Behavioral models are models of the dynamic behavior of the system as it is executing. They show what happens or what is supposed to happen when a system responds to a stimulus from its environment. Mainly behavioral model has two types. First is data-driven modeling and second is event-driven modeling. So data-driven modeling means some data arrives that has to be processed by the system. And event-driven modeling means some event happens that triggers the system processing and events may have associated data. So first we will see in detail about data-driven modeling and let us discuss about event-driven modeling. Let us see first data-driven modeling. Data-driven models were among us the first graphical software models. Many business systems are data processing systems that are primarily driven by data. They are controlled by the data input to the system with relatively little external event processing. Data-driven models show that it includes the sequence of actions in processing input data and generating an associated output. For example, a phone billing system will accept information about calls made by a customer. Then calculate the cost of these calls and generate a bill to be sent to that customer. This is also known as DFD, DFD is nothing but data flow diagram and it is useful in tracking and documentation purpose and during the analysis of requirements. Now about DFD, DFD is from a functional perspective. It helps analysts and designers understand what is going on particularly in the system. It shows data exchange between a system and other systems in its environment. These are simple and intuitive. For example, this figure shows an activity model of the Insulin-Purms operation. The chain of processing involved in the Insulin-Purm software. In this diagram, you can see the processing steps represented as activities and the data flowing between these steps represented as objects. This is UML sequence diagram. Already we knew about sequence diagram in the previous lectures we will discuss. You have seen how these can be used to model interaction but if you draw these then messages are only sent from left to right. Then they show the sequential data processing in the system. This shows using a sequence model of the processing of an order and sending it to supplier. These models highlight objects in a system and the equivalent data flow diagram for order processing is shown on the next slide. Here in this example, the notations used in these models represent functional processing by rounded boxes. In data stores by using rectangular boxes and data movements between these functions by using labelled arrows. They are used to show how data flows through a sequence of processing steps. In this example, simple blood sugar is taken and through sensor it is analyzed and according to that the required insulin computation is done and proper amount of insulin is given to that person to control the sugar level. So related to that all the processes are included. The data flows in sequential manner to acquire the system goal. We have to fulfill all the requirements of user. This process done from top to bottom. We will see second type of behavioral model that is event driven modeling. Event based modeling was introduced in real time design methods such as those proposed by Ward and Maylor in 1985 and Harrell in 1985 to 1987. This model the behavior of the system in response to external and internal events. It is based on the assumptions that a system has a finite number of states and that events may cause a transition from one state to another. This type of system is particularly appropriate for real time systems. It is used to represent state machine model. State machine models show system states as nodes and events as arcs between these nodes. When an event occurs the system moves from one state to another. The UML supports event based modeling using state diagrams which were based on the state charts. So in this state diagrams also included and states charts also. This is an example of state diagram of microwave oven. Real microwave ovens are actually much more complex than this system but the simplified system is easier to understand. This simple microwave has a switch to select full or half power, then numeric keypad to input the cooking time, then start and stop button and an alpha numeric display. The oven power is set to 300 watts. The display shows half power and the oven power is set to 600 watts. At that time the display shows full power. Here we have assumed that the sequence of actions in the microwave is. So first is select the power level either half power or full power. Second input the cooking time using a numeric keypad. Press start. There are two conditions door open and door closed. If the door is open then disable the operation and if the door is closed then time is set and the start button is enabled. Pushing this button starts the oven operation and cooking takes place for specified time. This is the end of cooking cycle and the system returns to the waiting state. For safety reasons the oven should not operate when the door is open and if the door is open during operation the system moves to the disabled state and on completion of cooking a buzzer is sounded. The oven has a very simple alpha numeric display that is used to display various alerts and warning messages. The next the stable shows the states for the microwave oven. It shows a tabular description of each state and the problem with state based modelling is that the number of possible states increases rapidly. For large system models therefore you need to hide detail in the model and this table shows the stimulus for the microwave oven. How the stimuli that four state transitions are generated? Pause the video and you have to think for a while and write down the differentiate points between data driven modelling and event driven modelling. So first point in data modelling data arrives that has to be processed by the system and in event modelling event happens that triggers system processing. Then second point data driven diagrams highlight the functions and event driven models highlight objects in a system. And last point will be data modelling is known as data flow diagram and event driven modelling is known as state diagram. Now these are the two types of behavioural modelling we are discussed in this video. These are the references for this video lecture. Thank you.