 Hello everyone welcome to this session. I am Priyanka Bidla and today we are going to see one of the types of the system model that is interaction model. These are the learning outcomes of this video lecture. At the end of this session students will be able to explain communication between systems with interaction model and second outcome will be explain use case modeling and sequence diagram. These are the contents we will be covering in this session. Now let us see about interaction model. Interaction may be user interaction or system interaction. Interaction which involves user inputs and outputs. Then interaction between the systems being developed and other systems or interaction between the components of the system being developed. It helps to identify user requirements and modeling system. The system interaction highlights the communication problem that may arise. It helps us understand if a proposed system structure is likely to deliver the required system performance and dependability. There are two approaches to interaction modeling. So first use case modeling and second sequence diagrams. Use case models and sequence diagrams present interaction at different levels of detail and so may be used together. Let us see in detail information about these approaches. So first use case modeling. Use case modeling was originally developed by Jacobson in 1990s. It was incorporated into the first release of the UML. It is mostly used to model interactions between a system and external actors and external actors may be users or other systems. Then it is used to support requirements elicitation. Now recall requirements elicitation and analysis. Before moving towards pause this video for few seconds and you have to recall the requirements elicitation and analysis. So it is a process of deriving the system requirements through observation of existing systems. Then it involves the development of one or more system models and prototypes also. This help you understand the system to be specified. Continued with the use case modeling it involves two actors in this use case. So one so first is the medical receptionist and other is patient record system. So here in its simplest form a use case is shown as an ellipse with the actors. Use informally to indicate that the medical receptionist initiate the transaction and they ties transferred to the patient record system. Each use case represents a discrete task that involves external interaction with the system. This figure shows a use case from the mhcpms that is represents the task of uploading data from the mhcpms to the prs and arrows in the UML indicate the direction flow of messages. Now this shows a tabular description of the transfer data use case. In such cases you may develop several diagrams each of which shows related use case as given in the table. For example medical receptionist is the actor and number of use cases are related to mhcpms. Those are resistor, patient, patient unresisted, view patient info, transfer data and contact patient. Those are connected with the actor. This figure shows all of the use cases in the mhcpms in which the actor is medical receptionist involved in that. Let us see the second approach of interaction modeling that is sequence diagram. This is the second type of interaction modeling. It is in the UML are primarily used to model the interactions between the actors and the objects in a system and the interactions between the object themselves. As the name implies a sequence diagram shows sequence of interactions that take place during a particular use case or use case instance. It has the UML has a rich syntax for sequence diagrams which allows many different kinds of interaction to be modeled. This is an example of sequence diagram that illustrates the basics of notation. The objects and actors involved are listed along the top of the diagram with a dotted line drawn vertically from this. Interactions between objects are indicated by annotated arrows. So the vertical rectangle on the dotted lines indicate the lifeline of the object concerned that is the time that object instant is involved in the computation and the sequence of interactions always read from top to bottom. The annotations on the arrows indicate the calls to the objects, their parameters and the return values. So here so first the interaction involved in view patient information use case. So first the medical receptionist triggers the view info method of the patient info which supplying PID is nothing but patient's identifier. So P is the object class which is showing patient information. Then the instant P calls to the mhcpmsdb that is database to return the information required. Supplying the receptionist identifier to allow security checking. At that time database checks with an authorization system that the user is authorized for this action. A box name ALT is used with the conditions indicate in square brackets. If authorization okay then patient information is returned from the database and form is filled. If authorization fails then error message is written. Then this is a second example of sequence diagram from the same system that illustrated two additional features. These are direct communication between the actors in the system and objects as part of sequence property as a part of sequence of operations. Again in this there are five actors are listed along the top of the diagram. Medical receptionist, patient info, mhcpms, authorization and PRS. In this example there are two sections. One is for sending information and another for sending summary. Summary is created to hold the summary data that is to be uploaded to the PRS that is patient record system. So first the receptionist logs on to the PRS. There are two options available. So first option is these allow the direct transfer of updated patient information to the PRS and the second option is transfer of summary health data from mhcpms to the PRS. In each case the receptionist permissions are checked using only the authorization system and personal information may be transferred directly from the user interface object to the PRS. Alternatively a summary record may be created from the database and that record is transferred. On completion of the transfer the PRS issues a status message and the user logs off. So here we have seen the interaction model and their approaches that are use case modeling and sequence diagram. These are the references for this video lecture. Thank you.