 ఏరాఇకవ�พెకాధిచనాటిటం. నిణమెల్uentల్వేదితలికా. ఎలెడృఏందిదితారూ. DEAR Provost Deals గావీం తెచ్ల్యా ధిముడు లాత్న్ే మీనోథిదు కిుమేపాన్స్తుం ద్ర్ల్ధో గావస్ని నోనిరానెపా నెస్పాస్త్స్తత్శి నోబిస్తు మీనై వీన the data flow and stored data. There is a prominent difference between DFD and FlowChart. The FlowChart depicts flow of control in program modules. DFD depicts flow of data in the system at various levels. DFD does not contain any control or branch element. So, data flow is nothing but the graphical representation of how data can be flow from one model to another model in the information system. There are two types of DFD. One is logical DFD. This type of DFD concentrates on the system process and flow of data in the system. For example, in banking software system, how data is moved between the different entities, physical DFD. This type of DFD shows how the data flow is actually implemented in the system. It is more specific, close to the implementation. Now, we are going to see the example of data flow diagram. This is the zero level data flow diagram. This is called zero level DFD of reservation system. It is also known as the context diagram. It is assigned to be an abstract view showing the system as a single process with its relationship to extended entities. It represents the entire system with a single bubble with input and output indicated by incoming or outgoing errors. So, here in zero level DFD, it is just like context diagram. The whole system can be shown at the central part and the internal external entities can be shown around of this circle. In the central part, you have to show the main system. The behavior of the internal external components should be shown outside the main system. The main system is the railway reservation. The external entity is the passenger and the administrator. The passenger will be making the reservation. The reservation information can be given to the administrator. Then, he will be checking the passenger information and evaluating the reservation. Then, he will be up-down train information also checking. Then, he will be providing the ticket information to the passenger. If cancellation is also done by the passenger towards the railway reservation system, that cancellation also can be done by using this administrator. The whole system can be shown in the middle circle. The passenger and admin can be shown in the rectangle. The errors can be shown in the data flow. What is the return on that error is the data flow. The next level DFD is one level DFD. For the same figure, we are entering into depth wise. In one level DFD, context diagram is decomposed into multiple bubbles or processes. In this level, we might highlight the main function of the system and break down the high level process of zero level DFD into sub-processing. See, the main system is the reservation process. The entity is the passenger. The data store is the own storage. The data store is the reservation storage. Up storage, down storage, enquiry is the one use case shown here. Many use cases are decomposed here. That is the ticket generation process, report to admin process. The reservation process is divided into the ticket generation process, report to admin process, enquiry process. The enquiry uses these two data stores. The reservation process is using these data stores, reservation stores. The passengers are interacting with the reservation process. This means we can decompose the reservation system into number of use cases, number of data stores, number of entities. Then, two level DFD. Again, it will be decomposed into the depth in detail. Two level DFD goes one step deeper into the part of one level DFD. It can be used to plan or record the specific necessary detail about the system functioning. Here, the reservation process can be decomposed into query processing, enquiry processing, relevant department, then cancellation process, then searching process, confirmation process, waiting process, then ticket generation process. What you can say, the passengers will be interacting with the enquiry, relevant system. Then, through this, it will be relevant system is passed to the information query processing for the reservation and it will be passing the information to the under use case relevant department and it will be using data store, waiting table, reservation, generate report. Then, cancellation will be another use case. Then, the cancellation table, it will be interacting with this and also, it will be interacting with the cancellation process. Then, searching process using data store reservation, confirmation process using reservation data store. Then, waiting process is using the waiting data store, ticket generation process using the interacting with the entity generate ticket. Likewise, the different sub processes are decomposed at two level DFD. So, data store entities and number of use cases are shown here. Next is data dictionary. In a DFD, arrows are labeled with the data atoms. Data dictionary defined data flows in DFD, showed structure of data, structure become more visible when exploiting, use regular expression to express that structure of data. The example of data dictionary is for timesheet DFD, weekly timesheet, then employee name plus ID, plus regular hours plus overtime, multiply by period equal to hour daily or weekly, plus dollar amount, employee name is last name plus first name plus middle name, ID is full digit, digit plus digit plus digit plus digit. This is the data dictionary, nothing but data repository. All the data can be stored in the data dictionary. Now, I am going to ask one question to all the students. Pause the video and write the answer. Question is, data flow diagram is dash representation of flow of data in information system. A graphical, B physical, C logical, D textual. Pause the video and write the answer. The correct answer is graphical. Data flow is a graphical representation of flow of data in information system. Now, we are going to see the year diagram. Year diagram is nothing but entity relationship diagram. An entity relationship model, year diagram describes the structure of the database with the help of the diagram which is known as entity relationship diagram. Year model is the design of blueprint of the database that can be later implemented in the database. The main components of year model are entity set and relationship set. Year diagram shows the complete logical structure of the database. A simple year diagram can be shown where students studies in college, student having the entity attributes, student ID, name and address, college attributes, college ID and college name. In following diagram, we have two entities, student and college and the relationship. The relationship between student and college is many to one as a college can have many students. However, a student cannot study in multiple colleges at the same time. Student entity has an attribute such as student ID, student name and student address. College has an attribute such as college ID and college name. These are the year diagram symbols. Rectangle represents entity set, ellipse represents attributes, diamond represents relationship set. Lines represents the link attributes of entity set and entity set to relationship set. Double ellipse, multi-valued attributes, dashed ellipse, derived attribute, double rectangle, weak entity set, double lines, total participation of entity in the relationship set. These are the year diagram symbols that rectangle entity ellipse represents attribute, diamond represents relationship, line represents attribute to entity set or entity to set to relationship. Then double ellipse represents multi-valued attribute, dotted ellipse represents derived attribute. Then double lines represent total participant entity, double rectangle represents weak entity, double diamond represents weak relationship. Then next is represent complex attribute, ellipse and line represent the key attribute, single-valued attribute. The components of year diagram are year diagram nothing but weak entity, then attribute and key, there are four types, three types of attribute, the key attribute, composite attribute, multi-valued attribute, derived attribute. Relationships are one-to-one relationship, one-to-many, many-to-one and many-to-many relationship. This is the simple year diagram for the shopper, where shopper buys the atoms, so atom is having the attribute, atom type, atom price and atom source. This can be shown by using the rectangle, diamond, this rectangle and this. So atom has these three attributes and buys the relationship and entity are shopper and atom. So year diagram of shopping. So there is the year diagram of lab, every management system can be shown, where books, publisher and member are the entities, relationship is published by and is borrowed by. So here books having the attributes, author, book, id, title, price and available. Then borrow is the relationship having the attribute, due date and return date and issue. This publisher having the attribute, publisher id, address, name, then member is having this member id, member date, member type address, name and expiry date, these are attributes of member. So books can be published by the publisher and this can be borrowed by the member of that library. So here there is a relationship between book and publisher, repented or published by, relation between book and member is given by borrowed by. These are the references. Thank you.