Computer Systems Analysis and Design

Questions : 1. Draw a context diagram data flow diagram for the system described above. The format should be similar to the context diagram in figure 5-13 of your textbook.2. Draw the Level 0 DFD (Data Flow Diagram). All processes on this diagram should be functional primitives. The format should be similar to the context diagram in figure 5-16 of your textbook.3. Draw an ERD (Entity Relationship Diagram) which represents the entities described in the case study, fully normalised to reflect all entities, relationships, cardinality and optionality. Ensure to follow the crows feet notation to indicate cardinality. The format should be similar to the figure 9-21 of your textbook.4. Create a 3NF design for the system described in the case study. Provide the entity attribute list in 3rd normal form to support the ERD in Task 3. Make sure that all primary and foreign keys are identified properly. It is not necessary to provide the earlier normalisation forms (1NF and 2NF) as these will not be marked.5 . Draw a class diagram for the system described in the case study. The format should be similar to the class diagram in figure 6-30 of your textbook. Make sure to include all relevant attributes and methods for each class.6. The Manager of Dazzling Costumes is most interested in your work. She has no knowledge of Systems Analysis and Design and has asked for a brief explanation of what you have done and what these mean to her. Write - 1 page report explaining your work in Tasks 1 5. 7.Briefly describe various system changeover methods. Suggest a changeover method for the system described in the case study and provide specific reasons to support your choice. Answers : 1. The context diagram for Dazzling Costumes system is, There is the system and three external entities, customer, customer service staff, manager. 2. The level 0 DFD is, There are 4 processes, 2 data stores and three external entities in this diagram. 3. The ERD is, Here are 4 entity sets, 4 binary one to many relationships and one relationship set. 4.The 3NF design is, CUSTOMER (CustomerID, FirstName, LastName, Gender, DOB, Address, Email) ITEM (ItemCode, name, brand, GeneralDescription ) ITEM_PIECE (ItemPieceCode, ItemCode, DateOfPurchase, PurchaseCost, Color. Size, SpecialGeneralNote, Status) HIRE_ORDER (HireOrderCode, CustomerID, ItemPieceCode, ReportCode, DateOfHire, ExpectedDateReturn, ReturnDate, Status) REPORT (ReportCode, Date) The primary keys are underlined and the foreign keys are in italics. 5. The class diagram is, There are 5 classes with attributes and associates among the classes. 6.Explanation In this report there are system design and analysis diagram including context diagram, level 0 DFD diagram, ER diagram, 3NF design of the ER diagram and Class diagram. Each of these diagrams has different aspects in the diagrams. The context diagram will give a top level view of the whole system. There will be flow of information between different external entities and the system. All these interactions have been represented in this diagram. Then the level 0 DFD diagram has been developed from the context diagram. Here is whole system will be seen as a collection of several processes, data stores etc. The processes are the main functions of the system. The data stores represents what kind of data is stores across the system. (Satzinger, et al., 2011) Here also, the flow of data through the processes, data stores and external entities have been represented in the diagram. Next is the ER diagram. This is a conceptual database design diagram. There are several entities related to the system, the system needs to store information about those entities. Also there are relationships among those entities. The ER diagram shows the entities, attributes of the entities and the relationships among those entities. The cardinalities, primary keys, foreign keys etc. everything are given in the diagram. A 3NF logical database design has been created from the ER diagram. The entity sets and the relationships from the ERD have been transformed into relations in the 3NF. The 3NF relations ensures that the relations will be optimized to have minimal redundancy and there will be no duplicate record in the relations. (Shelly Rosenblatt, 2011) 7. When an information system is replaced with a new one then system changeover takes place. It is true for the cases where some manual system is replaced by new information system. There are 4 kinds of system changeover process. Those are, Total changeover process, is where the whole new system is developed separately without the old system. Then the whole system is replaced by the new one at a time. This is cheaper by highly risky process. As the old system will be replaced at once, there may be chances of losing data during the data transition from old to new system. Also there are chances that the new system will not be able to represent the business process properly. Phased system changeover process is the process where the new system is developed and implemented in multiple phases. Possible, in one part of the business at a time. Then the performance of the implemented system is checked. If everything goes right with the new system then it is implemented for the whole business. This is costlier but the risks are reduced. The cost is incurred from the parallel run of old and new system until the new system is fully implemented for the whole business. As, at first the implementation is done for a part of the business, so, if there is some error in the new system, it is highly likely to get uncovered in the first phase. Thus the impact of the risks will be less. (Shelly Rosenblatt, 2011) Parallel system changeover process is, where the old and new systems for the business runs in parallel until the new system takes over the whole business process. This is the most secure process but is highly costly. As there are two completed system runs simultaneously for the same business process for quite some time. But there is very little chance to loss any data as there is the old system always for backup. There is another method called pilot changeover process. Where the whole new system is implemented in a smaller subset of the business, possibly in one site. The performance is checked and then it is expanded over the whole business. (Shelly Rosenblatt, 2011) For dazzling costumes, the system is smaller and there is no previous information system. So, they can follow the direct changeover process. References Satzinger, J. W., Jackson, . R. Burd, S. D., 2011. Systems Analysis and Design in a Changing World. s.l.:Cengage Learning. Shelly, G. Rosenblatt, H. J., 2011. Systems Analysis and Design. s.l.:Cengage Learning.