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44220: Database Design & Implementation Introduction to Module Ian Perry Room: C41C Ext.: 7287 E-mail: [email protected] http://itsy.co.uk/ac/0809/sem2/44220_DDI/ The Structure of the Module The Database Design & Implementation Module is concerned with three things: Ian Perry Why data storage (and information retrieval) needs to be organised in some manner. How a data storage system might be designed in such a way that it is demonstrably robust. How such a robust design might be implemented using a Relational DataBase Management System (RDBMS). 44220: Database Design & Implementation: Introduction to Module Slide 2 Lectures & Workshops Fri, 10:15 (C17a) ------------------ Fri, 11:15 (IT3) 19. 20. 21. 22. 23. 24. Introduction to Module Modelling the ‘Real’ World Conceptual Data Modelling ER Diagramming Logical Data Modelling Avoiding Data Anomalies 19. 20. 21. 22. 23. 24. Explore the DD&I Web-site Modelling Exercises Conceptual Modelling Ex. Drawing ER Diagrams Logical Modelling - Part 1 Logical Modelling - Part 2 [ Ass 1 Deadline – Wednesday, 18th of March ] 28. 29. Physical Data Modelling Implementing Domains 28. 29. MS Access – Workshop 1 MS Access – Workshop 2 ----------------- Easter Break ----------------30. 31. 32. Review & Ass 2 Reqs. -- No Lecture – -- No Lecture – 30. 31. 32. Assignment 2 Support Assignment 2 Support Assignment 2 Support [ Ass 2 Deadline – Wednesday, 13th of May ] Ian Perry 44220: Database Design & Implementation: Introduction to Module Slide 3 Assessment – based on a Case Study Perry’s Newsagents Read the Case Study Carefully There is a lot more to it than you might think initially; and don’t forget to re-read it from time to time. Your Role Deliver a variety of Daily/Weekly/Monthly Newspapers and Magazines to a large number of customers in the town of Beverley (East Yorkshire). You have been asked take part in the development of a Database System for Perry’s Newsagents that can: record the Newspapers and/or Magazines supplied by specific Suppliers. record Customer Orders for Newspapers and/or Magazines. plan the Daily Delivery of Newspapers and Magazines to Customers. Your database ‘solution’ MUST be able to ‘answer’ 10 specific questions (i.e. at the end of the Case Study), e.g.: A. What Newspapers & Magazines do we sell? C. Which Newspapers & Magazines are supplied by Supplier X? F. Which Newspapers and Magazines has Customer X ordered? Ian Perry 44220: Database Design & Implementation: Introduction to Module Slide 4 Two Assignments Assignment 1 (50%) – 18th of March, 2009 Develop and document an appropriate Conceptual Data Model. Develop and document a robust Logical Data Model. Assignment 2 (50%) – 13th of May, 2009 Implement your logical database model as a Physical Data Model, using Microsoft Access. Test this physical data model by building a number of Database Queries, to make sure that it ‘works’. Ian Perry 44220: Database Design & Implementation: Introduction to Module Slide 5 Data & Information Data? A series of observations, measurements, or facts. Information? Data that have been transformed into a meaningful and useful form for people. Data Information Process (perhaps!) Ian Perry 44220: Database Design & Implementation: Introduction to Module Slide 6 Information Attributes Information (or do I mean data?) can be thought of as having three dimensions: Time Content Accuracy, Relevance, Completeness, etc. Form Timeliness, Currency, Frequency, etc. Clarity, Detail, Order, Presentation, etc. Information is often affected by more than one of the above. Ian Perry 44220: Database Design & Implementation: Introduction to Module Slide 7 Information = ? Structure & Context People tend to look for a familiar structure & place data in a familiar context, e.g.: 120509: => DD/MM/YY = 12/05/09 = 12 May 2009 We use structure & context to transform the data we receive into information. Information = Data + Structure + Context The same data can be ‘interpreted’ as different information, if a different structure and/or context is applied. Ian Perry 44220: Database Design & Implementation: Introduction to Module Slide 8 To sum up so far! Data Information. Information is a people thing, only they can: Data are simply facts relating to ‘things’ like events, transactions, etc. determine the structure & context with which data might become information. and make decisions based upon the knowledge gained by the possession of that information. Must understand the difference between Data & Information: Ian Perry in order to Design (Ass 1) & Implement (Ass 2) a Database that is both Efficient & Effective. 44220: Database Design & Implementation: Introduction to Module Slide 9 Traditional Data Storage Computing has often been introduced to organisations in piecemeal manner. With the addition of each new software application comes the need to create a new set of files; containing that application’s required records. with each record containing that application’s required fields. and each field storing an ‘important’ data item. Over time the same data items will tend to be stored again and again (and again?) in the file systems of multiple applications: which leads to a number of problems! Ian Perry 44220: Database Design & Implementation: Introduction to Module Slide 10 Data Redundancy The repetition, in two or more files, of the same data item. There are an uncontrolled number of copies, which is: Expensive in Storage Expensive in Time Ian Perry 44220: Database Design & Implementation: Introduction to Module Slide 11 Data Inconsistency The problem of version control. With many versions of the data likely: Which one is the most up to date? Which one should I believe? Destroys user confidence. Very confusing. Potentially very expensive. Ian Perry 44220: Database Design & Implementation: Introduction to Module Slide 12 Data Dependence Applications and their data are ‘bound’ (i.e. stored) together. Ian Perry This doesn’t represent the way business organisations need to use data. The road to ‘information’ is impeded by the binding ‘glue’. 44220: Database Design & Implementation: Introduction to Module Slide 13 Data Sequencing If (when?) we need to combine the data from two, or more, business areas then the physical HOWs can be complex. Which often requires complicated patching systems; in order to: extract the data from one system. enter that data into the next. In extreme cases this may mean: printing out the data from one system. manually re-entering it into the next. Ian Perry 44220: Database Design & Implementation: Introduction to Module Slide 14 A Database Approach Take a holistic view of an organisation’s information requirements, so that: Laying a foundation of: data is thought of as a pivotal, company wide, resource. shared, common, data in which all have confidence. with well maintained & controlled access to that data. In other words: Ian Perry a Database! 44220: Database Design & Implementation: Introduction to Module Slide 15 Definitions A database is: A database management system (DBMS) is: an organised collection of data. software designed to assist in maintaining and utilising large collections of data. A relational database management system (RDBMS) is: Ian Perry a specific type of DBMS. 44220: Database Design & Implementation: Introduction to Module Slide 16 What does a RDBMS do? Main Features: Data is stored independently of the means of data manipulation. Data addition, alteration, retrieval are all controlled, consistent tasks. Different users see different data collections. Which gives us some advantages, i.e.: Ian Perry Minimal Data Redundancy (+ Data Consistency) Data Independence (+ Data Flexibility) Data Sharing (+/- Data Security) 44220: Database Design & Implementation: Introduction to Module Slide 17 Why should we care? “Data is only potential information; information is potential knowledge; and knowledge is potential competitive advantage if it is used in a creative, flexible, and above all, accurate way.” Adrian M (1990) Let’s Get Serious. Focus News. Winter. Ian Perry 44220: Database Design & Implementation: Introduction to Module Slide 18