2 Lecture’s Objectives Put all the previous lectures into context Chapter NameSeptember 98Lecture’s ObjectivesPut all the previous lectures into contextLearn the main stages of database application development.Use these stages as guidelines for your MSc project (if you choose to undertake a project which involves developing a Database System).22
3 Software DepressionLast few decades have seen a proliferation of software applications, many requiring constant maintenance involving:correcting faults,implementing new user requirements,modifying software to run on new or upgraded platforms.As a result, many major software projects werelate,over budget,unreliable,difficult to maintain,performed poorly.This led to a ‘software crisis’, now referred to as the ‘software depression’.
4 Software DepressionMajor reasons for failure of software projects include:- lack of a complete requirements specification;- lack of appropriate development methodology;- poor decomposition of design into manageable components.Structured approach to development was proposed called information systems lifecycle.
5 Information SystemResources that enable collection, management, control, and dissemination of information throughout an organisation.Database is fundamental component of I.S., and its development/usage should be viewed from perspective of the wider requirements of the organisation.
6 Database Application Lifecycle Database planningSystem definitionRequirements collection and analysisDatabase designDBMS selectionApplication designPrototypingImplementationData conversion and loadingTestingOperational maintenance.
9 Overview of the Case Study DreamHome is a company that specialises in property renting, by taking an intermediate role between property owners and clients who require to rent a property.DreamHome operates several branches throughout the UK. Each branch has a number of staff including a Manager, Supervisors, and Assistants. Each branch offers a range of properties for rent.The Director of the company feels that a database could help in avoiding the many mistakes occurring in the current paper-based operations of the company.
10 1. Database Planning: (A. Mission Statement) Mission statement for the database project defines major aims of database application.Those driving database project normally define the mission statement.Mission statement helps clarify purpose of the database project and provides clearer path towards the efficient and effective creation of required database application.
11 DreamHome – Database Planning – Mission statement Typical questions we might ask the Director:“What is the purpose of your company?”“Why do you feel that you need a database?”Example of a mission statement: “The purpose of the database system is to maintain the data that is used and generated to support the property rentals business for our clients and property owners and to facilitate the cooperation and sharing of information between branches”.
12 1. Database Planning (B. Mission Objectives) Once mission statement is defined, mission objectives are defined.Each objective should identify a particular task that the database must support.May be accompanied by some additional information that specifies the work to be done, the resources with which to do it, and the money to pay for it all.
13 DreamHome – Database Planning – Objectives Typical questions to various members of staff include:“What is your job description?”“What kinds of tasks do you perform in a typical day?”“What kinds of data/reports do you use?”Examples of objectives:To maintain (enter, update, and delete) data on branchesTo perform searches on branchesTo report on branches…
14 1. Database PlanningDatabase planning should also include development of standards that govern:how data will be collected,how the format should be specified,what necessary documentation will be needed
15 2. System DefinitionDescribes scope and boundaries of database application and the major user views.
16 DreamHome – System Definition –System’s boundary PropertyAdvertisingRentalsCustomerServicesStaffHumanResourcesPayrollMarketingSalesSystem’s Boundary
17 2. System DefinitionUser view defines what is required of a database application from perspective of:a particular job role (such as Manager or Supervisor) orenterprise application area (such as marketing, personnel, or stock control).
18 Representation of a Database Application with Multiple User Views
19 DreamHome – System Definition – Major user views DataAccess TypeDirectorManagerSupervisorAssistantAll BranchesMaintainQueryXReportSingle BranchAll StaffBranch Staff… etc
20 3. Requirements Collection and Analysis Process of collecting and analyzing information about the part of organization to be supported by the database application, and using this information to identify users’ requirements of new system.
21 3. Requirements Collection and Analysis Data model representing single user view is called a local data model, composed of diagrams and documentation describing requirements of a particular user view of database.Local data models are then merged to produce a global data model, which represents all user views for the database.
22 Fact-Finding Techniques Database developer normally uses several fact-finding techniques during a single database project including:examining documentation,interviewing,observing organisation in operation,research,questionnaires.
23 DreamHome – Requirements Collection & Analysis Data Requirements:Branches: The data held on each branch office includes a unique branch number, address (street, city, and postcode)…Staff: The data stored on each member of staff includes staff number, name……
24 DreamHome – Requirements Collection & Analysis Transaction Requirements:Data entry:Enter the details of a new branch…Data update/deletion:Update/delete the details of a member of staff at a branch…Data queries:List the names of staff supervised by a named supervisor…
25 DreamHome – Requirements Collection & Analysis System’s specification:Initial database sizeDatabase rate of growthThe types and average number of record searchesNetworking and shared access requirementsPerformanceSecurityBackup and recoveryLegal issues
26 DreamHome – Requirements Collection & Analysis Initial database size:There are approximately 2000 members of staff at 100 branches. There is an average of 20 and a maximum of 40 members at each branch…Database rate of growth:Approximately 500 new properties and 200 new owners are added to the database each month…Types and average number of record search:Searching for the details of a branch – approximately 10 per day…Networking and shared access requirements:All branches should be networked to a centralised database at the main office. The system should allow for at least three people concurrently accessing the system for each branch…
27 DreamHome – Requirements Collection & Analysis Performance:During non-peak periods expect less than 1 second response time for all single record searches…Security:The database should be password protected…Backup and Recovery:The database should be backed up daily at 12 midnight.Legal issues:Implement UK’s law on the computerised storage of personal data (staff, clients and owners).
28 4. Database Design Major aims: Represent data and relationships between data required by all major application areas and user groups.Provide data model that supports any transactions required on the data.Specify a minimal design that is appropriately structured to achieve stated performance requirements for the system (such as response times).
29 4. Database Design Three phases of database design: Conceptual database designLogical database designPhysical database design.
30 5. DBMS SelectionSelection of an appropriate DBMS to support the database application.Undertaken at any time prior to logical design provided sufficient information is available regarding system requirements.Main steps to selecting a DBMS:define Terms of Reference of study;shortlist two or three products;evaluate products;recommend selection and produce report.
31 6. Application DesignDesign of user interface and application programs that use and process the database.Database and application design are parallel activities.Includes two important activities:transaction design (e.g., Queries);user interface design (e.g., Forms).
32 6. Application Design (A. Transactions) Important characteristics of transactions:data to be used by the transaction;output of the transaction;importance to the users;expected rate of usage.Three main types of transactions: retrieval, update, and mixed.
33 6. Application Design (B. User Interface) Guidelines for User Interface design:Meaningful titleComprehensible instructionsLogical grouping and sequencing fieldsVisually appealing layout of the form/reportFamiliar field labelsConsistent use of colourVisible space and boundaries for data-entry fieldsConvenient cursor movementError messages for unacceptable valuesOptional fields marked clearlyExplanatory messages for fieldsCompletion signal
34 7. PrototypingBuilding working model of a database application.Purposeto identify features of a system that work well, or are inadequate;to suggest improvements or even new features;to clarify the users’ requirements;to evaluate feasibility of a particular system design.
35 8. Data Conversion and Loading Transferring any existing data into new database and converting any existing applications to run on new database.Only required when new database system is replacing an old system.DBMS normally has utility that loads existing files into new database.May be possible to convert and use application programs from old system for use by new system.
36 9. TestingProcess of executing application programs with intent of finding errors.Use carefully planned test strategies and realistic data.Testing cannot show absence of faults; it can only demonstrate that database and application programs appear to be working according to requirements.
37 10. Operational Maintenance Process of monitoring and maintaining system following installation.Monitoring performance of system.if performance falls, may require tuning or reorganization of the database.Maintaining and upgrading database application (when required).Incorporating new requirements into database application.
38 Data Administration and Database Administration Data Administration: Management of data resource including:database planning,development and maintenance of standards, policies...Database Administration: Management of physical realisation of a database application including:physical database design and implementation,setting security controls,monitoring system performance...