Presentation Transcript

1. Lecture IS3318

   29/11/11
2. Intro to Databases File organization concepts Computer system organizes data in a hierarchy Field: Group of characters as word(s) or number Record: Group of related fields File: Group of records of same type Database: Group of related files Record: Describes an entity Entity: Person, place, thing on which we store information Attribute: Each characteristic, or quality, describing entity E.g., Attributes Date or Grade belong to entity COURSE
3. The Data Hierarchy A computer system organizes data in a hierarchy that starts with the bit, which represents either a 0 or a 1. Bits can be grouped to form a byte to represent one character, number, or symbol. Bytes can be grouped to form a field, and related fields can be grouped to form a record. Related records can be collected to form a file, and related files can be organized into a database. Figure 6-1
4. Problems with the traditional file environment (files maintained separately by different departments) Data redundancy and inconsistency Data redundancy: Presence of duplicate data in multiple files Data inconsistency: Same attribute has different values Program-data dependence: When changes in program requires changes to data accessed by program Lack of flexibility Poor security Lack of data sharing and availability
5. Database Collection of data organized to serve many applications by centralizing data and controlling redundant data Database management system Interfaces between application programs and physical data files Separates logical and physical views of data Solves problems of traditional file environment Controls redundancy Eliminates inconsistency Uncouples programs and data Enables organization to central manage data and data security
6. Human Resources Database with Multiple Views A single human resources database provides many different views of data, depending on the information requirements of the user. Illustrated here are two possible views, one of interest to a benefits specialist and one of interest to a member of the company’s payroll department. Figure 6-3
7. Relational DBMS Represent data as two-dimensional tables called relations or files Each table contains data on entity and attributes Table: grid of columns and rows Rows (tuples): Records for different entities Fields (columns): Represents attribute for entity Key field: Field used to uniquely identify each record Primary key: Field in table used for key fields Foreign key: Primary key used in second table as look-up field to identify records from original table
8. Relational Database Tables A relational database organizes data in the form of two-dimensional tables. Illustrated here are tables for the entities SUPPLIER and PART showing how they represent each entity and its attributes. Supplier_Number is a primary key for the SUPPLIER table and a foreign key for the PART table. Figure 6-4A
9. Relational Database Tables (cont.) Figure 6-4B
10. Capabilities of Database Management Systems Data definition capability: Specifies structure of database content, used to create tables and define characteristics of fields Data dictionary: Automated or manual file storing definitions of data elements and their characteristics Data manipulation language: Used to add, change, delete, retrieve data from database Structured Query Language (SQL) Microsoft Access user tools for generation SQL Many DBMS have report generation capabilities for creating polished reports (Crystal Reports)
11. The Database Approach to Data Management Microsoft Access Data Dictionary Features Figure 6-6 Microsoft Access has a rudimentary data dictionary capability that displays information about the size, format, and other characteristics of each field in a database. Displayed here is the information maintained in the SUPPLIER table. The small key icon to the left of Supplier_Number indicates that it is a key field.
12. Some Drawbacks… Complexity A DBMS is a complex piece of software all users must fully understand it to make use of its functionalities Cost of DBMS The cost varies significantly depending on the environment and the functionality provided. Must take into consideration recurrent annual maintenance costs
13. Continued.. Cost of Conversion Cost of converting existing applications to run on the new DBMS and hardware. (additional training costs) Performance DBMS is written for applications in general which means that some applications may run slower than before Higher Impact of Failure Centralization of resources increases vulnerability of the system
14. Database Administrator Oversees a staff of database specialists Final recommendations for DB design Load and maintain DB Establish security controls Perform backup and recovery
15. Data Administration Data Administrator Database technology And management Database Management System Data planning and modelling technology Users
16. Systems Analyst Or business analyst is a systems analyst that specializes in business problem analysis and technology-independent requirements analysis. A programmer/analyst (or analyst/programmer) includes the responsibilities of both the computer programmer and the systems analyst. Other synonyms for systems analyst include: Systems consultant Systems architect Systems engineer Information engineer Systems integrator
17. Variations on the Systems Analysts Title Other synonyms for systems analyst include: Systems consultant Systems architect Systems engineer Information engineer Systems integrator
18. Role of the Systems Analyst Study problems and needs of an organization Determine best approach to improving organization through use of: People Methods Information technology Help system users and managers define their requirements for new or enhanced systems
19. Skills of a Successful Systems Analyst Analytical Understanding of organizations. Problem solving skills System thinking Ability to see organizations and information systems as systems Technical Understanding of potential and limitations of technology.
20. Skills of a Successful Systems Analyst Managerial Ability to manage projects, resources, risk and change Interpersonal Effective written and oral communication skills
21. System Owners System owners are the information system’s sponsors and chief advocates. They are usually responsible for funding the project to develop, operate, and maintain the information system.
22. System Users System users are the people who use or are affected by the information system on a regular basis—capturing, validating, entering, responding to, storing, and exchanging data and information. A common synonym is client. Types include: Internal users Clerical and service workers Technical and professional staff Supervisors, middle managers, and executive managers Remote and mobile users (internal but disconnected) External users
23. Stakeholders: Players in the Systems Game A stakeholder is any person who has an interest in an existing or new information system. Stakeholders can be technical or nontechnical workers. For information systems, the stakeholders can be classified as: System owners System users Systems analysts System designers System builders IT vendors and consultants
24. Systems Development Lifecycle(SDLC) The systems development life cycle (SDLC) model is an approach to developing an information system or software product that is characterised by a linear sequence of steps that progress from start to finish without revisiting any previous step. The SDLC model is one of the oldest systems development models and is still probably the most commonly used.
25. SDLC Traditional systems development lifecycle (Waterfall Model) SDLC - very similar to a product life cycle in the consumer market because both a new product and information system develop through a number of stages.
26. The typical SDLC has the following steps: Initiation Feasibility study System Investigation System Analysis Systems Design Implementation Review and Maintenance These stages are frequently referred to as “conventional systems analysis”, “traditional systems analysis”, “the systems development life-cycle” or the Waterfall Model
27. SDLC or The Waterfall Model The waterfall model describes a development method that is linear and sequential. Once a phase of development is completed, the development proceeds to the next phase and there is no turning back. The advantage of waterfall development is that it allows for departmentalisation and managerial control.
28. The Waterfall Model Continued.. A schedule can be set with deadlines for each stage of development and a product can proceed through the development process and theoretically, be delivered on time. Development moves from concept, through design, implementation, testing, installation, troubleshooting, and ends up at operation and maintenance.
29. Initiation Traditional SDLC Investigation Analysis Design Implementation NO FEEDBACK!!!! Maintenance
30. SDLC This is now regarded as the “hard” systems approach because of its rigid demarcation between phases. It has shortfalls which lead to a number of difficulties One major criticism of the model is that it doesn’t cater for revisiting previous phases to correct defects. Feedback Loop– refinement of Waterfall Model
31. Potential Strengths of the Traditional SDLC It has been well tried and tested Use of documentation standards Following the methodology should aid (At least to some extent) that roll out dates, budgets and expected benefits are met. At the end of each phase, all parties involved in the project can review progress. Much greater control on the development of computer applications and make possible the use of project management tools and techniques
32. Potential Weaknesses of the Traditional SDLC Criticisms of the methodology or perhaps of the way it was used include: Failure to meet the needs of management Unambitious systems design Instability Inflexibility User dissatisfaction Problems with documentation Lack of control
33. Potential Weaknesses of the Traditional SDLC Incomplete systems Application backlog Maintenance workload Problems with the “ideal” approach It does not allow for much reflection or revision.
34. Prototyping Building an experimental system rapidly and inexpensively for end users to evaluate It will be refined until it conforms to the users’ requirements This is achieved through iterative development
35. Advantages of Prototyping Useful when there is uncertainty about system requirements or systems design Valuable for End-user interface design Encourages end-user involvement throughout the systems development lifecycle
36. Disadvantages of Prototyping Better suited for smaller application development. Prototyping may mean glossing over essential steps in the system development.
37. Application Software Packages A set of prewritten, precoded application software programs that are commercially available for sale or lease Packages have increased as many applications are common to many businesses: payroll, accounts and inventory control
38. Advantages of Software Packages Most of the design work has been completed in advance Little extensive testing required Vendor support and maintenance
39. Disadvantages of Software Packages Disadvantages may be increased with a complex system Required customisation and additional programming may be expensive Hidden implementation costs
40. End User Development The development of information systems by end users with little or no formal assistance from technical specialist It has been made possible by fourth generation software tools (4GL)
41. Encouraging End User Development The variety of application development tools available make it easier for end user development Guidelines for managers to encourage intranet website development by end users: Look for what makes sense Spur creativity Set some limits Give managers responsibility Make users comfortable
42. Advantages to End User Development Improved requirements determination Increased user involvement and satisfaction Reduced application backlog
43. Risks of End User Development It occurs outside the traditional mechanisms for information system management and control Problems in ensuring that end-user developed applications meet organisations objectives and standards Rapid systems development without a formal methodology may mean that testing and documentation is inadequate Loose control of organisational data
44. Definition - Outsourcing The practice of contracting computer centre operations, telecommunications networks, or application development to external vendors Example: Bank of Ireland, Dell
45. Outsourcing Outsourcing has become increasingly popular as companies believe that it is more cost effective than maintaining their own IS staff Many companies are outsourcing software procurement and support to application service providers (ASPs) who provide and support business application and other software via the Internet and intranets to all of a company’s employees workstations
46. Benefits of Outsourcing To reduce work in the information systems department. When the IS function within an organisation is limited. To improve the contribution of IT to enhance business performance. To create new sources of revenue.
47. Benefits of Outsourcing To reduce work in the information systems department When the IS function within an organisation is limited To improve the contribution of IT to enhance business performance To create new sources of revenue
48. Risks associated with Outsourcing May loose control over IS function Heavy reliance on the vendor Proprietary information may be leaked to the competition if sensitive data is available outside the organisation
49. Sample Questions Discuss Porter’s Competitive Forces Model, considering the role of information systems in gaining competitive advantage. Illustrate your answer with diagrams and examples. Outline and briefly explain the stages involved on the Systems Development Lifecycle (SDLC).