ISYS254 Systems Analysis and Design SDLC marks the phases or ...
ISYS254 Systems Analysis and Design SDLC marks the phases or steps of information systems development: 1. Systems Planning and Selection – where an organisation’s total information system needs are analysed and arranged and in which a potential information systems project is identified and an argument for continuing or not continuing with the project is presented. 2. Systems Analysis – phase in which the current system is studied and alternative replacement systems are proposed. 3. Systems Design – phase in which the system chosen for development in systems analysis is first described independently of any computer platform (logical design), and is then transformed into technology-specific details (physical design) from which all programming and system construction can be accomplished. 4. Systems Implementation and Operation – final phase where the information system is coded, tested and installed in the organisation, and in which the information system is systematically repaired and improved. Information Systems Analysis and Design is the process of developing and maintaining an information system. The main goal is to improve organisational systems, through applying software that can help employees accomplish key business tasks more easily and efficiently. Application Software is software designed to process data and support users in an organisation. E.g. Spreadsheets, word processors, and database management systems. Goal is to turn data into information. System is an interrelated set of business procedures used within one business unit working together for some purpose. Has 9 characteristics: 1. Components (an irreducible part or aggregation of parts that makes up a system; also called a subsystem) 2. Interrelated components (dependence of one part of the system on one or more other system parts) 3. Boundary (the line that marks the inside and outside of a system and that sets off the system from its environment) 4. Purpose (the overall goal or function of a system) 5. Environment (everything external to a system that interacts with the system) 6. Interfaces (point of contact where a system meets its environment or where subsystems meet each other) 7. Constraints (a limit to what the system can accomplish) 8. Input 9. Output Decomposition is the process of breaking down a system into its smaller components. It is useful for focusing on one area at a time without interference from other areas. Modularity is the direct result of a system where the system is divided into chucks or modules of a relatively uniform size. Coupling is the extent to which subsystems depend on each other, as subsystems should be as independent as possible. Cohesion is the extent to which a subsystem performs a single function. Systems Integration allows hardware and software from different vendors to work together in an application.
Systems Analyst is the organisational role most responsible for the analysis and design of information systems. Prototyping is building a scaled-down working version of the desired information system.
Advantages: (1) involves the user in analysis and design, and (2) captures the requirements in concrete form, rather than verbal or abstract.
CASE tools are computer aided software engineering tools that provide automated support for some portion of the systems development project, increasing productivity and improving the overall quality of the systems. Repository is a centralised database that contains all diagrams, forms and report definitions, data structures, data definitions, process flows and logic, and definitions of other organisational and system components; it provides a set of mechanisms and structures to achieve seamless data-to-tool and data-todata integration. JAD is joint application design which is a structured process in which users, managers and analysts work together for several days in a series of intensive meetings to specify or review system requirements. RAD is rapid application development which is a systems development methodology created to radically decrease the time needed to design and implement information systems. It can result in low quality. Agile Methodologies are a family of development methodologies characterized by short iterative cycles and extensive testing; prioritising and verifying requirements; and a focus on small teams of talented, experienced programmers. Outsourcing is the practice of turning over responsibility for some or all of an organisation’s information systems applications and operations to an outside firm.
Advantages: (1) may be cost effective, (2) can be used to overcome operating problems the organisation faces in the IS unit.
Sources of Application Software:
Information Technology Service Firms - help companies develop custom information systems for internal use; developing, hosting and running applications for customers. Packaged Software Providers – software companies develop off-the-shelf systems. Software offerings range from general, broad based packages to narrow niche packages. Vendors of Enterprise Solutions Software – a system that integrates individual traditional business functions into a series of modules so that a single transaction occurs seamlessly within a single information system rather than several separate systems. o Advantages: (1) single repository of data for all aspects of a business process – ensures more consistent and accurate data & less maintenance Cloud Computing is the provision of computing resources, including applications, over the Internet, so customers do not have to invest in the computing infrastructure needed to run and maintain the resources. o Advantages: (1) frees internal IT staff (2) allows access to applications faster than via internal development, and (3) achieves lower cost access to corporate-quality applications o Constraints: (1) reliability, (2) security and compliance with government regulations e.g. Sarbanes-Oxley Open-Source Software – software that is freely available and developed by a community of interested people, performing the same functions as commercial software In House Development - system software that is developed from scratch when resources and staff are available on hand
Systems Analyst is the organisational role most responsible for the analysis and design of information systems. Prototyping is building a scaled-down working version of the desired information system.
Advantages: (1) involves the user in analysis and design, and (2) captures the requirements in concrete form, rather than verbal or abstract.
CASE tools are computer aided software engineering tools that provide automated support for some portion of the systems development project, increasing productivity and improving the overall quality of the systems. Repository is a centralised database that contains all diagrams, forms and report definitions, data structures, data definitions, process flows and logic, and definitions of other organisational and system components; it provides a set of mechanisms and structures to achieve seamless data-to-tool and data-todata integration. JAD is joint application design which is a structured process in which users, managers and analysts work together for several days in a series of intensive meetings to specify or review system requirements. RAD is rapid application development which is a systems development methodology created to radically decrease the time needed to design and implement information systems. It can result in low quality. Agile Methodologies are a family of development methodologies characterized by short iterative cycles and extensive testing; prioritising and verifying requirements; and a focus on small teams of talented, experienced programmers. Outsourcing is the practice of turning over responsibility for some or all of an organisation’s information systems applications and operations to an outside firm.
Advantages: (1) may be cost effective, (2) can be used to overcome operating problems the organisation faces in the IS unit.
Sources of Application Software:
Information Technology Service Firms - help companies develop custom information systems for internal use; developing, hosting and running applications for customers. Packaged Software Providers – software companies develop off-the-shelf systems. Software offerings range from general, broad based packages to narrow niche packages. Vendors of Enterprise Solutions Software – a system that integrates individual traditional business functions into a series of modules so that a single transaction occurs seamlessly within a single information system rather than several separate systems. o Advantages: (1) single repository of data for all aspects of a business process – ensures more consistent and accurate data & less maintenance Cloud Computing is the provision of computing resources, including applications, over the Internet, so customers do not have to invest in the computing infrastructure needed to run and maintain the resources. o Advantages: (1) frees internal IT staff (2) allows access to applications faster than via internal development, and (3) achieves lower cost access to corporate-quality applications o Constraints: (1) reliability, (2) security and compliance with government regulations e.g. Sarbanes-Oxley Open-Source Software – software that is freely available and developed by a community of interested people, performing the same functions as commercial software In House Development - system software that is developed from scratch when resources and staff are available on hand
