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Slide 1: System Choice Overview, Principles and Techniques Chapter 2 © ITU, February 09 1 The System’s Context System User Problem domain Application domain The purpose of system choice is to define the context of the system © ITU, February 09 2 Activities Pro blemdo main ana lysis Re quirements for use Applicationdom ain analysis Situation And interpretations Ideas For system design Create foundation and criterion of relevance for Model Component design Speci fications of compo nents Systems System definition Specifications of archite cture Architectural design System definition: a concise description of a computerized system expressed in natural language © ITU, February 09 3 Side 1
Slide 2: Result (example) Systemdefinition: A computerized system used to prepare and plan an IFIP conference, with emphasis on administration of participants, articles, and the program itself. The system should primarily be an administrative tool, but secondarily serve as a communication medium for the program committee, the organizing committee, and the local administrative personnel to help them manage the conference. The system should be based on a cheap PC with current tools. The system should also be able to function in different types of environments, including use by volunteers who have great enthusiasm and greatly variable administrative experience. © ITU, February 09 4 Describe the Situation (using Rich Pictures) • • • Expresses different views Focus: – on change or stability #1 Tradition vs. change Principle: Appreciate the situation #2 Individual info. Processes such as: – work, production, information #3 processing, exchange, planning, control, development, organizational change Pool Standard inf o. Reorganizing Resources Personnel info. • Structures such as: – production, use, application, communication, deal, ownership, membership, relationship, power #4 #5 • Rich pictures – but not chaotic #6 Coordinating New entity Plans © ITU, February 09 5 Ideas for symbols for Rich Pictures ABC… 123… © ITU, February 09 6 Side 2
Slide 3: Rich Picture (example) with Focus on Stability reception of calls d isp atcher custome rs ta sks Where is it? When a re they re ad y? 5 0 cars emergency vehicle h osp ital © ITU, February 09 7 Create Ideas • Exemplars (e.g. for a financial system): – Study an existing system – Look at spreadsheets – Examine standard packages – Consider SAP • Experiments with prototypes: – Planning – – – – Development Preparation Test Summarizing • Metaphors (e.g. for a library): – Storage – Supermarket – School © ITU, February 09 8 Different kinds of prototyping • exploratory prototyping: – to clarify requirements – to discuss different solutions • experimental prototyping – determining the adequacy of a proposed solution • evolutionary prototyping – adapting the system to possibly changing requirements © Christiane Floyd © Christiane Floyd © ITU, February 09 9 Side 3
Slide 4: Systems are holistic views • A system definition expresses a perspective on something • Every system definition represents a specific perception of the real world filtered through the ideas, conceptions, educations and backgrounds of the people involved The Earth seen from Apollo 17. From a holistic perspective, the universe exists in and forms integrated webs of wholeness, often beyond our direct perception (Wikipedia) © ITU, February 09 10 System Definition (FACTOR) Functionality: The system functions that support the application-domain tasks. Application domain: Those parts of an organization that administrate, monitor, or control a problem domain. Conditions: The conditions under which the system will be developed and used. Technology: Both the technology used to develop the system and the technology on which the system will run. Objects: The main objects in the problem domain. Responsibility: The system’s overall responsibility in relation to its context. © ITU, February 09 11 Hair Salon A system for use in a hair salon in the daily work of managing customers and appointments, as well as earlier treatments of regular customers. The system should also be used by the salon owner for planning employees’ work schedules. Appointments are integrated to help arrange work schedules. The system should be a reliable and fast tool in the daily work and should also be a common medium for work schedules (appointments). The system is based on a single, small (and cheap) PC or Macintosh with a large graphical screen (17”), capable of showing detailed work schedules. The development process should be conducted in close cooperation with the salon employees. F Support for work planning (schedules) and appointments. A Managing customers, their treatments, and appointments, and planning employees’ work schedules. C Development in close collaboration with employees. T Smaller PC or Macintosh with large graphical screen. O Customers, employees, appointments, and work schedules.. R Tool for reliable administration and a common mediator in the salon. © ITU, February 09 12 Side 4
Slide 5: Define Systems and Alternatives • Functionality 1 – Register information about participants and produce a complete participant list. • Responsibility 1 – Support program design by producing overviews and allowing users to add components and save different versions. Support conference operations by emphasizing potential problems at regular intervals. • Functionality 2 – Register general participants as well as those with an active role such as author, speaker, or reviewer. Support the administration of finances and invitations. Support development of conference programs, including registration, paper acceptance, and sessions divisions. • Responsibility 2 – Automatic conference-planning program. Generate program from suggested sessions and incoming paper reviews. © ITU, February 09 13 Evaluation and Choice • Do this as early as possible • Iterate within the activity and in subsequent activities • The purpose is to choose one system • It is the choice of the customer • System developers provide support and organize the process • Approach: question overall decisions and evaluate alternatives © ITU, February 09 14 System Choice: Summary Purpose Concept Principles Results • To agree on the overall system characteristics. • System definition: A concise description of a computerized system expressed in natural language. • Appreciate the situation. • Cultivate new ideas. • Define alternative systems. • A system definition that fulfills the FACTOR criterion. © ITU, February 09 15 Side 5
Slide 6: Task for the rest of today and until the next OOA&D exercise • • Meet in groups and identify a simple system case you can use for your project Start to work on the system definition! 1. Describe the situation in your case by one or more rich pictures. 1. Create one each, and compare and explain 2. 3. 4. Generate ideas for computerized functions. Make a system definition. Formulate alternatives by varying one or more elements in the system definition (could be different opinions about the characteristics of the system). 16 © ITU, February 09 Examples of cases Find your own case - or use the • • • • Video rental (Ex. 13, ch 3) Mobile Phone (Ex. 14, ch 3) Teaching Administration (Ex. 15, ch 3) Elevator Control (Ex. 16, ch 3) .... the idea is to try out the techniques! © ITU, February 09 17 References • L. Mathiassen et al. Object Oriented Analysis and Design. 2000, chapter 16. © ITU, February 09 18 Side 6