Saturday, August 30, Elements of the System A system has three basic elements input, processing and output. The other elements include control, feedback, boundaries, environment and interfaces.
Loose Ends Introduction Requirements and specifications are very important components in the development of any embedded system. Requirements analysis is the first step in the system design process, where a user's requirements should be clarified and documented to generate the corresponding specifications.
While it is a common tendency for designers to be anxious about starting the design and implementation, discussing requirements with the customer is vital in the construction of safety-critical systems.
For activities in this first stage has significant impact on the downstream results in the system life cycle.
For example, errors developed during the requirements and specifications stage may lead to errors in the design stage. When this error is discovered, the engineers must revisit the requirements and specifications to fix the problem. This leads not only to more time wasted but also the possibility of other requirements and specifications errors.
Many accidents are traced to requirements flaws, incomplete implementation of specifications, or wrong assumptions about the requirements.
While these problems may be acceptable in non-safety-critical systems, safety-critical systems cannot tolerate errors due to requirements and specifications. Therefore, it is necessary that the requirements are specified correctly to generate clear and accurate specifications.
There is a distinct difference between requirements and specifications. A requirement is a condition needed by a user to solve a problem or achieve an objective. A specification is a document that specifies, in a complete, precise, verifiable manner, the requirements, design, behavior, or other characteristics of a system, and often, the procedures for determining whether these provisions have been satisfied.
For example, a requirement for a car could be that the maximum speed to be at least mph. The specification for this requirement would include technical information about specific design aspects.
Another term that is commonly seen in books and papers is requirements specification which is a document that specifies the requirements for a system or component. It includes functional requirements, performance requirements, interface requirements, design requirements, and developement standards.
So the requirements specification is simply the requirements written down on paper.
Key Concepts Establishing Correct Requirements The first step toward developing accurate and complete specifications is to establish correct requirements. As easy as this sounds, establishing correct requirements is extremely difficult and is more of an art than a science.
There are different steps one can take toward establishing correct requirements.
Although some of the suggestions sound fairly obvious, actually puttting them into practice may not be as easy as it sounds. The first step is to negotiate a common understanding. There is a quote by John von Neumann that states "There's no sense being exact about something if you don't even know what you're talking about.
There is no point in trying to establish exact specifications if the designers and customers cannot even agree on what the requirements are. Problem stems from ambiguities in stating requirements.
Possible interpretations of this requirement includes building a bus, train, or airplane, among other possibilities.System Re-Certification is the comprehensive re-evaluation of the management, operational, and technical security controls implemented for an information system that is performed during the Operations & Maintenance Phase to ensure that the system is .
(tools used in the analysis, design, and documentation of systems Narratives, flowcharts, diagrams, and other written materials that explain how a system works. results found, page 1 from for 'power system analysis and design solution manual'.
a traditional systems development technique that uses phases to plan, analyze, design, implement, and support an information system.
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Processes and data are treated as separate components. object oriented (O-O) analysis.