問題一覧
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a pictorial representation of reality.
model
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– a nontechnical pictorial representation that depicts what a system is or does. Synonyms for essential model, conceptual model, and business model
logical model
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a technical pictorial representation that depicts what a system is or does and how the system is implemented.
physical model
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a technique used to organize and document a system’s processes
process modeling
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a process model used to depict the flow of data through a system and the work or processing performed by the system.
data flow diagram
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What is dfd
data flow diagram
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an outside person, unit, system, or organization that interacts with a system. Also called an external entity.
external agent
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stored data intended for later use. Synonyms are file and database.
data store
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work performed by a system in response to incoming data flows or conditions. A synonym is transform.
process
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the act of breaking a system into sub-components. Each level of abstraction reveals more or less detail about the overall system or a subset of that system.
process decomposition
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a tool used to depict the decomposition of a system. Also called hierarchy chart.
decomposition diagrams
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a set of related and ongoing activities of a business.
function
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a discrete, detailed activity or task required to complete the response to an event. Also called a primitive process
elementary process
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data that is input to or output from a process
data flow
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a data flow that consists of other data flows
composite data flow
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a condition or nondata event that triggers a process.
control flow
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the smallest piece of data that has meaning to the users and the business.
data attributes
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a specific arrangement of data attributes that defines an instance of a data flow.
data structure
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- a class of data that be stored in an attribute
data type
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the legitimate values for an attribute.
domain
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a data flow that splits into multiple data flows.
diverging data flow
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the merger of multiple data flows into a single packet.
converging data flow