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Question
The value of a key attribute in a relation must uniquely identify every row in the relation.Answer
This answer is hidden. It contains 4 characters.
Related questions
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Conceptual data modeling for an Internet-based electronic commerce application differs significantly from the process followed when analyzing the data needs for other types of applications.
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The goal of conceptual data modeling is to capture as much of the meaning of data as possible.
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Relationships are labeled with verb phrases.
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Analysts should consider substituting single-attribute surrogate keys for large composite keys.
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When selecting an identifier, one should choose a candidate key that will not change its value over the life of each instance of the entity type.
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The names of data stores on primitive-level data flow diagrams often correspond to the names of data entities in entity-relationship (E-R) diagrams.
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Data on a customer form could be represented on a data-flow diagram as a data flow.
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A primitive level data-flow diagram is the first deliverable produced during requirements structuring.
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Structured analysis techniques, such as data-flow diagramming, can help companies avoid misunderstanding how existing systems will have to work with the new system and incorrect specifications for necessary data, forms, and reports.
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When you believe that you have shown each business form or transaction, computer screen, and report as a single data flow, you have probably reached the:
A) level-0 diagrams.
B) ternary-level diagrams.
C) primitive data-flow diagrams.
D) secondary-level diagrams.
E) context-level diagrams.
Q:
If an input from a source appears on a level-0 diagram, it must:
A) appear on the context diagram.
B) be connected to a data flow.
C) be connected to a sink.
D) be connected to a data store.
E) be connected to two entities.
Q:
Which of the following is a true statement regarding data flows?
A) A data flow to a data store means retrieve or use.
B) A data flow from a data store means update.
C) A data flow may have double-ended arrows.
D) A data flow represents data at rest.
E) A join in a data flow means that exactly the same data come from any of two or more different processes, data stores, or sources/sinks to a common location.
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Which of the following is true regarding the context diagram?
A) The process symbol is labeled "0."
B) The context diagram contains two processes.
C) Data stores must be shown on the context diagram.
D) The internal workings of the system are shown on the context diagram.
E) The context diagram organizes the processes in a tree-like structure.
Q:
A square on a data-flow diagram represents a sink or a:
A) data flow.
B) data store.
C) process.
D) predecessor.
E) source.
Q:
The shape of a data-flow (DFD) diagramming process is a(n):
A) arrow.
B) square.
C) rectangle.
D) rounded rectangle.
E) open box.
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A supplier of auto parts to your company would be represented on a data-flow diagram as a:
A) process.
B) source.
C) data flow.
D) data store.
E) relationship.
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Data contained on a customer order form would be represented on a data-flow diagram as a:
A) process.
B) data flow.
C) source.
D) sink.
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One of the primary purposes of a DFD is to represent time, giving a good indication of whether data flows occur constantly in real time, once a day, or once a year.
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A data flow repository entry would include the composition or list of data elements contained in the data flow.
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DFD cohesion means your DFDs include all of the necessary components for the system you are modeling.
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A process has a verb label.
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On a data-flow diagram, a rectangle with the right vertical line missing represents a data store.
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On a data-flow diagram, a diamond represents a process.
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Briefly identify and describe the participants of a JAD session.