Cierto o Falso Capítulo 4

1. 1Whether a developer uses an E-R model or a semantic object model, the eventual database design that is created should be exactly the same.

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2. 2The semantic object model is different from object-oriented database processing.

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3. 3Semantic objects represent the users’ perceptions more closely than the E-R model.

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4. 4Unlike entities, semantic objects are not grouped into classes.

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5. 5An “identifier” is a named collection of attributes that sufficiently describes a distinct identity.

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6. 6Semantic objects represent distinct identities.

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7. 7A semantic object must represent something with a physical existence.

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8. 8Attributes of a semantic object that contain only a single element are called link attributes.

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9. 99. A simple attribute has only one element.

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10. 10An attribute that contains a group of other attributes is called a composite attribute.

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11. 11Semantic object attributes are used to establish a relationship between one semantic object and another.

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12. 12All attributes of a semantic object are collectively referred to as “semantic object attributes”.

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13. 13For simple attributes in a semantic object model, only the maximum cardinality needs to be indicated.

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14. 14The cardinality of a group attribute is inherited by all the attributes in that group.

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15. 15The cardinalities of an attribute operate only between the attribute and the container of the attribute.

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16. 16Object attributes are always paired attributes.

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17. 17An object identifier is an attribute or group of attributes that always uniquely identifies object instances.

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18. 18Object identifiers may or may not be unique.

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19. 19The cardinality of an object identifier is almost always 1.1.

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20. 20The domain of simple and group attributes include both a physical description and a semantic description.

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21. 2121. The domain of an object attribute is a dynamically enumerated list containing all object instances of a particular type.

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22. 22The portion of a semantic object that is visible to a particular application is called the “application object”.

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23. 23An attribute that is computed from other values has a “formula domain”.

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24. 24A “simple object” is a semantic object that contains only single-value object attributes.

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25. 25A “simple object” can contain only simple attributes.

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26. 26A “composite object” is exactly like a “simple object” except that it contains at least one attribute with a maximum cardinality greater than 1.

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27. 27A “composite object” can not contain more than one multi-valued attribute.

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28. 28It is possible to include a multi-valued simple attribute within a multi-valued group attribute.

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29. 29A “compound object” contains at least one multi-value, simple or group attribute but no object attributes.

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30. 30A “compound object” can contain no multi-value attributes.

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31. 31A semantic object that has a multi-value group attribute containing an object attribute is called a “hybrid object”.

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32. 32A “hybrid object” is a semantic object that relates two or more objects and stores data that are peculiar to that relationship.

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33. 33Parent attributes appear as the first attribute of a subtype object and are always required.

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34. 34Subtype attributes in the parent object always have a minimum cardinality of 1.

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35. 35The parent object inherits all of the attributes of the subtype object.

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36. 36A semantic object can not have more than one subtype attribute.

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37. 37From a semantic object perspective, an entity in an E-R model represents only a portion of the data in the users’ model of that entity in their environment.

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Angel Perez

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Erstellt am 17 Sep 2016 · aktualisiert am 27 Sep 2016

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