INF2603 Ch7 – Data Modeling with ERD – True/False – Flashcards
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An ERM is dependent on the database type.
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False
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The word "entity" in the ER model corresponds to a table.
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True
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The Crow's Foot model is less implementation-oriented than the Chen model.
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False
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The ER diagram represents the conceptual database as viewed by the end user.
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True
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The ER model refers to a specific table row as an entity instance.
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True
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In both the Chen and Crow's Foot models, an entity is represented with a rectangle containing the entity's name.
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True
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The ER model refers to a specific table row as an entity occurrence.
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True
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Attributes are types of entities.
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False
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In the original Chen model, each attribute is represented using an oval with the attribute name connected to the entity with a line.
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True
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Software vendors have adopted the Chen representation because of its compact representation.
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False
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Attributes have a domain that specifies the data type of the attribute.
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False
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Attributes cannot share a domain.
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False
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In an ER diagram, primary keys are usually bolded.
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False
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Ideally, a primary key is composed of several attributes.
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False
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A composite identifier is a primary key composed of more than one attribute.
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True
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All attributes are either simple or composite.
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True
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All simple attributes are also single-valued.
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False
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In the Chen model, a multivalued attribute is connected to the owning entity with a double line.
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True
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The DBMS can easily handle multivalued attributes.
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False
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Derived attributes are stored in a special database table.
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False
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A relationship is identified by a name that describes the relationship.
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True
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Cardinality expresses the minimum and maximum number of entity occurrences associated with one occurrence of the related entity.
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True
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In Chen notation, there is no way to represent cardinality.
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False
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Connectivities and cardinalities are established by business rules.
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True
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A weak relationship exists if the primary key of the related entity contains at least one primary key component of the parent entity.
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False
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You should always load data from the 1 side of a 1:M relationship.
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True
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A weak entity has a primary key that is partially or totally derived from the parent entity in the relationship.
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True
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The existence of a mandatory relationship indicates that the minimum cardinality is 0 or 1 for the mandatory entity.
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False
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Relationships operate only in one direction.
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False
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A recursive relationship is one in which a relationship can exist between occurrences of the same entity set.
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True
