Data Management Midterm
A composite key consists of only one attribute. T/F
False
A constraint is a rule in a database system that can be violated by users. T/F
False
A foreign key is a primary key of a relation that also is a primary key in another relation. T/F
False
A member of a subtype does NOT necessarily have to be a member of the supertype. T/F
False
A relation is in first normal form if it has no more than one multivalued attribute. T/F
False
A subtype is a generic entity that has a relationship with one or more entities at a lower level. T/F
False
A transversal dependency is a functional dependency between two or more nonkey attributes. T/F
False
A user view is how the user sees the data when it is produced. T/F
False
A well-structured database establishes the entities between relationships in order to derive the desire information. T/F
False
CASE tools can model more complex data relationships, such as ternary relationships. T/F
False
Creating a data model from a packaged data model requires much more skill than creating one from scratch. T/F
False
Data intergrity consists of powerful operations to manipulate data stored in relations. T/F
False
Data redundancy is used to establish relationships between data but is never used to improve database performance. T/F
False
Database processing programs are coded and tested during the design stage of the systems development life cycle. T/F
False
Databases were developed as the first application of computers to data processing. T/F
False
Generalization is a top-down process. T/F
False
The relational data model does, at the time, directly support subtype.supertype relationships. T/F
False
The steps of the systems development life cycle can only be viewed as a linear process. T/F
False
The term legacy system refers to a newly installed database management system. T/F
False
The total specialization rule states that an entity instance of a supertype is allowed not to belong to any subtype. T/F
False
The truncate table statement in SQL creates a new table. T/F
False
There can be multivalued attributes in a relation. T/F
False
Unlike columns, the rows of a relation may not be interchanged and must be stored in one sequence. T/F
False
When subtypes are overlapping, an additional field must be added to the supertype to act as a discriminator. T/F
False
When transforming a one-to-one relationship, a new relation is always created. T/F
False
When transforming a unary many-to-many relationship to relations, a recursive foreign key is used. T/F
False
When transforming a weak entity, one should create one relation with both the attributes of the strong entity and the attributes of the weak entity. T/F
False
A candidate key is a attribute, or combination of attributes, that uniquely identifies a row in a relation. T/F
True
A cascading delete removes all records in other tables associated with the record to be deleted. T/F
True
Because a purchased data model is extensive, you begin by identifying the parts of the data model that apply to your data modeling situtation. T/F
True
Cost and complexity are just two of the disadvantages of database processing. T/F
True
Data from prior systems is converted to the new systems during the implementation phase of the systems development life cycle. T/F
True
Data structures include data organized in the form of tables with rows and columns. T/F
True
Database maintenance is typically the longest step of the database development process. T/F
True
Enterprise modeling sets the range and general contents of organizational databases. T/F
True
File processing systems have been replaced by database systems in most critical business aplications today. T/F
True
The overlap rule specifies that if an entity instance of the supertype is a member of one subtype, it can simultaneously be a member of two (or more) subtypes. T/F
True
When a regular entity type contains a multivalued attribute, two relations are created. T/F
True
When normalizing, the goal is to decompose relations with anomalies to produce smaller, well-structured relations. T/F
True
You will never need to map data in current databases to data in a package data model. T/F
False
when the total specialization rule is set for a supertype/subtype relationship, one could roughly compare the supertype to an abstract class in object-oriented programming. T/F
False
A universal data model is a generic or template data model that cen be reused as a starting point for a data modeling project. T/F
True
In 1998, ANSI/SPARC published an important document describing the three-schema architecture. T/F
False
In the relational data model, associations between tables are defined through the use of primary keys. T/F
False
It is easy to miss the opportunity to visualize future requirements shown in the full data model when using a packaged data model. T/F
False
Personal databases are designed to support a small group of individuals working together on project. T/F
False
Reduced program maintenance is an advantage of file processing systems. T/F
False
Subtypes at the lowest level of a hierarchy do not inherit attributes from their ancestors. T/F
False
Supertype/subtype relationships should be used when the instances of a subtype participate in not relationships which are unque to that subtype. T/F
False
The entity integrity rule states that a primary key attribute can be null. T/F
False
A completeness contraint may specify that each entity of the supertype must be a member of some subtype in the relationship. T/F
True
A partial functional dependency is a functional dependency in which one or more nonkey atributes are functionally dependent on part (but not all) of the primary key. T/F
True
A subtype can become a supertype if the subtype has other subtypes beneath it. T/F
True
A well-structured relation contains minimal redundancy and allows users to manipulate the relation without errors or inconsistencies. T/F
True
All vaues that appear in a column of a relation must be taken from the same domain. T/F
True
An enterprise data model describes the scope of data for only one information system. T/F
True
In practice, databases today may contain either data or information. T/F
True
The disjointed rules specifies that if an entity instance of the supertype is a member of one subtype, it MUST simultaneaously be a member of another subtype. T/F
False
The physical structure and storage organization of the database are decided upon during the implementation phase of the systems development life cycle. T/F
False
The primary key of the many side migrates to the one side when transforming a one-to-many relationship. T/F
False
With the traditional file processing approach, each application shares data files, enabling much data sharing. T/F
False
A physical schema contains the specifications for how data from a conceptual schema are stored in a computer's secondary memory. T/F
True
A primary key is an attribute that uniquely identifies each row in a relation. T/F
True
A referential integrity constraint is a rule that maintains consistency among the rows of two relations. T/F
True
A relational database establishes the relationships between entities by means of a common field. T/F
True
An entity instance of a subtype represents the same entity instance of the supertype. T/F
True
An extranet uses internet protocols to establish limited access to comapny data by the company's customers and suppliers. T/F
True
Applications built with a multitier architecture are meant to support departments. T/F
True
If an identifier is not assigned, the default primary key for an associative relation consists of the two primary key attributes from the other two relations. T/F
True
In a supertype/subtype hierarchy, attributes are assigned at the highest logical level that is possible in the hierarchy. T/F
True
In prototyping, implementation and maintenance activities are repeated as necessary until the product is correct. T/F
True
Informartion is processed date. T/F
True
Mapping existing data to new data in a packaged data model is useful for developing migration plans. T/F
True
Metadata are data that descrbe the properties of other data. T/F
True
One of the major challenges in a data modeling is to recognize and clearly represent entities that are almost the same. T/F
True
One property of a relation is that each attribute within a relation has a unique name. T/F
True
Prototyping is a type of rapid application development. T/F
True
Redundancy increases the risk of inconsistent data. T/F
True
Specialization is the reverse of generalization. T/F
True
The allowable range of values for a given attribute is part of the domain constraint. T/F
True
The most common way to support a group of individuals who work together on a project or group of similar projects is with a two-tier client/server database. T/F
True
The repository is populated during the analysis phase of the systems development life cycle. T/F
True
The systems development life cycle is the traditional methodology used to develop, maintain, and replace information systems. T/F
True
Unplanned duplicate data files are the rule rather than the exception in file processing systems. T/F
True
View integration is the process of merging relations together. T/F
True
