Chapter 9 Key Terms

Pregunta	Respuesta
access method	technique used to locate records and navigate through a database
anomalies	negative operational symptoms caused by improperly normalized tables
association	relationship among record types
attributes	equivalents to adjectives in the English language that serve to describe the objects
cardinality	a numerical mapping between entity instances
centralized database	database retained in a central location
composite key	composed of two attributes: INVOICE NUM and PROD NUM
concurrency control	a system that ensures that transactions processed at each site are accurately reflected in the database at all other sites
currency of information	problem associated with the flat-file model because of its failure to update all the user files affected by a change in status; may result in decisions based on outdated information
data attribute	the most elemental piece of potentially useful data in the database
data currency	when the firm's data files accurately reflect the effects of its transactions
data definition language	programming language used to define the database to the database management system
data dictionary	description of every data element in the database
data manipulation language	language used to insert special database commands into application programs written in conventional languages
data model	blueprint for what ultimately will become the physical database
data redunacny	state of data elements being represented in all user files
data storage	efficient information system that captures and stores data only once and makes this single source available to all users who need it
data structures	techniques for physically arranging records in a database
data updating	periodic updating of data stored in the files of an organization
database administrator	individual responsible for managing the database resource
database lockout	software control that prevents multiple simultaneous access to data
database management system	software system that controls access to the data resource
deadlock	"wait" state that occurs between sites when data are locked by multiple sites that are waiting for the removal of the locks from other sites
deletion anomaly	unintentional deletion of data from a table
distributed data processing	reorganizing the IT function into small information processing units that are distributed to end users and placed under their control
distributed databases	databases distributed using either the partitioned or replicated technique
first normal form	low degree of normalization of relational database tables
flat-file	file structure that does not support the integration of data
foreign key	key that permits the physical connection of logically related tables to achieve the associations described in the data model
hierarchical indexed direct access method	method in which the root segment of the database is organized as an indexed file
hierarchial model	database model that represents data in a hierarchical structure and permits only a single parent record for each child
indexed sequential file	sequential file structure accessed via an index
insertion anomaly	unintentional insertion of data into a table
internal view	physical arrangement of records in the database
inverted list	cross-reference created from multiple indexes
join	builds a new physical table from two tables consisting of all concatenated pairs of rows form each table
navigational models	model that possesses explicit links or paths amoung data elements
network model	variation of the hierarchical model
occurnence	used to describe the number of instances or records that pertain to a specific entity
partial dependencies	occurs when one or more nonkey attributes are dependent on (defined key) only part of the primary key rather than the whole key
partitioned database	database approach that splits the central database into segments or partitions that are distributed to their primary users
physical database	lowest level of the database containing magnetic spots on magnetic disks
primary key	characteristics that uniquely identify each record in the table
project	extracts specified attributes (columns) from a table to create a virtual table
relational model	data model that is more flexible than traditional navigational models. It allows users to create new and unique paths through the database to solve a wide range of business problems
repeating groups	database anomalies described above are symptoms of structural problems within tables
replicated databases	database approach in which the central database is replicated at each site
restrict	command to extracts specified rows from a specified table
schema	description of the entire database
second normal form	table that is free of both repeating group and partial dependencies
structured models	the data elements for predefined structured paths
structured query language	data processing tool for end users and professional programmers to access data in the database directly without the need for convential programs
task-data dependency	user's inability to obtain additional information as his or her needs change
temporary inconsistency	during accounting transactions, account balances pass through a state where the values are incorrectly stated
third normal form	normalization that occurs by dividing an unnormalized database into smaller tables until all attributes in the resulting tables are uniquely and wholly dependent on the primary key
transitive dependencies	a transitive dependency occurs in a table where nonkey attributes are dependent on another nonkey attribute and independent of the table's primary key
update anomaly	unintentional updating of data in a table, resulting from data redundancy
user view	set of data that a particular user needs to achieve his or her assigned tasks
users	individuals who employ systems, receive information, and act on the information received
view integration	combining the data needs of all users into a single schema or enterprise-wide view
view modeling	determines the associations between entities and document them with an ER diagram

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