The program module that is responsible to control the interaction among the concurrent transactions and protect the database consistency.
aggregation
A aggregation is an abstraction through which relationships are treated as higher-level entities.
attribute
Descriptive properties possessed by each member of an entity set. Attributes can be:
Simple or composite
Single-valued or multivalued
Null
Derived
attribute inheritance
The attributes of the higher-level entity sets are said to be inherited by the lower-level (specialized) entity sets.
consistency constraints
Requirements that apply to the data. For instance, in a student database, all students must have a Social Security number. Also known as business rules or integrity constraints.
data
A collection of known facts that can be recorded and have implicit meaning.
datum
A single fact.
data abstraction
Views of the data of differing complexity, physical level, logical level, and view level.
database
A collection of related data.
database administrator
The person(s) assigned overall responsibility for the correct operation of the DBMS.
database management system
Consists of a collection of interrelated data and a set of programs to access those data.
Data Definition Language (DDL)
A database schema is specified by a set of definitions expressed by a special language called a Data Definition Language.
Data Dictionary
A database schema is specified by a set of definitions expressed by a special language called a Data Definition Language. The schema is compiled and the results are stored in the data dictionary. The date dictionary contains metadata about the database and is used before the actual data is read or modified in the DBMS.
data independence
The ability to modify a schema definition in one level without affecting a schema definition in the next higher level, i.e., logical data independence and physical data independence.
Data Manipulation Language
A language that enables users to access or manipulate data as organized by the appropriate data model.
data model
A collection of conceptual tools for describing data, data relationships, data semantics, and consistency constraints.
data redundancy
Data is repeated in different locations, files, or formats
data inconsistency
Various copies of the data no longer agrees, such as different files having different addresses for the same student.
data isolation
Data is in different locations and different formats.
discriminator
A set of one or more attributes that allow distinguishing of all objects in a weak entity set that depend on one particular strong entity.
enterprise schema
Represents the overall logical structure of the database.
entity
A person, place or thing. Includes the attributes that provide additional information about the person, place or thing.
Entity-Relationship model
The entity-relationship (E-R) data model is based on a perception of a real world that consists of a collection of basic objects (entities) and of relationships among these things.
entity set
A set of entities of the same type that share the same properties, or attributes.
existence dependency
If the existence of entity x depends on the existence of entity y, then x is said to be existence dependent on y.
file processing system
A system where each user defines and implements the specific files needed for each application.
Hierarchical model
Data is represented as collections of tree of data and links to represent relationships.
Mapping cardinalities
Cardinalities ratios express the number of entities to which another entity can be associated via a relationship set.
one-to-one
one-to-many
many-to-one
many-to-many
metadata
Data about data.
Network model
Data are represented by collections of records and relationships are represented by arbitrary graphs.
object
A member of an entity set.
Object-oriented model
The object-oriented (O-O) model is based on a collection of objects, where the object contains the instance variable and the bodies of code that operate on that object.
physical data model
Physical data models are used to describe how the data is stored at the lowest level.
primary key
The candidate key that is chosen by the database designer as the principal means of identifying entities within an entity set.
Record-based model
Record-based models describe the data at the logical or view level, where the database is structured in fixed-format records of several types.
Relational model
The Relational model uses a collection of tables to represent both data and the relationships among those data.
relationship
The association among several entities. A relationship may also have descriptive attributes.
schema
A database schema is similar to a record in Pascal or a struct in C. It describes the data and its logical format.
Specialization
Subgroupings within entity sets that are distinct in some way from other entities in the set.
strong entity set
A set of entities that has sufficient attributes to form a primary key.
storage manager
Program module that is the interface between the low-level data stored in the database and the application programs.
superkey
A set of one or more attributes that taken collectively to identify uniquely an entity in the entity set.
weak entity set
A set of entities that does not have sufficient attributes to form a primary key.
References
Database Systems Concepts, Third Edition, Abraham Silberschatz, Henry F. Korth, S. Sudarshan, 1997, McGraw-Hill
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last modified on Wednesday, 10-Feb-1999 16:09:27 EST