Computer Science Glossary

Michael Henson's

Glossary of Computer Science Terms

Index | A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


data dictionary: a textual description of each class, its associations, attributes, and operations
data flow: the connection between the output of one object or process and the input to another
data flow diagram: a graphical representation of the functional model, showing dependencies between values and the computation of output values from input values without regard for when or if the functions are executed.
datagram: a packetlike communication mechanism that is addressed to a process rather than a host computer
data store: a passive object that stores data for later access.
data transfer rate: the speed (in bits per second) at which data can be transferred between two computers once transmission has begun
decimal: base 10 number system; a number system with ten digits:
0 1 2 3 4 5 6 7 8 9
decimal fraction: a fraction whose denominator is a power of 10
delegation: an implementation mechanism in which an object, responding to an operation on itself, forwards the operation to another object; a mechanism in which methods may be attached directly to instances and where the method resolution is performed by searching a chain of instance pointers, rather than by searching a class heirarchy.
derived association: an association that is defined in terms of other associations
derived attribute: an attribute that is computed from other attributes
descendent class: a class that is a direct or indirect subclass of a given class
despatcher: a procedure (on the server) that uses the procedure identifier of a client request message to select one of the server procedures and pass the client's arguments to it
directory service: a service that provides a mapping between file names and their UFIDs
discriminator: an attribute of enumeration type that indicates which property of a class is being abstracted by a particular generalization
distributed mutual exclusion: a mechanism for controlling resource access that involves allowing access to only one process at a time
distributed system: a collection of autonomous computers linked by a computer network and equipped with distributed system software that enables the computers to coordinate their activities and to share hardware, software, and data
domain transition: a switch between execution environments
duplex: a term applied to data transmission where data can be both sent and received
See also half-duplex and full-duplex; contrast with simplex
dynamic method binding: choosing the correct method to call at runtime based on an object's actual type, and not the type of reference referring to it
dynamic method lookup: See dynamic method binding
dynamic model: a description of aspects of a system concerned with control, including time, sequencing of operations, and interaction of objects