IPT Glossary D Flashcards
DAC
Digital to Analog Converter
Data Dictionary
A table identifying and describing the nature of each data item. Data dictionaries are used in many areas of system design, including the designs of databases.
Data Flow
A labelled arrow on context and data flow diagrams describing the nature and direction of data movement.
Data Flow Diagram
A Diagram that shows the logical flow of data through a system or subsystem
Data Independence
The separation of data and its management from the software applications that process the data
Data Integrity
A measure of how correct and accurately data reflects its source
Data Mart
Reorganised summary of specific data extracted from s larger database. Data marts are designed to meet the needs of an individual system or department in an organisation
Data Mining
The process of discovering non-obvious patterns within large collections of data
Data Store
Where data is maintained prior to or after it has been processed. Data stores are represented as open rectangles on data flow diagrams.
Data Verification
A check to ensure the data collected and stored matches and continues to match the source of the data.
Data Validation
A check, at the time of of data collection, to ensure the data is reasonable and meets certain criteria.
Data Warehouse
A large seperate combined copy of different databases used by an organisation. It includes historical data, which is used to analyse the activities of the organisation.
Database Schemas
A technique for modelling the relationships within a relational database. Also known as Entity Relationship Diagrams (ERDs)
DBMS
Database Management System
Decision
A decision between two alternatives. Committing to one alternative over other alternatives.
Decision Table
A tool for documenting the logic upon which decisions are made. They represent the rules, conditions and actions as a diagram.
Decryption
The process of decoding encrypted data using a key
Demodulation
The process of decoding a modulated analog wave back into its original digital signal. The opposite of modulation.
Device Driver
A program that provides the interface between the operating system and a peripheral device.
DFD
Data Flow Diagram
Dial-Up Modem
A Modem used to transfer data over a traditional voice telephone line.
Diary
A project management tool for recording the day-to-day progress and detail of completed tasks. Diaries tend to be used to record future appointments and factual information.
Digital
Discrete. Digital data is coded and represented as distinct numbers. Computers use binary computer data.
Direct Conversion
Completely replacing an old system with a complete new system at a particular point in time. Also called direct-cutover.
Display Adapter
Synonym for Video Card
Displaying
The information process that outputs information from an information system,
Distributed Processing
Multiple CPUs used to perform processing tasks, often over a network and transparent to the user.
DMD
Digital Micromirror Device. Used within DLP projectors.
DMT
Discrete MultiTone. A modulation standard used by ADSL to dynamically assign frequencies.
DNS
Domain Name Server. A server that determines the IP address associated with a domain name.
DOCSIS
Data Over Cable Service Interface Specifications. The standards specifying communication over a cable network.
Dot Pitch
The width of each pixel in mm. Commonly used to describe the resolution of screens.
Downloading Distributed Database
A type of distributed database whereby each server download copies of data as it is required from remote databases and stores the data within its local data.
DPI
Dots Per Inch. A measure of screen of printer output resolution.
Draw Software Applications
A software application for manipulating vector images.
DSL
Digital Subscriber Line
DSLAM
DSL Access Multiplexor. A device at the telephone exchange that combines multiple signals from ADSL customers onto a single line to ISPs, and extracts individual customer signals from a signal line.
DSP
Digital Signal Processor
DVI
Digital Video Interface
EFM
Eight to fourteen modulation. A system that converts each byte into fourteen bits such that all bit patterns include at least two but less than 10 consecutive zeros.
