© Tony Simmons 2010
Select the first letter of the word from the list above to jump to appropriate section of the glossary. If the term you are looking for starts with a digit or symbol, choose the '#' link.
Glossary of Automation & Control Engineering Terms
Data Dictionary
The name given to a list of all objects within a functional definition.
Data Link Layer
One of the protocol layers in the OSI seven layer model. The main task of the data link layer is to take a raw transmission facility and transform it into a line that appears free of transmission errors to the network layer. It does this by having the sender break data into data frames (typically a few hundred bytes), transmit the frames sequentially, and process the acknowledgement frames sent back by the receiver.
DCS
Distributed Control System such as produced by Honeywell, Fisher, Foxboro etc. The word ‘distributed’ refers to the fact that multiple processors are used for process control and these could, if plant needs allowed, be physically distributed around a site. These systems used to be characterised by have a proprietary operating systems but increasingly standard operating systems are being adopted by all vendors, at least for the operator display level.
Dead Source Code
Superseded code from an earlier version or abandoned as a result of change. Code that is never executed.
Debugging
Debugging is the act of correcting executable software code to make it function correctly or to temporarily change it in order to assist in the process of fault diagnosis.
[In the case of directly executable languages, debugging becomes synonymous with programming.]
Deliverable
A deliverable is the name given to the end product of a life cycle stage. A deliverable is a "tangible" item of documentation or software medium and not necessarily the final product which will be provided to the end user.
A deliverable is something which can have its progress measured and its quality judged.
Demand Rate
The frequency with which a (protective) system is called upon to perform its (protective) function.
DES
Discrete Event Simulation.
Design Review
A formal, documented, comprehensive and systematic examination of a design to evaluate the design requirements and the capability of the design to meet these requirements and to identify problems and proposed solutions. [BS 4778 Part 1]
Device
A field object such as an automated valve or an electrical drive which comprises a set of input/outputs controlled by the process control system. A typical plant will have relatively few types of device and the intention should be to provide the same software construct for each device type.
Diversity
Existence of different means of performing a required function (e.g. other physical principles or other ways of solving the same problem). [IEE/BCS report]
Documentation
System documentation comprises two categories of material:-
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Documents which comprise part of the delivered product such as the user manual, system manual, training manual, design document, etc.
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Documents which record the processes and intermediate products used in the production of the delivered product, such as inspection forms, error reports, change requests, release notes.
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DQ
Design Qualification
DSDM
Dynamic Systems Development Method
