New terms, glossary by glossary.

Cognition and analysis methods

Mental model

In cognitive science and usability, a mental model is an internal representation of how something works — a system, a situation or a relationship — that a person uses to understand, predict and decide, for example a user's belief about how a machine or software behaves.

Cognition and analysis methods

Five whys

In quality management, the five whys is a questioning technique that asks “why?” repeatedly — typically about five times — to trace a problem from its symptom to an underlying cause; it was developed at Toyota and described by Taiichi Ohno as part of the Toyota Production System.

First principles thinking and its adaptations

First principles thinking

In problem solving, first principles thinking is the practice of breaking a problem down into the basic facts or assumptions that cannot be reduced any further and reasoning upward from them to a solution, instead of reasoning by analogy with existing solutions or from convention.

Philosophy and logic

First principle (philosophy)

In philosophy and logic, a first principle is a basic proposition or assumption that is not deduced from any other proposition within a system of reasoning and from which further knowledge is derived; Aristotle called such starting points archai.

Philosophy and logic

Socratic questioning

In philosophy and education, Socratic questioning is a disciplined way of asking systematic questions to examine the definitions, assumptions, evidence and implications behind a claim, named after the Athenian philosopher Socrates (c. 470–399 BCE) as portrayed in Plato’s dialogues.

Philosophy and logic

Axiomatic method

In mathematics and logic, the axiomatic method builds a body of knowledge from a small set of explicitly stated definitions and axioms and derives every further statement from them by proof; Euclid’s Elements (c. 300 BCE) is its classic model and David Hilbert’s Foundations of Geometry (1899) its modern, formal form.

Philosophy and logic

Analysis and synthesis (method)

In the history of scientific method, analysis and synthesis is the two-way procedure of resolving a problem or phenomenon into its simpler parts and causes (analysis, resolution) and then reasoning back from them to the whole (synthesis, composition); it runs from Greek geometry, as described by Pappus of Alexandria, through Galileo to Newton.

Philosophy and logic

Cartesian method

In philosophy, the Cartesian method is the procedure René Descartes set out in his Discourse on the Method (1637): accept nothing as true that is not clearly and distinctly known, divide each difficulty into as many parts as needed, reason in order from the simplest to the most complex, and review everything so that nothing is left out.

First principles thinking and its adaptations

Destruction and creation (John Boyd)

In strategic theory, destruction and creation is the mental cycle described by US Air Force Colonel John R. Boyd in his essay of that name (September 3, 1976): existing concepts are broken apart into their constituents (destructive deduction) and the pieces are recombined into a new concept that matches reality better (creative induction).

First principles thinking and its adaptations

Reasoning by analogy

In logic and problem solving, reasoning by analogy draws a conclusion about one case from its similarity to another, known case — for example, designing or documenting a new product the way comparable products have been designed or documented.

First principles thinking and its adaptations

First-principles calculation

In physics, chemistry and materials science, a first-principles (ab initio) calculation predicts properties of atoms, molecules or materials directly from the fundamental laws of physics — in practice quantum mechanics — without parameters fitted to experimental data for the system being studied.

Mental models as thinking tools

Latticework of mental models

In the decision-making literature, a latticework of mental models is Charlie Munger’s image for a broad set of models from many disciplines that a person combines to understand problems, instead of relying on the models of a single discipline; he set it out in his talk “A Lesson on Elementary, Worldly Wisdom” at the USC Marshall School of Business on April 14, 1994.

2 · Topics and information design

Information foraging

In technical communication and human-computer interaction, information foraging is a theory that explains information seeking as behavior shaped by the value of the information sought and the effort needed to get it. Developed by Peter Pirolli and Stuart K. Card at Xerox PARC and published in Psychological Review in 1999, it borrows concepts from optimal foraging theory in ecology: readers move between information "patches", follow "information scent" given off by proximal cues such as link labels, headings, titles and metadata, and abandon a patch when the expected yield drops below what another patch promises. The theory is descriptive, not a standard or a method, and it predicts behavior rather than prescribing document structure. In documentation practice it is used as a rationale for making individual pages self-sufficient and for strengthening the cues by which readers judge, enter and leave a page.

1 · Documentation models

Technical documentation model

In technical communication, a technical documentation model is a set of principles for dividing, organizing and expressing technical content so that readers can find and use it. A model answers questions such as how large a unit of content should be, what each unit is about, how units connect, how content is marked up and how much prose a reader needs. The term is an umbrella label rather than a standardized one: no standard defines "technical documentation model", and the individual models come from technical communication literature and from publishing practice. Models are design principles, not deliverables, and they say nothing by themselves about whether a documentation set meets a legal or contractual requirement.

1 · Documentation models

Structured authoring

In technical communication, structured authoring is a way of writing in which content is created as discrete information units that follow a formally defined content model — a schema, document type definition, or specification — rather than as free-form pages shaped by a word processor. Meaning is marked up explicitly (a warning is tagged as a warning, a step as a step), while typography, pagination, and layout are applied later by a publishing process. Because the markup is validated against the model, the same source can be checked automatically, reused across deliverables, and rendered to print, HTML, or machine-readable formats. Structured authoring is one of the six documentation models described in the encyclopedia subject area Technical documentation models and is usually combined with the others rather than used alone.

2 · Topics and information design

Topic (technical communication)

In technical communication, a topic is a self-contained unit of content that covers a single subject and serves a single purpose, written so that it makes sense without the content that precedes or follows it. Topics are the units that authors write, review, approve, translate, reuse, and assemble into deliverables such as manuals, help systems, and content delivery portals. The general concept is not fixed by a single standard: structured formats such as DITA and iiRDS each define their own topic constructs, and in-house information models define topic types of their own. What the implementations share is the pairing of one title with one subject and one communicative purpose.

2 · Topics and information design

Information Mapping

In technical communication, Information Mapping is a structured writing method that analyzes subject matter into small labeled units, classifies each unit by the reader question it answers, and presents the result in a standardized visual format. Its core building blocks are the information block (a labeled unit covering one idea) and the information map (a set of related blocks under a heading), with each block assigned an information type such as procedure, process, concept, principle, fact or structure. The method is applied in three steps — analyze, organize, present — guided by writing principles such as chunking, relevance, labeling and consistency. Information Mapping is also a registered trademark of Information Mapping, Inc., which offers training, certification and authoring software for the method.

1 · Documentation models

Every page is page one

In technical communication, Every Page is Page One (EPPO) is a model for topic-based writing, set out by Mark Baker in the book of the same name (XML Press, 2013), in which every topic is designed to work as a reader's first page. It assumes that readers arrive from search, links, or in-product help rather than from a table of contents, so each topic has to carry its own context and purpose instead of relying on a preceding chapter. Baker describes seven characteristics of an EPPO topic: it is self-contained, has a specific and limited purpose, conforms to a type, establishes its context, assumes the reader is qualified, stays on one level, and links richly. EPPO is an authoring and information-architecture model, not a markup standard or a conformance scheme.

6 · Quality, risk and governance

Accountability (AI)

In AI governance, accountability is the assignment of a named person, role or organization that answers for a decision, output or system — including the duty to explain it, correct it and bear its consequences. It presupposes intent, authority and the ability to act, so it rests with people and organizations rather than with a model or an agent, however autonomous the system appears. <cite index="7-1,7-4">The OECD AI Principles put it as a duty of organisations and individuals that develop, deploy or operate AI systems to be held accountable for their proper functioning, based on their roles, the context and their ability to act.</cite> In practice, accountability becomes visible only when it is documented: a role, a review step and a record that shows who decided what.

6 · Quality, risk and governance

Accountability gap (AI)

In AI governance, an accountability gap is a situation in which an AI system contributes to an outcome while no identified person or organization is clearly answerable for it. It typically arises when AI output is accepted without a named reviewer, when the tool chain records no attribution, or when roles were defined for a workflow that no longer matches how the system is actually used. The term is an analytic label from the ethics and policy debate rather than a definition fixed by a standard or a law; frameworks such as the OECD AI Principles and the NIST AI Risk Management Framework instead state the accountability expectation the gap violates.

Document and evidence governance

Human review record

In document and evidence governance, a human review record is the documented proof that a named, competent person examined a specific output — a document version, a translation, a code change, a model output — before it was accepted. It captures what was reviewed, against which criteria, what was changed or rejected, who decided and when. Where a law, a contract or a quality system requires human oversight or approval, this record is what makes the review verifiable after the fact; without it, a required review leaves no trace that it took place. Holding such records shows that a review happened; it does not by itself show that the reviewed product, system or documentation is compliant.

Automation software engineering and architecture

AI usage telemetry

In software engineering, AI usage telemetry is measurement data about how AI tools are used in a development or authoring organization: which tools and models are called, in which repositories or projects, at what volume, and how often proposed output is accepted, edited or discarded. Organizations collect it for license management, adoption reporting, cost control and oversight of AI-assisted work. Whether such data may be collected and evaluated per individual person is not a technical question but a legal one, decided by data protection law, labor law and — in Germany — by co-determination of the works council.

Automation software engineering and architecture

Defect triage

In software engineering, defect triage is the process of reviewing incoming defect reports and deciding for each one whether it is valid and reproducible, how severe its impact is and how urgent the work on it is, which component and team it belongs to, and when it will be addressed. The decision is recorded in the issue tracker as a set of fields — state, severity, priority, component, owner, target release — so that later work and reporting can rely on it. Triage is a management decision about work, not a technical fix: it neither changes the product nor explains the cause. The term itself is not defined in a standard; the attributes it assigns, such as severity and priority, correspond to the anomaly classification attributes described in IEEE Std 1044.

Functional safety

Demand mode

In functional safety under IEC 61508, the demand mode or mode of operation describes how often a safety function is called upon: in low-demand mode no more than once per year, in high-demand mode more than once per year, and in continuous mode as part of normal operation; it decides whether the SIL target is expressed as PFDavg or as PFH.

Functional safety

Average probability of dangerous failure on demand (PFDavg)

In functional safety under IEC 61508 and IEC 61511, the average probability of dangerous failure on demand (PFDavg) is the mean unavailability of a safety-related system to perform its safety function when a demand occurs; it is the failure measure used to specify and verify the SIL of low-demand safety functions.

Functional safety

SIL 1

In functional safety under IEC 61508, SIL 1 is the lowest of four safety integrity levels. It corresponds to an average probability of dangerous failure on demand (PFDavg) from 10^-2 to less than 10^-1 in low-demand mode, or an average frequency of dangerous failure (PFH) from 10^-6 to less than 10^-5 per hour in high-demand or continuous mode.

Functional safety

SIL 2

In functional safety under IEC 61508, SIL 2 is the second of four safety integrity levels. It corresponds to an average probability of dangerous failure on demand (PFDavg) from 10^-3 to less than 10^-2 in low-demand mode, or an average frequency of dangerous failure (PFH) from 10^-7 to less than 10^-6 per hour in high-demand or continuous mode.

Functional safety

SIL 4

In functional safety under IEC 61508, SIL 4 is the highest of four safety integrity levels. It corresponds to an average probability of dangerous failure on demand (PFDavg) from 10^-5 to less than 10^-4 in low-demand mode, or an average frequency of dangerous failure (PFH) from 10^-9 to less than 10^-8 per hour in high-demand or continuous mode.

Functional safety

SIL claim limit (SIL CL)

In functional safety of machinery under IEC 62061, the SIL claim limit (SIL CL) is the maximum safety integrity level that can be claimed for a subsystem, with regard to its architectural constraints and its systematic safety integrity; the SIL of a safety function can't exceed the lowest SIL CL of the subsystems that perform it.

Functional safety

Systematic capability (SC)

In functional safety under IEC 61508, systematic capability (SC) is a measure, expressed on a scale from SC 1 to SC 4, of the confidence that the systematic safety integrity of an element meets the requirements of a specified SIL, when the element is used as described in its safety manual.

Distributed automation and IEC 61499

Adapter interface

In IEC 61499, an adapter interface is a reusable bundle of event and data inputs and outputs, defined as an adapter interface type, that connects two function blocks through a single adapter connection: the providing block exposes it as a plug, the accepting block as a socket, and events and data flow in both directions.

Distributed automation and IEC 61499

Communication function block

In IEC 61499, a communication function block is a service interface function block that exchanges events and data between resources or devices, either unidirectionally with a PUBLISH/SUBSCRIBE pair or bidirectionally with a CLIENT/SERVER pair, while the protocol behind it is fixed by the device and the compliance profile.

Distributed automation and IEC 61499

Eclipse 4diac

Eclipse 4diac is an open-source environment for distributed control applications based on IEC 61499, hosted by the Eclipse Foundation, consisting mainly of the engineering tool 4diac IDE, the runtime 4diac FORTE for embedded devices and a library of function block types.

Distributed automation and IEC 61499

Event-driven execution (IEC 61499)

In IEC 61499, event-driven execution is the principle that a function block executes only when an event arrives at one of its event inputs: the event samples the associated data inputs, triggers the block's behavior and may issue output events that trigger further blocks, instead of every block being executed in a fixed scan cycle.

Distributed automation and IEC 61499

Event function block

In IEC 61499, an event function block is one of the standard function block types defined in Annex A of IEC 61499-1 that generate, split, merge, select, delay, count or otherwise process events, such as E_SPLIT, E_MERGE, E_PERMIT, E_DELAY, E_CYCLE and E_CTU.

Distributed automation and IEC 61499

Execution semantics (IEC 61499)

In IEC 61499, execution semantics are the rules that determine when and in which order function blocks execute in response to events; IEC 61499-1 fixes the behavior inside a function block, but leaves parts of the scheduling of events between blocks in a resource to the implementation, so different runtimes can execute the same application differently.

Distributed automation and IEC 61499

IEC 61499 runtime environment

In IEC 61499, a runtime environment is the software on a device that implements the device and resource models: it hosts resources, creates and connects function block instances on management commands, delivers events and schedules algorithm execution, and provides the services behind service interface function blocks such as I/O, timers and communication.

Distributed automation and IEC 61499

Simple function block

In IEC 61499, a simple function block is a function block type in which each event input triggers exactly one algorithm, after which the block issues its output event; it has no user-designed execution control chart with states and transitions and keeps no execution state between events.

Distributed automation and IEC 61499

Subapplication

In IEC 61499, a subapplication is a reusable network of function block and subapplication instances with its own event and data interface, used to structure an application; unlike a composite function block, its component function blocks can be mapped to different resources and devices.

Distributed automation and IEC 61499

System configuration (IEC 61499)

In IEC 61499, a system configuration is the complete description of a control system: its devices with their resources, the communication segments and links between them, the applications, and the mapping of the applications' function block instances to resources, together with the parameters needed to deploy it.

Motion control and drives

Absolute maximum ratings

In datasheets of electronic components, absolute maximum ratings are the limit values of voltage, current, temperature and similar quantities that must not be exceeded even briefly, because the device may be damaged; they are stress limits, not operating conditions, and functional operation is specified only within the recommended operating conditions.

Motion control and drives

Back EMF

In electric motors, back EMF is the voltage induced in the windings by the motion of the rotor's magnetic field, which opposes the supply voltage and rises with speed; drives use it to estimate speed, rotor position or mechanical load without extra sensors.

Motion control and drives

Chopper mode

In stepper motor drivers, a chopper mode is the method by which the driver regulates the phase currents with pulse-width modulation, switching the supply voltage on and off at high frequency and choosing how the current decays, so that the winding current follows its target value; modes differ in noise, precision and dynamic behavior.

Motion control and drives

CiA 402 drive profile

In motion control, the CiA 402 drive profile is the CANopen device profile for drives and motion control, published by CAN in Automation and as IEC 61800-7-201, which defines a common state machine, modes of operation and object dictionary entries for servo drives, stepper drives and frequency converters; it is also used over EtherCAT as CANopen over EtherCAT (CoE).

Motion control and drives

Closed-loop stepper

In motion control, a closed-loop stepper is a stepper motor operated with position feedback, usually from an encoder, so that the driver detects and corrects deviations such as lost steps and can adapt the current to the load, combining stepper construction with servo-like monitoring.

Motion control and drives

Dynamic speed adaptation

In stepper motor control, dynamic speed adaptation is a driver function that lowers the motor speed automatically when the load exceeds the available torque, instead of losing steps or stalling, and returns to the commanded speed when the load decreases.

Motion control and drives

Evaluation kit

In electronics development, an evaluation kit is a set of boards, software and documentation that lets engineers test and characterize a component such as a motion control IC before designing their own hardware; it is intended for laboratory evaluation, not for use in machines or end products.

Motion control and drives

Following error

In motion control, following error is the difference between the commanded position of an axis and its actual position measured by the feedback device during motion; drives monitor it against a limit and signal a fault when the axis can no longer follow the command.

Motion control and drives

Full step

In stepper motor control, a full step is the smallest rotor movement the motor makes when the driver switches the winding currents from one of its basic energizing states to the next; its size is the motor's step angle, for example 1.8° or 200 full steps per revolution.

Motion control and drives

H-bridge

In power electronics, an H-bridge is a circuit of four switches, usually MOSFETs, arranged around a load so that the voltage across it can be applied in either polarity; drivers use one H-bridge per motor phase to reverse and regulate the winding current.

Motion control and drives

Holding torque

In stepper motor technology, holding torque is the maximum torque that can be applied to the shaft of an energized motor at standstill, with rated current in the windings, before the rotor is forced out of its position.

Motion control and drives

Index pulse

In motion control, the index pulse is a signal that an incremental encoder outputs once per revolution (or at defined reference marks on a linear scale), used during homing to set the reference position with the repeatability of the encoder rather than of a switch.

Motion control and drives

Load-adaptive current control

In stepper motor control, load-adaptive current control is a driver function that adjusts the motor current automatically to the measured load, lowering it when little torque is needed and raising it when the load increases, so that the motor runs cooler and uses less energy while keeping a torque reserve.

Automation fundamentals, platforms and components

Microcontroller (MCU)

In embedded electronics, a microcontroller (MCU) is a single integrated circuit that combines a processor core, program and data memory and peripherals such as timers, analog-to-digital converters and serial interfaces, and runs the firmware that controls a device.

Motion control and drives

Microstepping

In stepper motor control, microstepping is the operating mode in which the driver sets the currents in the motor phases to intermediate values, typically along a sine and cosine curve, so that each full step is divided into smaller microsteps, up to 256 microsteps per full step in current motion control ICs.

Motion control and drives

Motion control IC

In motion control, a motion control IC is an integrated circuit that combines motion profile generation (a ramp generator), current or torque control of the motor windings, evaluation of sensors such as encoders and reference switches, and protection functions against overcurrent, undervoltage, short circuit and overtemperature, forming the link between a microcontroller and the motor.

Motion control and drives

Overcurrent protection

In motor drivers and motion control ICs, overcurrent protection is a built-in function that detects currents above a set threshold, for example from a short circuit in the motor cable or to ground, and switches off the power stage to protect the electronics.

Motion control and drives

Pulse-width modulation (PWM)

In power electronics, pulse-width modulation (PWM) is a method of controlling the average voltage or current delivered to a load by switching it fully on and off at a fixed frequency and varying the ratio of on-time to period, the duty cycle.

Motion control and drives

Quadrature signals

In motion control, quadrature signals are the two square-wave signals A and B of an incremental encoder, phase-shifted by 90 electrical degrees, from which the controller derives position by counting edges and the direction of motion from which signal leads.

Motion control and drives

Reference switch

In motion control, a reference switch is a switch or sensor at a defined position of an axis whose signal the controller uses during homing to establish the axis's reference position, often combined with the index pulse of an encoder for higher repeatability.

Motion control and drives

Sensorless load measurement

In motion control, sensorless load measurement is the estimation of a motor's mechanical load from electrical quantities the driver already measures, such as the back EMF or the phase current behavior, without a torque sensor or encoder; it is the basis for stall detection and load-adaptive current control.

Automation fundamentals, platforms and components

Serial Peripheral Interface (SPI)

In embedded electronics, the Serial Peripheral Interface (SPI) is a synchronous serial bus in which a controller device exchanges data with one or more peripheral devices over a clock line, two data lines (MOSI, controller out/peripheral in, and MISO, controller in/peripheral out) and one chip select line per peripheral, typically to read and write registers of ICs on the same board.

Motion control and drives

Stall detection

In motion control, stall detection is a driver function that recognizes when a motor is blocked or overloaded to the point of losing steps, typically without sensors by evaluating the back EMF or current behavior, and signals this to the controller so that it can stop the axis or rehome it.

Motion control and drives

Step angle

In stepper motor technology, the step angle is the rotation of the motor shaft per full step, determined by the motor's construction; typical hybrid stepper motors have 1.8° (200 steps per revolution) or 0.9° (400 steps per revolution).

Motion control and drives

Step/direction interface

In motion control, a step/direction interface is a command interface of a motor driver with two digital inputs: each pulse on the step input moves the motor by one step or microstep, and the level on the direction input sets the direction of rotation.

Motion control and drives

Step loss

In stepper motor control, step loss is the condition in which the rotor fails to follow the steps commanded by the driver, for example due to overload, excessive acceleration or resonance, so that the actual position deviates from the position counted by the controller.

Motion control and drives

Stepper motor resonance

In stepper motor technology, resonance is the oscillation of the rotor and load around their step positions at certain step rates, which causes vibration, noise and torque loss up to step loss; low-speed resonance occurs near the motor's natural frequency, mid-band resonance at medium speeds as an instability of the drive system.

Motion control and drives

Thermal shutdown

In power electronics, thermal shutdown is a built-in function of a driver or IC that switches off the power stage when its junction temperature exceeds a threshold, often after an earlier overtemperature warning, and allows restart only after it has cooled down.

Automation fundamentals, platforms and components

Universal asynchronous receiver-transmitter (UART)

In embedded electronics, a universal asynchronous receiver-transmitter (UART) is a hardware interface that sends and receives serial data frames without a shared clock, each frame framed by a start bit, data bits, an optional parity bit and stop bits, at a baud rate agreed by both sides.

Motion control and drives

Undervoltage lockout (UVLO)

In power electronics, undervoltage lockout (UVLO) is a built-in function of a driver or IC that keeps the power stage switched off while the supply voltage is below a defined threshold, and switches it off when the voltage falls below it, so that the circuit doesn't operate in an undefined state.

Industrial communication

CANopen over EtherCAT (CoE)

In EtherCAT, CANopen over EtherCAT (CoE) is the mailbox protocol that carries the CANopen application layer, with its object dictionary, SDO parameter access, PDO mapping and device profiles such as CiA 402 for drives, over EtherCAT.

Industrial communication

EtherCAT Slave Information (ESI)

In EtherCAT, the EtherCAT Slave Information (ESI) is the XML device description, specified by the EtherCAT Technology Group, that tells configuration tools a subdevice's identity, supported mailbox protocols, process data objects, object dictionary, sync manager settings and distributed clock modes.

Industrial communication

EtherCAT state machine

In EtherCAT, the EtherCAT state machine is the communication state model of every subdevice, controlled by the main device, with the states Init, Pre-Operational, Safe-Operational and Operational, plus the optional Bootstrap state for firmware updates.

Industrial communication

GSDML file

In PROFINET, a GSDML file is the XML device description, written in the General Station Description Markup Language defined by PROFIBUS & PROFINET International, that tells engineering tools which modules, submodules, I/O data, parameters, diagnostics and communication features an IO device has.

Industrial communication

Last will and testament (MQTT)

In MQTT, the last will and testament is a will message that a client registers with the broker when it connects and that the broker publishes on the client's behalf to a defined topic if the connection ends without a normal disconnect, for example after a network failure or a missed keep-alive.

Industrial communication

MQTT broker

In MQTT, a broker (called the Server in the OASIS specification) is the central application that accepts client connections, receives published messages, matches their topics against the clients' subscriptions and forwards the messages, and that keeps retained messages, will messages and session state.

Industrial communication

MQTT topic

In MQTT, a topic is the UTF-8 string, organized in levels separated by slashes, to which a client publishes a message and against which the broker matches subscriptions, where subscribers may use the wildcards + for exactly one level and # for all remaining levels.

Industrial communication

OPC UA address space

In OPC UA, the address space is the set of nodes that a server makes visible to clients, where each node belongs to one of eight node classes (Object, Variable, Method, ObjectType, VariableType, ReferenceType, DataType, View), is identified by a NodeId within a namespace, and is linked to other nodes by typed references.

Industrial communication

OPC UA client

In OPC UA, a client is an application that connects to an OPC UA server, opens a secure channel and a session, and uses the server's services to browse its address space, read and write values, call methods and subscribe to data changes and events.

Industrial communication

OPC UA FX

In industrial communication, OPC UA FX (Field eXchange, UAFX) is the family of OPC Foundation specifications from the Field Level Communications initiative that extends OPC UA to vendor-independent communication between controllers and, in later parts, with field devices, based on OPC UA PubSub, client-server and optionally Time-Sensitive Networking.

Industrial communication

OPC UA security policy

In OPC UA, a security policy is the named set of cryptographic algorithms and key lengths that an endpoint uses to sign and encrypt messages, and it is combined with a message security mode of None, Sign or SignAndEncrypt and with X.509 application instance certificates to protect the communication between client and server.

Industrial communication

OPC UA server

In OPC UA, a server is an application that exposes an address space of nodes and provides the OPC UA services with which clients browse and read that information, write values, call methods and subscribe to data changes and events.

Industrial communication

Persistent session (MQTT)

In MQTT, a persistent session is session state that the broker keeps for a client identifier beyond a single connection, including its subscriptions and the QoS 1 and QoS 2 messages it has not yet received, requested with Clean Session = 0 in MQTT 3.1.1 or with Clean Start = 0 and a session expiry interval in MQTT 5.0.

Industrial communication

PROFINET conformance class

In PROFINET, a conformance class is one of the defined feature sets CC-A, CC-B, CC-C and CC-D that state which functions a device or network supports: CC-A basic real-time (RT) communication, CC-B additional network diagnostics and topology information, CC-C isochronous real-time (IRT) with bandwidth reservation, and CC-D PROFINET over Time-Sensitive Networking (TSN).

Industrial communication

PROFINET IO controller

In PROFINET, an IO controller is the device, usually a PLC, that establishes application relations with the configured IO devices, assigns their IP addresses by device name, sends them output data and receives their input data cyclically.

Industrial communication

PROFINET IO device

In PROFINET, an IO device is a field device, such as remote I/O, a drive or a valve terminal, that is assigned to an IO controller and exchanges the input and output data of its modules and submodules with that controller cyclically.

Industrial communication

Retained message (MQTT)

In MQTT, a retained message is a message published with the retain flag set, which the broker stores as the last known value of its topic and delivers immediately to every client that subscribes to a matching topic later.

Industrial communication

Safety over EtherCAT (FSoE)

In industrial communication, Safety over EtherCAT (FSoE, FailSafe over EtherCAT) is the functional safety communication protocol specified in IEC 61784-3-12, in which an FSoE main instance and FSoE subdevices exchange safety data in safety frames over EtherCAT or another channel according to the black channel principle.

PLC and control programming

IEC 61131-3

IEC 61131-3 is the international standard that defines the programming languages, data types, program organization units and software model for programmable logic controllers, including ladder diagram, function block diagram, structured text and sequential function chart.

Distributed automation and IEC 61499

IEC 61499

IEC 61499 is the international standard series that defines an event-driven function block architecture for distributed industrial process measurement and control systems, covering the architecture (Part 1), software tool requirements (Part 2) and rules for compliance profiles (Part 4).

PLC and control programming

Structured text (ST)

In IEC 61131-3, structured text (ST) is a high-level textual programming language with a syntax similar to Pascal, providing assignments, IF and CASE statements, loops, and calls of functions and function blocks.

PLC and control programming

Sequential function chart (SFC)

In IEC 61131-3, the sequential function chart (SFC) is a graphical language for structuring programs as steps and transitions, where actions are associated with steps and transitions define the conditions for moving from one step to the next.

Process instrumentation and analytical measurement

4–20 mA current loop

In process instrumentation, a 4–20 mA current loop is an analog signal circuit in which a measured or set value is represented by a DC current between 4 and 20 milliamperes; the live zero at 4 mA allows wire break detection and powering of two-wire devices.

Motion control and drives

Servo drive

In motion control, a servo drive is a drive that powers a servo motor and closes the current, velocity and often position loops using motor feedback, so the axis follows commanded positions, speeds or torques precisely and dynamically.

Motion control and drives

Encoder

In motion control, an encoder is a sensor that converts the position or motion of a shaft or linear scale into electrical signals, either as incremental pulses or as an absolute position value, for use as feedback by a drive or controller.

Automation fundamentals, platforms and components

Module Type Package (MTP)

In process automation, the Module Type Package (MTP) is a vendor-neutral description of the automation interface of a process equipment assembly (module), covering its HMI, services, parameters and communication, specified in the VDI/VDE/NAMUR 2658 series. A process orchestration layer imports MTPs to integrate modules.

Automation fundamentals, platforms and components

PackML (ISA-TR88.00.02)

In packaging and discrete automation, PackML is an implementation guideline, published by ISA as ISA-TR88.00.02, for a standard machine state model, operating modes and data tags (PackTags). It is based on ISA-88 concepts and is promoted by OMAC.

Robotics

Collaborative robot

In industrial robotics, a collaborative robot is a robot designed to be used in a collaborative application, where people and the robot work in a shared space during automatic operation. Whether the application is safe is decided by the risk assessment of the whole application, not by the robot alone.

Machine vision

Machine vision

In industrial automation, machine vision is the use of cameras, lighting, optics and image processing to automatically inspect, measure, identify or guide in manufacturing and logistics, with results passed to the machine or plant control.

MES and ISA-95

ISA-95 hierarchy

In ISA-95 / IEC 62264, the functional hierarchy divides manufacturing functions into levels: Level 0 the physical process, Level 1 sensing and manipulating, Level 2 monitoring and supervisory control, Level 3 manufacturing operations management and Level 4 business planning and logistics.

Batch and process operations

ISA-88 procedural model

In ISA-88 batch control, the procedural control model is the hierarchy of procedural elements used to describe how a batch is made: procedure, unit procedure, operation and phase.

Industrial communication

OPC UA PubSub

In industrial communication, OPC UA PubSub is the publish-subscribe communication model of OPC UA, specified in OPC 10000-14, in which publishers send data set messages to any number of subscribers, either brokerless over UDP multicast or via a message broker such as MQTT or AMQP.

IIoT, data and AI

Asset Administration Shell (AAS)

In Industrie 4.0, the Asset Administration Shell (AAS) is the standardized digital representation of an asset, such as a device, machine or plant, made up of submodels that describe its properties, functions and documents in a machine-readable way. Its structure is defined by the AAS metamodel published by the Industrial Digital Twin Association (IDTA) and standardized in IEC 63278.

Industrial communication

Time-Sensitive Networking (TSN)

In networking, Time-Sensitive Networking (TSN) is a set of IEEE 802.1 standards that add deterministic behavior to standard Ethernet, including time synchronization, scheduled traffic, frame preemption, bandwidth reservation and seamless redundancy. IEC/IEEE 60802 defines a TSN profile for industrial automation.

Industrial communication

IO-Link

In industrial automation, IO-Link is a point-to-point communication interface between an IO-Link master and a single sensor or actuator over a standard unshielded three-wire cable. It transmits process data, parameters and diagnostics and is standardized in IEC 61131-9 as SDCI.

OT cybersecurity

Zero trust architecture (ZTA)

In cybersecurity, a zero trust architecture (ZTA) is an enterprise security design in which no user, device or network location is trusted implicitly; every access request to a resource is authenticated, authorized and evaluated per session based on identity, device state and policy. NIST SP 800-207 describes its principles and components.

Engineering, integration and validation

Virtual commissioning

In automation engineering, virtual commissioning is the testing and commissioning of control software against a simulation model of the machine or plant before the physical equipment is available. The real or emulated controller exchanges signals with the model as it would with the real plant.

Engineering, integration and validation

Hardware-in-the-loop (HIL)

In control engineering, hardware-in-the-loop (HIL) is a test method in which the real control hardware, running its real software, is connected to a real-time simulation of the machine or process. The simulation supplies sensor signals and reacts to the controller's outputs.