vocabulary: name: SCADA Domain Vocabulary description: >- Domain vocabulary for Supervisory Control and Data Acquisition (SCADA) systems covering industrial control system architecture, field devices, communication protocols, process data management, and operational technology (OT) security concepts. Used in manufacturing, energy, water treatment, oil and gas, and critical infrastructure sectors. version: "1.0.0" created: "2026-05-02" modified: "2026-05-02" domains: - name: SCADA Architecture description: Core architectural components of a SCADA system terms: - term: SCADA definition: >- Supervisory Control and Data Acquisition — a control system architecture comprising computers, networked data communications, and graphical user interfaces for high-level process supervisory management. SCADA systems are used to monitor and control industrial equipment in industries such as energy, water, manufacturing, and transportation. acronym: SCADA - term: HMI definition: >- Human-Machine Interface — the graphical interface through which operators monitor process variables, acknowledge alarms, and issue control commands to the SCADA system. Modern HMIs are web-based and mobile-accessible. acronym: HMI related: [SCADA, Operator Station] - term: RTU definition: >- Remote Terminal Unit — a microprocessor-based field device that collects data from sensors and transmits it to the SCADA master station over wide-area network connections. RTUs are used in geographically dispersed infrastructure like pipelines and substations. acronym: RTU related: [PLC, SCADA] - term: PLC definition: >- Programmable Logic Controller — an industrial computer used for automation of industrial processes. PLCs execute control logic in real-time and communicate tag data to SCADA systems via protocols such as Modbus, OPC-UA, and EtherNet/IP. acronym: PLC related: [RTU, DCS] - term: DCS definition: >- Distributed Control System — a computerized control system used in large-scale industrial processes (e.g., oil refining, chemical plants) where control elements are distributed throughout the plant. DCS differs from SCADA in that it focuses on continuous process control rather than remote monitoring. acronym: DCS related: [PLC, SCADA] - term: Historian definition: >- A time-series database dedicated to storing industrial process data from SCADA and DCS systems. Historians support high-frequency data collection (sub-second), compression algorithms, and long-term retention for compliance and analysis. Major vendors include AVEVA PI System, Aspen InfoPlus.21, and GE Proficy Historian. related: [Tag, Time-Series Data] - term: SCADA Master Station definition: >- The central server(s) in a SCADA architecture responsible for aggregating data from RTUs and PLCs, running alarm management, storing historian data, and serving the HMI interface to operators. - name: Data and Tags description: Concepts related to SCADA process data representation terms: - term: Tag definition: >- A named data point in a SCADA system representing a process variable (sensor reading), setpoint, or control output. Tags have a path (e.g., Plant/Area/Device/Variable), a data type, a current value, a timestamp, and a quality code. related: [Tag Path, Engineering Units, Quality] - term: Tag Path definition: >- The hierarchical address of a tag in the SCADA namespace, organized by plant, area, unit, and variable (e.g., Plant1/Reactor/Feed/FlowRate). Tag paths map to ISA-88 and ISA-95 equipment hierarchy standards. - term: Engineering Units abbreviation: EU definition: >- The physical measurement unit associated with a tag value (e.g., PSI, °C, RPM, m3/hr, kW). Engineering units are metadata stored with the tag definition and essential for correct data interpretation. - term: Quality Code definition: >- An OPC-UA standard status indicator applied to each tag reading, indicating whether the data is reliable: Good, Uncertain, Bad, or Stale. Bad quality typically indicates a device communication failure. values: - Good: Data is reliable and current - Uncertain: Data may be from a backup source or stale - Bad: Communication failure — data is unreliable - Stale: Data not updated within expected scan interval - term: Scan Rate definition: >- The frequency at which a SCADA system polls a field device to update a tag's value. Scan rates range from milliseconds (fast control loops) to minutes (slow trend data). - term: Deadband definition: >- A filtering setting that prevents a tag value from being reported unless it changes by a minimum amount. Deadbands reduce unnecessary data volume in historians and communications. - name: Alarms and Events description: Concepts related to SCADA alarm management terms: - term: Alarm definition: >- A notification generated when a tag value exceeds a configured threshold or an abnormal condition is detected. SCADA alarms require operator acknowledgment and are governed by ISA-18.2. related: [Alarm Priority, ISA-18.2] - term: Alarm Priority definition: >- A numeric ranking of an alarm's urgency (typically 1-4): 1=Critical/High-High, 2=High, 3=Medium, 4=Low. Priority determines operator response time requirements. - term: ISA-18.2 definition: >- The ISA (International Society of Automation) standard for Management of Alarm Systems for the Process Industries. Defines best practices for alarm philosophy, rationalization, prioritization, and key performance indicators like alarm flood rate and standing alarms. - term: Alarm Flood definition: >- A condition in which more alarms are generated than operators can effectively respond to, often caused by a single equipment failure triggering cascading alarms. ISA-18.2 recommends no more than 10 alarms per 10-minute period under abnormal conditions. - term: Alarm Rationalization definition: >- The systematic process of reviewing each alarm to confirm it represents a genuine abnormal situation requiring operator response, and setting appropriate setpoints and priorities. - term: Dead Time definition: >- The time delay between when an abnormal condition occurs and when the operator acknowledges the alarm. A key performance indicator in alarm management. - name: Communication Protocols description: Industrial communication protocols used in SCADA architectures terms: - term: OPC-UA definition: >- OPC Unified Architecture (IEC 62541) — the industrial interoperability standard for secure, reliable data exchange in industrial automation and IoT environments. Provides a platform-independent, service-oriented architecture supporting client/server and pub/sub models. related: [MQTT, Modbus] - term: Modbus definition: >- A serial communication protocol originally developed by Modicon (1979) for connecting PLCs. Modbus TCP/IP is the most widely deployed field device protocol in SCADA due to its simplicity and universality. - term: DNP3 definition: >- Distributed Network Protocol 3 — a robust, secure protocol used primarily in electric utilities and water/wastewater SCADA systems for communication between RTUs, IEDs, and master stations over unreliable WAN links. - term: MQTT definition: >- Message Queuing Telemetry Transport (ISO/IEC 20922) — a lightweight pub/sub messaging protocol used in SCADA and IIoT for high-volume, low-bandwidth sensor data streaming. Used with MQTT brokers like Mosquitto, EMQX, and HiveMQ. - term: EtherNet/IP definition: >- An industrial Ethernet protocol developed by Rockwell Automation and ODVA for Allen-Bradley PLCs and other industrial devices. Based on the Common Industrial Protocol (CIP) over standard Ethernet. - name: Security and Compliance description: OT/ICS security concepts specific to SCADA environments terms: - term: OT Security definition: >- Operational Technology security — practices and technologies for protecting industrial control systems from cyber threats. OT security differs from IT security due to real-time requirements, legacy equipment, and safety criticality. acronym: OT related: [ICS, SCADA] - term: ICS definition: >- Industrial Control System — umbrella term for systems used to control industrial processes including SCADA, DCS, PLCs, and RTUs. ICS cybersecurity is governed by standards such as IEC 62443 and NIST SP 800-82. acronym: ICS related: [SCADA, DCS, OT Security] - term: Purdue Model definition: >- A reference architecture for industrial network segmentation dividing OT and IT networks into hierarchical zones (Level 0-4). Defines the boundary between field devices (Level 0-1), control systems (Level 2), operations (Level 3), and enterprise systems (Level 4). - term: DMZ definition: >- Demilitarized Zone — a network segment separating the OT network from the IT enterprise network. SCADA systems requiring IT integration place data historians and API gateways in the DMZ to avoid direct IT-OT connectivity. - term: IEC 62443 definition: >- The international standard for cybersecurity of industrial automation and control systems. Defines security levels, zones, conduits, and requirements for ICS vendors and operators.