Glossary of building automation & IoT terms

BACnet

BACnet (Building Automation and Control Networking Protocol) is an open, ASHRAE/ISO-standardized communication protocol purpose-built for building automation and control equipment such as HVAC controllers, chillers, and air handling units. It defines a common set of data objects and services so devices from different manufacturers can share information over IP or MS/TP networks without proprietary gateways. BACnet is inside the designed scope of the xSERVA protocol module — addressed at object and property level rather than as a flat point count — but that module is on the roadmap and does not ship today.

BACnet/SC

BACnet Secure Connect is the current secure transport for BACnet, carrying BACnet messages inside an authenticated TLS connection over a WebSocket rather than as raw BACnet/IP broadcasts. It removes the need to route unauthenticated BACnet traffic across a network or open BACnet ports through a firewall, which is what made older BACnet/IP installations difficult to defend on a shared corporate network.

BAS

A Building Automation System (BAS) is the software and hardware layer that centralizes monitoring and control of a building's mechanical and electrical systems, most commonly HVAC, lighting, and access control. A BAS collects data from field devices and controllers, presents it to operators, and allows scheduling, alarming, and automated responses so a facility runs efficiently without constant manual intervention.

BLE

Bluetooth Low Energy is the low-power variant of Bluetooth used by sensors, beacons, locks and mobile credentials. It is designed for devices that transmit small amounts of data intermittently and must run for months or years on a coin cell, which is the opposite trade-off from Bluetooth Classic’s continuous audio streaming.

BMS

A Building Management System (BMS) is closely related to a BAS, but typically describes the broader operational layer that supervises multiple building subsystems, sometimes across an entire site or portfolio, providing dashboards, reporting, and centralized control on top of the underlying automation. In practice the terms BAS and BMS are often used interchangeably, and xSERVA is designed to serve as both the automation layer and the management layer in one platform.

BTL

BTL Listed refers to products that have passed conformance testing administered by the BACnet Testing Laboratories (BTL), the independent body that verifies a device or software system correctly implements the BACnet standard it claims to support. BTL Listing gives specifiers and integrators confidence that a product will interoperate correctly with other certified BACnet equipment on a project.

CoAP

The Constrained Application Protocol is a compact request/response protocol for very constrained devices, providing roughly REST-like semantics over UDP instead of TCP. It appears where a device is too small or too power-limited to hold open a TCP connection, and is the transport underneath LwM2M device management.

DALI-2

DALI-2 is the current generation of the Digital Addressable Lighting Interface, the two-wire bus used to address, dim and monitor individual luminaires. Where the original DALI certified control gear only, DALI-2 also certifies control devices, sensors and input devices, which is what allows an occupancy sensor and a luminaire from different manufacturers to work together predictably. D4i extends it further with energy and diagnostic data reported from inside the luminaire itself.

Demand Response

Demand Response is the practice of temporarily adjusting a building's electricity consumption, usually by shedding non-critical loads or shifting them to off-peak periods, in response to grid signals, pricing changes, or capacity constraints. A platform with real-time visibility into every connected load, like xSERVA, can identify which systems can be curtailed automatically without affecting occupant comfort or critical operations.

Digital Twin

A Digital Twin is a live, data-driven virtual representation of a physical building or system, continuously updated from real sensor and controller data rather than static as-built drawings. Because it mirrors actual current conditions, a digital twin can be used to simulate scenarios, test changes before applying them physically, and give operators a spatial, contextual view of how a building is performing right now.

DLMS/COSEM

DLMS/COSEM is the international standard for smart electricity metering, combining a messaging specification with a common object model for meter data. It is the data model behind most utility-grade meters, and it matters for buildings because it defines how a tariff, a register and a load profile are represented consistently across manufacturers.

DPT

A Datapoint Type (DPT) is the KNX standard that defines how a specific kind of value, such as a temperature reading, a percentage, or an on/off switch state, is encoded on the KNX bus. DPTs ensure that when one device sends a value, any other KNX-certified device reading that same group address interprets the data the same way, which is essential for interoperability between different manufacturers' KNX products.

Edge Computing

Edge Computing refers to processing data close to where it is generated, such as on a local gateway or controller inside the building, rather than sending every raw data point to a remote server first. In building automation this reduces latency for time-sensitive control decisions, cuts bandwidth usage, and allows systems to keep functioning locally even during a temporary loss of connectivity to the cloud.

Edge Gateway

An edge gateway is a device on the local network that terminates field protocols on site and speaks a single authenticated, encrypted path to the platform. It exists because most building protocols were designed for a trusted local network and have no answer for internet exposure, so the gateway is what keeps a plant bus off the public internet while still letting a cloud platform see it. It is also what allows a site to keep operating during a loss of connectivity.

EMS

An Energy Management System (EMS) is the software layer focused specifically on monitoring, analyzing, and optimizing a building's energy consumption, covering electricity, water, gas, and other utilities. An EMS typically tracks meter data, identifies waste or abnormal usage patterns, and supports reporting for cost control and sustainability goals. xSERVA integrates EMS functionality directly with its BAS/BMS layer so energy data and operational data live in one system rather than separate tools.

EnOcean

EnOcean is a wireless standard for batteryless sensors and switches that harvest the energy they need from the environment, most recognisably from the mechanical act of pressing a switch. It is used in retrofit projects where running new cable is impractical and replacing batteries across thousands of devices would be worse.

ESG

ESG stands for Environmental, Social, and Governance, a framework used by investors, regulators, and tenants to evaluate an organization's sustainability and ethical impact. For buildings, the environmental component in particular depends on accurate energy, water, and emissions data, which is why a platform that captures granular, real-time operational data is central to producing credible ESG reporting rather than relying on estimates.

ETS

ETS (Engineering Tool Software) is the official KNX Association software used to design, configure, and commission KNX installations, including assigning group addresses, setting parameters on KNX devices, and programming automation logic. Integrators use ETS as the standard tool for building and documenting a KNX project before and during commissioning.

Fieldbus

A fieldbus is a digital network that connects field-level devices — sensors, actuators, controllers — on a shared cable rather than by individual point-to-point wiring. BACnet MS/TP, Modbus RTU, PROFIBUS and KNX TP are all fieldbuses. The defining trait is that many devices share one physical medium, which is why addressing and bus arbitration matter so much at this level.

Group Address

A Group Address is the addressing mechanism used on a KNX network to link devices that should communicate with each other, for example a light switch and the dimmer actuator it controls. Rather than addressing individual devices directly, KNX communication is organized around these logical group addresses, which is what allows KNX installations to be reconfigured through software rather than rewiring.

IoT

IoT (Internet of Things) describes the broad category of physical devices, sensors, and equipment that connect to a network to send and receive data, extending automation beyond traditional building controllers to things like wireless sensors, smart meters, and connected equipment. In building automation, IoT devices often communicate over lightweight protocols like MQTT and feed additional granularity into a platform like xSERVA alongside data from BACnet, KNX, and Modbus systems.

KNX

KNX is an open, internationally standardized (ISO/IEC 14543) protocol widely used for lighting, blinds, HVAC room control, and other room-level automation, particularly common in European-influenced building designs. KNX devices communicate over a dedicated twisted-pair bus, IP, or radio frequency, and are configured using group addresses defined in the ETS engineering tool. KNX, including KNXnet/IP and KNX Secure, is inside the designed scope of the xSERVA protocol module, addressed at group-address and datapoint-type level. That module is on the roadmap and does not ship today.

M-Bus

Meter-Bus (EN 13757) is a two-wire bus purpose-built for reading utility meters — heat, water, gas and electricity. Its wireless variant, Wireless M-Bus, is widely used where meters sit in risers or private apartments that cannot practically be wired. M-Bus is often the only way to read the meters a building already has without replacing them.

Matter

Matter is an application-layer interoperability standard intended to let smart devices from different manufacturers work together without a vendor-specific hub for each. It runs over IP, most commonly carried by Thread or Wi-Fi, and defines device types and their behaviours rather than a new radio.

Modbus

Modbus is a simple, widely adopted serial and TCP/IP communication protocol originally developed for industrial equipment, and now commonly used in buildings for interfacing with meters, generators, chillers, and other mechanical plant. Its simplicity and long track record make it a common lowest-common-denominator protocol for equipment that predates newer standards. Modbus TCP and RTU are inside the designed scope of the xSERVA protocol module, addressed at register level with per-device typing. That module is on the roadmap and does not ship today.

Modbus Register

A Modbus register is the addressable unit of data in a Modbus device — a numbered 16-bit location holding one value. Larger values such as a 32-bit float occupy consecutive registers, and the standard does not say which order those registers come in or how they should be interpreted, so the same energy reading can be decoded three different ways by three different systems. Correct per-device typing is therefore not a detail; a wrongly typed register produces a plausible number that is simply wrong.

MQTT

MQTT (Message Queuing Telemetry Transport) is a lightweight, publish-subscribe messaging protocol designed for low-bandwidth, high-latency, or unreliable networks, which has made it a de facto standard for IoT sensors and edge devices. Rather than devices polling each other directly, MQTT clients publish data to named topics on a broker, and any subscribed client receives updates instantly. MQTT 5, including Sparkplug B, is inside the designed scope of the xSERVA protocol module, addressed at topic and payload level. That module is on the roadmap and does not ship today.

MS/TP

Master-Slave/Token-Passing is BACnet’s serial data link layer, running over RS-485. It is how field-level unitary controllers such as VAV boxes and fan coil units are usually reached, because running Ethernet to every terminal unit in a building is rarely justifiable. MS/TP is slower than BACnet/IP and its token-passing scheme makes bus segment design and device count genuinely matter.

OCPP

The Open Charge Point Protocol governs communication between an EV charger and its central management system — authorisation, transactions, smart charging limits, diagnostics and firmware. Version 1.6 remains the field majority while 2.0.1 and 2.1 are the current generations. In a building context OCPP matters because EV charging is often the largest new electrical load added to a site, and it is controllable.

ONVIF

ONVIF is the interoperability standard for IP video and physical security devices, defining how cameras, recorders and clients discover each other and exchange streams, events and configuration. Its profiles describe capability sets — Profile T covers modern video streaming. ONVIF is what makes it possible to put cameras from several manufacturers behind one system without a separate driver for each model.

OPC UA

OPC Unified Architecture is a platform-independent industrial interoperability standard with a rich information model, built-in security and both client/server and publish-subscribe communication. It is the usual bridge between industrial plant and IT systems, and it appears in buildings wherever there is manufacturing, process plant or serious mechanical infrastructure behind the building services.

OSDP

The Open Supervised Device Protocol is the modern standard for communication between an access control reader and its controller. Unlike Wiegand it is bidirectional, supervised so a cut or removed reader is detected, and encrypted under Secure Channel. Its practical significance is that reader-to-controller wiring stops being an unmonitored, cloneable plaintext link.

PDPA

The Personal Data Protection Act (PDPA) is Malaysia's legislation governing the collection, use, and disclosure of personal data by organizations in the course of commercial transactions. For building platforms that process occupant, tenant, or employee data, such as access logs or biometric records, PDPA compliance shapes how that data is stored, secured, and retained.

Predictive Maintenance

Predictive Maintenance is a maintenance strategy that uses ongoing equipment data, and increasingly machine learning models trained on that data, to anticipate a failure before it happens rather than servicing equipment on a fixed schedule or waiting for a breakdown. By continuously analyzing live signals such as vibration, temperature, or run-hours trends, a platform like xSERVA can flag equipment that is drifting toward failure early enough for a planned intervention instead of an emergency callout.

PTP

Precision Time Protocol (IEEE 1588) synchronises clocks across a network to sub-millisecond accuracy, far tighter than NTP. It matters wherever events from different systems must be correlated precisely — in electrical protection and in any analysis that tries to establish which of two events actually happened first.

RS-485

RS-485 is a physical layer, not a protocol: a differential, multidrop serial standard that allows many devices to share one twisted pair over long distances with good noise immunity. BACnet MS/TP and Modbus RTU both run over it. This distinction matters because specifications frequently treat RS-485 as an alternative to Modbus, when in fact Modbus RTU runs on it and Modbus TCP does not.

Sparkplug B

Sparkplug B is a specification that defines a topic namespace, a payload format and a state model on top of MQTT. Plain MQTT says nothing about what topics mean or how to tell whether a device is alive, so Sparkplug adds birth and death certificates and a defined structure. It is what turns a loose broker into something a system can reason about.

Thread

Thread is a low-power IPv6 mesh networking protocol for battery-operated devices. It is a network layer rather than an application layer, and it is the transport underneath a large share of Matter deployments. Because every node is IP-addressable, a Thread device does not need a protocol translation gateway to be reached.

Wiegand

Wiegand is the legacy interface between an access reader and its controller: one-way, unencrypted, and unsupervised, meaning a controller cannot tell whether a reader has been removed or replaced. It remains enormously widespread, which is why it cannot simply be dismissed — but its replacement, OSDP, exists precisely because a plaintext, unmonitored link on the unsecured side of a door is a genuine weakness.

Zigbee

Zigbee is a low-power wireless mesh protocol widely deployed in lighting control and sensing. Devices relay for each other, so coverage grows with density rather than requiring every device to reach a central hub, which is what makes it practical across a large floor plate.

What is this glossary for?

It defines the core protocols, standards, and concepts referenced across the xSERVA site, so specifiers, integrators, and building owners share a common vocabulary when evaluating the platform.

Does xSERVA support every term listed here?

No, and this glossary deliberately defines more than xSERVA does. Many entries — OPC UA, DALI-2, EnOcean, Zigbee, Thread and others — are here because they are part of the landscape a specifier has to reason about, not because they are xSERVA features. BACnet, KNX, MQTT and Modbus sit inside the designed scope of the protocol integration module, which is on the roadmap and does not ship today. The protocol landscape page states the status of each one individually.

Where can I see these protocols explained in more depth?

BACnet, KNX, MQTT and Modbus each have a dedicated page under /protocols with a deeper technical explainer. The protocol landscape page at /protocols/landscape.php groups the wider set of standards by the job they do and marks the status of each one.

Why does the glossary separate protocols from transports?

Because they are different layers and confusing them causes real problems in specifications. RS-485 is a physical layer that Modbus RTU and BACnet MS/TP both run on; TCP, IP and Ethernet carry Modbus TCP and MQTT; TLS encrypts several of them. None of those is an alternative to KNX or BACnet, and a requirement written as though it were cannot be satisfied as stated.

Can I request a term be added to the glossary?

Yes. Message our team on WhatsApp using the button on this page and we will consider adding it.