---
id: glossary
title: "Glossary"
summary: "The terms used across the Viaducta documentation, from alarm to type."
audience: user
keywords: "glossary, terms, definitions"
---
# Glossary

**Alarm.** A notification raised by a flow (with the [Alarm](/documentation/plugins/flow/alarm-plugin) component) or by the system,
shown in the designer's **Alarms** panel and optionally sent by e-mail or as a web push notification. Alarm
definitions are kept in the repository.

**Assistant.** The AI assistant in the designer (**Viaducta AI**). It builds, explains, changes and fixes flows.

**Auto start.** A flow setting: the flow starts when its environment starts, optionally only after other flows it
depends on are running.

**Binding.** A configuration value with placeholders in braces, such as `{input.Customer.Name}`, compiled with the
flow and evaluated for every message. See [Configuration values](./concepts#configuration-values).

**Certificate.** A certificate stored in the repository of an environment and used by components for TLS or signing.

**Cloud bridge.** A small program installed at a remote site. It connects out to Viaducta and makes network routes
work in both directions, so flows reach systems at that site without a VPN.

**Component.** One plugin placed in a flow, with its own configuration.

**Connection.** The link from an output pin of one component to an input pin of another; the path a record takes.

**Controller.** The process that runs an execution environment: it owns the repository, starts and supervises the
hosts, and starts auto-start flows. See [Architecture](/documentation/architecture/).

**Data monitor.** A designer view that shows the records and metadata crossing a component's pins while the flow runs.

**Database link.** A named connection to a database, stored in the repository of an environment and used by the
database components.

**Debugger.** Runs a flow in debug mode, pauses it at breakpoints on components and in C# scripts, and lets you inspect
the paused message.

**Execution environment.** A place where flows run, such as development, test or production, with its own controller,
repository and hosts.

**Expression settings.** Named packages of settings in the repository of an environment. A configuration field reads
one with `=Package.Setting`.

**Flow.** A set of connected components that does one job, compiled into its own .NET assembly.

**Host.** The process that compiles and runs flows. A controller starts as many hosts as the hosting strategies need.

**Hosting strategy.** How flows share host processes: **Private host** (a process per flow), **Tag based host** (flows
with the same hosting tag share a process) or **Shared host** (all flows in one process).

**Keep alive.** A flow setting, also declared by listener plugins, that keeps a flow running after its start calls
return.

**Manager.** The designer's backend: the web API, sign-in, the AI assistant and the MCP endpoint. One Manager serves
every environment of its tenants.

**MCP.** Model Context Protocol. External AI agents such as Claude Code connect to Viaducta through its MCP endpoint.

**Metadata.** The data that travels with each record: correlation id, session id and entries added by components.

**Namespace.** The .NET namespace a flow and its types are compiled into.

**Network route.** A named route through a cloud bridge, from Viaducta to a system at a remote site or the other way.

**Pin.** A connection point of a component: input, output, start, continue, no data, error, timeout and a few others.
See [Pins and connections](./concepts#pins-and-connections).

**Plugin.** A kind of building block (Timer, Sql query, Http client, C# script). Each plugin has a reference page under
[Plugins](/documentation/plugins/).

**Plugin port.** The component that makes a flow publishable as a plugin. See [Plugin port](/documentation/plugins/flow/entry-point).

**Record.** One message's data, an instance of a type.

**Repository.** The files of an execution environment: flows, types, expression settings, database links,
certificates, network routes, alarm definitions and hosting tags, versioned with Git.

**Route id.** A name on a connection. Components such as the [Decision router](/documentation/plugins/flow/decision-plugin) send a
record only to the connections with a matching route id.

**Tenant.** An organisation using Viaducta. A tenant has one or more execution environments and its own users.

**Type.** The structure of a record: named, typed fields, nested types and lists. Every type becomes a C# class when
the flow is compiled.