Workflow Engine Concepts
Workflow Engine provides seventeen concepts organised into two groups. The seven core concepts cover everything you need to configure, run, and persist a workflow. The ten additional concepts control what happens when a transition fires, handle advanced scenarios, or extend the workflow with logging, localization, and scheduling. Use this page to find the concept you need and jump to its full description.
Core Concepts
These seven concepts are required for every Workflow Engine integration.
Activity
A stable state where the process waits for input. Think of it as a step in the process, like Draft, Review, or Approved.
Transition
A directed connection between two activities. A transition fires when its trigger activates and its conditions pass.
Command
A named action that advances the process from one activity to the next. A command can be triggered by a user or by the system.
Scheme
The blueprint that defines a process: its activities, transitions, and commands. One scheme can spawn many process instances.
Process Instance
A single running instance of a scheme. Each instance tracks its own current activity and history.
Workflow Runtime
The engine that executes schemes, manages process instances, and fires transitions.
Persistence
The database adapter that stores schemes, instances, history, timers, and parameters.
Additional Concepts
How transitions get triggered, gated, enriched with code, and extended with metadata, logging, localization, and scheduling.
Action
C# code that runs when a transition fires. Use actions to send emails, call APIs, update databases, or any side-effect.
Parameter
Named data attached to a process instance. Parameters carry values through the lifecycle.
Condition
A guard on a transition that decides whether it actually fires. A transition with a failing condition stays dormant.
Rule
A permission check that determines which users or roles can execute a command from the current activity.
Timer
An automatic trigger that fires a transition after a delay or on a schedule, without any user action.
Subprocess
A child process instance spawned by a parent. The parent can wait for the subprocess to complete before continuing.
Annotation
Key-value metadata attached to activities and transitions in a scheme.
Process Logs
A record of events and errors scoped to a single process instance.
Localization
Translations for activity names, command names, and parameter labels displayed to users.
Work Calendar
A schedule that defines working days and hours for calendar-aware timers.
Frequently asked questions
Do I need to understand all concepts before building my first workflow?
No. The seven core concepts are enough to build and run a workflow. Behaviour concepts can be added as your workflows need conditions, custom code, or automatic triggers.
Which concepts are required for a minimal workflow?
Activity, Transition, Command, Scheme, Process Instance, Workflow Runtime, and Persistence. Create a scheme with at least two activities and one transition, configure the runtime with a persistence provider, then create an instance and execute a command.
Can I use Workflow Engine without a database?
No. The runtime requires a persistence provider to store schemes, instances, and history. SQLite is the lightest option for local development.
What is the difference between a Condition and a Rule?
A condition guards whether a transition fires - it evaluates data or state. A rule guards who can fire a transition - it evaluates the user's identity. Both run during transition evaluation but serve different purposes.