Glossary
Definitions of key terms used in the Vyuh Workflow Engine.
A
Activity
A unit of work within a workflow. In BPMN terminology, activities include tasks and sub-processes.
AND Gateway
See Parallel Gateway.
B
Branch
A path from a gateway to subsequent nodes. Branches can be conditional (evaluated at runtime) or unconditional (always taken).
BPMN
Business Process Model and Notation. An industry standard for workflow and process modeling that influences the Vyuh Workflow Engine's design.
C
Compensation
The process of undoing completed work when a later step fails. Used in saga patterns for distributed transactions.
Condition Executor
An executor that evaluates gateway conditions to determine which branches to activate.
Correlation ID
An external identifier used to link workflow instances to external systems or business entities.
D
Default Branch
A fallback branch in an exclusive gateway that activates when no other branch conditions match.
E
Edge
A connection between two nodes that defines the flow of execution.
End Node
A terminal node that marks workflow completion. Workflows can have multiple end nodes representing different outcomes.
Exclusive Gateway
A gateway (XOR/oneOf) that activates exactly one branch based on conditions. Only the first matching branch executes. In Vyuh, this is represented by NodeType.oneOf.
Execution Loop
The engine's main processing cycle that advances tokens through the workflow graph.
F
Fork
The point where a single token splits into multiple tokens for parallel execution.
G
Gateway
A node that controls flow divergence (fork) or convergence (join). Types include exclusive (XOR), inclusive (OR), and parallel (AND).
H
Executor
A component that executes specific logic for tasks, user tasks, or conditions. Executors are registered via WorkflowDescriptor and matched to nodes by schemaType.
I
Idempotent
An operation that produces the same result whether executed once or multiple times. Critical for crash recovery.
Inclusive Gateway
In traditional BPMN, a gateway (OR) that activates all branches whose conditions evaluate to true. Note: Vyuh uses anyOf for race semantics (first to complete wins) rather than traditional inclusive gateway behavior.
Instance
See Workflow Instance.
Interpolation
The process of substituting placeholder values (e.g., ) with actual data from workflow output.
J
Join
The point where multiple tokens merge into a single token after parallel execution.
L
Loop
A pattern where execution returns to a previous node, creating iteration.
M
Merge
The process of combining multiple tokens into one at a join gateway.
N
Node
A discrete step in a workflow. Types include start, end, task, user task, signal wait, and gateways.
Node Executor
A component that executes a specific node type and returns a NodeResult.
NodeResult
The outcome of node execution that determines the next step (continue, wait, complete, or error).
O
OR Gateway
See Inclusive Gateway.
Output
The accumulated data produced by workflow execution, accessible via context.output.
P
Parallel Gateway
A gateway (AND/allOf) that activates all branches simultaneously. The join waits for all branches to complete. In Vyuh, this is represented by NodeType.allOf.
Payload
The data carried by a signal or token.
Priority
The urgency level of a user task (low, normal, high, urgent).
R
Descriptor
A WorkflowDescriptor that provides executors to the engine. Descriptors register TaskExecutors, UserTaskExecutors, and ConditionExecutors.
Resume
The process of continuing a paused or waiting workflow instance.
S
Schema Type
A unique identifier for an executor type, used to match nodes to their executors during workflow execution and serialization.
Service Task
See Task.
Signal
An external event that triggers workflow continuation. Used for async operations and external integrations.
Signal Wait
A node that pauses execution until a specific signal is received.
Split
The process of creating multiple tokens from one at a fork gateway.
Start Node
The entry point of a workflow. Every workflow has exactly one start node.
storeAs
A configuration option that specifies where to store a node's output in the workflow output map.
Storage Adapter
An abstraction layer for persisting workflow state to various databases.
T
Task
An automated task that executes logic without human intervention. Called "Service Task" in BPMN terminology.
ExecutionContext
The execution context provided to task executors, containing input, output, config, and workflow instance reference.
TaskResult
The outcome of task execution (TaskSuccess or TaskFailure).
Token
A marker that tracks execution position within a workflow. Tokens can split (fork) and merge (join).
Type Descriptor
Metadata that describes an executor, including its schema type and deserialization function.
U
User Task
A task that requires human interaction to complete. Creates a work item for assignment.
User Task Instance
A runtime representation of a user task, including assignment, status, and response.
V
Validation
The process of checking input data or workflow structure for correctness.
Version
A number identifying a specific revision of a workflow definition.
W
Wait
A state where workflow execution is paused, typically waiting for a signal or user task completion.
Workflow
A blueprint describing the structure and behavior of a business process. In Vyuh, this is a unified model that is both storable and executable.
Workflow Builder
A fluent API for constructing workflows programmatically.
Workflow Engine
The runtime component that executes workflow instances.
Workflow Instance
A running or completed execution of a workflow.
Workflow Status
The current state of a workflow instance (pending, running, paused, completed, failed, cancelled, waitingForUser, waitingForSignal).
X
XOR Gateway
See Exclusive Gateway.
X
XOR Gateway
See Exclusive Gateway.
BPMN Equivalents
| Vyuh Term | BPMN Equivalent |
|---|---|
| Start Node | Start Event |
| End Node | End Event |
| Task | Service Task |
| User Task | User Task |
| Signal Wait | Intermediate Catch Event (Signal) |
| oneOf | Exclusive Gateway (XOR) |
| allOf | Parallel Gateway (AND) |
| anyOf | Race (first to complete wins) |
| Edge | Sequence Flow |
| Token | Token (execution marker) |
| Subflow | Call Activity |
| Timer Wait | Timer Intermediate Catch Event |
See Also
- Architecture - System overview
- Node Types - Node reference
- API Reference - Complete API documentation