This topic describes and defines terms used in Serverless Workflow to help you better understand and use Serverless Workflow.

Serverless Workflow
A fully managed serverless cloud service that coordinates the execution of multiple distributed tasks. Serverless Workflow allows you to orchestrate distributed tasks in sequence, branch, or parallel. This way, Serverless Workflow can coordinate multiple tasks based on the preset sequence.
distributed task
A distributed task in Serverless Workflow can be a function, an API integrated with a cloud service, and a program that runs on a virtual machine or a container.
flow
A series of sequential steps, which define the business logic and contain all the information of the sequential steps.
step
The work unit in a flow. A step can be a simple atomic step, such as task, succeed, fail, wait, or pass. A step can also be a complex control step, such as choice, parallel, or foreach. Multiple steps can be used together to build complex business logic.
parent step
If Step A contains Step B, Step A is the parent step of Step B.
child step
If Step A contains Step B, Step B is a child step of Step A.
task step
One of the step types, which is used to define the information about function invocation of Function Compute. When a task step is executed, functions are invoked based on this step.
pass step
One of the step types, which is used to show a constant and convert the input to the expected output. Pass steps can be used to debug the flow logic of functions for which no task steps are created.
wait step
One of the step types, which is used to suspend the execution of a flow. You can select a relative duration or specify an absolute end time in the timestamp format for a wait step.
choice step
One of the step types, which allows Serverless Workflow to execute different steps based on selected conditions.
parallel step
One of step types, which allows Serverless Workflow to execute multiple different steps in parallel.
foreach step
One of the step types, which allows Serverless Workflow to execute multiple identical steps in parallel.
succeed step
One of the step types, which is used to end a series of sequential steps in advance. A succeed step is typically used together with a choice step. When the conditions of a choice step are met, the flow goes to a succeed step, and no other steps are executed.
fail step
One of the step types, which is used to end a series of sequential steps in advance. After a fail step is executed, the steps following the fail step are not executed, which causes the parent step of the fail step to fail. Then, the steps following the failed parent step are not executed, which causes the parent step of this failed parent step to fail. This knock-on effect continues until the flow execution fails.
Flow Definition Language (FDL)
The language that is used to describe and define business logic. When a flow is executed, Serverless Workflow executes steps based on the flow definition.
time-based schedule
A schedule that is performed by Serverless Workflow at a specified interval.