---
title: "Key concepts"
canonical: "https://support.appfire.com/space/CW/69304905/Key%20concepts"
format: markdown
---
> Macro (aura-html)

This section explains key concepts of the app such as workflow post functions, validators, issue fields, as well as when to use Original vs. Parent values.

## Workflow Post Function

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As a Jira administrator, one of the aspects of a workflow that you can control are post functions. The primary purpose of a post function is to carry out additional processing that may be required after a workflow transition has been executed. Examples include:

- creating a change history record for the issue
- adding a comment to an issue
- updating an issue's field
- creating an event to trigger one or more email notifications

Jira has both [essential](https://confluence.atlassian.com/adminjiracloud/advanced-workflow-configuration-776636620.html#Advancedworkflowconfiguration-essentialpostfunctionsEssentialpostfunctions) and [optional](https://confluence.atlassian.com/adminjiracloud/advanced-workflow-configuration-776636620.html#Advancedworkflowconfiguration-optionalpostfunctionsOptionalpostfunctions) post functions and it is important that you understand their differences as they pertain to the introduction of new post functions with Update on Transition.

## Validators

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Validators check that any input made to the transition is valid *before* the transition is performed. Input can include that gathered from the user on the transition's screen. If a validator fails, the issue does not progress to the destination status of the transition, and the transition's [post functions](https://confluence.atlassian.com/adminjiracloud/advanced-workflow-configuration-776636620.html#Advancedworkflowconfiguration-postfunctions) are not executed. 

## Issue Fields

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<span style="color: #333333">Update Issues post function supports quite a number of fields (Issue Fields) that can be configured to help you control both:</span>

- <span style="color: #333333"> </span><u>when</u><span style="color: #333333"> the issue should be updated and</span>
- <u>what</u><span style="color: #333333"> information is associated with the issue once updated</span>

<span style="color: #333333">Many of our customers have found it helpful to </span><span style="color: #333333">[review each issue field](https://appfire.atlassian.net/l/cp/PM1krt9z)</span><span style="color: #333333"> and capability ahead of updating their first post function.</span>

## Original vs. Parent Values

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<span style="color: #333333">**Original Issue**</span><span style="color: #333333"> - The original issue that started the workflow transition. This could be an issue or sub-task.</span>

<span style="color: #333333">**Parent Issue**</span><span style="color: #333333"> - The parent issue of the original issue. If the original issue is </span><u><span style="color: #333333">not</span></u><span style="color: #333333"> a sub-task, then parent is the </span><u><span style="color: #333333">same</span></u><span style="color: #333333"> as original.</span>