The official Appian Documentation is the primary and most authoritative source for information on all platform features, including Appian functions. It provides comprehensive details on syntax, parameters, return values, usage notes, and practical examples. When encountering a new function while developing an expression rule, consulting the documentation is the most direct and efficient first step. The expression editor itself often provides a direct link to the relevant documentation page for any selected function, reinforcing this as the intended initial action for developers.

B. The Knowledge Base is designed for troubleshooting specific issues, known product behaviors, or workarounds, not for fundamental function definitions.

C. Posting on Appian Community is a valuable resource for complex scenarios or when documentation is unclear, but it is not the first step for basic function information.

1. Appian Documentation, "Using the Expression Rule Designer": This page describes the development interface. In the section "Writing Expressions," it states, "When you select a function from the list, a brief description of the function and its parameters appears below the expression editor... A link to the documentation for that function will appear below the description." This confirms the intended workflow is to use the integrated link to the official documentation.

2. Appian Documentation, "Appian Functions": This serves as the central repository and index for all functions available on the platform. It is the canonical reference for developers seeking to understand how any specific function works.

3. Appian Documentation, "Expression Editor": This page details the features of the expression editor, noting that it provides "a list of all functions that match what you've typed" and shows descriptions, which are sourced from the main documentation. This integration makes the documentation the most immediate resource.