About expressions

An Appian expression is a statement composed of one or more literal values, operators, functions, and variables. Expressions are evaluated by the rules engine to produce a single value. The construction of Appian expressions will be immediately familiar to anyone experienced building formulas in spreadsheet software.

Use this browser to learn how to create more sophisticated expressions and use them throughout your application. Expressions are a versatile tool that allow you to build powerful logic in your processes.

Expressions can access contextual data via variables like process variables, node inputs, constants, record types, CDTs, and process properties. Beyond their returned value, expressions do not modify any data inside or outside the Appian system.

You can create an expression in a design object by typing it directly into an expression field or using the guided experience of the Expression Editor. Expression fields are marked by an Expression Editor icon.

Browsing these pages

The pages in this browser are organized into the following categories:

• Design Objects: In this category, you'll learn about the design objects you can use in expressions. You'll also learn how to save an expression as an expression rule, which you can then reuse in any expression field in your application.
• Build: Learn about the building blocks of expressions and take a tour of the Expression Editor, which allows you to easily write expressions. Then, learn more about how to build expressions using functions, rules, data types, and local variables.
• Troubleshoot: These pages contain information to help you test and troubeshoot your expressions.
• Evaluation: These pages describe the way Appian evaluates expressions and advanced evaluation options you can use when building expressions.