Model elements

Model elements are the basic building blocks of models. There are three types:

The diagram below shows how model elements are classified in ModelBuilder:

Model elements




Data variable

Input data

Existing data added to a model. Typically, data variables are the result of specifying a tool's input parameter. This existing data is sometimes referred to as project data.

Derived or output data variable

Derived data

Derived or output data is new data created by a tool in the model. When a tool is added to a model, a variable for the tool's derived data is automatically created and connected to the tool.

New derived data

The tool creates a new dataset that is written to disk when the model is executed.

In/Out derived data

The tool alters the input data when the model is executed. By default, the in/out derived data variable will have the same name as the input data but with a unique number appended at the end.

Value variable

Input value

Values that are input to a tool.

Value variable

Derived value

Values that are the result of a tool. Derived values can be inputs to other tools. The Calculate Value tool, for example, outputs the result of a logical or mathematical calculation.


System tool

Built-in tool. These tools are built using ArcObjects and a compiled programming language like .NET.

Built-in tools are typically system tools (those installed with ArcGIS)


Iterators are tools that repeat the same operation or loop through a set of input data or values. Iterators work only within ModelBuilder, not in scripting.

Learn more about iterators in ModelBuilder

Model Only tool

Model only tools functionally enhance ModelBuilder and only work within ModelBuilder, not in scripting.

Learn more about Model Only tools

Stop Model Only tool

The tool with this symbology is the Stop (Model Only) tool. This tool is only different than other Model Only tools in symbology in the model (looks like a red stop sign).


Script tool

Script tool. These tools are created using the Script tool wizard and they run a script file on disk, such as a Python file (.py), AML file (.aml), or executable (.exe or .bat).


Model tool

Model tool. A model is a collection of many tools connected together representing a workflow. A model tool can be run from its tool dialog box or added and used in another model or a script.

Description of model elements

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