Terminology OOP – IEC 61131-3

The following list shows a comparison of the terminology in UML as well as its equivalent in IEC 61131-3 and its extension in CODESYS.

Terms in UML Object Orientation	Equivalent in IEC 61131-3 or Extension in CODESYS
Class: `class`	. POU types Program PRG: `PROGRAM` Function block FB: `FUNCTION_BLOCK` Function FUN: `FUNCTION`
Attribute: `attribute` Internal variable Parameter: `{input}` Property: `{property}` Output parameter: `{output}`	. Variable types: Variable: `VAR` Input variable: `VAR_INPUT` Property: `PROPERTY` Output variable: `VAR_OUTPUT`
Operation (`operation`)	Method: `METHOD` Action: `ACTION`
Interface: `interface`	Interface: `INTERFACE`
Composition: `composition`	Variable declaration or function block instantiation
Association: `association`	`POINTER TO` or `REFERENCE TO`
Realization: `realization`	`IMPLEMENTS`
Generalization: `generalization`	`EXTENDS`