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# Port Polymorphism and Data Integrity

The data that connects to or passes through an ICENodePort or ICENodePort can be described in three different ways:

- Data Type

  This is the usual concept of data type in most programming languages: boolean, integer and floating point numbers, more complex structures like vector, matrices, colors, etc. The siICENodeDataType enum basically encapsulates the possible values and combinations possible. See also ICENodePort.DataType or ICENodePort::GetDataType and ICEAttribute.DataType or ICEAttribute::GetDataType.

- Structure

  This defines whether the data is structured as a scalar (single value) or as an array of values. The possible values are available in the siICENodeStructureType enum. See also ICENodePort.StructureType or ICENodePort::GetStructureType and ICEAttribute.StructureType or ICEAttribute::GetStructureType.

- Context

  This describes the type of data being pushed/pulled (the element set associated with the data set). This can be vertices, polygons, or newly created particles. The possible values are available in the siICENodeContextType enum. See also ICENodePort.ContextType or ICENodePort::GetContextType and ICEAttribute.ContextType or ICEAttribute::GetContextType.

Some ICENodePort or ICENodePorts support polymorphism, which basically means that the data passing through does not need to match some preset criteria on type, structure and context. For example, the CompareNode takes any boolean, integer, float, vector, matrix, rotation, or quaternion in its two input ports; however, these types must match each other. In other words, you want to avoid comparing apples and oranges.

The way that the integrity of the port data is enforced is to create a kind of a constraint, or limitation on the type, structure, and context of port data when needed. These are noted in the reference documentation under the Restrictions section. So following the previous CompareNode example, this section notes that the types must match for the data connected in the first port and the second port (but since the result port will always be boolean, it has no restriction). In addition, all input and output nodes are constrained to the same structure and context.

Tip

Understanding how to constrain port data because very important when it comes to creating your own custom nodes. For more information, see Handling Port Polymorphism.