Objects, types, and classes

Schemas consist of objects, types, and classes.


A data object is a complete unit that exists in your input or is built on output. A data object can be simple (such as a date) or complex (such as a purchase order).

A data object is some portion of data in a data stream that can be recognized as belonging to a specific type. When you create types, identify all of the objects that make up the data: input objects and output objects.


A type defines a set of data objects that have the same characteristics. For example, the type "Date" can be defined as representing data objects in the form MM-DD-YY. The type "CustomerRecord" can be defined as representing data objects, each of which consists of a Company, Address, and Phone data object.


A type is classified according to whether or not it consists of other objects. Each type in a schema must be defined in one of three classes: item, group, or category.
  • Item type

    An item type represents a simple data object that does not consist of other objects.

  • Group type

    A group type represents a complex data object that consists of other objects. For example, "FullName" is a group type that contains the components: FirstName, MiddleInitial, and LastName.

  • Category type

    A category type is used for inheritance and for organizing other types in a schema. For example, you might have a category named "OrderField" to organize the different kinds of order fields in your schema.