Relationship Between Object and Object Structure

Object and object structure represent the BPMN elements Item Aware Element and Item Definition. Occurrence of an object in a process is differentiated between the definition of the object and its structure.

Occurrence of an object in a process is differentiated between the definition of the object and its structure, just in the same way as a variable is differentiated between its variable definition.

Object

An object represents the BPMN element Item Aware Element. Use objects (Item Aware Elements) to model the use of physical or information business objects in processes and collaborations.

Objects are the data object, the data store reference and the data store itself, the data input and the data output. The data store is a bit out of the ordinary as it is a reusable element itself and is reused in various processes using the data store reference.

Object Structure

An object structure can be traced back to the BPMN concept of the item definition and extends it to include the definition of the structure.

The object structure is the actual pendant in the model for the business object which is described by the modeler. The object structure combines the object definition and structure into one element. It can be an input or output of an activity or process, can be sent as a message or simply be stored as a data store in the process which is linked with tasks.

You can also view an object structure as a kind of term definition: It defines a business concept or term which is a business object for you and which furthermore has a structure. The concept of object structure thus brings together three aspects: term definition, reusable data object and structure definition.

Basic Concept of an Object Structure

An object structure contains structure entities which can be typed. An entry's type can be a class, data type, enumeration type or primitive type; it is also possible for the type to be an object structure. If a structure entry is typed with an object structure, this nests various structures. The nesting can be as deep as required. However, only two levels down can be expanded in the structure diagram.

Object Structure Vs. Item Definition (BPMN)

BPMN does not specify how an item definition's structure should be defined. A structure definition can be referenced if needed. If you have many business objects which have different structures, you need to create two elements for each: one business object corresponding to the item definition and one element which can be used as structure definition, e.g. a UML class.

Innovator for Business Analysts sees two use cases for modeling structures:

Including all structures which you find to start with. e.g. you have an application's input masks or form in front of you and want to make its contents into a model. This is precisely what the object structure is designed for and/or the concept of a structure was fused with the item definitions concept to create an object structure precisely for this use case.
You analyze which concepts lie behind your problem domain's structures. You take existing, concrete structures, model relationships and derivations, store reusable parts etc. Object structures and the structure diagram are not primarily designed for such structure analysis models. You are better off using a class diagram or ER model with the respective model elements for this use case.

Object Structure Properties from BPMN

The following object structure properties have been taken directly from the BPMN specification:

Term category (BPMN: ItemKind) differentiates between an information object and an object which physically exists. If settings for one or both values do not suit you, set the value to Unspecified; this is not part of BPMN.
Multiple elements (BPMN: isCollection) shows that the object structure represents multiple objects of the same structure.

Object Structure Properties Regarding Structure Information Aspects

Structure information is referenced in BPMN using the optional structureRef relationship, without further defining the type of the structure definition. Innovator for Business Analysts has the following properties for this:

Composition Type refers to the structure entries in the object structure. This property is irrelevant if you do not have any structure entries there. It specifies whether the structure entries are unordered (all) or appear in the predefined order (sequence) - or whether only one of the specified entries is relevant for a given object (selection).
XSD structure type saves which type the element had in an XSD file (if the structure was taken from an import) or that which the element should have (regarding future exports). The property is only relevant for you if you want to export the structures as XSD files - if this is the case, you should set the value you want here. These are descriptions taken directly from XSD concepts.

Object Structure Properties Regarding Term Definition Aspects

An object structure is a special term definition and has properties which the general technical term element has, such as Definition and elements attributed through the term.