Theory of Aggregate Objects
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The Theory of Aggregate Objects was developed by Dave Ackley and David Tryon in 1989, as part of a business enterprise modeling project. The purpose was to explain the nature of aggregation and emergence in the modeling of complex systems.


The Living Systems Model relies heavily on the Theory of Aggregate Objects to explain the nature of living systems and their evolution into a three-level architecture. The following describes some of the highlights of that theory. Links to the source documents are provided at the bottom of the page. Here are a couple of key definitions to start it off:
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An object is something whose characteristics we can perceive (or imagine).
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An aggregate object is an object whose internal structure is also known to us.

Internal Structure
If an object has an internal structure we know that it was constructed through some process to produce that state. The process may have been natural, as in creation of an aggregate rock, or it may have been deliberate, as in assembly of an automobile.

Constraints
When a process is producing an aggregate object, it is assembling the component parts and binding them together with constraints on their behavior. For an automobile, creating these constraints takes the form of welding, bolting, gluing or fastening. For a business organization they may take the form of job instructions and management directives. In both cases, the constraints control the components' behavior by limiting their freedom-of-movement.

Unique Properties
The nature of the component parts and their binding constraints determine the characteristics of the resulting aggregate object. These characteristics are new, unique properties that were not present in the components themselves. For an automobile, they might include such things as top-speed, load-carrying capability, gas-mileage, etc. For a business organization they might include product volume, production schedule, profitability, etc.

Emergence
The unique properties of an aggregate object are thought to emerge from the construction process. The resulting set of new properties is then interpreted as a single unified whole, i.e., an aggregate object. The concept of emergence helps explain the transition that takes place from lower-level components and their structure to a higher-level aggregate object. This concept is applied throughout the Living Systems Model to explain how lower-level entities can joint together to produce a higher-level entity.

Abstraction
Aggregation is a form of abstraction. It is a conceptual way of viewing "the whole" of a structure while filtering out details about its parts. It recognizes the identity of a higher-level aggregate object whose properties transcend the characteristics of its component parts. It allows us to focus on the higher-level object itself, while ignoring its internal aggregate structure details. It lets us to concentrate on driving an automobile without thinking closely about its body, wheels, motor, etc. It allows managers of a company to evaluate their company's financial condition, without thinking about its individual employees and product components.


For details, see these technical papers:
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      Aggregation and Emergence
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      Aggregate Objects and their Properties


©1995-2012 Ackley Associates   Last revised: 7/20/11
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