Aggregate Objects and Their PropertiesDave Ackley, Ackley Associates
July 27, 1996
The concept of aggregation and "aggregate objects" is important to understanding the structure of a business or other complex organizations. Their goals and objectives can be viewed in terms of aggregate objects, and the work performed to achieve them can be viewed in terms of processes that produce or "construct" the aggregate objects. This provides a framework for more precise understanding of the nature of a business or organization, and a tool for rigorous analysis of organizational and system structures.
Aggregation is a form of abstraction. It is a conceptual way of viewing "the whole" while filtering out details about its parts. This is sometimes referred to as "seeing the forest for the trees." It recognizes the identity of a "higher level" aggregate object whose characteristics transcend the characteristics of its component parts.
The "whole" of an aggregate object is made up of component parts that are bound together in constraining relationships. When one part is "assembled" with other parts into an aggregate object, it loses some of its "freedom of movement." The assembly process integrates the parts into an orchestrated and cooperative (but constraining) structure that becomes the higher level aggregate object.
When a wheel is attached to an automobile structure, it loses some freedom of movement. It can still turn around on its axle, but only when all parts of the automobile are moving together.Where do the aggregate objects characteristic properties come from? There are three sources, each of which produces a different kind of property. One kind or property "emerges" from the nature of the component parts and the way they are connected together. Another kind comes from the "elevation" of a highly visible component part. A third kind is "assigned" from outside the aggregate object for identification or rating purposes.
Emergent PropertiesEmergent properties are the inherent functional characteristics of an aggregate object. They are essential to its existence -- without them, there is no aggregate object.
There is a big difference between a kit with all the parts and materials needed to build a model airplane, and the actual assembled model. The kit cannot fly, but the assembled model airplane can. "Ability to fly" is a unique property of the aggregate whole that "emerges" as the parts are joined together. Unless the parts of the model have been glued and fastened together properly, there will be no functional model airplane. None of the parts is able to fly by itself.More formally: An emergent property is a unique functional characteristic of an aggregate object that "emerges" from the nature of its component parts plus the constraining relationships that have been formed to bind them together. This functional characteristic is unique to the aggregate object, and cannot be found in any of its parts.
A "motor vehicle" is an aggregate object that is made up of a body, engine, transmission, suspension, steering, wheels, brakes, tires, seats, etc. We recognize that it is a "motor vehicle," because these component parts are assembled in such a way that the resulting aggregate object can be driven to carry passengers or goods from one location to another. It has the unique functional property of being "drivable as a means of transportation." Where does this property come from? It "emerges" from the nature of the wheels that allow it to roll on the pavement, the engine and transmission that provide power to the wheels, the suspension that connects the wheels to the body that holds the engine, and the way they have been joined together.A general type of aggregate object can be classified into subtypes, based on differences in their functional properties. Each such subtype has all the characteristics of the general type, plus some unique properties of its own.
The Department of Motor Vehicles recognizes many types of motor vehicle. There are passenger cars, sportscars, buses, trucks, etc. All types of motor vehicle share common characteristics, such as the ability to be driven and transport passengers or goods. Each subtype also has additional properties that are unique to its type. Where do these additional properties come from? They also emerge from the nature of the component parts and the way they are joined together, but in this case there is are additional requirements on the nature of the parts and their assembly.Consider what makes a "sportscar" different from other kinds of motor vehicle. We may describe a sportscar as having great "road handling ability," and being "sleek and low to the ground." Like all aggregate object properties, the "road handling capability" that makes this aggregate object a "sportscar" emerges from the component parts and their constraining relationships. In this case, however, the body must have a low center of gravity, the engine must be powerful and located for good balance, the suspension system must provide for a low profile with a wide track, the bucket seats must be mounted low within the body, etc. The result of all this refinement is a sportscar.
Elevated PropertiesAn elevated property is a component part that is highly visible at the aggregate object level, and is considered so important that its very existence is looked upon as a property of the aggregate object itself.
"This automobile has a trailer-towing package." To a prospective buyer who wants to be able to tow a trailer, the existence of the "trailer-towing package" component may be a critical attribute for any automobile he/she is willing to buy.An elevated property may also include a value judgment about the component part. In some cases, the value judgment is meaningful only at the aggregate object level, not at the component level:
What does it mean to say that "this automobile has good tires"? The goodness of a particular set of tires depends on how they are to be used. Putting brand new truck tires on a sportscar would not result in the sportscar having good tires. They might be good on a truck, but these tires would be very bad on a sportscar. In this case, "good" is meaningful only at the aggregate object level.In other cases, the value judgment may apply at both the aggregate object level and the component level:
"This automobile has a factory-rebuilt engine." In this case, "factory-rebuilt" is important at the aggregate object level, but it is also significant at the component level -- independent of the aggregate object.
Assigned PropertiesAn assigned property is a property that has been appended to the aggregate object, and may have nothing to do with the nature of its component parts or its emergent properties. An assigned property is often evidenced by a label affixed to the object.
A washing machine has been assigned a manufacturers serial number "123456." A manufacturers label with this number is permanently attached to the machine. The label is attached in such a way that it does not interfere with the functionality (emergent properties) of the washing machine aggregate object.
Aggregate Object Properties and SyntaxTo help clarify its type, a formal statement can be used to define each property of an aggregate object. Each formal statement takes the form:
aggregate object -- relationship -- propertyTo distinguish among them, a different relationship syntax is used for each type or property. Use of the appropriate relationship syntax is key to determining the correct property type.
Syntax for Identifying Emergent Properties
"Is" is used to identify an aspect of the aggregate objects state of being, based on one of its inherent attributes. The property cannot be attributed to any one of its components.
"Has" is used to identify an aspect of the aggregate objects state of being, which may be based solely on the existence of a component part:
"Has been assigned" is used to identify the aggregate objects relationship with another object, expressed as a factor or label. Sometimes the factor is based on an external perception of the aggregate objects state of being:
Components Often Produce Inherent Aggregate PropertiesThe existence of a particular component as part of an aggregate object may be a major factor in creating an inherent property of the aggregate whole. For example, consider:
ConclusionThe concept of "aggregate objects" is critical to understanding the internal structure of complex objects, whether they be physical (motor vehicle) or non-physical (business enterprise). It brings to light the fundamental link between a producing process and the inherent properties of the resulting object. Consistent use of this concept can provide rigor and clarity to the analysis of both business processes and enterprise structures.