Holon

Description

The word "holon’’ comes from the Greek "holos, meaning 'whole', and "-on, meaning 'part'. The word aptly captures the duality of entities which are at once single, distinct en­tities, and at the same time parts of a more comprehensive whole. For exam­ple, a cell in your body falls under the holon category. Cell exists as a distinct, living entity; it has inputs, out­puts, and a distinct cell wall defining its interface with the rest of the world. A cell, however, consists of smaller and more fundamental parts, such as RNA, DNA, mitochondria etc. Each component can be studied as a separate entity; however, each component can be broken down further - into molecules, atoms, and ultimately to quarks. This decomposition of cells is characteristic for a holonic organisation.

We can also go the other way, and see that cells group togeth­er with other cells to become organs. Organs, in turn, form parts of the human body. Here, we see that holonic organisation also supports composition as well.

We can find many other examples of this part-whole relation­ship in the world around us. Ants, for example, exhibit such characteristics. We can study ants as separate entities in their own rights; but, they also form parts of a society. Trees and forests as well as people and cities form other examples. More artificial examples would include agents that have been used in Distributed Artificial Intelligence and even the humble sub routine in a program.

Characteristic of Holons and Holonic Systems

In addition to the part-whole characteristic, holons have a number of other characteristics:

01: Each holon can function autonomously. It means that each holon carries out its own activities without the direction of oth­er holons; yet, it still forms a part of, and contributes to, the overall functioning of a larger system.

02: Holons naturally form distributed systems. This comes on from the autonomous attribute.

03: Each holon has a simple, singular task to perform and con­centrates exclusively on that task. The system accomplishes larger scale tasks through the combination of a number of holons, either through combining them together to form a larg­er holon, or through cooperation or competition between holons.

04: Although holons function autonomously, their interaction with other holons may yield complex flows of information in order to achieve each interacting holon’s goals. Therefore, a holon must process and respond to in-bound data from exter­nal sources, as well as provide other holons with requested information.

05: As holons interact, the sum of their actions could become greater than the action of the individual holon. Some exam­ples could include ant hills, where a number of ants cooperate to construct a mound, yet no single ant would have the capa­bility to achieve the construction individually. The construction of cities forms another example. The shapes of many of the world's cities were not the result of centralised plan­ning. Nonetheless, the organisation and interaction of a num­ber of people and organisations has resulted in some of the most spectacular cities on Earth, such as San Francisco, New York, Rome, and others.

Advantages/Disadvantages

The Advantages of Holonic Systems

Holons are particularly well suited for complex and/or dis­tributed systems. Some reasons follow:

• Scalability As each holon has the property of being au­tonomous, it can function with little or no knowledge of other holons. Thus, we can add additional holons to the system, de­pending on the system in question, without affecting the oper­ation of the previously existing holons. As additional holons are contributed to the system, a coherent organisation will tend to form naturally, such as a hierarchy where higher-lev­el, more abstract holons manage lower-level, more detail-ori­ented holons. Consider, as another example, any plant or ani­mal, which starts as one cell, but which divides and grows to many cells, forming organs along the way.

• Robustness Robustness also results from the autonomous na­ture of a holon. Just as we can add holons, we can also re­move them without, in general, affecting the functioning of other holons or the system as a whole. For example: human body can lose many cells without even noticing it. It can even survive the loss of a substantial por­tion of the body, such as a limb.

• Simplicity of control As each holon has a simple, usually singular, task to accomplish, it only needs a simple control mechanism, which can be understood more easily when compared to a centralised control system.

Disadvantages of Holonic System

Distributed and autonomous holons, for all their advantages, also have some disadvantages compared to centralised mechanisms.

• Tragedy of the commons The autonomous attribute can lead holons to consume shared resources without consideration for others, and end up taking more than their fair share. This could limit the ability of other holons to work, and may even bring an end to the common resources. Example: a farmer allowing his cow to eat all the common grass, preventing other farmers from grazing their cattle.

• Losing their way We can see another problem with the autonomous attribute. Autonomous holons could conduct activi­ties that do not contribute to the overall goal of the system. They could even conduct activities that are contrary to the overall goal. Cancer cells would form an example of holons that have gone out of control and became a danger to the sys­tem as a whole.

The root cause of the first deficiency we can usually at­tribute to a lack of negative feedback in the holon’s opera­tion. For example, if the farmer knew a priori of the impact the cow would have on the field, and therefore other farmers, he would take steps to alleviate the problem before it got out of hand. The farmer would need a bigger picture to achieve this in­sight. However, this leads to one possible solution, where a higher-level holon could administer lower-level holons. Not an ideal situation. It is pre­ferred that the other farmers communicate with the offending farmer, so that issues are resolved locally and quickly.

We may, however, have diffculty understanding the cause for the latter deficiency, since there is a number of issues to consider. For in­stance, simple miscommunication or misunderstanding may result in an erroneous interpretation of the holon's goal. Indeed, scientists have traced most causes of genetic defects that, in a sense, we can consider as miscommunication in genetic programming of the cell. We could see another cause as the autonomous nature of the holon, which could deliberately decide to change its own goals. The "bait-and-switch’’ manoeuvre that con-artists and other petty criminals use exemplify this." (http://en.technocracynet.eu/index.php?option=com_content&task=view&id=75&Itemid=103)