ESOA

'''Engineering Self-Organizing Applications''' (ESOA) is the attempt
to apply the concept of [[Self-Organization|self-organization]] to engineering, 
esp. software engineering. Wether this is possible or not is still controversial.
The goal (or hope) is to achieve complex collective tasks with relatively 
simple individual elements, units and behaviors. The name ESOA is sometimes
also used as an abbreviation for "Enterprise [[Service-Oriented_Architecture|SOA]]", 
i.e. to describe a "Service-Oriented Architecture for Enterprises".

== A Name for a Problem ==

EOSA is like [[AOSE]] more a name for a problem than its solution.
It is closely related to the problem of "engineering [[Emergence|emergence]]".
Engineering is at odds with [[Emergence|emergence]], a phenomenon which 
usually accompanies self-organization, and planned organization 
as it is found in engineering contradicts more or less the concept 
of self-organization. It is obviously difficult to organize a system
which is able to organize itself.

== Demands ==

Why do we need [[Self-Organization|self-organization]] at all?
A demand for self-organization exists for instance in the 
following systems:

*highly distributed systems without central control
*open systems embedded in fast changing dynamic environments
*pervasive or [[Ubiquitous_Computing|ubiquitous computing]] where computers become invisible

In short, self-organization is needed if the system is (or becomes)
very large, very distributed or very complex. Here is already
the first problem: such systems are not easy to create.

== Problems ==

Many systems in nature demonstrate that self-organization is
indeed possible. These natural system are of course quite 
different from traditional software applications, they
are more like [[Agent|agent]]-based systems and 
[[Multi-Agent System|multi-agent systems]] (MASs). There is also no clear
or precise definition of [[Self-Organization|self-organization]]
which makes an easy application to any domain difficult.
Another problem with [[Organic Computing|biologically inspired systems]]
is that there number is limited. There is certainly not a
countless number of techniques used in natural self-organizing 
systems. A concrete application often boils down to the use
of pheromones, [[Stigmergy|stigmergy]] and [[Ant-Based_Systems|ant-based systems]].

The core problem of ESOA is to create a system with a certain
macroscopic global behavior by specifying only local 
behavior and microscopic interactions.
It is the old contradiction or antagonism between 
forced engineering and spontaneous [[Emergence|emergence]], 
imposed purpose and independent autonomy,
planned organization and self-organization.
All these items pairs are more or less contrary to each 
other.

In traditional engineering, the structure, function and
organization of the systems is carefully planned and
impressed from the outside on the system. If a situation occurs 
which has not been anticipated or tested before, the system usually 
crashes. The system is predictable, reliable and comprehensible,
but it is not always robust, adaptive and scalable.

In ESOA and [[Multi-Agent System|MASs]], the systems are partly able to 
organize themselves, and the tolerance for unpredictable properties and
situations is a bit higher. If a situation occurs which has not 
been anticipated before the system is expected to handle it.
A self-organizing system is robust, adaptive and scalable,
but usually less predictable, reliable and comprehensible.

== A possible solution ==

A possible solution to the fundamental ESOA problem is
the application of the scientific method by the engineer,
the step-by-step investigation of hypotheses with experiments
and simulations. The scientific method is an iterative process 
that is the basis for any scientific inquiry, and it can also
be used to examine artificial systems and simulated worlds
(for instance synthetic societies of multi-agent systems).
The scientific method follows a series of steps: (1) identify a problem 
you would like to solve, (2) formulate a hypothesis, (3) test the 
hypothesis, (4) collect and analyze the data, (5) make conclusions
and restart with (1) (see also the paper preprint
[http://arxiv.org/abs/nlin.AO/0601002 On Engineering and Emergence]).

== References ==

ESOA 2003 workshop (from the AAMAS 2003 conference):
* Giovanna Di Marzo Serugendo et al., ''Engineering Self-Organizing Systems'', Springer LNAI 2977, 2004

ESOA 2004 workshop (from the AAMAS 2004 conference):
* Sven A. Brueckner et al., ''Engineering Self-Organizing Systems'', Springer LNAI 3464, 2005