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problem. Usually, this solution generation phase, due to the distributed nature and
to the autonomous character of the elementary pieces, is very efficient and parallel.
When the possible solutions are formed, a phase of solution selection starts for fil-
tering the true solutions of the problem in question. This schema corresponds to the
Adleman-Lipton extract model of DNA computing; however, it generally suggests
possible applications which can be extended to many other situations. These meth-
ods become effective when the self-assembly generation phase is able to provide
the whole (or a great part of the) solution space for a given problem. In this case,
a trade-off between time and matter has to be evaluated. In fact, if we start with
20 elementary pieces where each piece has two different companions, the possible
solutions are 2
10
. This means that any elementary piece has to be provided with this
multiplicity if we want to generate the complete space of the possible solutions.
4.3
Replication and Autopoiesis
As we have often remarked, metabolism and replication are the basis of life and
the synchronization and cooperation of their activities is the key of life's birth. In
this section, we want to stress again this point by using a metaphor which could
illuminate the main aspects of their crucial relationship. Let us consider an airport
and let us assume that according to some strategy of an economic, industrial, and
social nature it was decided to replicate the same structure within a given time, say
of some years, in the same region, but in a given place at a given distance from
the existing airport. Firstly, this is a problem of a system replication, but not only,
because it is also required that no service interruption can be tolerated, and moreover
that the newborn airport has to work almost instantaneously, even with a gradual
organization process, in such a way that, in a specified period, it has to be completely
comparable with the airport from which it derives. Let us consider carefully how we
will plan all this phenomenon, or better, how the original airport has to be organized
in order to provide for the realization of its replication.
Let us analyze the main airport structures and functionalities, without aspiring
to any completeness and adequacy regarding real cases, because we are mostly in-
terested in the elements which are relevant to the chosen metaphor. In an airport
we can distinguish a number of basic components and services going from the ter-
minals, control towers, ramps, runways, taxiway, maneuvering and parking areas,
passenger areas, cargo areas, passengers and personnel hosting, internal transport
services, security, surveillance, maintenance, communication, etc.
All the services are controlled and directed by a central management which is
at the top of a hierarchical structure with a complex network of interactions, and
organized at different coordination and subordination levels. Moreover, a system
of evaluation of the activities has to be defined. All the services are performed by
operative units with an internal organization which depends on the type of service.
The structures have a sort of operative kernel devoted to their maintenance, which
is related to suitable stores.
