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Definition 3 (Operation). An operation is any π -calculus expression such
that:
- its names belong to the set ENames ;
- it signals its termination with the done event.
The second condition is particularly important because it will allow the sequen-
tial composition of operations, as we shall see in Sect. 3.1.
Of course such an abstract definition of operations cannot be used directly.
Nevertheless, it su ces to define the basic model for environments. Concrete
operations shall be given in Sect. 3.2.
2.3 Environment Structures
The environment is the central structure of EMMAS specifications. It defines
which agents are present, how they are initially connected, and what dynamic
behaviors exist in the environment itself. The presentation below follows a top-
down approach. We begin by defining the overall environment, and then proceed
to examine the nature of its constituent parts.
Definition 4 (Environment). An environment is a tuple
AG, AT, EB
such
that:
- AG
= {
ag 1 ...ag l }
is a set of agent profiles ;
- AT
= {
t 1 ...t m }
is a set of action transformers ;
- EB
is a set of operations (Def. 3), which are called here
environment behaviors .
= {
eb 1 ...eb n }
Moreover, let ENames
. Then the corresponding π -calculus
expression for the environment is defined as:
= {
en 1 ,...,en o }
[
AG, AT, EB
] π =(
νen 1 ,...,en o )
([
ag 1 ] π | [
ag 2 ] π |
...
| [
ag l ] π |
[
t 1 ] π | [
t 2 ] π |
...
| [
t m ] π |
[
eb 1 ] π | [
eb 2 ] π |
...
| [
eb n ] π |
!
NewAT
)
where
NewAT
=
ccn
emit, stop, absent, beginning, stable, ending, destroy
.
T
(
emit, stop, absent, beginning, stable, ending, destroy
)
and T is given in Def. 6.
This definition merits a few comments. First, all elements are put in parallel com-
position, which allows them to interact. Notice that all names from ENames
are restricted to the environment, which ensures that events are always used
in such an interaction (i.e., events cannot be sent to outside the environment
 
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