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Fig. 1.
Heterogeneous Connections with Weather Station NSs
2 Emergent Middleware
Emergent Middleware is synthesised in order to overcome the interoperability
issue arising from two independently-developed Networked Systems (NSs). Given
two Networked Systems where one implements the functionality required by the
other, an Emergent Middleware that mediates application- and middleware-layer
protocols implemented by the two NSs is deployed in the networked environment,
based on the run-time models of the two NSs and provided that a protocol
mediator can indeed be computed. The following section defines the NS model
we use to represent the networked systems and reason about their interoperation.
Then we present the by
Enablers
, i.e., active software entities that collaborate
to realise the Emergent Middleware ensuring their interoperation.
2.1 Networked System Model
The definition of NS models takes inspiration from system models elaborated
by the Semantic Web community toward application-layer interoperability. As
depicted on Figure 2.(a), the NS model then decomposes into:
-
Interface
: The NS interface provides a microscopic view of the system by
specifying fine-grained
actions
(or methods) that can be performed by (i.e.,
external action required by NS in the environment for proper functioning)
and on (i.e., actions provided by the given NS in the networked environment)
NS.
There exist many interface definition languages and actually as many lan-
guages as middleware solutions. In our approach, we use a SAWSDL-like
3
XML schema. In particular, a major requirement is for interfaces to be an-
notated with ontology concepts so that the semantics of embedded actions
and related parameters can be reasoned about.
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