Machine Learning for Emergent Middleware - Trustworthy Eternal Systems via Evolving, Software Data and Knowledge - page 19

1

Networked
System

Interface

0..n

1

Affordance Behaviour

1

0..n

1 0..n

Kind
Req/Prov

Functionality Input Output

Fig. 2. The Networked System (NS) Model

- Affordances : The affordances ( a.k.a. capabilities in OWL-S [16]) describe the
high-level roles an NS plays, e.g., weather station, which are implemented as
protocols over the system's observable actions (i.e., actions specified in the
NS interface). The specification of an affordance decomposes into:
•

The ontology-based semantic characterisation of the high level Func-
tionality implemented by the affordance, which is given in terms of the
ontology concepts defining the given functionality and of the associated
Input and Output . An affordance is further either requested or provided
by the NS in the networked environment. In the former case, the NS
needs to access a remote NS providing the affordance for correct oper-
ation; in the latter, the NS may be accessed for the implementation of
the given affordance by a remote NS.

• The affordance's behaviour describes how the actions of the interface

are co-ordinated to achieve the system's given affordance. Precisely, the
affordance behaviour is specified as a process over actions defined in the
interface, and is represented as a Labelled Transition System (LTS).

2.2 Emergent Middleware Enablers
In order to produce an Emergent Middleware solution, an architecture of En-
ablers is required that executes the Emergent Middleware lifecycle. An Enabler
is a software component that executes a phase of the Emergent Middleware,
co-ordinating with other Enablers during the process.
The Emergent Middleware Enablers are informed by domain ontologies that
formalise the concepts associated with the application domains (i.e., the vo-
cabulary of the application domains and their relationship) of interest. Three
challenging Enablers must then be comprehensively elaborated to fully realise
Emergent Middleware:

1. The Discovery Enabler is in charge of discovering the NSs operating in a
given environment. The Discovery Enabler receives both the advertisement
messages and lookup request messages that are sent within the network