Environmental Engineering Reference
In-Depth Information
shown by Argent and Rizzoli
(2004)
. MODCOM (Hillyer et al.
2003)
is the linking
framework used in the current release of APES.
Component Design
Components are discrete software units used for composition. Hence, components
cannot be used in isolation. Further, the reason for adopting a component-based
paradigm for implementing models as computer programs is to achieve specific
functionalities not available with monolithic structures. Consequently, the component
architecture and its implementation are crucial in developing a component based
system for biophysical simulations that enables solutions to biophysical modelling
problems to be implemented using different designs and technologies. Developing
a design for a component architecture and selecting a technology for its implemen-
tation should be the result of a careful definition of requirements. The following
requirements were defined for the APES model components:
Functional requirements:
-
Estimation and generation of variables from different models
-
Estimation of parameters from observational data
-
Provision of data at run time, accessing either observational or generated data,
and making available model outputs
Provision of quality checks on imported data
-
-
Provision of quality checks on outputs
-
Robust behaviour of the component that degrades gracefully, raising appropriate
exceptions
Traceable component behaviour with traces that are scaleable, i.e. browsable at
-
different debug levels
Non-functional requirements:
-
Ease of use: the components must be easily usable by clients; this has an impact
on technology and on documentation.
Extensibility: the capability to easily add alternative processing capabilities to
-
the ones of the component from the side of the component user, without needing
to recompile the component, and using the same interface.
Re-usability: the practical possibility of using the component in different software
-
systems; ease of use and solution to a common modelling problem are the
pre-requisites.
Replaceability: the capability for components to be replaced by a different
-
component conforming to the same specification. “Different” here means either a
newer version of the same component, or an implementation from a different party.
Availability of fit-for-purpose documentation of models, software design, and
-
code.
Successful unit tests: unit tests for each public method, input-output tests should
-
be reported in the documentation.
