Models with Sectors and Multiple Authors
Posted: Sat Apr 20, 2002 4:56 pm
Andy Ford schrieb:
> We managed to keep the sectors integrated in a
> manner that led to insights, not confusion...
I have long thought that object-oriented modelling and system dynamics
had much to learn from each other. In particular, several stocks in a
model are often attributes of a single "object", and several flows are
processes linked to a single "object".
What Andy describes here are precisely the fundamentals of OO modelling:
First analyse the model as a set of use-cases which thread through the
model as it is seen by actors lying outside the system, then seek the
classes of objects which must communicate with each other to support
these use-cases.
In the context of system dynamics modelling, the use-case corresponds to
the reference mode which drives the entire modelling process. Also, at
the heart of object-oriented modelling lies the idea of an ADT (Abstract
Data Type). An ADT defines the communications processes between objects
in a system, while leaving the internal implementation of the objects
undefined. This means that separate developers can work simultaneously
on the design of separate objects in the system, knowing that they share
a common understanding of the interface between their separate
components. Larger scale modelling is supported in UML (Unified
Modelling Language) by "packages", which would broadly correspond to
"sectors".
There is a new journal starting from Springer in September called
"Software and Systems Modeling". My hope is that this will bring several
groups of modellers together to learn from each other. You can find out
more about this journal at: http://www.sosym.org/
Best wishes,
Niall.
From: Niall Palfreyman <niall.palfreyman@fh-weihenstephan.de>
> We managed to keep the sectors integrated in a
> manner that led to insights, not confusion...
I have long thought that object-oriented modelling and system dynamics
had much to learn from each other. In particular, several stocks in a
model are often attributes of a single "object", and several flows are
processes linked to a single "object".
What Andy describes here are precisely the fundamentals of OO modelling:
First analyse the model as a set of use-cases which thread through the
model as it is seen by actors lying outside the system, then seek the
classes of objects which must communicate with each other to support
these use-cases.
In the context of system dynamics modelling, the use-case corresponds to
the reference mode which drives the entire modelling process. Also, at
the heart of object-oriented modelling lies the idea of an ADT (Abstract
Data Type). An ADT defines the communications processes between objects
in a system, while leaving the internal implementation of the objects
undefined. This means that separate developers can work simultaneously
on the design of separate objects in the system, knowing that they share
a common understanding of the interface between their separate
components. Larger scale modelling is supported in UML (Unified
Modelling Language) by "packages", which would broadly correspond to
"sectors".
There is a new journal starting from Springer in September called
"Software and Systems Modeling". My hope is that this will bring several
groups of modellers together to learn from each other. You can find out
more about this journal at: http://www.sosym.org/
Best wishes,
Niall.
From: Niall Palfreyman <niall.palfreyman@fh-weihenstephan.de>