Dear Christopher, (01)
> CS: Kickability? You can't kick a pump from a Bill-of-Materials or
> BOM
> explosion either, and P101 at plan stage is at least the same kind of
> pump, or "pump-requirement", if you wish, even though "P101" or even
> P101 may later be used in referring to the actual pump installed at any
> given time (i.e. "P101" as a mere label, P101 as the fuller entity at
> that point in the system). (02)
MW: The question to ask, is what is it that is required? If it isn't
something kickable, then it isn't going to be much use. A requirement is
something that is going to exist in the future, but does not exist now.
There is a lot of rubbish about not being able to talk about things that
don't exist (yet) but we have no problem talking about things that exist in
the past, so why do we have a problem with things that exist in the future.
For example, the required thing referred to will likely have an installation
date. That is the installation date of the system component. (03)
MW: Now there is an obvious challenge here, which is that things often don't
turn out the way we planned. This can be dealt with either by some kind of
modal logic, or my preference, possible worlds, where you plans and
requirements are in your world as planned, and the outcome is in the actual
world, but the objects are still very physical pumps.
>
> MW: In 4D it is a breeze. The system component consists of the temporal
> parts of the things installed whilst they are installed. You have both
> the pattern and the physicality required. In 3D you have to admit a new
> kind of particular.
>
> CS: Quite frankly, I have never had the need to make the 3D/4D
> distinction so often made in "ontological" circles. On the other hand,
> in my architecture I have long insisted - even since 1977, years before
> "ontology" was ever used in IT - on what I already then referred to,
> albeit loosely, as the ever-present "time component of data". (04)
MW: The 3D/4D distinction is about identity, and how temporality is dealt
with (states of objects, rather than temporal relationships), not whether it
is dealt with. The strong 4D that I adopt says not only that individuals are
extended in time as well as space, but that the identity basis for
individuals is spatio-temporal extension, i.e. of two objects have the same
spatio-temporal extent, they are the same object. (05)
Regards (06)
Matthew West
Information Junction
Tel: +44 1489 880185
Mobile: +44 750 3385279
Skype: dr.matthew.west
matthew.west@xxxxxxxxxxxxxxxxxxxxxxxxx
http://www.informationjunction.co.uk/
http://www.matthew-west.org.uk/ (07)
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