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Each lot is presumably picked more than once during harvest, to catch
late-ripening grapes and allow for vintages with different sugar content.
The association between picker and lot may not be invariant. Different
pickers may be assigned on different days. In such cases, you might have
<lot id=...>...</lot> *
<picker id=...>...</picker>*
<picking date=... lot-id=... picker-id=... >
<total-picked>40 bushels</total-picked>
<lot-status>sparse drying berries remaining</lot-status>
</picking> *
So the relationship between lots and pickers is more complex and represented
separately, although you could put the <picking> elements inside the
appropriate <lot>.
I think this kind of thing is what Frank Manola had in mind in discussing
the relevance of requirements.
Jeff
----- Original Message -----
From: "Roger L. Costello" <costello@mitre.org>
To: "'XML Developers List'" <xml-dev@lists.xml.org>
Sent: Tuesday, February 01, 2005 4:35 AM
Subject: [xml-dev] What is coupling? [Was: 3 XML Design Principles]
> Hi Folks,
>
> Again, many thanks for the excellent comments. I am working hard to
> assimilate all your comments, and will create a summary of all the
> discussion soon.
>
> One question that several people asked was, "What do you mean by
coupling?"
> Below I have made an attempt at defining coupling. Do you agree with my
> definition? Is it complete, i.e., are there other factors that should be
> incorporated into a definition of coupling?
>
> Note that I have changed version #2 to this:
>
> <Lot id="1">
> -- info about the lot --
> </Lot>
> <Picker id="John">
> -- info about the picker --
> </Picker>
> <Assignment picker="John" lot="1"/>
>
> The Lot component just contains information about the Lot. And the Picker
> component just contains information about the Picker. The Assignment
> element connects the Lot and Picker. ["Assignment" is not really the
> correct name. Can someone think of a better name?]
>
> Okay, now for my definition of coupling:
>
> What is Coupling?
>
> Definition: There exists a coupling between two components if there exists
a
> "dependency" between the components. The greater the dependency, the
> greater the coupling.
>
> An obvious dependency is physical dependency. In version #1 the Lot and
the
> Picker are physically dependent (coupled) on each other:
>
> <Lot id="1">
> <Picker id="John">
> .
> </Picker>
> </Lot>
>
> The Picker is a child of Lot. The Lot is the parent of Picker. There
> exists a definite physical co-dependency between the Picker and Lot
> components.
>
> A more nebulous dependency is semantic dependency. In version #1 not only
> does there exist a physical dependency, but there also exists a semantic
> dependency. Namely, the Picker is located on the Lot.
>
> Now consider version #2:
>
> <Lot id="1">
> .
> </Lot>
> <Picker id="John">
> .
> </Picker>
> <Assignment picker="John" lot="1"/>
>
> The Lot and Picker components are physically completely separate. There
is
> no physical dependency. The Assignment element creates a semantic
> dependency between the Lot and Picker, by identifying that the Picker is
on
> the Lot.
>
> So, in version #1 there exists both a physical and semantic dependency
> between the Picker and the Lot. In version #2 there exists only a
semantic
> dependency. Thus, there is a stronger coupling between the Picker and Lot
> components in version #1. We say that there exists a tight coupling
between
> the components in version #1. There exists a loose coupling between the
> components in version #2.
>
> Comments? /Roger
>
>
>
>
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