Re: Mapping, take II

[Mark Baker <mbaker -at- OMNIMARK -dot- COM>]

Gwen Thomas wrote


>And earlier, Mark wrote:
>"The best way to manage relationships is to manage those
>properties which form the basis of relationships, making the relationship
>explicit is less effective because it does not hold out the possibility of
>discovering new relationships based on the properties of other objects."


>Then I'm not sure I follow.

By way of example. Lets say I have a database of movie reviews. In that
database I use XML markup (just to trendy) to make some relationships
explicit. So in the text of a review I find:

"The role of Tex was played by John Wayne."

You and I recognize that the "John Wayne" referred to here is an actor, but
the computer doesn't know that. As far as the computer is concerned there
are lots of John Waynes in the phone book and this could be any one of them.

So we make it explicit:

"The role of Tex was played by <actor>John Wayne</actor>."

Now we have identified the meaning of the text John Wayne unambiguously.
This is the actor John Wayne, (and the Screen Actors Guild makes sure there
will never be another by that name). We haven't made any particular
relationship between those words and any other piece of information, but we
have established the basis for building many different relationships between
this information and other pieces of information.

Just to make this part of the story complete, I will point out that we can
extend the markup just a little to allow for nicknames in the original text:

"The role of Tex was played by <actor name="John Wayne">the Duke</actor>."

This does the same thing: it makes clear that property of the text on which
relationships can be built.

What I could have done instead is this. Knowing that we have another table
of actor biographies in our database we could have expressed an explicit
relationship to that table like this:

"The role of Tex was played by <link table="bios" id="453">John
Wayne</link>."

Though it is more explicit, this kind of linking is less flexible. We've
committed ourselves to a single explicit relationship where we could have
had many relationships by expressing a property of the text instead of
expressing the link directly.

You cannot always avoid doing the second kind of relationship building. It
is not always possible to do the first kind. But it is always preferable
where possible.

(Incidentally, this is a good example of why XLink is the wrong way to do
linking in XML.)

---
Mark Baker
Senior Technical Communicator
OmniMark Technologies Corporation
1400 Blair Place
Gloucester, Ontario
Canada, K1J 9B8
Phone: 613-745-4242
Fax: 613-745-5560
Email mbaker -at- omnimark -dot- com
Web: http://www.omnimark.com


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