Discussion:
[Modeling-users] What for?
Luciano Andrade
2004-04-11 20:15:07 UTC
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I whant to know what meens the attributeUseForLooking,
what mees that a relation is a classpropety, what if
a propiety is not a classpropety, what the join's
semantics meens, what about circular relations, can
the module handled.

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Sebastien Bigaret
2004-04-14 17:23:05 UTC
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Hi,

...And sorry for the late answer
Post by Luciano Andrade
I whant to know what meens the attributeUseForLooking,
The 'usedForLocking' property is not used yet --it will be used to
indicate which attributes should be monitored when the forthcoming
optimistic locking feature is implemented.
Post by Luciano Andrade
what mees that a relation is a classpropety, what if
a propiety is not a classpropety,
The 'classProperty' flag indicates whether the related attribute is part
of the class' attributes. For example, 'firstName' is a class property
in entity Person: any object of class Person has a property 'firstName';
on the contrary, the primary key is not a class property, it is just a
column in the database that is not exposed at the object level (so in
this case the DB's table has a 'id' column but class Person does not
have any 'id' attribute)
Post by Luciano Andrade
what the join's semantics meens,
This has to do with different sets of objects returned by a SQL query
--I myself only use inner joins (ie themost natural one, at least for
me;), so instead of trying to explain things I do not master at all, I
prefer to give you some links that ill do the job better then I could:


Getting the Right Data with SQL Joins:
http://www.devx.com/dbzone/Article/17403/0/page/1

Fropm postgresql:
http://www.postgresql.org/docs/7.4/interactive/tutorial-join.html

O'Reilly:
(pointed to by: http://www.onlamp.com/pub/ct/19)

http://www.onlamp.com/pub/a/onlamp/2001/05/24/aboutSQL.html
http://www.onlamp.com/pub/a/onlamp/2001/06/01/aboutSQL.html
http://www.onlamp.com/pub/a/onlamp/2001/06/15/aboutSQL.html
http://www.onlamp.com/pub/a/onlamp/2001/06/27/aboutSQL.html
Post by Luciano Andrade
what about circular relations, can the module handled.
Not sure what you mean: do you mean reflexive relationships,
i.e. where the source and destination entities are the same entity?
If this is the case, have a look at the sample model in the User's
Guide:

http://modeling.sourceforge.net/UserGuide/model-author-books.html

It has a reflexive relationship Writer-->Writer (it is a directional
relationship, but you can have a one-to-many bi-directional
relationship as easily), which is modeled exactly the same than
"standard" relationships. The corresponding PyModel is exposed here:

http://modeling.sourceforge.net/UserGuide/pymodel-sample.html


Should you have other questions, feel free to ask for more here!


-- Sébastien.

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