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From Michael Watzek <mwa.t...@spree.de>
Subject Re: Some words for the spec
Date Thu, 04 Aug 2005 10:53:21 GMT
Hi Craig,

the different mappings strategies below make perfect sense. Also, the 
strategy names are self-explanatory.

My understanding is that these strategy names correspond with attribute 
names "serialized" and "embedded" of element <field>, respectively with 
nested element <embedded>. Would it make sense to write up the 
correspondence explicitly, e.g. assign strategies to each of the 
examples in chapters 15.3, and 15.4.:

   Example4: single-valued by reference.
   Example5: multi-valued by reference to the primary table.
   Example6: multi-valued by reference to the primary table.
   Example7: multi-valued by reference to the primary table.
   Example8: multi-valued by reference in a join table.
   Example9: single-valued embedded (businessAddress, primaryAddress),
             multi-valued embedded in a join table (secondaryAddresses).

Would it make sense to add examples for the remaining mapping strategies 
"single valued serialized", "multi valued serialized", "multi valued 
serialized in a join table"?

Regards,
Michael

> Javadogs,
> 
> I'd like to add some text to the spec. This is intended to improve the 
> basic description of mapping relationships.
> 
> <spec 15.3>
> Mapping Strategies
> For single-valued relationships, there are three basic ways to map 
> references from one persistence-capable class (the referring class) to a 
> related class:
> 
> serialized: The entire related instance is serialized into a single 
> column in the primary or secondary table of the referring class.
> 
> embedded: The related instance is mapped, field by field, to columns in 
> the primary or secondary table of the referring class.
> 
> by reference: The related instance is in a different table, and the 
> column in the primary or secondary table of the referring class contains 
> a reference (often, a foreign key) to the primary table of the related 
> class. 
> 
> For multi-valued relationships, there are five basic ways to map 
> references from one persistence-capable class (the referring class) to a 
> related class:
> 
> serialized: The entire collection, array, or map is serialized into a 
> single column in the primary or secondary table of the referring class.
> 
> serialized in a join table: A join table is used to associate multiple 
> rows in the join table with a single row in the primary or secondary 
> table of the referring class, and the related instances are serialized, 
> one per row, into a single column in the join table.
> 
> embedded in a join table: A join table is used to associate multiple 
> rows in the join table with a single row in the primary or secondary 
> table of the referring class, and each related instance is mapped, one 
> per row, field by field, into multiple columns in the join table.
> 
> by reference to the primary table of the related class: The related 
> class has a reference (often, a foreign key) to the primary table of the 
> referring class.
> 
> by reference in a join table: A join table is used to associate multiple 
> rows in the join table with a single row in the primary or secondary 
> table of the referring class, and a column in the join table contains a 
> reference (often, a foreign key) to the primary table of the related class. 
> </spec>
> 
> Craig Russell
> 
> Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
> 
> 408 276-5638 mailto:Craig.Russell@sun.com
> 
> P.S. A good JDO? O, Gasp!
> 
> 


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