Querying nested MagmaCollections

[Amir Ansari]

Dear List,

I'm not lazy!  I've gone through the mailing list, and various  
Smalltalk books.  There's little information on how to handle nested  
collections, much less nested MagmaCollections.  But I can imagine this  
would be a fairly common task, especially since object databases are  
structured in a different way to relational databases.  (This also came  
up on the mailing list a while ago:  
http://lists.squeakfoundation.org/pipermail/magma/2007-March/ 
000598.html)


I've created two example classes: Writer (with 'books' and 'name'  
instance variables and accessors), and Book (with 'title' instance  
variable and accessors).

'books' is a MagmaCollection of Book items, contained within Writer  
(ie. a Writer creates many Books!). This is initialised in Writer:

initialize
	books := MagmaCollection new.
	books addIndex: (MaKeywordIndex attribute: #title)


OK, now I create a MagmaCollection called myLibrary and add some  
example books:


myLibrary := MagmaCollection new.
myLibrary addIndex: (MaKeywordIndex attribute: #name).

writer1 := Writer new name: 'Margaret Mitchell'.
writer1 books
	add: (Book new title: 'Gone With the Wind');
	add: (Book new title: 'Lost Laysen').

writer2 := Writer new name: 'Kenneth Grahame'.
writer2 books
	add: (Book new title: 'The Wind in the Willows');
	add: (Book new title: 'The Reluctant Dragon').

writer3 := Writer new name: 'Anne McCaffrey'.
writer3 books
	add: (Book new title: 'Dragonriders of Pern');
	add: (Book new title: 'Crystal Singer').

myLibrary
	add: writer1;
	add: writer2;
	add: writer3.


The problem I'm struggling with is how to query this data structure!  I  
would like to generate collections based on the following queries:

1.	All books with titles containing the word 'wind'
2.	All writers who have books with titles containing the word 'dragon'


Thanks for any help!

Amir