I am planning the implemention an Inheritance Mapper pattern for an application component http://martinfowler.com/eaaCatalog/inheritanceMappers.html

One feature it needs to have is for a domain object to reference a large list of aggreageted items (10,000 other domain objects)

So I need some kind of lazy loading collection to be passed out of the aggregate root domain object to other domain objects.

To keep my (php) model scripts organised i am storing them in two folders:

MyComponent\
 controllers\
 models\
  domain\     <- domain objects, DDD repository, DDD factory
  daccess\    <- PoEAA data mappers, SQL queries etc
 views\

But now I am racking my brains wondering where my lazy loading collection sits.

Any suggestions / justifications for putting it in one place over another another?

DDD = Domain Driven Design Patterns, Eric Evans - book PoEAA = Patterns of Application Architecture Patterns, Martin Fowler - book