How to take care of fetching related objects of one object? For example object project has some tags. How and when should I fetch those object? In user initialization in mapper? That would be a big overload. The best way would be to load them dynamicly when system ask user for tags, but how to do that if model does not know anything about the mapper? Or just use Doctrine and forgot all about those problems?
Im asking this in relation to PHP Zend Framework. But any technology would suffice I think for this problem.