After a lot of
playing around, I'm really starting to like the practical nature of using
queries as a data transfer mechanism for simple displayable objects where you
need to display 1..n objects and where you do NOT need to display any ..n
aggregates or compositions (it gets a little convoluted where you have to
display 10 insured persons and the three dependents for
each).
The weakness of
queries is that they are dumb. There are no methods, so you end up with the
ultimate anemic domain model with all of the methods in the service layer. On
the other hand, for simple objects that mainly have CRUD features that need to
work on both 1 and n instances, queries provide a simple display method and
putting validation into the service layer means that it can be used efficiently
for 1 or n objects without the overhead of creating an array of objects and
iterating through n-objects when trying to delete 200 records or even save
updated pricing for 40 products from a single screen.
Any
thoughts/experiences?
Also, does anyone
have a clean data structure for working with lists of objects each of which have
..n aggregations/compositions. Example - I want to display 10 insured persons
with a list of dependents below each of the 10. Obviously you can create an
object for each item which could contain a property which would be a struct of
the sub objects (or a query if you were willing to create 10 objects but not 40
objects), but I'm not in a rush to be generating 40 or 50 additional objects per
page request and I can see situations where I'd have too many objects to cache
them in a more persistent scope (imagine a list of products with associated
attribtues where you have a database of 500,000 products). XML gives the same
capabilities but now with the serialization/deserialization overhead instead of
the object instantiation overhead and then you probably need designers capable
of writing XSLT's which is not something most of the designers I work with would
want to learn. I'm actually playing with a structure using naming conventions
for associated structures and an entity level templates, so if you want to
display 10 insured persons with 3 depenents, you describe the person list
template, stick a little "Dependent" tag inside it and then create a separate
template for displaying the dependents which is then iterated through and
dropped into the list template in the appropriate
place.
Anyone else trying anything similar, and does anyone have any great ideas on performant ways of passing data that involved multiple objects each of which may be composed of n ..n compositions (i.e. anything other than creating all the objects or serializing/deserializing into somehting like XML)?
As always,
any thoughts/ideas much appreciated.
Best
Wishes,
Peter
Peter
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