Thursday, August 10, 2006

Two quick things

1. All operations must be idempotent. I'm not sure (yet) how to enforce may just be a really strong suggestion.

2. Versioning will be a big part of the system. We need to be able to add fields to an entity and remove fields from and entity, inline an entity (more on that later) and extract an entity. I'm sure there are a number of "refactoring" tools that come from this, but I want them FIRST, not "when there is time." For instance, if I want to add a Title to a Name, then that needs to be as easy as adding title as Title to the Name class and running an upgrade program with an optional map function to create the title given the name (the map could set them all to a default (blank) title or it could try to guess a title of Mr or Mrs based on a derived gender).

Right now, I know I want automated upgrades when I
a) add a field
b) remove a field
c) inline an entity
d) extract an entity
e) add/change the validation method
f) add/change the normalization method
g) add an implied attribute

Also, we better darn well be able to downgrade!!!!!

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