Data Modeling...Immutable Data
Recently I had an email dialog with a colleague that I have a great deal of respect for. The general topic was on accessing data within a database by know/constant values. Basically we needed to retrieve data from a table with one value, and cross reference it to a second value. Everyone is thinking, "Okay...What's the big deal? We do that every day.", and I agree. At first blush this is something software developers do all of the time. But in this specific case the lookup value was going to be persisted within XML, and at the same time the persisted value is visible to end-users. One more point. Within our system there is no place that the end-user can change the lookup value, they can only see it. We want the lookup value to be immutable because there is no way to ensure that if one of the values changes, we will remember to change the other. The end-user cannot change it, and the software application don’t change it. So let’s get to the point. Immutable data is inf