CAM

However, semantically aligning systems via services or any other method allows systems to change, to a great degree, at differing rates and locations.

I see federated systems working where there is a high level of governance and a high level of common management control. But even then I’d rather see services used over forcing technical objects to be the same.

I prefer to base my decisions on technical merits, not marketing trends. And I have seen relational modeling work in almost every type of data storage exercise. Yes, I read Codd’s work. But I do not subscribe to a ‘pure’ relational approach. I do not subscribe to a ‘pure’ anything; again, I base my decisions on technical considerations, which are based in reality.

If I find a perfect approach that works in its pure form, I’ll be sure to let the world know. Right after I find a way to patent it.

“Valid/invalid” will not be sufficient; I need more status options than that. I won’t bore you with the details.

Sorry to ‘jack a comment thread with my issues. But thanks for the reference to Chris Date. I’ve been looking for some decent online reference material on his work; I’m not buying anything until I know whether or not there is value in it.

I presume what you’re REALLY looking for is a view that has three revision-related columns — First_Valid_Date, Last_Valid_Date, and Is_Still_Valid — except that you want to be clean about the natural redundancy. In that case, I really would recommend looking up what Date has to say about that and seeing whether you judge it to be worth the trouble.

Commercial RDBMS also have various kinds of snapshot/timestamp/rollback features. Indeed, there’s a boom in them because they’re relevant to compliance.

Thanks for the kind words,

CAM

I also agree that specific alignment approaches such as SOA are superior to ‘database federation’ for almost any business case I can conceive. So, as much as I’d like to argue (just ’cause I like to argue), I’m not going to do so.

Regarding my needs: I just need to track various ‘revisions’ of a record over time. Each revision gets a revision number, and no revision is ever deleted for any reason. Changing a usage name (to pick a data element at random) creates a new revision. I’m just trying to think of the best way to model it for purposes of efficiency, performance, integrity, and historical data.

Overall, pretty good site. I think I’ll check back, time to time.

1. Relational data modeling has uses, and should be done. However, it’s not nearly as valuable as proponents claim.

A typical discussion with the application developers I most respect might go:

“Is relational data modeling good for anything any more?”
“Not much.”
“Do you do it?”
“Yes.”

2. The relational data model is a clever theoretical construct. It is not as universally applicable as proponents claim, however. For example, modeling text search via predicates is, depending on how you look at it, either a bad idea or an utterly incomplete one.

3. Most pros and cons of the relational model are more or less equally applicable to today’s commercial products. However, that begs a related question, namely which of today’s commercial products one should use. I believe that one should use a combination of them, and that the idea of consolidation into a single database is greatly overblown.

You haven’t said much about your specific needs, but I’m guessing that you’re trying to solve too big a problem. The more rigorous and disciplined you want to be about data modeling, the more data you have to leave out. I’m sure you’re not trying to model every e-mail or bookmark file on everybody’s PC. Well, there may also be some rows-and-columns stuff you should leave out as well. Just build walled cities where data is all neat and tidy, with clean interfaces (trade roads) between them. If the policies and procedures are different in each of the cities, that’s not necessarily a bad thing.

CAM

Not that data-level revision control isn’t easy, but there are so many options that I’m at a stand-still looking for a ‘good’ (or the ‘best’?) one.

Anyway, you seem to have a grudge against relational data modeling in several areas. In every case, however, most of your issues seem to relate to designers’ errors in the use of relational models, not the concept itself.

You seem to advocate SOA because “you need only do the alignment necessary”, but you do not like direct federation because of the “temptation” to do everything at once. That’s not really fair, now is it?