1. Rank the importance of being compatible with each of the other
databases of concern.
Most important to me is the SQL standard.
If we focus on compatibility with that, then I think DB2 will be a close second as IBM seem to have a tendency of being closer to the standard that other vendors (disclaimer, my opinion and I do *not* work for IBM).
Assuming we can avoid conflicts with the standard then the next two platforms for me are Oracle and Microsoft SQL Server due to their broad enterprise adoption, and MySQL due to its dominance in the LAMP arena.
Let me add, I really really appreciate IBM's contribution but, as with all children, it is essentialy that Derby develops its own identity and learns to fly on its own.
2. How important (on a scale of 1-10) is portability in migrating
FROM Derby to other databases?
If you look at the embedded arena, I don't think this that important an issue because of the close relationship between the application and the database and that often the database is not really visible to the end user.
If you look at the bundled arena where an ISV is distributing Derby with a product (perhaps as a seed/low-end offering) but also wants to allow end-users to use an existing production database then portability becomes much more important; the ISV wants to minimize the discrepancies between the platforms they support.
If you look at the application arena, then portability may not matter that much because the user is primarily interested in one database platform. What becomes important here is that Derby's dialect is supported by the tools (EJB, JDO, O/R mapping) that people are using.
3. How important is portability in migrating TO Derby from other
databases?
I don't see this as that important as I don't think SQL portability will be the major decision factor in such a migration decision, tooling will.
4. Should Derby adopt the Least Common Denominator standard?
Absolutely not.
In an ideal world, the SQL standard would be the LCD and implementations would be offering features over and beyond. With the current state of the market, *none* of the implementations, commercial or open source, is anywhere near implementing even that baseline.
I would like to see Derby as the innovator here, offering features not available even in the leading commercial alternatives. Let Oracle and IBM play catch up ;-)
-- Jeremy
