I was leafing through an old ODMG reference and wondered what the relationship is between hibernate and ODMG.

+Does the ODMG standard have a following?
+Is HQL closely related to OQL?
+How does the ODMG interface map onto the hibernate code?
+Is ODMG a good standard to follow or will JDO or some other standard dominate?
+Or is it better to forget about standards and just use hibernate natively?

Thanks,
zakons

Not really, which is unfortunate in a way, since it is superior to other, more recent, solutions.



Yes, actually the Hibernate query parser supports a very decent subset of ODMG OQL. HQL may be considered a dialect of OQL, adapted to use with ORM rather than object databases. For example, HQL introduces the IS NULL operator and the JOIN syntax, which we have found necessary for use with relational databases. Similarly, HQL does not support OQL method calls, since that is virtually impossible to implement in a relational database.



There is an ODMG-compatible wrapper in the net.sf.hibernate.odmg package. It is not popular, since Hibernate APIs are more powerful.



Don't ask me to predict the future! However, the ODMG standard is certainly dead.



That is much better.

I anyway argue that if an open source project has a dominant market share, then it should be considered the de facto standard. (For example, log4j is the standard logging toolkit for Java, and Ant is the standard build system.) It's quite convenient for me to adopt this view since that would imply that Hibernate is now the de facto standard for ORM in Java. ;)

If you want some empirical evidence for this, note that our website now gets 27000 pageviews/day. #19 on sf.net:

http://sourceforge.net/top/toplist.php? ... views_proj

Thanks Gavin.

I think it helps to know that HQL has an antecedent in OQL because the object query semantic in OQL is fairly clean, and it makes sense that HQL didn't just fall from the sky. While looking at OQL, the similarities with HQL were to strong to ignore. It also helps to know that all the work that went into ODMG was not for naught.

I definitely know all about de facto standards, having worked on OSI protocols for a good several years, just prior to the tidal wave of TCP/IP.

Yes, I certainly paid attention to OQL and was motivated by it. However we usually say that HQL is a dialect of ANSI SQL, rather than of OQL, since it does adhere very closely to SQL in most places (except for the fact of being object oriented of course!).