There is some confusion about SDO in the industry. I've recently seen posts and comments in various blogs and expert groups spreading misconceptions about SDO.
It seems they are afraid by SDO or DAS trying to define yet another standard for persistence.
Here is my answer to them:
AFAIK, I think the SDO group is not trying to redefine a new persistence standard... as SDO is not really related to persistence by itself.
IMHO, you should rather look at SDO as a standard for DTO. The DAS itself is in charge of accessing and manipulating the data sources. The DAS expert group is certainly not willing to specify a new way to manipulate data sources. The DAS specification is rather focusing on defining the protocol between the various DAS components and their interaction with SDO. So existing standards like JPA and JDO are obviously best candidates for Java-ORM-oriented DAS implementations. But keep in mind the DAS specification is neither limited to Java nor to RDBMS. And even in the case of a single RDBMS, mapping (ORM) is not mandatory.
I think that is more or less what Tuscany is illustrating today (JDBC-based DAS).
BTW: Tuscany is just an example of what a DAS could be. I'm aware of at least 2 other DAS implementations built upon JPA and another one relying on top of JDO. I think there is nothing in JPA today preventing implementation of a DAS on top of it. The same way, I cannot see missing features in JPA today for a DAS implementation.
See also Michael Rowley's (BEA) point of view.