Hi Otavio, I'm fine, thank you! :)
This is the world where enterprise's developers have (and it's rightly must be so) the data saved, for several reasons, in varios types of databases. And it's an own (Jakarta EE) responsibility, at last, to give them the freedom of switching, as easy as possible, from one database (or database type) to another, manipulate data and write the combined data in yet another db.
If you think about it for a moment, varios SQL (RDBMS) databases are very-very different at the base, but what join them is the small surface interface - the set of rules that let them be classifies as RDBMS (nearly RDBMS :)) ). This surface interface from now should be Jakarta DBCS.
We have already enough knowlenge to combine them in an multipurpose product that will be at the right place in the present world that JDBC held in the past-only-SQL world.
About presence and absence of transactions in MongoDB and Cassandra, if you look at page 9 of "The Third Manifesto" of C. J. Date and Hugh Darwen, you can read:
"Each transaction shall interact with exactly one database. However, distinct transactions shall be allowed to interact with distinct databases, and distinct databases shall not necessarily be disjoint."
i.e., in the case of Cassandra, a transaction may be the same (parallel) think of connection.
Thinking more deeply about Date's phrase above - with our future "Jakarta DBCS" we finally have the possibility to implement one of the fundamental rules of the fathers of database concept (Codd, Date): "distinct databases shall not necessarily be disjoint". :)
If our surface interface of Jakarta DBCS will allow to communicate with 90% of existing databases, the last 10% databases will adjust their surface interface, in one way or another, to enable users to use them via our multipurpose product.
About meetup by hangout or zoom - it's a great idea. I live in Italy - we should agree about the time of meetup.
Thank you. :)