db4o is an object database for Java and all .NET environments. Its features include ACID transactions, automatic class schema recognition, query-by-example, a S.O.D.A. object querying API, native queries, LINQ support on .NET, callback methods, memory files, cascade-on-delete, multi-threaded access, and Java Webstart and servlet support.
MundoCore is a lightweight and easy-to-use communication middleware to integrate heterogeneous software systems, consisting of services written in different programming languages and running on different operating systems. It also offers specific support for mobile and ubiquitous computing environments.