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.
MUSCLE (Multi User Server Client Linking Environment) is an N-way messaging server and networking API. It includes client-side networking APIs for various languages, including C, C++, C#, Delphi, Java, and Python. MUSCLE lets programs communicate over a network via streams of serialized Message objects. The included server program ("muscled") lets its clients message each other and store information in its server-side hierarchical database. The database supports flexible queries via hierarchical wildcarding, and "live" updates via a subscription mechanism.
OpenIsis provides a library and tools to access CDS/ISIS databases, which are mostly used for bibliographic data (ISO2709, Z39.50) but also well suited for other catalogues due to the very flexible indexing mechanism. Based on a C library, there are also bindings for Perl and Java (Tcl to come).
ObjectDB for Java/JDO is a powerful yet compact Java Data Objects (JDO) Object Database (ODBMS), written entirely in Java, and compliant with the Java Data Objects (JDO) standard developed by Sun (JSR12). ObjectDB for Java/JDO is designed to efficiently handle databases of various sizes, ranging from a few KBs to hundreds of GBs. Among its features are small footprint, high performance, rapid development, easy deployment, and flexible architecture (1-Tier, 2-Tier, or N-Tier).
Servertec Persistent Object Store (POS) is a high-performance cross-platform object oriented database engine written entirely in Java. With it, developers can easily create standalone database applications, including mobile and wireless devices and embedded systems. It can be used on any platform that supports Java version 1.1.x or later.
Berkeley DB XML is a native XML database engine for use within your product. Made available as a C++ library with language bindings for Java, Perl, Python, PHP, and Tcl, it integrates directly into your application (it is not a standalone database server). It provides XQuery access into a database of document containers. XML documents are stored and indexed in their native format using Berkeley DB as the transactional database engine.
StelsCSV is a JDBC driver that allows performing SQL statements and other JDBC operations upon text files (comma separated, tab-separated, fixed length, etc.). Using this driver, users can easily create a simple database consisting of plain text files. The driver can be used for writing data importing programs and migration tools. It supports most keywords of ANSI SQL92, table joins, INSERT, UPDATE, and DELETE statements, data types, aggregate, converting, string, and user-defined SQL functions.
StelsEngine is a fast in-memory SQL engine (in-memory JDBC) for storing and processing tabular data in Java applications. Using StelsEngine, you can make processing data in your software considerably easier and quicker. It implements the JDBC API standard. It is a JDBC Type 4 driver, supports most keywords of ANSI SQL 92, supports integer, floating point, string, date/time, and Java object data types, supports aggregate, numeric, string, conversion, and user-defined SQL functions, supports data loading from a DBMS, and is platform independent.