PostGIS adds support for geographic objects to the PostgreSQL object-relational database. In effect, PostGIS "spatially enables" the PostgreSQL server, allowing it to be used as a backend spatial database for geographic information systems (GIS), much like ESRI's SDE or Oracle's Spatial extension.
hamsterdb Embedded Storage is an embedded database engine written in ANSI-C. It includes B+Trees with variable length keys and records. It supports in-memory databases and endian-independent files, database cursors, multiple databases in one file, "record number" databases, and duplicate keys. hamsterdb is very fast and highly configurable. It compiles and runs on Unix platforms, Linux, Microsoft Windows, and Windows CE.
hamsterdb Transactional Storage is an ANSI-C implementation of a key/value database engine. It has a lock-free architecture, thus supporting an arbitrary number of long-running transactions and resolves transaction conflicts in memory without accessing the disk. hamsterdb uses logical, idempotent logging for recovery. It is thread-safe and concurrent, moving performance intensive operations to the background. Every hamsterdb handle can be used from arbitrary threads.
DeveelDB is an embedded SQL database management system for .NET, implementing all the features of the SQL92 specifications (transactions, triggers, procedures, functions, etc.). The aim is to provide .NET and Mono developers with a fully functional, powerful, and embeddable database system that can be used in several contexts, managing small to large amounts of data.
VoltDB is a blazingly fast relational database system. It is specifically designed to run on modern scale-out architectures: fast, inexpensive servers connected via high-speed data networks. It is aimed at a new generation of database applications - real-time feeds, sensor-driven data streams, micro-transactions, low-latency trading systems - requiring database throughput that can reach millions of operations per second. What’s more, the applications that use this data must scale on demand, provide flawless fault tolerance, and enable real-time visibility into the data that drives business value. It includes client application drivers for applications written in Java, C++, C#, PHP, and Python. VoltDB community members have also authored client libraries for Erlang, Ruby and Node.js. There are streaming export capabilities for leading analytic database environments, including Apache Hadoop.
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.
The OODBMS/DBMS ODABA is an terminology-oriented database management system (TODBMS) on a high conceptual level. This is an extension of the ODBMS concept according to ODMG 3. It provides a number of enhanced features based on natural language analysis. Beside the database kernel, a number of tools are provided for database design, documentation, and fast development. ODABA provides a powerful interface (C++, .NET) and an ODABA Script Interface (OSI), a C++/JAVA like scripting language, which provides easy access to the database.
MckoiDDB is a distributed database system for applications that need to support low latency random access (read and write) queries on datasets that span a cluster of machines in a network. The software provides the system for managing the storage of data over the network cluster and a client API for accessing and querying the data. The MckoiDDB system can scale up or down as resources are added or removed in the network, and is flexible in how the logical data models of an application are designed and implemented. MckoiDDB can be installed on high-speed private networks and over instances in Cloud service providers.
Neo4j is a graph database, a fully transactional database that stores data structured as graphs. A graph is a flexible data structure that allows for a more agile and rapid style of development. You can think of Neo4j as a high-performance graph engine with all the features of a mature and robust database. The programmer works with an object-oriented, flexible network structure rather than with strict and static tables, yet enjoys all the benefits of a fully transactional, enterprise-strength database. The community edition is GPLv3 licensed, while the advanced and enterprise editions are AGPLv3 licensed.