HailDB is a relational database in shared library form that can be embedded into applications. It is not a SQL database, although you can use this library as the storage backend for a SQL database. It features a clean and simple API and is a continuation of the Embedded InnoDB project. With the addition of the HailDB plugin to Drizzle, you get a full SQL interface.
MariaDB is a database server that offers drop-in replacement functionality for MySQL. It is built by some of the original authors of MySQL, with assistance from the broader community. In addition to the core functionality of MySQL, it offers a rich set of feature enhancements including alternate storage engines, server optimizations, and patches.
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.
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.
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.
SymmetricDS Pro is software for data replication, change data capture, and data transformation in a heterogeneous enterprise environment. Performance and scalability allow it to replicate thousands of databases asynchronously in near real time. With flexible configuration and powerful scripting and programming interfaces, it can be extended to meet a range of requirements. Based on the popular open source version of SymmetricDS, the Pro edition enhances the experience with a click-through installer, Web management console, and production support.
Triceps is an innovative embeddable Complex Event Processing (CEP) system. It can be thought of as an in-memory database driven by triggers, or a data-flow machine working on a stream of events, or a spreadsheet on steroids. The major architectural advantages of Triceps include the direct use of procedural logic (as opposed to all-SQL systems), support of both compiled and general scripting languages (C++, Perl), light weight, and easy extensibility.