BaseX is a light-weight, high-performance, and scalable XML database system and XPath/XQuery processor, including full support for the W3C Update and Full Text extensions. An interactive and user-friendly GUI frontend gives you great insight into large XML data instances. It is platform independent and works out of the box.
TM++ is an embedded, portable, persistent Topic Maps engine. It is designed to work according to the ISO standards for TMDM 1.0 and XTM 1.0/2.0 on Windows and most POSIX-compliant operating systems like Unix and Linux. It has interfaces for C++, ALLEGROCL, CHICKEN, CLISP, CFFI, C#, Guile, Java, Lua, Modula 3, Mzscheme, Ocaml, Octave, Perl, PHP4, PHP5, Pike, Python, R (aka GNU S), Ruby, Lisp S-Expressions, Tcl, Common Lisp/UFFI, and XML.
With MetaModel, you use a type-safe SQL-like API for querying any datastore. It is a data access framework providing a common interface for exploration and querying of different types of datastores. It isn't a data mapping framework. Instead, it emphasizes abstraction of metadata and the ability to add data sources at runtime, making MetaModel great for generic data processing applications, but less so for applications modeled around a particular domain.
The NCBI C++ Toolkit provides portable libraries and applications for assisting genetic science. These include libraries for networking, SQL and BerkeleyDB access, CGI and HTML handling, ASN.1 and XML handling, sequence alignment engines, sequence retrieval engines, BLAST database engines, FLTK and OpenGL graphics toolkits, and basic system utilities.
QOF (Query Object Framework), provides a set of C Language utilities for performing generic structured complex queries on a set of data held by a set of C/C++ objects. This framework is unique in that it does not require SQL or any database at all to perform the query. Thus, it allows programmers to add query support to their applications without having to hook into an SQL database.
nexB OpenAssets is a tool for inventorying, managing, and monitoring applications, software, hardware, networks, and generally any IT asset. It is designed so that system administrators, IT, and finance can determine what they have, how it is configured, what it is used for, and how much it is being used, so that informed decisions can be made. It complements existing network management software, integrates with a growing number of protocols and tools, and features no-agent discovery and inventory, configuration management including dependencies and correlation, monitoring, and reporting. It makes extensive and innovative use of XML, Xpath, and Xquery.
PhiloLogic is a full-text database engine developed for humanities computing text analysis by the ARTFL Project and the Digital Library Development Center at the University of Chicago. It is optimized for fast searching across very large collections of documents. It currently supports TEI-Lite, TEI XML, and TEI SGML documents.