Redland is a set of C libraries providing a high-level API for the Resource Description Framework (RDF), allowing it to be stored, parsed, serialized, queried, and manipulated. It has an object-based, modular design and comes with detailed reference documentation and examples. Redland supports all RDF vocabularies such as FOAF, RSS 1.0, Dublin Core, DOAP, and OWL, the query languages SPARQL and RDQL, and all RDF syntaxes including Turtle, RDF/XML, RDF/JSON, RSS, Atom, RDFa, and GRDDL.
HyperSQL is like the doxygen program with Javadoc added, but for SQL. It hypermaps SQL views, packages, procedures, and functions to HTML source code listings, and it shows all the code locations where these are used. You can use JavaDoc-style comments for documentation and even embed UnitTests with them.
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.
POPsearch is a desktop search engine that is designed to help you easily find information on your computer. With features that other search engines don't have,it lets you index your entire collection of email messages and files. As information is indexed, it is immediately available for analysis from any Web browser. When POPsearch is configured correctly, you can also access your data remotely with RSS feeds, email feeds, or from any computer that has a Web browser.
XMLDB uses an RDBMS to persist arbitrary XML documents. Due to its storage mechanism, searching for and recalling documents is extremely quick. You can also perform XSL translation on documents with surprising speed. The library can be used in any program to store libxml2 documents. A PHP module is also included, making XMLDB into a complete three-tier Web application development suite.
Net::Z3950::SimpleServer is a Perl module which implements the server side of the Z39.50 (information retrieval) protocol. It hides the complexity of network exchanges, packet serialization, and session handling. You are required only to implement simple callbacks to support searching and record retrieval. It is the basis of the "Zoogle" project, which is a Z39.50 gateway to the Google web index.
The Data Mine is a search engine designed to make a more useful interface available to users. It is designed around human-computer intelligent interaction considerations. It divides the screen into two halves. One lets you find all the instances of your query's keywords, and the other lets you look through a highlighted version of the results you choose.