Apache Marmotta Apache Marmotta

Apache Marmotta is a Linked Data server, SPARQL server, and Linked Data development environment. Marmotta provides a Linked Data Platform (LDP) for human-readable and machine-readable read-write data access via HTTP content negotiation. Marmotta features modules and libraries for LD application development. The modular server architecture makes it possible to implement the required functionalities only. For instance, if you don’t need reasoning for your project, you can exclude the reasoner module. Marmotta provides a collection of Linked Data libraries for common LD tasks such as access to LD resources and query Linked Data (through LDPath, a simple LD query language). The triplestore is segregated from the server, so it can be used independently. The Apache Marmotta platform is implemented as a Java web application and deployed as a .war file. It is a service-oriented architecture using Contexts and Dependency Injection (CDI), a set of services of Java web application development. The Marmotta Core, a fundamental component of Apache Marmotta, provides Linked Data access, RDF import and export functionality, and an admin interface. Marmotta Core unites the service and dependency injection, the triplestore, the system configuration, and logging.

Apache Marmotta

As a SPARQL server, Marmotta provides a public SPARQL 1.1 query and update endpoint, and full support for SPARQL 1.1 through HTTP Web services. Marmotta features a fast, native SPARQL implementation in KiWi triplestore, a high-performance, highly scalable transactional triplestore backend for OpenRDF Sesame building on top of a relational database such as MySQL, PostgreSQL, or H2. To make SPARQL queries easier, Apache Marmotta provides Squebi, a lightweight user interface. Beyond KiWi, Marmotta’s default triplestore backend, you can also choose Sesame Native (based on Sesame Native RDF backend), BigData (based on the BigData clustered triplestore), or Titan (based on the Titan graph database). Marmotta Reasoner, an optional module, is a rule-based reasoned for the KiWi triplestore. It implements datalog-style rules over RDF triples. The Marmotta Loader is a command line tool for loading RDF data in various formats to different triplestores. It supports RDF serializations, and can also import directories, split-files, gzip and bzip2 compressed files, as well as Tar and Zip archives.

Apache Marmotta Architecture
Apache Marmotta Architecture

Apache Marmotta Architecture. Retrieved from Apache.org

The Marmotta software libraries can be used not only as components of the Marmotta platform, but also as standalone lightweight Java libraries. The Apache Marmotta LDClient library is a flexible and modular RDFizer suitable for Linked Data projects to retrieve remote Linked Data resources via different protocols and data providers. The modules of Marmotta support RDF/XML, Turtle, N3, JSON-LD, RDFa, XML, HTML, and can process Freebase, Facebook, YouTube, Vimeo, and MediaWiki contents. The software library is extensible through Java’s ServiceLoader class, enabling custom wrappers for legacy data sources such as RDF, RDFa, Facebook, YouTube, and Wikipedia, as well as base classes for mapping other formats like XML and JSON. Marmotta LDCache, another library, can access remote Linked Data resources as if they were local. It supports wrapping for legacy data sources such as Facebook Graph. LDCache features a local triplecache. Another optional library is Marmotta LDPath, a query language less expressive than SPARQL but specifically designed for querying Linked Data in the cloud. LDPath features a path-based navigation which starts at the resource and follows the links. If you use SPARQL queries, LDPath is recommended over LDCache. LDPath includes a large function library which can be integrated in your own applications. LDPath can be used with LDCache and LDClient, and supports backends such as Jena and Sesame.