N-Triples
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| N-Triples | |
|---|---|
| Name | N-Triples |
| Developer | World Wide Web Consortium member community |
| Released | 2004 |
| Latest release | 1.1 (2014) |
| Programming language | Plain text |
| Operating system | Cross-platform |
| Genre | Data serialization format |
| License | Public domain / specifications by W3C |
N-Triples is a line-based, plain-text serialization format for expressing Resource Description Framework graphs. It was specified by the World Wide Web Consortium to provide a simple, robust interchange format suitable for large-scale processing and debugging, and complements other RDF serializations such as RDF/XML and Turtle. N-Triples is intentionally minimal to enable streaming, easy parsing, and straightforward generation by tools in diverse environments such as Apache Jena, RDF4J, and Virtuoso.
Overview
N-Triples was designed to serve interoperable data exchange among projects including DBpedia, Wikidata, Europeana, OpenLink Virtuoso, and research deployments at institutions like MIT, Stanford University, and University of Oxford. It targets scenarios similar to those associated with the Semantic Web initiatives of the World Wide Web Consortium and projects at Google, Microsoft Research, and Facebook that require scalable graph storage and indexing. Because of its strict, line-oriented nature, N-Triples is often used in batch workflows for conversion tasks that also involve systems such as Apache Hadoop, Apache Spark, and Neo4j when RDF graphs are ingested or exported.
Syntax and Data Model
N-Triples expresses RDF graphs as a sequence of triples: subject, predicate, and object, each separated by whitespace and terminated by a period. The data model reflects the RDF model used by standards bodies like the World Wide Web Consortium and institutions such as Library of Congress for linked data. Subjects and predicates are expressed as absolute or relative IRIs originally drawn from initiatives like Internationalized Resource Identifiers and examples used by CERIF and Dublin Core metadata records in projects such as Europeana. Objects may be IRIs, blank nodes, or literal values with optional language tags or datatype IRIs, echoing approaches used in ISO metadata integration and Unicode text handling in multinational projects at United Nations agencies. Escape sequences and Unicode handling follow recommendations aligned with practices at ICANN and IETF for interoperable identifiers.
Serialization and MIME Types
N-Triples files are typically stored with the .nt extension and are associated with the MIME type text/plain or the more specific application/n-triples registered in community practice. This mirrors other RDF serialization MIME choices such as application/rdf+xml for RDF/XML and text/turtle for Turtle, as used in exchanges between services like LinkedIn, Wikimedia Foundation, and scholarly repositories like arXiv. Because N-Triples is line-oriented, it is well-suited for streaming over protocols used by projects involving Apache Kafka, AMQP, or simple HTTP transfers between endpoints managed by Amazon Web Services or Google Cloud Platform.
Comparison with Other RDF Formats
Compared with RDF/XML, N-Triples is far simpler and easier to parse in streaming scenarios common to Apache Flink or MapReduce pipelines at organizations like Yahoo! and Twitter. Relative to Turtle, N-Triples is less compact, as Turtle supports syntactic sugar and prefix declarations popular in datasets curated by W3C community groups and libraries like British Library and Library of Congress. Unlike binary serializations such as HDT (Header, Dictionary, Triples), N-Triples prioritizes human readability over on-disk efficiency, a tradeoff also encountered when comparing with formats used by Oracle or Microsoft SQL Server RDF stores. In linked data publishing, projects like DBpedia often provide datasets in multiple formats—including N-Triples—to accommodate diverse consumer requirements spanning W3C validators, scholarly data aggregators at Europe PMC, and enterprise knowledge graphs at IBM.
Implementations and Tools
A broad ecosystem supports N-Triples. RDF libraries and toolkits like Apache Jena, RDF4J, Redland, and DotNetRDF provide parsers and writers. Triple stores such as AllegroGraph, Blazegraph, Virtuoso, and Stardog can import and export N-Triples dumps. Conversion and processing utilities include command-line programs in GNU toolchains and scripting environments at Python packages (e.g., projects maintained by contributors from MIT and University of Oxford), Perl modules used in bioinformatics communities like NCBI, and JavaScript libraries applied in web projects at Mozilla and Google. Data publishing platforms such as CKAN, Data.gov, and repositories run by The British Library often ingest N-Triples during harvest and transformation workflows.
Examples
A minimal triple in N-Triples might state that a resource identified by an IRI has a label: <http://example.org/resource1> <http://www.w3.org/2000/01/rdf-schema#label> "Example"@en . Blank nodes are represented with identifiers like _:b0 and datatypes use IRIs such as <http://www.w3.org/2001/XMLSchema#integer> for numeric values, patterns consistent with datasets produced by organizations like Wikidata, DBpedia, and digital archives at National Library of France. Large-scale exports from projects like OpenStreetMap and scholarly corpora at Europeana often provide extensive .nt files where each line is a discrete triple suitable for parallel processing with systems developed at Facebook research labs or cloud infrastructures offered by Amazon.