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\section{library(semweb/rdf_ntriples): Process files in the RDF N-Triples format}

\label{sec:rdfntriples}

\begin{tags}
    \tag{See also}
\url{http://www.w3.org/TR/n-triples/}
    \tag{To be done}
Sync with RDF 1.1. specification.
\end{tags}

The \file{library(semweb/rdf_ntriples)} provides a fast reader for the RDF
N-Triples and N-Quads format. N-Triples is a simple format, originally
used to support the W3C RDF test suites. The current format has been
extended and is a subset of the Turtle format (see
\file{library(semweb/turtle)}).

The API of this library is almost identical to \file{library(semweb/turtle)}.
This module provides a plugin into \predref{rdf_load}{2}, making this predicate
support the format \const{ntriples} and \const{nquads}.\vspace{0.7cm}

\begin{description}
    \predicate[det]{read_ntriple}{2}{+Stream, -Triple}
Read the next triple from \arg{Stream} as \arg{Triple}. \arg{Stream} must have UTF-8
encoding.

\begin{arguments}
\arg{Triple} & is a term \verb$triple(Subject,Predicate,Object)$.
Arguments follow the normal conventions of the RDF
libraries. NodeID elements are mapped to \verb$node(Id)$.
If end-of-file is reached, \arg{Triple} is unified with
\verb$end_of_file$. \\
\end{arguments}

\begin{tags}
    \tag{Errors}
\verb$syntax_error(Message)$ on syntax errors
\end{tags}

    \predicate[det]{read_nquad}{2}{+Stream, -Quad}
Read the next quad from \arg{Stream} as \arg{Quad}. \arg{Stream} must have UTF-8
encoding.

\begin{arguments}
\arg{Quad} & is a term \verb$quad(Subject,Predicate,Object,Graph)$.
Arguments follow the normal conventions of the RDF
libraries. NodeID elements are mapped to \verb$node(Id)$.
If end-of-file is reached, \arg{Quad} is unified with
\verb$end_of_file$. \\
\end{arguments}

\begin{tags}
    \tag{Errors}
\verb$syntax_error(Message)$ on syntax errors
\end{tags}

    \predicate[det]{read_ntuple}{2}{+Stream, -Tuple}
Read the next triple or quad from \arg{Stream} as \arg{Tuple}. \arg{Tuple} is one
of the terms below. See \predref{read_ntriple}{2} and \predref{read_nquad}{2} for
details.

\begin{shortlist}
    \item \verb$triple(Subject,Predicate,Object)$
    \item \verb$quad(Subject,Predicate,Object,Graph)$.
\end{shortlist}

    \predicate[det]{rdf_read_ntriples}{3}{+Input, -Triples, +Options}
\nodescription
    \predicate[det]{rdf_read_nquads}{3}{+Input, -Quads, +Options}
True when \arg{Triples}/\arg{Quads} is a list of triples/quads from \arg{Input}.
\arg{Options}:

\begin{description}
    \termitem{anon_prefix}{+AtomOrNode}
Prefix nodeIDs with this atom. If \arg{AtomOrNode} is the term
\verb$node(_)$, bnodes are returned as \verb$node(Id)$.
    \termitem{base_uri}{+Atom}
Defines the default anon_prefix as _\Smapselect{}baseuri$>$_
    \termitem{on_error}{Action}
One of \const{warning} (default) or \const{error}
    \termitem{error_count}{-Count}
If \verb$on_error$ is \const{warning}, unify \arg{Count} with th number of
errors.
    \termitem{graph}{+Graph}
For \predref{rdf_read_nquads}{3}, this defines the graph associated
to \textit{triples} loaded from the input. For \predref{rdf_read_ntriples}{3}
this opion is ignored.
\end{description}

\begin{arguments}
\arg{Triples} & is a list of \verb$rdf(Subject, Predicate, Object)$ \\
\arg{Quads} & is a list of \verb$rdf(Subject, Predicate, Object, Graph)$ \\
\end{arguments}

    \predicate{rdf_process_ntriples}{3}{+Input, :CallBack, +Options}
Call-back interface, compatible with the other triple readers.
In addition to the options from \predref{rdf_read_ntriples}{3}, this
processes the option \verb$graph(Graph)$.

\begin{arguments}
\arg{CallBack} & is called as \verb$call(CallBack, Triples, Graph)$,
where Triples is a list holding a single \verb$rdf(S,P,O)$
triple. Graph is passed from the \const{graph} option and
unbound if this option is omitted. \\
\end{arguments}

\qpredicate[semidet,multifile]{rdf_db}{rdf_load_stream}{3}{+Format, +Stream, :Options}Plugin rule that supports loading the \const{ntriples} and \const{nquads}
formats.

\qpredicate[multifile]{rdf_db}{rdf_file_type}{2}{+Extension, -Format}Bind the ntriples reader to files with the extensions \const{nt},
\const{ntriples} and \const{nquads}.
\end{description}