NAME

Plack::App::RDF::Files - Serve RDF data from static files

VERSION

version 0.01

DESCRIPTION

This Plack application serves RDF from static files. In short, each RDF resource to be served corresponds to a directory in the file system, located in a common based directory base_dir. All RDF resources must share a common base URI, which is either taken from the PSGI request or configured with base_uri.

EXAMPLE

Let's assume you have a base directory /var/rdf/ with some subdirectories foo, bar, and doz. Given a base URI, such as <http://example.org/>, an instance of Plack::App::RDF::Files will serve RDF data for the following URIs:

http://example.org/
http://example.org/foo
http://example.org/bar
http://example.org/doz

The actual RDF data is collected and combined from RDF files (*.nt, *.ttl, *.rdfxml...) in each directory. There is no need to set up a triple store, just create and modify directories and RDF files.

METHODS

negotiate( $env )

This internal methods selects an RDF serializer based on the PSGI environment variable negotiate.format (see Plack::Middleware::Negotiate) or the negotiate method of RDF::Trine::Serializer. Returns first a RDF::Trine::Serializer on success or undef on error) and second a (possibly empty) list of HTTP response headers.

CONFIGURATION

base_dir

Mandatory base directory that all resource directories are located in.

base_uri

The base URI of all resources.

path_map

Optional code reference that maps a local part of an URI to a relative directory. Set to the identity mapping by default.

file_types

An array of RDF file types (extensions) to look for. Set to ['rdfxml','nt','ttl'] by default.

include_index

By default a HTTP 404 error is returned if one tries to access the base directory. Enable this option to also serve RDF data from this location.

index_property

RDF property to use for listing all resources connected to the base URI (if <include_index> is enabled). Set to rdfs:seeAlso by default. Can be disabled by setting a false value.

namespaces

Optional namespaces for serialization, passed to RDF::Trine::Serializer.

PSGI environment variables

The following PSGI environment variables are relevant:

rdf.uri

The requested URI

rdf.iterator

The RDF::Trine::Iterator that will be used for serializing, if psgi.streaming is set. One can use this variable to catch the RDF data in another post-processing middleware.

rdf.files

An hash of source filenames, each with the number of triples (on success) as property size, an error message as error if parsing failed, and the timestamp of last modification as mtime. size and error may not be given before parsing, if rdf.iterator is set.

rdf.files.mtime

Maximum value of all last modification times (this may be removed!).

LIMITATIONS

This module is an early developer release. Be warned!

All resource URIs to be served must have a common URI prefix (such as http://example.org/ above) and a local part that may be restricted to a limited set of characters. For instance the character sequence ../ is not allowed.

NOTES

If an existing resource does not contain triples, the axiomatic triple ?uri rdf:type rdfs:Resource is returned.

To update the files, add a middleware that catches 404 and 202 responses.

TODO

VoID descriptions could be added, possibly with RDF::Generator::Void.

SEE ALSO

Use Plack::Middleware::Negotiate to add content negotiation based on an URL parameter and/or suffix.

See RDF::LinkedData for a different module to serve RDF as linked data. See also RDF::Flow and RDF::Lazy for processing RDF data.

See http://foafpress.org/ for a similar approach in PHP.

AUTHOR

Jakob Voß <voss@gbv.de>

COPYRIGHT AND LICENSE

This software is copyright (c) 2013 by Jakob Voß.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

cpanm Plack::App::RDF::Files

perl -MCPAN -e shell
install Plack::App::RDF::Files