NAME
RDF::LinkedData::RWHypermedia - Experimental read-write hypermedia support
for Linked Data
SYNOPSIS
This module extends RDF::LinkedData, and you would most likely not call
this module directly, but rather configure it using the tools that
RDF::LinkedData provides.
DESCRIPTION
This module is an experiment to manipulate Linked Data using human and
machine readable hypermedia descriptions. The intention is to have
messages that are intuitive to newcomers, so that they can get going using
it without much training. For now, it has very basic, prototypical
functionality, but it represents an implementation of an idea that the
author thinks is worth discussing.
To use it, please see the README of RDF::LinkedData. To that
configuration, add the two options
"class" : "RDF::LinkedData::RWHypermedia",
"writes_enabled" : 1,
Also, hypermedia is on by default, ensure that it isn't turned off.
Then, start the server as you would with Plack::App::RDF::LinkedData.
Behaviour
In addition to the behaviour documented in Plack::App::RDF::LinkedData,
this module will add a predicate to any data about a certain resource that
tells the user it can check a certain URI to see if it may edit the
resource description. If the user goes there, they will be challenged to
authenticate, and if authorized (currently, an authenticated user has all
privileges), they will be shown how to edit the resource description.
Extending the examples of Plack::App::RDF::LinkedData,
`http://host.name/rdf/example/data` points to
`http://host.name/rdf/example/controls`, which when authorized, shows the
users triples like
<http://host.name/rdf/example/data> hm:canBe hm:replaced .
thus encouraging the user to replace the data with a new resource
description. The idea is further that `hm:replaced` can be defined with
protocol-specific semantics, for example that in HTTP, it means that the
user may PUT data in an RDF format to the URL.
TODO
The idea is also that this approach should be extended to support
different identity (WebID is an obvious candidate) and authorization
regimes (I started implementing the W3C access control lists ontology, but
found it more urgent to get the hypermedia ideas coded). Eventually, I
think this approach should reach parity with the Linked Data Platform, but
without an out-of-band specification.
METHODS AND ATTRIBUTES
`response`
This module wraps RDF::LinkedDatas `response` method, taking control
of write methods and data to be added to the response for controls and
data. The latter is achieved by also wrapping the private `_content`
method.
`user`
Can be read or set to the username of the logged in user.
`is_logged_in`
Indicates whether a user is logged in.
`log_out`
Log out user.
`add_rw_pointer ($hypermedia_model, $uri)`
A method that will add a triple to the data page for the given URI to
the model building the hypermedia of the response.
`credentials_ok`, `unauthorized`, `authenticator`, `credentials`
Methods that deals with authentication and authorization. This part is
really not stable, just for demo purposes at present. The last is
currently a hashref so that a configured username and password can be
passed to the authenticator.
FEEDBACK
Since this is a prototype, I hope this will spark discussion. There are
some discussion items inline in the code. They include how and what data
should be merged to a given URL, what the responses should look like.
Apart from comments to my email, the IRC channels
<irc://irc.perl.org/#perlrdf> and <irc://irc.freenode.net/#swig> are good
forums for discussing this topic.
I will be blogging about this work at
<http://kjetil.kjernsmo.net/category/technology/hypermedia/>.
Bugs
Please report any bugs to
<https://github.com/kjetilk/p5-rdf-linkeddata-rwhypermedia/issues>.
Author
Kjetil Kjernsmo <kjetilk@cpan.org>.
COPYRIGHT AND LICENCE
This software is copyright (c) 2017, 2018 by Kjetil Kjernsmo.
This is free software; you can redistribute it and/or modify it under the
same terms as the Perl 5 programming language system itself.
DISCLAIMER OF WARRANTIES
THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.