NAME
    RDF::ACL - access control lists for the semantic web

SYNOPSIS
      use RDF::ACL;
  
      my $acl  = RDF::ACL->new('access.ttl');
      my $auth = $acl->allow(
        webid => 'http://example.com/joe#me',
        item  => 'http://example.com/private/document',
        level => ['Read', 'Write'],
        );
      $acl->save('turtle', 'access.ttl');
  
      # later...
  
      if ($acl->check('http://example.com/joe#me',
                      'http://example.com/private/document',
                      'Read'))
      {
        print slurp("private/document");
      }
      else
      {
        print "Denied";
      }
  
      # later...
  
      foreach my $reason ($acl->why('http://example.com/joe#me',
                                    'http://example.com/private/document',
                                    'Read'))
      {
        $acl->deny($reason) if defined $reason;
      }
      $acl->save('turtle', 'access.ttl');

VERSION
    0.100

DESCRIPTION
    Note that this module provides access control and does not perform
    authentication!

  Constructors
    "$acl->new($input, %args)"
        Creates a new access control list based on RDF data defined in
        $input. $input can be a serialised string of RDF, a file name, a URI
        or any other input accepted by the rdf_parse function (see
        RDF::Trine::Shortcuts).

        "new()" can be called with no arguments to create a fresh, clean ACL
        containing no authorisations.

    "$acl->new_remote($endpoint)"
        Creates a new access control list based on RDF data accessed via a
        remote SPARQL Protocol 1.0 endpoint.

  Public Methods
    "$acl->check($webid, $item, $level, @data)"
        Checks an agent's authorisation to access an item.

        $webid is the WebID (URI) of the agent requesting access to the
        item.

        $item is the URL (URI) of the item being accessed.

        $level is a URI identifying the type of access required. As special
        cases, the case-insensitive string 'read' is expanded to the URI
        <http://www.w3.org/ns/auth/acl#Read>, 'write' to
        <http://www.w3.org/ns/auth/acl#Write>, 'append' to
        <http://www.w3.org/ns/auth/acl#Append> and 'control' to
        <http://www.w3.org/ns/auth/acl#Control>.

        If the access control list is local (not remote), zero or more
        additional RDF graphs can be passed (i.e. @data) containing data to
        take into consideration when checking the agent's authorisation.
        This data is trusted blindly, so should not include data that the
        user has themselves supplied. If the access control list is remote,
        then this method throws an error if any additional data is provided.
        (A remote ACL cannot take into account local data.)

        If $level is provided, this method returns a boolean.

        If $level is undefined or omitted, this method returns a list of
        URIs which each represent a type of access that the user is
        authorised.

    "$acl->why($webid, $item, $level, @data)"
        Investigates an agent's authorisation to access an item.

        Arguments as per "check", however $level is required.

        Returns a list of authorisations that justify a user's access to the
        item with the given access level. These authorisations are
        equivalent to $authid values provided by "allow()".

        In some cases (especially if the authorisation was created by hand,
        and not via "allow()") an authorisation may not have an identifier.
        In these cases, the list will contain undef.

    "$acl->allow(%args)"
        Adds an authorisation to the ACL. The ACL must be mutable.

        The method takes a hash of named arguments:

          my $authid = $acl->allow(
            webid => 'http://example.com/joe#me',
            item  => 'http://example.com/private/document',
            level => ['Read', 'Write'],
            );

        'item' is the URI of the item to authorise access to. As an
        alternative, 'item_class' may be used to authorise access to an
        entire class of items (using classes in the RDFS/OWL sense of the
        word). If neither of these arguments is provided, then the method
        will throw an error. Both may be provided. Either or both may be an
        arrayref, because an authorisation may authorise access to more than
        one thing.

        'container' is an alternative to using 'item' or 'item_class'. It
        specifies the URI for a resource which in some way is a container
        for other resources. Setting authorisations for a container allows
        you to set a default authorisation for new items created within that
        container. (You must use the "created()" method to notify the ACL
        about newly created items.)

        'webid' is the WebID (URI) of the person or agent being granted
        access. As an alternative, 'agent_class' may be used to authorise
        access to an entire class of agents. If neither is provided, an
        agent_class of <http://xmlns.com/foaf/0.1/Agent> is assumed. Both
        may be provided. Either or both may be an arrayref, because an
        authorisation may authorise access by more than one agent. (For
        consistency with 'item', 'agent' is supported as a synonym for
        'webid'.)

        'level' is the access level being granted. As with the "check"
        method, the shortcuts 'read', 'write' and 'control' may be used. An
        arrayref may be used. If no level is specified, 'read' is assumed.

        This authorisation is not automatically saved, so it is probably
        useful to call "save()" after adding authorisations.

        The method returns an identifier for the authorisation. This
        identifier may be needed again if you ever need to "deny()" the
        authorisation.

        This method is aware of "i_am()"/"who_am_i()".

    "$acl->deny($authid)"
        Completely removes all traces of an authorisation from the ACL.

        The authorisation identifier can be found using "why()" or you may
        have remembered it when you first allowed the access. In some cases
        (especially if the authorisation was created by hand, and not via
        "allow()") an authorisation may not have an identifier. In these
        cases, you will have to be creative in figuring out how to deny
        access.

        Returns the number of statements removed from the ACL's internal
        model as a result of the removal. (This will normally be at least
        3.)

        This authorisation is not automatically saved, so it is probably
        useful to call "save()" after removing authorisations.

        This method is aware of "i_am()"/"who_am_i()".

    "$acl->created($item, $container)"
        Finds all authorisations which are the default for new items within
        $container and clones each of them for newly created $item.

        Returns a list of authorisation identifiers.

    "$acl->i_am($webid)"
        Tells the ACL object to "act like" the agent with the given WebID.

        If the ACL object is acting like you, then methods that make changes
        to the ACL (e.g. "allow()" and "deny()") will only work if you have
        'Control' permission over the resources specified.

        $webid can be null to restore the usual behaviour.

        Returns the previous WebID the ACL was acting like as a URI object.

    "$acl->who_am_i"
        Returns the WebID of the agent that ACL is acting like (if any).

    "$acl->save($format, $filename)"
        Serialises a local (not remote) ACL.

        $format can be any format supported by rdf_string (see
        RDF::Trine::Shortcuts).

        If $filename is provided, this method writes to the file and returns
        the new file size in bytes.

        If $filename is omitted, this method does not attempt to write to a
        file, and simply returns the string it would have written.

    "$acl->is_remote"
        Returns true if the ACL is remote; false if local.

    "$acl->is_mutable"
        Can this ACL be modified?

    "$acl->model"
        The graph model against which authorisation checks are made.

        Returned as an RDF::Trine::Model object.

    "$acl->endpoint"
        The endpoint URI for remote (non-local) ACL queries.

        Returned as a URI object.

BUGS
    Please report any bugs to <http://rt.cpan.org/>.

SEE ALSO
    CGI::Auth::FOAF_SSL.

    <http://www.w3.org/ns/auth/acl.n3>.

    <http://www.perlrdf.org/>,
    <http://lists.foaf-project.org/mailman/listinfo/foaf-protocols>.

AUTHOR
    Toby Inkster <tobyink@cpan.org>.

COPYRIGHT
    Copyright 2010 Toby Inkster

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

