Kalimba

Kalimba is an clone of ActiveRecord, based on ActiveModel framework. Combined with the raw power of Redlander gem, it introduces the world of Ruby on Rails to the world of RDF, triple storages, LinkedData and Semantic Web. The resources of semantic graph storages become accessible in a customary form of "models".

Installation

Add this line to your application's Gemfile:

gem 'kalimba'

And then execute:

$ bundle

Or install it yourself as:

$ gem install kalimba

Backends

You won't be able to do much without a backend to handle your RDF statements. Please add "kalimba-redlander" gem dependency to your Gemfile, and make sure to "require 'kalimba-redlander'" before invoking "require 'kalimba'".

For now, the backends are developed as a part of Kalimba gem for convenience. However, you are free to develop your own backend as a separate gem.

Kalimba::Persistence::Redlander

Redlander adapter for Kalimba. It provides the RDF storage backend for Kalimba.

Usage

Your model must be inherited from Kalimba::Resource:

class Person < Kalimba::Resource
  # Note that type is *not* inherited,
  # it must be explicitly declared for every subclass.
  # And types better be unique!
  type "http://schema.org/Person"

  # Define base URI for the instances of this resource
  base_uri "http://example.org/people"

  property :name, :predicate => NS::FOAF["name"], :datatype => NS:XMLSchema["string"]

  has_many :friends, :predicate => "http://schema.org/Person", :datatype => :Person
end

From this point on, you may treat your model just like any fully-fledged clone of ActiveModel (i.e. ActiveRecord model)

$ alice = Person.new(:name => "Alice")
$ alice.valid?
$ alice.save!
...
$ alice.friends << bob

Note that Kalimba associations are not fully API-compliant with ActiveRecord associations (yet?). One major feature missing is "association proxy" which would enable tricks like alice.friends.destroy_all. Presently, Kalimba "associations" return a simple collection (Array).

For other details refer to YARD documentation for Kalimba::Resource module.

Regarding RDFS/OWL features

It should be also noted that "special" features of RDFS/OWL like inverse properties or transitive properties and so on, are not specifically handled by Kalimba (or Redlander backend). Availability of any "virtual" data which is supposed to be available as a product of reasoning, is up to the graph storage that you use with the backend.

So (provided that "hasFriend" is "owl:inverseOf" "isFriendOf") you may end with something like this:

alice.has_friend  # => bob
bob.is_friend_of  # => nil

... unless your graph storage provides reasoning by default.

That said, certain graph storages that are said to have reasoning capabilities, do not have reasoning enabled by default (e.g. Virtuoso), and require that you explicitly enable it using special options or a custom SPARQL syntax. While it is possible to "hack" and modify the options or SPARQL queries that are generated by Kalimba (or its backend), this is not currently available.

Validations

For details, refer to ActionModel::Validations documentation.

class Human < Kalimba::Resource
  base_uri "http://example.com/people/"
  property :name, :predicate => NS::FOAF["name"], :datatype => NS:XMLSchema["string"]

  validates_presence_of :name
end

$ bob = Human.create  # => bob will have an error on :name

Callbacks

Kalimba supports :before, :after and :around callbacks for :save, :create, :update and :destroy actions.

class Human < Kalimba::Resource
  base_uri "http://example.com/people/"

  before_save :shout

  private

  def shout
    puts "Hey!"
  end
end

For details, refer to ActionModel::Callbacks documentation.

Contributing

Fork it
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Added some feature')
Push to the branch (git push origin my-new-feature)
Create new Pull Request