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https://github.com/Swirrl/tripod

ActiveModel-style Ruby ORM for RDF Linked Data. Works with SPARQL 1.1 HTTP endpoints.
https://github.com/Swirrl/tripod

activemodel linkeddata orm rails rdf ruby

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ActiveModel-style Ruby ORM for RDF Linked Data. Works with SPARQL 1.1 HTTP endpoints.

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# Tripod



ActiveModel-style Ruby ORM for RDF Linked Data. Works with SPARQL 1.1 HTTP endpoints.



* [ActiveModel](https://github.com/rails/rails/tree/master/activemodel)-compliant interface.

* Inspired by [Durran Jordan's](https://github.com/durran) [Mongoid](http://mongoid.org/en/mongoid/) ORM for [MongoDB](http://www.mongodb.org/), and [Ben Lavender's](https://github.com/bhuga) RDF ORM, [Spira](https://github.com/ruby-rdf/spira).

* Uses [Ruby-RDF](https://github.com/ruby-rdf/rdf) to manage the data internally.



## Quick start, for using in a rails app.



1. Add it to your Gemfile and bundle



        gem tripod



        $ bundle



2. Configure it (in application.rb, or development.rb/production.rb/test.rb)



        # (values shown are the defaults)

        Tripod.configure do |config|

          config.update_endpoint = 'http://127.0.0.1:3030/tripod/update'

          config.query_endpoint = 'http://127.0.0.1:3030/tripod/sparql'

          config.timeout_seconds = 30

        end



3. Include it in your model classes.



        class Person

          include Tripod::Resource



          # these are the default rdf-type and graph for resources of this class

          rdf_type 'http://example.com/person'

          graph_uri 'http://example.com/people'



          field :name, 'http://example.com/name'

          field :knows, 'http://example.com/knows', :multivalued => true, :is_uri => true

          field :aliases, 'http://example.com/alias', :multivalued => true

          field :age, 'http://example.com/age', :datatype => RDF::XSD.integer

          field :important_dates, 'http://example.com/importantdates', :datatype => RDF::XSD.date, :multivalued => true

        end



        # Note: Active Model validations are supported



4. Use it



        uri = 'http://example.com/ric'

        p = Person.new(uri)

        p.name = 'Ric'

        p.age = 31

        p.aliases = ['Rich', 'Richard']

        p.important_dates = [Date.new(2011,1,1)]

        p.save!



        people = Person.all.resources #=> returns all people as an array



        ric = Person.find('http://example.com/ric') #=> returns a single Person object.



## Note:



Tripod doesn't supply a database. You need to install one. I recommend [Fuseki](http://jena.apache.org/documentation/serving_data/index.html), which runs on port 3030 by default.



## Some Other interesting features



## Eager Loading



        asa = Person.find('http://example.com/asa')

        ric = Person.find('http://example.com/ric')

        ric.knows = asa.uri



        ric.eager_load_predicate_triples! #does a big DESCRIBE statement behind the scenes

        knows = ric.get_related_resource('http://example.com/knows', Resource)

        knows.label # this won't cause another database lookup



        ric.eager_load_object_triples! #does a big DESCRIBE statement behind the scenes

        asa = ric.get_related_resource('http://example.com/asa', Person) # returns a fully hydrated Person object for asa, without an extra lookup



## Defining a graph at instantiation-time



        class Resource

          include Tripod::Resource

          field :label, RDF::RDFS.label



          # notice also that you don't need to supply an rdf type or graph here!

        end



        r = Resource.new('http://example.com/foo', 'http://example.com/mygraph')

        r.label = "example"

        r.save



        # Note: Tripod assumes you want to store all resources in named graphs.

        # So if you don't supply a graph at any point (i.e. class or instance level),

        # you will get an error when you try to persist the resource.



## Reading and writing arbitrary predicates



        r.write_predicate(RDF.type, 'http://example.com/myresource/type')

        r.read_predicate(RDF.type) #=> [RDF::URI.new("http://example.com/myresource/type")]



## Finders and criteria



        # A Tripod::Criteria object defines a set of constraints for a SPARQL query.

        # It doesn't actually do anything against the DB until you run resources, first, or count on it.

        # (from Tripod::CriteriaExecution)



        Person.all #=> returns a Tripod::Criteria object which selects all resources of rdf_type http://example.com/person, in the http://example.com/people graph



        Resource.all #=> returns a criteria object to return resources in the database (as no rdf_type or graph_uri specified at class level)



        Person.all.resources #=> returns all the actual resources for the criteria object, as an array-like object



        Person.all.resources(:return_graph => false) #=> returns the actual resources, but without returning the graph_uri in the select (helps avoid pagination issues). Note: doesn't set the graph uri on the instantiated resources.



        Person.first #=> returns the first person (by crafting a sparql query under the covers that only returns 1 result)



        Person.first(:return_graph => false) # as with resources, doesn't return / set the graph_uri.



        Person.count  #=> returns the count of all people (by crafting a count query under the covers that only returns a count)



        # note that you need to use ?uri as the variable for the subject.

        Person.where("?uri  'Joe'") #=> returns a Tripod::Criteria object



        Resource.graph("http://example.com/mygraph") #=> Retruns a criteria object with a graph restriction (note: if graph_uri set on the class, it will default to using this)



        Resource.find_by_sparql('SELECT ?uri ?graph WHERE { GRAPH ?graph { ?uri ?p ?o } }') #=> allows arbitrary sparql. Again, use ?uri for the variable of the subjects (and ?graph for the graph).



## Chainable criteria



        Person.all.where("?uri  'Ric'").where("?uri  ).first



        Person.where("?uri  ?name").limit(1).offset(0).order("DESC(?name)")



## Running tests



With a Fuseki instance ready and up, edit the config in `spec/spec_helper.rb` to reflect your settings. Make sure you `bundle` to pull in all dependencies before trying to run the tests.



Some tests require memcached to be set up and running. The tests that require memcached are tagged with `:caching_tests => true`; do with this information what you will. 



[Full Documentation](http://rubydoc.info/gems/tripod/frames)



Copyright (c) 2012 [Swirrl IT Limited](http://swirrl.com). Released under MIT License