--- title: What's New in RDF.rb 0.3.0 date: '2010-12-30T13:00:00Z' categories: - Technology tags: - RDF - Ruby - RDF.rb - linked data - semantic web - SPARQL projects: - rdf.rb summary: RDF.rb 0.3.0 adds transactions, basic graph pattern queries, and fast parsers and serializers for RDFa, Notation3, Turtle, and RDF/XML. original: url: http://blog.datagraph.org/2010/12/rdf-for-ruby archive: https://web.archive.org/web/20161228105332/http://blog.datagraph.org/2010/12/rdf-for-ruby --- It has now been nine months since the [initial public release](/2010/03/rdf-for-ruby) of [RDF.rb](https://web.archive.org/web/20101230/http://rdf.rubyforge.org/), our [RDF](https://web.archive.org/web/20101230/http://www.w3.org/RDF/) library for [Ruby](https://web.archive.org/web/20101230/http://www.ruby-lang.org/), and today we're happy to announce the release of RDF.rb 0.3.0, a significant milestone. As the [changelog](https://web.archive.org/web/20101230/https://github.com/bendiken/rdf/compare/0.2.3...0.3.0) attests, this has been a long release cycle that incorporates 170 commits by 6 different authors. The major new features include transactions and basic graph pattern (BGP) queries, as well as the availability of robust and fast parser/serializer plugins for the RDFa, Notation3, Turtle, and RDF/XML formats, complementing other already previously supported formats. In addition, many bugs have been fixed and general improvements, including significant performance improvements, implemented. RDF.rb 0.3.0 is immediately available via [RubyGems](https://web.archive.org/web/20101230/http://rubygems.org/), and can be installed or upgraded to as follows on any Unix box with Ruby and RubyGems: ```console $ [sudo] gem install rdf ``` In all the code examples that follow below, we will assume that RDF.rb and the built-in N-Triples parser have already been loaded up like so: ```ruby require 'rdf' require 'rdf/ntriples' # Enable facile references to standard vocabularies: include RDF ``` ## RDFa, N3, Turtle, and RDF/XML Support While RDF.rb 0.3.0 continues with our [minimalist policy](/2010/03/rdf-for-ruby) of only supporting the [N-Triples](/2010/03/grepping-ntriples) serialization format in the core library itself, support for every widely-used RDF serialization format is now available in the form of plugins. Thanks to the hard work of [Gregg Kellogg](https://web.archive.org/web/20101230/http://twitter.com/gkellogg), the author of [RdfContext](https://web.archive.org/web/20101230/https://github.com/gkellogg/rdf_context), there are now RDF.rb 0.3.0-compatible plugins available for the RDFa, Notation3, Turtle, and RDF/XML formats, complementing the already previously-available plugins for the RDF/JSON and TriX formats. See [Gregg's blog post](https://web.archive.org/web/20101230/http://www.kellogg-assoc.com/2010/12/27/rdf-rdfa-0-3-0) for more details on the particulars of these plugins. We are also pleased to announce that Gregg has joined the RDF.rb core development team, which now consists of him, [Ben Lavender](https://web.archive.org/web/20101230/http://twitter.com/bhuga), and myself. This merger between the RDF.rb and RdfContext efforts is a perfect match, given that Ben and I have been focused more on storing and querying RDF data while Gregg has been busy single-handedly solving all RDF serialization questions. To facilitate typical [Linked Data](https://web.archive.org/web/20101230/http://linkeddata.org/) use cases, we now also provide a metadistribution of RDF.rb that includes a full set of parsing/serialization plugins; the following will install all of the `rdf`, `rdf-isomorphic`, `rdf-json`, `rdf-n3`, `rdf-rdfa`, `rdf-rdfxml`, and `rdf-trix` gems in one go: ```console $ [sudo] gem install linkeddata ``` Similarly, instead of loading up support for each RDF serialization format one at a time, you can simply use the following to load them all; this is helpful e.g. for the automatic selection of an appropriate parser plugin given a particular file name or extension: ```ruby require 'linkeddata' ``` For a tutorial introduction to RDF.rb's [reader](https://web.archive.org/web/20101230/http://rdf.rubyforge.org/RDF/Reader.html) and [writer](https://web.archive.org/web/20101230/http://rdf.rubyforge.org/RDF/Writer.html) APIs, please refer to my previous blog post [Parsing and Serializing RDF Data with Ruby](/2010/04/parsing-rdf-with-ruby). ## Query API: Basic Graph Patterns (BGPs) The [query API](https://web.archive.org/web/20101230/http://rdf.rubyforge.org/RDF/Query.html) in RDF.rb 0.3.0 now includes [basic graph pattern](https://web.archive.org/web/20101230/http://www.w3.org/TR/rdf-sparql-query/#basicpatterns) (BGP) support, which has been a much-requested feature. BGP queries will already be a familiar concept to anyone using [SPARQL](https://web.archive.org/web/20101230/http://en.wikipedia.org/wiki/SPARQL), and in RDF.rb they are constructed and executed like this: ```ruby # Load some RDF.rb project information into an in-memory graph: graph = RDF::Graph.load("http://rdf.rubyforge.org/doap.nt") # Construct a BGP query for obtaining developers' names and e-mails: query = RDF::Query.new({ :person => { RDF.type => FOAF.Person, FOAF.name => :name, FOAF.mbox => :email, } }) # Execute the query on our in-memory graph, printing out solutions: query.execute(graph).each do |solution| puts "name=#{solution.name} email=#{solution.email}" end ``` Executing a BGP query returns a solution sequence, encapsulated as an instance of the [`RDF::Query::Solutions`](https://web.archive.org/web/20101230/http://rdf.rubyforge.org/RDF/Query/Solutions.html) class. Solution sequences provide a number of convenient methods for further narrowing down the returned solutions to what you're actually looking for: ```ruby # Filter solutions using a hash: solutions.filter(:author => RDF::URI("http://ar.to/#self")) solutions.filter(:author => "Arto Bendiken") solutions.filter(:updated => RDF::Literal(Date.today)) # Filter solutions using a block: solutions.filter { |solution| solution.author.literal? } solutions.filter { |solution| solution.title =~ /^SPARQL/ } solutions.filter { |solution| solution.price < 30.5 } solutions.filter { |solution| solution.bound?(:date) } solutions.filter { |solution| solution.age.datatype == XSD.integer } solutions.filter { |solution| solution.name.language == :es } # Reorder solutions based on a variable: solutions.order_by(:updated) solutions.order_by(:updated, :created) # Select particular variables only: solutions.select(:title) solutions.select(:title, :description) # Eliminate duplicate solutions: solutions.distinct # Limit the number of solutions: solutions.offset(20).limit(10) # Count the number of matching solutions: solutions.count solutions.count { |solution| solution.price < 30.5 } ``` BGP-capable storage adapters should override and implement the following [`RDF::Queryable`](https://web.archive.org/web/20101230/http://rdf.rubyforge.org/RDF/Queryable.html) method in order to provide storage-specific optimizations for BGP query evaluation: ```ruby class MyRepository < RDF::Repository def query_execute(query, &block) # ... end end ``` ## Repository API: Transactions The [repository API](https://web.archive.org/web/20101230/http://rdf.rubyforge.org/RDF/Repository.html) in RDF.rb 0.3.0 now includes basic transaction support: ```ruby # Load some RDF.rb project information into an in-memory repository: repository = RDF::Repository.load("http://rdf.rubyforge.org/doap.nt") # Delete one statement and insert another, atomically: repository.transaction do |tx| subject = RDF::URI('http://rubygems.org/gems/rdf') tx.delete [subject, DOAP.name, nil] tx.insert [subject, DOAP.name, "RDF.rb 0.3.0"] end ``` As you would expect, if the transaction block raises an exception, the current transaction will be aborted and rolled back; otherwise, the transaction is automatically committed when the block returns. Transaction-capable storage adapters should override and implement the following three [`RDF::Repository`](https://web.archive.org/web/20101230/http://rdf.rubyforge.org/RDF/Repository.html) methods: ```ruby class MyRepository < RDF::Repository def begin_transaction(context) # ... end def rollback_transaction(tx) # ... end def commit_transaction(tx) # ... end end ``` The [`RDF::Transaction`](https://web.archive.org/web/20101230/http://rdf.rubyforge.org/RDF/Transaction.html) objects passed to these methods consist of a sequence of RDF statements to delete from, and a sequence of RDF statements to insert into, a given graph. The default transaction implementation in `RDF::Repository` simply builds up a transaction object in memory, buffering all inserts/deletes until the transaction is committed, at which point the operations are then executed against the repository. Note that whether transactions are *actually* executed atomically depends on the particulars of the storage adapter you're using. For instance, the [`RDF::DataObjects`](https://web.archive.org/web/20101230/http://rdf.rubyforge.org/do/) plugin, which provides a storage adapter supporting SQLite, PostgreSQL, MySQL, and other RDBMS solutions, will certainly be able to offer ACID transaction support (albeit it has not been updated for that, or other 0.3.x features, just yet.) On the other hand, not e.g. all [NoSQL](/2010/04/rdf-nosql-diff) solutions support transactions, so storage adapters for such solutions may choose to omit explicit transaction support and have it supplied by RDF.rb's default implementation. ## Performance & Scalability Improvements In earlier RDF.rb releases, our focus was strongly centered on defining the core APIs that have enabled the thriving [plugin ecosystem](https://web.archive.org/web/20101230/http://rubygems.org/search?query=rdf-) we can witness today. The focus was not so much, therefore, on the performance of the bundled default implementations of those APIs; in some cases, these implementations could have been described as being of only proof-of-concept quality. In particular, the in-memory graph and repository implementations were suboptimal in RDF.rb 0.1.x, and only somewhat improved in 0.2.x. However, reflecting the increasing production-readiness of RDF.rb in general, matters have been much improved in RDF.rb 0.3.0. Of course, performance improvements are an open-ended task, and I'm sure we'll see more work on this front in the future as need arises and time permits. But it's likely that RDF.rb 0.3.0 now offers a *sufficient* out-of-the-box performance level for many if not most common use cases. Scalability has also been addressed by making use of [enumerators](https://web.archive.org/web/20101230/http://ruby-doc.org/core-1.9/classes/Enumerator.html) throughout the APIs defined by RDF.rb. That means that all operations are generally performed in a *streaming* fashion, enabling you to build pipelines for hundreds of millions of RDF statements to flow through while still maintaining constant memory usage by ensuring that the statements are processed one by one. ## RSpec 2.x Compatibility Lastly, RDF.rb 0.3.0 has been upgraded to use and depend on [RSpec](https://web.archive.org/web/20101230/http://relishapp.com/rspec) 2.x instead of the previous 1.3.x branch. This requires minor changes to the `spec/spec_helper.rb` file in any project that relies on the [`RDF::Spec`](https://web.archive.org/web/20101230/http://rdf.rubyforge.org/spec/) library. The most minimal `spec_helper.rb` contents are now as follows: ```ruby require 'rdf/spec' RSpec.configure do |config| config.include RDF::Spec::Matchers end ``` ## Kudos to Our Contributors In tandem with the soon [10,000 downloads](https://web.archive.org/web/20101230/http://rubygems.org/gems/rdf) of RDF.rb on [RubyGems.org](https://web.archive.org/web/20101230/http://rubygems.org/), a very positive sign of all the interest and ongoing work around RDF.rb is our growing contributor list. We thank everyone who has sent in bug reports, and in particular the following people who have contributed patches to RDF.rb and/or an RDF.rb plugin; in alphabetical order: [Călin Ardelean](https://web.archive.org/web/20101230/http://github.com/clnx), [Christoph Badura](https://web.archive.org/web/20101230/http://github.com/b4d), [John Fieber](https://web.archive.org/web/20101230/http://github.com/jfieber), [Joey Geiger](https://web.archive.org/web/20101230/http://github.com/jgeiger), [James Hetherington](https://web.archive.org/web/20101230/http://github.com/jamespjh), [Gabriel Horner](https://web.archive.org/web/20101230/http://github.com/cldwalker), [Nicholas Humfrey](https://web.archive.org/web/20101230/http://github.com/njh), [Fumihiro Kato](https://web.archive.org/web/20101230/http://github.com/fumi), [David Nielsen](https://web.archive.org/web/20101230/http://github.com/drankard), [Thamaraiselvan Poomalai](https://web.archive.org/web/20101230/http://github.com/selvan), [Keita Urashima](https://web.archive.org/web/20101230/http://github.com/ursm), [Pius Uzamere](https://web.archive.org/web/20101230/http://github.com/pius), and [Hellekin O. Wolf](https://web.archive.org/web/20101230/http://github.com/hellekin). (My apologies if I have inadvertently omitted anyone from the previous, and please let me know about it.) ## Looking Forward to Hearing From You As always, if you have feedback regarding RDF.rb please contact us either [privately](https://web.archive.org/web/20101230/http://github.com/datagraph) or via the [public-rdf-ruby@w3.org](https://web.archive.org/web/20101230/http://lists.w3.org/Archives/Public/public-rdf-ruby/) mailing list. Plain and simple bug reports, however, should more preferably go directly to the [issue queue](https://web.archive.org/web/20101230/http://github.com/bendiken/rdf/issues) on GitHub. Be sure to follow [@datagraph](https://web.archive.org/web/20101230/http://twitter.com/datagraph), [@bendiken](https://web.archive.org/web/20101230/http://twitter.com/bendiken), [@bhuga](https://web.archive.org/web/20101230/http://twitter.com/bhuga), and [@gkellogg](https://web.archive.org/web/20101230/http://twitter.com/gkellogg) on Twitter for the latest updates on RDF.rb as they happen.