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https://github.com/ruby-rdf/rdf-turtle

Turtle reader/writer for Ruby
https://github.com/ruby-rdf/rdf-turtle

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Turtle reader/writer for Ruby

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# RDF::Turtle reader/writer



[Turtle][] reader/writer for [RDF.rb][RDF.rb] .



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## Description

This is a [Ruby][] implementation of a [Turtle][] parser for [RDF.rb][].



## Features

RDF::Turtle parses [Turtle][Turtle] and [N-Triples][N-Triples] into statements or triples. It also serializes to Turtle.



Install with `gem install rdf-turtle`



* 100% free and unencumbered [public domain](https://unlicense.org/) software.

* Implements a complete parser for [Turtle][].

* Compatible with Ruby >= 3.0.

* Optional streaming writer, to serialize large graphs

* Provisional support for [RDF 1.2][].



## Usage

Instantiate a reader from a local file:



    graph = RDF::Graph.load("etc/doap.ttl", format:  :ttl)



Define `@base` and `@prefix` definitions, and use for serialization using `:base_uri` an `:prefixes` options.



Canonicalize and validate using `:canonicalize` and `:validate` options.



Write a graph to a file:



    RDF::Turtle::Writer.open("etc/test.ttl") do |writer|

       writer << graph

    end



## RDF 1.2



Both reader and writer include provisional support for [RDF 1.2][] triple terms.



Both reader and writer include provisional support for [RDF 1.2][] directional language-tagged strings, which are literals of type `rdf:dirLangString` having both a `language` and `direction`.



Internally, an `RDF::Statement` is treated as another resource, along with `RDF::URI` and `RDF::Node`, which allows an `RDF::Statement` to have a `#subject` or `#object` which is also an `RDF::Statement`.



**Note: This feature is subject to change or elimination as the standards process progresses.**



### Serializing a Graph containing reified triples



    require 'rdf/turtle'

    triple = RDF::Statement(RDF::URI('bob'), RDF::Vocab::FOAF.age, RDF::Literal(23))

    graph = RDF::Graph.new << [RDF::URI('r'), RDF::URI("ex:certainty"), RDF::Literal(0.9)]

    graph << RDF::Statement(RDF::URI('r'), RDF.reifies, triple)

    graph.dump(:ttl, validate: false, standard_prefixes: true)

    # => '<< foaf:age 23>>  9.0e-1 .'



### Reading a Graph containing reified triples



By default, the Turtle reader will reject a document containing a subject resource.



    ttl = %(

      @prefix foaf:  .

      @prefix ex:  .

      << foaf:age 23>> ex:certainty 9.0e-1 .

    )

    graph = RDF::Graph.new do |graph|

      RDF::Turtle::Reader.new(ttl) {|reader| graph << reader}

    end

    # => RDF::ReaderError



Readers support a boolean valued `rdfstar` option; only one statement is asserted, although the reified statement is contained within the graph.



    graph = RDF::Graph.new do |graph|

      RDF::Turtle::Reader.new(ttl, rdfstar: true) {|reader| graph << reader}

    end

    graph.count #=> 2



### Reading a Graph containing statement annotations



Annotations are introduced using the `{| ... |}` syntax, which is treated like a `blankNodePropertyList`,

where the subject is the the triple ending with that annotation.



    ttl = %(

      @prefix foaf:  .

      @prefix ex:  .

       foaf:age 23 {| ex:certainty 9.0e-1 |} .

    )

    graph = RDF::Graph.new do |graph|

      RDF::Turtle::Reader.new(ttl) {|reader| graph << reader}

    end

    # => RDF::Graph.new do |g|

      triple = RDF::Statement.new(RDF::URI('bob'), RDF::FOAF.age, RDF::Literal(23))

      bn = RDF::Node.new('anno)

      g << triple

      g << RDF::Statement.new(bn, RDF.reifies, triple)

      g << RDF::Statement.new(bn, RDF::URI("http://example.com/certainty"), RDF::Literal.new(9.0e-1))

    end



Annotations can also have a reifier identifier



    ttl = %(

      @prefix foaf:  .

      @prefix ex:  .

       foaf:age 23 ~ ex:anno {| ex:certainty 9.0e-1 |} .

    )



Note that this requires the `rdfstar` option to be set.



## Documentation

Full documentation available on [Rubydoc.info][Turtle doc]



### Principle Classes

* {RDF::Turtle::Format}

* {RDF::Turtle::Reader}

* {RDF::Turtle::Writer}



### Variations from the spec

In some cases, the specification is unclear on certain issues:



* The LC version of the [Turtle][] specification separates rules for `@base` and `@prefix` with closing '.' from the SPARQL-like `BASE` and `PREFIX` without closing '.'. This version implements a more flexible syntax where the `@` and closing `.` are optional and `base/prefix` are matched case independently.

* Additionally, both `a` and `A` match `rdf:type`.



### Freebase-specific Reader

There is a special reader useful for processing [Freebase Dumps][]. To invoke

this, add the `freebase:  true` option to the {RDF::Turtle::Reader.new}, or

use {RDF::Turtle::FreebaseReader} directly. As with {RDF::Turtle::Reader},

prefix definitions may be passed in using the `:prefixes` option to

RDF::Turtle::FreebaseReader} using the standard mechanism defined

for `RDF::Reader`.



The [Freebase Dumps][] have a very normalized form, similar to N-Triples but

with prefixes. They also have a large amount of garbage. This Reader is

optimized for this format and will perform faster error recovery.



An example of reading Freebase dumps:



    require "rdf/turtle"

    fb = "../freebase/freebase-rdf-2013-03-03-00-00.ttl"

    fb_prefixes = {

      ns:  "http://rdf.freebase.com/ns/",

      key:  "http://rdf.freebase.com/key/",

      owl:  "http://www.w3.org/2002/07/owl#>",

      rdfs:  "http://www.w3.org/2000/01/rdf-schema#",

      rdf:  "http://www.w3.org/1999/02/22-rdf-syntax-ns#",

      xsd:  "http://www.w3.org/2001/XMLSchema#"

    }

    RDF::Turtle::Reader.open(fb,

      freebase:  true,

      prefixes:  fb_prefixes) do |r|



      r.each_statement {|stmt| puts stmt.to_ntriples}

    end



## Implementation Notes

This version uses a hand-written parser using the Lexer from the [EBNF][] gem instead of a general [EBNF][] LL(1) parser for faster performance.



## Change Log



See [Release Notes on GitHub](https://github.com/ruby-rdf/rdf-turtle/releases)



## Dependencies



* [Ruby](https://ruby-lang.org/) (>= 3.0)

* [RDF.rb](https://rubygems.org/gems/rdf) (~> 3.3)

* [EBNF][] (~> 2.5)



## Installation



The recommended installation method is via [RubyGems](https://rubygems.org/).

To install the latest official release of the `RDF::Turtle` gem, do:



    % [sudo] gem install rdf-turtle



## Mailing List

* 



## Author

* [Gregg Kellogg](https://github.com/gkellogg) - 



## Contributing

This repository uses [Git Flow](https://github.com/nvie/gitflow) to mange development and release activity. All submissions _must_ be on a feature branch based on the _develop_ branch to ease staging and integration.



* Do your best to adhere to the existing coding conventions and idioms.

* Don't use hard tabs, and don't leave trailing whitespace on any line.

* Do document every method you add using [YARD][] annotations. Read the

  [tutorial][YARD-GS] or just look at the existing code for examples.

* Don't touch the `.gemspec`, `VERSION` or `AUTHORS` files. If you need to

  change them, do so on your private branch only.

* Do feel free to add yourself to the `CREDITS` file and the corresponding

  list in the the `README`. Alphabetical order applies.

* Do note that in order for us to merge any non-trivial changes (as a rule

  of thumb, additions larger than about 15 lines of code), we need an

  explicit [public domain dedication][PDD] on record from you,

  which you will be asked to agree to on the first commit to a repo within the organization.

  Note that the agreement applies to all repos in the [Ruby RDF](https://github.com/ruby-rdf/) organization.



## License

This is free and unencumbered public domain software. For more information,

see  or the accompanying {file:UNLICENSE} file.



A copy of the [Turtle EBNF][] and derived parser files are included in the repository, which are not covered under the UNLICENSE. These files are covered via the [W3C Document License](https://www.w3.org/Consortium/Legal/2002/copyright-documents-20021231).



[Ruby]:         https://ruby-lang.org/

[RDF]:          https://www.w3.org/RDF/

[YARD]:         https://yardoc.org/

[YARD-GS]:      https://rubydoc.info/docs/yard/file/docs/GettingStarted.md

[PDD]:              https://unlicense.org/#unlicensing-contributions

[RDF.rb]:       https://ruby-rdf.github.io/rdf

[EBNF]:         https://rubygems.org/gems/ebnf

[N-Triples]:    https://www.w3.org/TR/rdf12-n-triples

[Turtle]:       https://www.w3.org/TR/rdf12-turtle

[RDF 1.1]:          https://www.w3.org/TR/rdf11-concepts/

[RDF 1.2]:          https://www.w3.org/TR/rdf12-concepts/

[Turtle doc]:   https://ruby-rdf.github.io/rdf-turtle/master/file/README.md

[Turtle EBNF]:  https://w3c.github.io/rdf-turtle/spec/turtle-bnf.html

[Freebase Dumps]: https://developers.google.com/freebase/data