Module: OaiPmh

Defined in:
lib/oaipmh/set.rb,
lib/oaipmh/model.rb,
lib/oaipmh/helpers.rb,
lib/oaipmh/metadata.rb,
lib/oaipmh/provider.rb,
lib/oaipmh/constants.rb,
lib/oaipmh/exceptions.rb,
lib/oaipmh/extensions/camping.rb

Overview

provider.rb

Copyright © 2006 William Groppe

Will Groppe [email protected]

Open Archives Initiative - Protocol for Metadata Harvesting see www.openarchives.org/

Features

  • Easily setup a simple repository

  • Simple integration with ActiveRecord

  • Dublin Core metadata format included

  • Easily add addition metadata formats

  • Adaptable to any data source

Current shortcomings

  • No resumption tokens

  • Doesn’t validate metadata

  • No deletion support

  • Many others I can’t think of right now. :-)

ActiveRecord integration

To successfully use ActiveRecord as a OAI PMH datasource the database table should include an updated_at column so that updates to the table are tracked by ActiveRecord. This provides much of the base functionality for selecting update periods.

To understand how the data is extracted from the AR model it’s best to just go thru the logic:

Does the model respond to ‘to_prefix’? Where prefix is the metadata prefix. If it does then just include the response from the model. So if you want to provide custom or complex metadata you can simply define a ‘to_prefix’ method on your model.

Example:

class Record < ActiveRecord::Base

  def to_oai_dc
    xml = Builder::XmlMarkup.new
    xml.tag!('oai_dc:dc',
      'xmlns:oai_dc' => "http://www.openarchives.org/OAI/2.0/oai_dc/",
      'xmlns:dc' => "http://purl.org/dc/elements/1.1/",
      'xmlns:xsi' => "http://www.w3.org/2001/XMLSchema-instance",
      'xsi:schemaLocation' => 
        %{http://www.openarchives.org/OAI/2.0/oai_dc/ 
        http://www.openarchives.org/OAI/2.0/oai_dc.xsd}) do

        xml.oai_dc :title, title
        xml.oai_dc :subject, subject
    end
    xml.to_s
  end

end

If the model doesn’t define a ‘to_prefix’ then start iterating thru the defined metadata fields.

Grab a mapping if one exists by trying to call ‘map_prefix’.

Now do the iteration and try calling methods on the model that match the field names, or the mapped field names.

So with Dublin Core we end up with the following:

  1. Check for ‘title’ mapped to a different method.

  2. Call model.titles - try plural

  3. Call model.title - try singular last

Extremely contrived Blog example:

class Post < ActiveRecord::Base
  def map_oai_dc
    {:subject => :tags, 
     :description => :text, 
     :creator => :user, 
     :contibutor => :comments}
  end
end

Supporting custom metadata

See OaiPmh::Metadata for details.

Examples

Sub classing a provider

class MyProvider < OaiPmh::Provider
  name 'My little OAI provider'
  url 'http://localhost/provider'
  prefix 'oai:localhost'
  email 'root@localhost'             # String or Array
  deletes 'no'                       # future versions will support deletes
  granularity 'YYYY-MM-DDThh:mm:ssZ' # update resolution
  model MyModel                      # Class to get data from
end

# Now use it

provider = MyProvider.new
provider.identify
provider.list_sets
provider.list_metadata_formats

# these verbs require a working model

provider.list_identifiers
provider.list_records
provider.get_record('oai:localhost/1')

Configuring the default provider

class OaiPmh::Provider
  name 'My little OAI Provider'
  url 'http://localhost/provider'
  prefix 'oai:localhost'
  email 'root@localhost'             # String or Array
  deletes 'no'                       # future versions will support deletes
  granularity 'YYYY-MM-DDThh:mm:ssZ' # update resolution
  model MyModel                      # Class to get data from
end

Defined Under Namespace

Modules: Const, Goes, Helpers, Metadata, Model Classes: ArgumentException, FormatException, IdException, MetadataFormatException, NoMatchException, OAIException, Provider, ResumptionTokenException, Set, SetException, VerbException

Constant Summary collapse

METADATA = 
{}

Class Method Summary collapse

Class Method Details

.register_metadata_class(metadata_class) ⇒ Object 



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# File 'lib/oaipmh/metadata.rb', line 4

def OaiPmh.register_metadata_class(metadata_class)
  METADATA[metadata_class.to_s] = metadata_class
end