# Hydra::PCDM

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Hydra implementation of the Portland Common Data Model (PCDM)

## Installation

Add these lines to your application's Gemfile:

```ruby
  gem 'active-fedora', '~> 9.3'
  gem 'hydra-pcdm', '~> 0.9'
```

And then execute:

    $ bundle install

Or install it yourself:

    $ gem install hydra-pcdm

## Access Controls

We are using [Web ACL](http://www.w3.org/wiki/WebAccessControl) as implemented in [hydra-access-controls](https://github.com/projecthydra/hydra-head/tree/master/hydra-access-controls).

## Portland Common Data Model

Reference: [Portland Common Data Model](https://github.com/duraspace/pcdm/wiki)

### Model Definition

![PCDM Model Definition](https://raw.githubusercontent.com/wiki/duraspace/pcdm/images/coll-object-file.png)

## Usage

Hydra::PCDM provides three core classes:

```
Hydra::PCDM::Object
Hydra::PCDM::Collection
Hydra::PCDM::File
```

A `Hydra::PCDM::File` is a NonRDFSource (in [LDP](http://www.w3.org/TR/ldp/) parlance) &emdash; a bitstream. You can use this to store content. A PCDM::File is contained by a PCDM::Object. A `File` may have some attached technical metadata, but no descriptive metadata. A `Hydra::PCDM::Object` may contain `File`s, may have descriptive metadata, and may declare other `Object`s as members (for complex object hierarchies). A `Hydra::PCDM::Collection` may contain other `Collection`s or `Object`s but may not directly contain `File`s. A `Collection` may also have descriptive metadata.

Typically, usage involves extending the behavior provided by this gem. In your application you can write something like this:

```ruby
class Book < ActiveFedora::Base
  include Hydra::PCDM::ObjectBehavior
end

class Collection < ActiveFedora::Base
  include Hydra::PCDM::CollectionBehavior
end

collection = Collection.create
book = Book.create

collection.members = [book]
# or: collection.members << book
collection.save

file = book.files.build
file.content = "The quick brown fox jumped over the lazy dog."
book.save
```

## Contributing

If you'd like to contribute to this effort, please check out the [Contributing Guide](CONTRIBUTING.md)