CircleCI Test Coverage Maintainability Gem Version OpenAPI Validator


The cocina-models gem is a Ruby implementation of the Stanford Digital Repository (SDR) data model, which we named "Cocina." The data being modeled is oriented around digital repository objects.

The data model is expressed in an OpenAPI specification that lives in this codebase. Expressing the model in such a spec allows for rich validation (using gems such as OpenAPIParser and committee). The gem provides a set of generators (see below) to generate Ruby classes from the specification, with modeling provided by dry-struct / dry-types. Together, these provide a way for consumers to validate objects against models and to manipulate those objects.

Note that the data model encodes properties as camelCase, which the team believes to be consistent with other HTTP APIs and the original design of the Cocina data model. While using camelCase in Ruby code may look and feel wrong, we did explore automagic conversion between camelCase in the model and snake_case in the Ruby context. We ultimately concluded that we have enough representations of the data model in enough codebases to reasonably worry about data inconsistency problems, none of which we need in our work on SDR.

For more about the model for description see


Set the PURL url base:

Cocina::Models::Mapping::Purl.base_url = Settings.release.purl_base_url

Generate models from openapi.yml

Note that only a small subset of openapi is supported. If you are using a new openapi feature or pattern, verify that the model will be generated as expected.


exe/generator generate

Single model

exe/generator generate_schema DRO

Controlled vocabularies

exe/generator generate_vocab

Descriptive documentation

exe/generator generate_descriptive_docs


The generator is tested via its output when run against openapi.yml, viz., the Cocina model classes. Thus, generate should be run after any changes to openapi.yml.

Beyond what is necessary to test the generator, the Cocina model classes are not tested, i.e., they are assumed to be as specified in openapi.yml.

Testing validation changes

If there is a possibility that a model, mapping, or validation change will conflict with some existing objects then validate-cocina should be used for testing. This must be run on the sdr-infra VM since it requires deploying a branch of cocina-models.

  1. Create a cocina-models branch containing the proposed change and push to GitHub.
  2. On the sdr-infra VM, while logged in as the deploy user, check out main, update the Gemfile so that cocina-models references the branch, and bundle install.
  3. Select the appropriate environment vars below - they are set to values in puppet. (first 2 lines are the same; last two lines use different variables)

For QA:

export DATABASE_NAME="dor_services"

For stage:

export DATABASE_NAME="dor_services"

For production:

export DATABASE_NAME="dor_services"
  1. Run bin/validate-cocina (NOTE: You likely want to run this in a screen session, as it can take many hours to complete, especially against prod): export RUBYOPT='-W:no-deprecated -W:no-experimental' RAILS_ENV=production bin/validate-cocina -p 8
  2. Check validate-cocina.csv for validation errors.

Running Reports in DSA

Custom reports stored in dor-services-app can be run similarly to validation testing described above.

  1. Connect to the sdr-infra box: shell ssh sdr-infra
  2. Start a shell as the deploy user: shell # you may or may not need to supply the `-n SUNETID` argument ksu deploy
  3. Go to the ~/dor-services-app directory and reset to main if needed (verify nobody else is using this first though): shell cd ~/dor-services-app git status # see if there are any unsaved changes, if so, you may need to git stash them git pull # OR git reset --hard main to just ditch any local unsaved changes
  4. Connect to the desired database by setting the environment variables as described in the section above. This must be done each time you SSH back into the box to run a new report.
  5. Run the report (good idea to do it in a screen or via background process in case you get disconnected): shell bundle exec bin/rails r -e production "" > BadIso8601Dates.csv
  6. When done, you can pull the report to your laptop as needed: shell scp sdr-infra:/opt/app/deploy/dor-services-app/BadIso8601Dates.csv .

Releasing a patch change

A patch change is a change that (1) does not affect the data model; (2) does not alter the openapi.yml; and more broadly (3) does not matter if some applications have the change and others do not.

A patch change can be released as part of regular dependency updates or selectively released for individual applications.

Releasing major or minor change

NOTE: If dependency updates are about to be released, you have the option of shortening the process and stopping after Step 3. This is because Steps 4 onwards will be taken care of by the regular dependency updates process (basically the updating of cocina-models, dor-services-client and sdr-client as needed in the rest of the associated apps). You still do need to manually bump some gems and the pinned version of cocina-models in a couple apps and get those PRs approved and merged, as described in Steps 1-3 below.

IMPORTANT: If you do opt to skip steps 4 onward, you should NOT merge the cocina-models bump dor-services-app and sdr-api PRs you created in step 3 until you are ready to finish the dependency updates process. You can have them reviewed and approved, but if you merge, you will greatly increase the risk of issues if the main branch of DSA or sdr-api are deployed after steps 1-3 are complete but before the rest of the apps are updated to use the new cocina-models via regular dependency updates. The fix for this is to either roll-back DSA and sdr-api to the previous release tag, or proceed forwards with step 4-5.

Before you release a major or minor change, think about if this release will include new validations. Even if your change didn't make any changes that would affect validation, there may be other unreleased changes since the previous version of the gem was cut and released. Best practice is to scan back through the commit history until you get to the last version bump and see if there any significant changes that may affect validation.

If unsure, ask the team or ask for help to just run the validation report anyway (as described above).

Step 0: Share intent to change the models

Send a note to #dlss-infra-chg-mgmt on Slack to let people know what is changing and when.

Step 1: Cut the release

The release process is much like any other gem. First bump the version in lib/cocina/models/version.rb, and commit the result. Then run:

bundle exec rake release

which pushes the gem to

Step 2: Update client gems coupled to the models

Release new versions of sdr-client and dor-services-client pinned to use the new cocina-models version because applications such as Argo and Dor-Services-App depend on these gems using the same models.

Step 3: Update services directly coupled to the models

This list of services is known to include:

NOTE: You can skip step 3A if there have not been any changes to the cocina-models OpenAPI spec since the prior release.

Step 3A: Update API specifications

The cocina-models gem is used in applications that have an API specification that accepts Cocina models. Make sure that the openapi.yml for these applications include the openapi.yml schema changes made in cocina-models.

This can be accomplished by copying and pasting the cocina-models schemas to the openapi.yml of the associated project. By convention, these schemas are listed first in the openapi.yml of the associated projects, followed by the application-specific schemas.

Step 3B: Bump gems and create the PRs

If step 3A was needed, use the same PRs to also bump the versions of cocina-models, sdr-client, and dor-services-client in these applications/services. Why? When dor-services-app, for example, is updated to use the new models (via the auto-update script), these clients should be updated at the same time or there is risk of models produced by dor-services-app not being acceptable to the clients.

With or without step 3A, perform bundle update for cocina-models, sdr-client, and dor-services-client gems in the listed services and then make PRs for those repos. You may first need to update how these gems are pinned in the Gemfile in order to bump them. Note that dor-services-app only needs a bump to cocina-models gem and sdr-api only needs a bump to cocina-models and dor-services-client gems.

Step 3C: Merge 'em

Get the directly coupled services PRs merged before the deploy in step 5.

Step 4: Update other dependent applications

Once the above listed steps have been completed, all applications that use cocina-models should be updated and released at the same time. "Cocina Level 2" describes this set of updates. The applications that use cocina-models are those in this list that are NOT marked with cocina_level2: false.

There are scripts to help with updating other dependent applications:

Step 4A: Create the Cocina Level 2 PRs

There is a Jenkins CI job that you can run manually to create all the PRs you need. Head to and then click Build Now. Click the new build that is created and then Console Output to watch the build. Once it has completed, you can proceed with the next step.

If for some reason the above method does not work, the sul-dlss/access-update-scripts repo has a script for this: cocina_level2_prs.rb. You will need a github access token with scopes of "read:org" and "repo" (see to run it, as noted in the comments at the top of that script.

Step 4B: Merge the Cocina Level 2 PRs

sul-dlss/access-update-scripts has a switch in the merge-all.rb script for this, as noted in the comments at the top of that script.

REPOS_PATH=infrastructure GH_ACCESS_TOKEN=abc123 COCINA_LEVEL2= ./merge-all.rb

Step 5: Deploy all affected applications together

sul-dlss/sdr-deploy has a flag (-c) in the deploy script to limit deploys to cocina dependent applications. Refer to instructions in the sdr-deploy/README.

Note that running the integration tests is currently the best way we have to check for unintended effects and/or bugs when rolling out cocina-models changes.

Step 5A: Deploy to QA and/or Stage

Step 5B: Run infrastructure_integration_tests

It is safest to ensure all the integration tests run cleanly. However, patch releases of cocina-models may only warrant running individual tests that exercise the changes.

Step 5C: Deploy to Production

Turn off Google Books when deploying to production. This avoids failed deposit due to a temporary Cocina model mismatch. Unlike other applications, the deposits will fail without retry and require manual remediation.

Usage conventions

The following are the recommended naming conventions for code using Cocina models:

  • cocina_item: Cocina::Models::DRO instance
  • cocina_agreement: Cocina::Models::DRO with type of Cocina::Models::ObjectType.agreement
  • cocina_admin_policy: Cocina::Models::AdminPolicy instance
  • cocina_collection: Cocina::Models::Collection instance
  • cocina_object: Cocina::Models::DRO or Cocina::Models::AdminPolicy or Cocina::Models::Collection instance

RSpec matchers

As of the 0.69.0 release, the cocina-models gem provides RSpec matchers for downstream apps to make it easier to compare Cocina data structures. The matchers provided include:

  • equal_cocina_model: Compare a Cocina JSON string with a model instance. This matcher is especially valuable coupled with the super_diff gem (a dependency of cocina-models since the 0.69.0 release). Example usage:
    • expect(http_response_body_with_cocina_json).to equal_cocina_model(cocina_instance)
  • cocina_object_with (AKA match_cocina_object_with): Compare a Cocina model instance with a hash containining part of the structure of a Cocina object. Example usage:
    • expect(CocinaObjectStore).to have_received(:save).with(cocina_object_with(access: { view: 'world' }, structural: { contains: [...] }))
    • expect(updated_cocina_item).to match_cocina_object_with(structural: { hasMemberOrders: [] })
  • cocina_object_with_types: Check a Cocina object's type information. Example usage:
    • expect(object_client).to have_received(:update).with(params: cocina_object_with_types(content_type:, viewing_direction: 'left-to-right'))
  • cocina_admin_policy_with_registration_collections: Check a Cocina admin policy's collections. Example usage:
    • expect(object_client).to have_received(:update).with(params: cocina_admin_policy_with_registration_collections([collection_id]))