What is the way to exchange modals between two Ruby on Rails applications?

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The best way to exchange modals between two Ruby on Rails applications is to create a gem that includes the model definitions and then use that gem in both applications. This allows for easy maintenance and updates to the models, as well as ensuring that both applications are using the same model definitions. Another option is to use a microservices architecture, with the models being hosted and accessed through a separate API, allowing for more decoupling between the two applications.