Resource Object is not available in the primary object list for Process, even if the event enabled flag is checked.
The Resource object is not process enabled because many of the uses for a resource are tied to other objects in the product. For example, resource allocation is tied to staffing on a project. Resource skills are tied to the skills object. The financial properties and contact information are stored as separate properties and are not part of the Resource object.
Resource and User are two different implementations (Users are not ODF-objects); thus it would be difficult to process enable a resource without a way to tie it back to the User record for that resource.
Due to the way the Resource object is used within the product, it cannot be process enabled as a stand-alone object.
The resource object is not process enabled and cannot be assigned as primary object when creating a process.
But a resource object can be added as a linked object in the process. For example in a Timesheet process, the resource object can be added as linked object . This is the reason why it is event enabled.
When using a 'linked object' on a process, only the active attributes that are defined on that object are available for use in the process expressions. You can create custom attributes within the primary or linked object and the attribute will appear for selecting in the expression builder. Not all attribute data types are available for selection and use. If an object has related attributes that do not appear on the object attribute listing, these attributes won't be available for use in a process. For example, the Resource Object is 'Event Enabled' and is available to be used as a 'linked object' in the process definition, however any of the Resource financial attributes are NOT available at all for use in the process definition. You will notice that the financial attributes do not appear on the attribute listing for the Resource Object.