I am looking at a migration/adoption of a master data stratagy and specificlaly to a hub master data architecture for a number of transactional and analytical systems under our control (we own the database and application development and deployment)

Many of the discrete systems (separate application deployment/lifecycles and separate DB schema) share a common concept of a port call and in particular a PortCall_ID (in effect a 'super' transaction ID) this may be as a primary key or a foreign key binding asynchronous system level transactions/workflows together. Now my question is, does this key in itself constitute Master Data? Or does the subset of data that is shared between the systems keyed off of the PortCall_ID constiture master data. It is afterall transactional in nature. Should it be stored in the MD system when an entry is generated for each 'super transaction in the principal transactional system. And if not, what is its role within the context of MDM?