A domain is defined as a group of tables, concept groups and concepts, it is used to allow a specific subject area to be managed together as a single group of entities. To define a domain, please plan your model carefully:
Matching, each domain is stored physically in a different collection of data. This implies that if you store Product and Customer tables in two different domains then it is not possible to match between them. Only tables in a single domain can match to a table in the same domain.
Foreign Keys, can jump domains, so a table in one domain can link to a table in another domain in a M:1 type fashion this would mean that an employee table in a Persons domain can link to a “Job Position” table in a reference domain using a simple attribute in the Person that indicates his/her role.
Relationships, can not jump domains only tables in a single domain can relate to tables in the same domain, to create a M:M type linking across a domain, the designer should consider creating a M:M resolver table in the data, although this would require more manual data entry or data loading to be effective,
Either use the Switch Context from the Project Menu, or click the Context button on the topbar:
Choose the [Create One] option to create a new domain, it will also switch to that domain, after this you will notice that all the tables, concept groups, concepts and indexes will no longer be visible. Switching back to the original domain using the same Switch Concept option will enable you to see them.