If your system interacts with many external systems, you can combine several of these external systems by explicit criteria. You should explicitly state these criteria. Such criteria may include systems:

• share common or similar data
• communicate within the same use case or at the same time
• communicate using identical or similar technologies (e.g. categorized by ftp- and WebService)
• belong to the same or similar organization, such as: all systems of garages, insurances, glass manufacturing and tax advisors
• have similar domain or technical tasks to solve (all systems printing documents, dealing with chip cards, etc.)

Examples: With and without

The following diagram (the detailed version) shows three specific neighbour systems, all stereotyped with the category « logistics ».

The next diagram groups these neighbours into one single “Logistics” external system on the left, stereotyped as « category ».