Method for checking system requirements of cyber-physical systems (220, 320, 420) in a composite system, the system requirements comprising requirements of the cyber-physical systems (220, 320, 420) imposed on their environment and/or boundary conditions for using the cyber-physical systems (220, 320, 420), comprising: - creating a digital twin (200, 300, 400) for at least one cyber-physical system (220, 320, 420) in each case, wherein the digital twin (200, 300, 400) comprises an engineering part which is used to engineer the cyber-physical systems (220, 320, 420) and to combine the cyber-physical systems (220, 320, 420) to form a composite system, and wherein the engineering part comprises all engineering information relating to the cyber-physical system (220, 320, 420), including documentation, in order to use the cyber-physical system (220, 320, 420) in a composite system; - stipulating system requirements for each of the cyber-physical systems (220, 320, 420); - storing the system requirements of the cyber-physical systems (220, 320, 420) directly and/or indirectly in those digital twins (200, 300, 400) which are each assigned to the cyber-physical system (220, 320, 420); - linking at least two or more digital twins (200, 300, 400); - wherein the linked digital twins (200, 300, 400) each communicate in pairs with one another and at least partially interchange their system requirements with each other; - wherein the digital twins (200, 300, 400) compare the stored system requirements with the received system requirements; - wherein the digital twins (200, 300, 400) adapt their system requirements on the basis of the comparison carried out with the received system requirements and can stipulate these as a new system requirement; - wherein the digital twins (200, 300, 400) adapt their system requirements if one of the digital twins has restricted system requirements; - wherein the digital twins (200, 300, 400) forward their own system requirements to the respectively linked digital twins (200, 300, 400) for a comparison if the system requirements of the digital twin itself are more restricted; - wherein the digital twins (200, 300, 400) adapt their system requirements when combined with other digital twins and retain their own original system requirement; - wherein the digital twins (200, 300, 400) communicate their newly stipulated system requirements to the other digital twins (200, 300, 400), and - wherein the original system requirements of the digital twins (200, 300, 400) are stored and, if a digital twin is removed from a composite system, the remaining digital twins (300, 400) can resort to their original system requirements. - creating a digital twin (200, 300, 400) for at least one cyber-physical system (220, 320, 420) in each case, wherein the digital twin (200, 300, 400) comprises an engineering part which is used to engineer the cyber-physical systems (220, 320, 420) and to combine the cyber-physical systems (220, 320, 420) to form a composite system, and wherein the engineering part comprises all engineering information relating to the cyber-physical system (220, 320, 420), including documentation, in order to use the cyber-physical system (220, 320, 420) in a composite system; - stipulating system requirements for each of the cyber-physical systems (220, 320, 420); - storing the system requirements of the cyber-physical systems (220, 320, 420) directly and/or indirectly in those digital twins (200, 300, 400) which are each assigned to the cyber-physical system (220, 320, 420); - linking at least two or more digital twins (200, 300, 400); - wherein the linked digital twins (200, 300, 400) each communicate in pairs with one another and at least partially interchange their system requirements with each other; - wherein the digital twins (200, 300, 400) compare the stored system requirements with the received system requirements; - wherein the digital twins (200, 300, 400) adapt their system requirements on the basis of the comparison carried out with the received system requirements and can stipulate these as a new system requirement; - wherein the digital twins (200, 300, 400) adapt their system requirements if one of the digital twins has restricted system requirements; - wherein the digital twins (200, 300, 400) forward their own system requirements to the respectively linked digital twins (200, 300, 400) for a comparison if the system requirements of the digital twin itself are more restricted; - wherein the digital twins (200, 300, 400) adapt their system requirements when combined with other digital twins and retain their own original system requirement; - wherein the digital twins (200, 300, 400) communicate their newly stipulated system requirements to the other digital twins (200, 300, 400), and - wherein the original system requirements of the digital twins (200, 300, 400) are stored and, if a digital twin is removed from a composite system, the remaining digital twins (300, 400) can resort to their original system requirements.