What relationship between the nouns 'service' and 'company' does the preposition 'of' serve to indicate in the below sentence?
He is in the service of the company.
In the sentence 'The house of Mary is large.', for example, the preposition 'of' indicates that 'the house' belongs to 'Mary'. The genitive may also be used to indicate this relationship (and this use is indeed more common): 'Mary's house is large'.