you are likely to find Vendor in/at/on Conference. you are likely to find Person in/at/on Conference. Person is related to Ordinary. 
you are likely to find Bucket in/at/on Laundry. Bucket is a type of Transport. Van can Transport. Van is related to Automobile. 
Vendor --AtLocation--> Conference <--AtLocation-- Person <--RelatedTo--> Ordinary 
Laundry <--AtLocation-- Bucket --IsA--> Transport <--CapableOf-- Van <--RelatedTo--> Automobile 