you are likely to find Specialist in/at/on Conference. you are likely to find Hall in/at/on Conference. Hall is related to Lecture. Lecture is related to Educational. 
you are likely to find President in/at/on Government. 
Specialist --AtLocation--> Conference <--AtLocation-- Hall <--RelatedTo--> Lecture <--RelatedTo--> Educational 
Government <--AtLocation-- President 