Urban Square Framework

Hi, i am currently a university student working on a paper relating to the succesful design of a city centre square. During this paper i am trying to establish a framework for the design of a city centre square.

ALthough i have managed to find a lot of information realting to the three-dimensional gemoetry of a square, i am failing to answer a couple of questions.

These are;

What is the relationship between the square and its openings (streets)?

Is there a max and min for the size of opening into a street square?

How many openings should there be into a square (max/min)?

If any one could point me in the direction of literature to which i could answer these questions, i would be very grateful.

Any other information you feel would be of use to me, would be a great help.

Thank you for your time James