of Walls and Roofs

I had a very interesting discussion with professors Gary Moye and Pat Piccioni about the definition of a wall. Pat stated that the primary characteristic of a wall is that is defined by stacking up material against the force of gravity. I argued that it was mearly a linear form that seperated one thing from another. Can you have a wall that is not perpendicular to gravity? Is 45 degrees made of concrete still a wall? What is a fence? How is it different from a wall? Regardless of the particulars this question is extremely interesting when using grid shells. Using the structural capacities of grid shells we can form walls or wall type forms that are shaped, and seem to fly in the face of walls defined by gravity. The walls and roof often are of one form, and the same materials. How do you create place if you have trouble creating the elements of spacial composition. Is the grid shell unique because the roof touches the ground or because the walls also make the enclosure? I think this final question is of particular importance because it starts to get out how people will experience the unquiness of the gridshell. I personally am more interested in using the walls to also make the enclosure attitude. Touching a roof is not that new of an experience and shaping a roof so that it touches the ground goes back to atleast as far as the pyramids. However, being able to build a form that carry an experience of a wall into an enclosure is something that only a very few structural systems can accomplish. And while it is diserable in most cases to have a clear roof and wall, the exceptional quality of the grid shell allows for a dynamic play of these elements that can make for an extraordinary user experience. As Gary proposed maybe gridshells need a different vocabulary than roof and walls.