The roles are not solid. People go into various roles, depending on their mixture of their skills and what they want to do at that time, or somebody calls them up and says, "Hey, we need a X. Come on down."
The roles are not solid. People go into various roles, depending on their mixture of their skills and what they want to do at that time, or somebody calls them up and says, "Hey, we need a X. Come on down."