Showing that a function that depends only on a single attribute of a map like data structure is also possible with static records/structs. This allows adding/removing attributes from the record without modification of the all_members function.

Decoupling.hs

data Project = Project {
                     projId :: String,
                     projKind :: ProjectKind,
                     projDescription :: String,
                     projBudget :: Int,
                     projTeam :: [Person]
                }

all_members :: [Project] -> [Person]
all_members projects = concat $ map projTeam projects