Defining EVAL

• EVAL(inTable,X="a")

  • tempTable = table with one attribute X and one tuple <"a">
  • return NJOIN(tempTable,inTable)

• EVAL(inTable,X=Y)

  • return SELECT(X=Y,inTable)

• EVAL(inTable,X<Y)

  • return SELECT(X<Y,inTable)

• EVAL(inTable,X<"5")

  • return SELECT(X<"5",inTable)

• EVAL(inTable,ri(X,Y))

  • If ri is IDB, return NJOIN(inTable,Ti).
  • If ri is EDB, with input attributes (X). Fire the wrapper
  • associated with ri on PROJECT(X,inTable). Return result.

• EVAL(inTable, (ri(X,Y) , expr(Y,Z)))

• EVAL(inTable, (ri(X,Y) ; expr(Y,Z)))

  • return NJOIN(EVAL(inTable,ri),EVAL(inTable,expr(Y,Z)))

Previous slide

Next slide

Back to first slide

View graphic version