// CSE 414 Unit 2 -- Relational Data Model
// Souffle demo
// run using souffle [filename]

// here we declare an EDB called ParentChild
.decl ParentChild(p: number, c: number)

ParentChild(1,2).   // person 1 is the parent of person 2
ParentChild(2,3).
ParentChild(1,4).

.decl Descendents(p: number, c: number)
.output Descendents(IO=stdout)

Descendents(x,y) :- ParentChild(x,y).
Descendents(x,z) :- Descendents(x,y), ParentChild(y,z).

// group descendents by parent's name
.decl Grouped(p: number, c: number)
.output Grouped(IO=stdout)

Grouped(p,c) :- Descendents(p, _), c = count: { Descendents(p,_) }.

// final output: count descendents of person 1
.decl Q(p: number, c:number)
.output Q(IO=stdout)

Q(p,c) :- Grouped(p, c), p=1.