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

// here we declare an EDB called edge
// the type 'symbol' means 'string' or 'varchar' in souffle
.decl edge (n: symbol, m: symbol)

// add some facts about cities
edge("Seattle", "Portland").
edge("Portland", "SF").
edge("SF", "Portland").
edge("SF", "LA"). 

// we declare reachable to be an IDB to be computed and 
// printed on the console
.decl reachable (n: symbol, m: symbol) 
.output reachable(IO=stdout)

// anything in edge is reachable
reachable(x, y):- edge(x, y).

// anything that is already in reachable and can further be reached 
// by checking the IDB edge is also reachable
reachable(x, z):- edge(x, y), reachable(y, z).