Introduction and Motivation

Christian Kaestner and Eunsuk Kang

Who is to blame?

Algorithms.shortestDistance(g, "Tom", "Anne");

> ArrayOutOfBoundsException

Algorithms.shortestDistance(g, "Tom", "Anne");

> -1

Who is to blame?

class Algorithms {
    /**
     * This method finds the shortest distance between to 
     * verticies. It returns -1 if the two nodes are not 
     * connected. 
    */
    int shortestDistance(…) {…}
}

class Algorithms {
    /**
     * This method finds the shortest distance between to 
     * verticies. Method is only supported 
     * for connected verticies.
    */
    int shortestDistance(…) {…}
}

System decomposition with interfaces

/*@ requires amount >= 0;
    ensures balance == \old(balance)-amount &&
            \result == balance;
@*/
public int debit(int amount) {
    ...
}

(JML specification in Java, pre- and postconditions)

/**
  * Calls the <code>read(byte[], int, int)</code> overloaded [...]
  * @param buf The buffer to read bytes into
  * @return The value retured from <code>in.read(byte[], int, int)</code>
  * @exception IOException If an error occurs
  */
public int read(byte[] buf) throws IOException
{
    return read(buf, 0, buf.length);
}

(textual specification with JavaDoc)

Who is to blame?

Math.sqrt(-5);

> 0

Specifications in Machine Learning?

/**
  ????
*/
String transcribe(File audioFile);

/**
  ????
*/
List<Product> suggestedPurchases(List<Product> pastPurchases);

Introduction and Motivation Christian Kaestner and Eunsuk Kang