[rules-users] Design Question (hashCode/equals/fact maintenance)

[Fenderbosch, Eric]

I'm just looking for a bit of verification that this is a reasonable
solution.  This just feels like a hack and there's probably a better way
that I'm just not seeing.  Alternate ideas are welcome and appreciated.

Thanks in advance.

The objective is to find the best workers for a job:
Jobs have a location.
Workers have a location.
Scores are calculated based on miles and minutes of a route from the
worker to a job.
When a job or worker location changes, then the route should be
recalculated so that scores can be recalculated.  It is possible for a
location to get re-inserted that might be the functionally the same as a
previous location for a job/worker, but a different instance.  In this
case, the route should not be recalculated and the old scores should
remain.

assert behavior = equality
logical override = discard
maintain tms = true
remove identies = true
shadow proxies are enabled

public class JobLatitudeLongitude {

	private String jobId;
	private double latitude;
	private double longitude;
	private long timestamp = System.currentTimeMillis();

	// getters & setters omitted for brevity

	public int hashCode() {
		return jobId.hashCode();
	}

	public boolean equals(Object obj) {
		// not null or type safe, just simple version for
brevity
		JobLatitudeLongitude other = (JobLatitudeLongitude) obj;
		return this.jobId.equals(other.jobId) && this.timestamp
== other.timestamp;
		// would "return false;" work ???
	}
}

rule "retract redundant job latitude/longitude facts"
// if more than one lat/long with same position for a job, keep the
oldest
	salience 600
	when
		older : JobLatitudeLongitude()
		newer : JobLatitudeLongitude(jobId == older.jobId,
latitude == older.latitude, longitude == older.longitude, timestamp >=
older.timestamp)
	then
		retract(newer);
end

rule "retract old job latitude/longitude facts"
// if more than one lat/long with different position for a job, keep the
newest
	salience 600
	when
		older : JobLatitudeLongitude()
		newer : JobLatitudeLongitude(jobId == older.jobId,
latitude != older.latitude, longitude != older.longitude, timestamp >=
older.timestamp)
	then
		retract(older);
end

rule "add Route fact"
	salience 450
	when
		jobLatitudeLongitude : JobLatitudeLongitude()
		workerLatitudeLongitude : WorkerLatitudeLongitude()
	then
		// calculateRoute is an imported function
		Route route = calculateRoute(workerLatitudeLongitude,
jobLatitudeLongitude);
		insertLogical(route);
end