// expiration in minutes
int intExpiration = Integer.valueOf(expiration).intValue();
Date expire = new Date(System.currentTimeMillis() + intExpiration*1000*60);
SlideToken slideToken = new SlideTokenImpl(new CredentialsToken(caller));
Lock lock = nat.getLockHelper();
try {
nat.begin();
lock.lock(slideToken, new NodeLock(uri, subject, type, expire, isInherit, isExclusive, uri));