CommandCell cmd = (CommandCell) boundColumn.getValue();
Map executionContext = prepareExecutionContext(validCoord, new HashMap());
// cmd == null when on default column of a rule axis
ruleValue = cmd == null ? isZero(ruleAxisBindCount.get(axisName)) :
new DefaultExecutor().executeCommand(cmd, executionContext);
// Wrap rule return value, so that a rule that returns null is not mistaken for a cache miss.
ruleExecutionCache.put(boundColumn.id, new Object[]{ruleValue});
if (didRuleFire(ruleValue))