elk-reasoner/src/main/java/org/semanticweb/elk/reasoner/stages/ClassExpressionQueryState.java
boolean registerQuery(final ElkClassExpression classExpression) {

		LOGGER_.trace("class expression query registered {}", classExpression);

		lastQueries_.clear();
		queriedEvictor_.add(classExpression);
		lastQueries_.add(classExpression);

		QueryState state = queried_.get(classExpression);
		if (state != null) {
			return false;
		}
		// Create query state.
		state = new QueryState();
		queried_.put(classExpression, state);
		toLoad_.offer(classExpression);

		return true;
	}
boolean registerQuery(final ElkClassExpression classExpression) {

		LOGGER_.trace("class expression query registered {}", classExpression);

		lastQueries_.clear();
		queriedEvictor_.add(classExpression);
		lastQueries_.add(classExpression);

		QueryState state = queried_.get(classExpression);
		if (state != null) {
			return false;
		}
		// Create query state.
		state = new QueryState();
		queried_.put(classExpression, state);
		toLoad_.offer(classExpression);

		return true;
	}
Registers the supplied class expression for querying. If the expression
has already been registered, returns {@code false}. Otherwise, if this
state did not keep track of the expression yet, returns {@code true}. If
all necessary stages are run after doing this, the result retrieval
methods, e.g., {@link #isSatisfiable(ElkClassExpression)}, will not throw
{@link ElkQueryException}.

@param classExpression
@return {@code true} if this is a new query, {@code false} if this class
expression has already been registered.