Try to bind together queries, triggers, and actions.

diff --git a/src/main/java/net/pterodactylus/reactor/Reaction.java b/src/main/java/net/pterodactylus/reactor/Reaction.java
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+/*
+ * Reactor - Reaction.java - Copyright © 2013 David Roden
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package net.pterodactylus.reactor;
+
+/**
+ * A {@code Reaction} binds together {@link Query}s, {@link Trigger}s, and
+ * {@link Action}s, and it stores the intermediary {@link State}s.
+ *
+ * @param <S>
+ *            The type of the state
+ * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
+ */
+public class Reaction<S extends State> {
+
+       /** The query to run. */
+       private final Query<S> query;
+
+       /** The trigger to detect changes. */
+       private final Trigger<S> trigger;
+
+       /** The action to perform. */
+       private final Action<S> action;
+
+       /** The current state of the query. */
+       private S currentState;
+
+       /** The previous state of the query. */
+       private S previousState;
+
+       /**
+        * Creates a new reaction.
+        *
+        * @param query
+        *            The query to run
+        * @param trigger
+        *            The trigger to detect changes
+        * @param action
+        *            The action to perform
+        */
+       public Reaction(Query<S> query, Trigger<S> trigger, Action<S> action) {
+               this.query = query;
+               this.trigger = trigger;
+               this.action = action;
+       }
+
+       //
+       // ACCESSORS
+       //
+
+       /**
+        * Returns the query to run.
+        *
+        * @return The query to run
+        */
+       public Query<S> query() {
+               return query;
+       }
+
+       /**
+        * Returns the trigger to detect changes.
+        *
+        * @return The trigger to detect changes
+        */
+       public Trigger<S> trigger() {
+               return trigger;
+       }
+
+       /**
+        * Returns the action to perform.
+        *
+        * @return The action to perform
+        */
+       public Action<S> action() {
+               return action;
+       }
+
+       /**
+        * Returns the current state of the query.
+        *
+        * @return The current state of the query
+        */
+       public S currentState() {
+               return currentState;
+       }
+
+       /**
+        * Returns the previous state of the query.
+        *
+        * @return The previous state of the query
+        */
+       public S previousState() {
+               return previousState;
+       }
+
+}