From 0b8a199743bc60d2b0912f196d5cd6a26a2f3583 Mon Sep 17 00:00:00 2001
From: Daniel <daniel@harvey>
Date: Mon, 23 Nov 2020 16:39:52 +0100
Subject: [PATCH] DOC: Added (C) notices and some documentation and comments.

---
 .../caosdb/server/entity/ClientMessage.java   |  26 +++-
 .../org/caosdb/server/jobs/ScheduledJob.java  |  23 ++++
 .../jobs/core/CheckStateTransition.java       |  36 +++++-
 .../server/jobs/core/EntityStateJob.java      | 111 ++++++++++++++----
 .../server/jobs/core/InitEntityStateJobs.java |  30 ++++-
 .../server/jobs/core/MakeStateMessage.java    |  23 ++++
 .../server/jobs/core/MakeStateProperty.java   |  27 +++++
 .../org/caosdb/server/transaction/Update.java |   2 +
 .../server/utils/AbstractObservable.java      |   1 +
 .../org/caosdb/server/utils/Observer.java     |   2 +
 10 files changed, 254 insertions(+), 27 deletions(-)

diff --git a/src/main/java/org/caosdb/server/entity/ClientMessage.java b/src/main/java/org/caosdb/server/entity/ClientMessage.java
index 40a8c713..f6b99677 100644
--- a/src/main/java/org/caosdb/server/entity/ClientMessage.java
+++ b/src/main/java/org/caosdb/server/entity/ClientMessage.java
@@ -1,3 +1,26 @@
+/*
+ * ** header v3.0
+ * This file is a part of the CaosDB Project.
+ *
+ * Copyright (C) 2020 IndiScale GmbH <info@indiscale.com>
+ * Copyright (C) 2020 Timm Fitschen <t.fitschen@indiscale.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ *
+ * ** end header
+ */
+
 package org.caosdb.server.entity;
 
 import java.util.HashMap;
@@ -12,7 +35,7 @@ import org.jdom2.Element;
  *
  * <p>If no plug-in handles the client message, it is printed back to the response unaltered.
  *
- * <p>Client message can have arbitrary key-value tuples {@link #properties}.
+ * <p>Client message can have arbitrary key-value (string-string typed) tuples {@link #properties}.
  *
  * @author Timm Fitschen (t.fitschen@indiscale.com)
  */
@@ -40,6 +63,7 @@ public class ClientMessage extends Message {
     parent.addContent(e);
   }
 
+  /** NB: This is the only place where properties are set in this class. */
   public static ClientMessage fromXML(Element pe) {
     ClientMessage result = new ClientMessage(pe.getName(), pe.getText());
     for (Attribute a : pe.getAttributes()) {
diff --git a/src/main/java/org/caosdb/server/jobs/ScheduledJob.java b/src/main/java/org/caosdb/server/jobs/ScheduledJob.java
index d9fa9c42..ee0c2980 100644
--- a/src/main/java/org/caosdb/server/jobs/ScheduledJob.java
+++ b/src/main/java/org/caosdb/server/jobs/ScheduledJob.java
@@ -1,3 +1,26 @@
+/*
+ * ** header v3.0
+ * This file is a part of the CaosDB Project.
+ *
+ * Copyright (C) 2020 IndiScale GmbH <info@indiscale.com>
+ * Copyright (C) 2020 Timm Fitschen <t.fitschen@indiscale.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ *
+ * ** end header
+ */
+
 package org.caosdb.server.jobs;
 
 /**
diff --git a/src/main/java/org/caosdb/server/jobs/core/CheckStateTransition.java b/src/main/java/org/caosdb/server/jobs/core/CheckStateTransition.java
index b64acf50..9634192b 100644
--- a/src/main/java/org/caosdb/server/jobs/core/CheckStateTransition.java
+++ b/src/main/java/org/caosdb/server/jobs/core/CheckStateTransition.java
@@ -1,3 +1,26 @@
+/*
+ * ** header v3.0
+ * This file is a part of the CaosDB Project.
+ *
+ * Copyright (C) 2020 IndiScale GmbH <info@indiscale.com>
+ * Copyright (C) 2020 Timm Fitschen <t.fitschen@indiscale.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ *
+ * ** end header
+ */
+
 package org.caosdb.server.jobs.core;
 
 import org.caosdb.server.entity.DeleteEntity;
@@ -11,6 +34,9 @@ import org.caosdb.server.transaction.WriteTransaction;
 /**
  * Check if the attempted state transition is allowed.
  *
+ * <p>This job checks if the attempted state transition is in compliance with the state model. This
+ * job runs during the CHECK phase and should do all necessary consistency and permission checks.
+ *
  * @author Timm Fitschen (t.fitschen@indiscale.com)
  */
 @JobAnnotation(time = JobExecutionTime.CHECK, transaction = WriteTransaction.class)
@@ -41,7 +67,7 @@ public class CheckStateTransition extends EntityStateJob {
         checkStateTransition(oldState, newState);
       } else if (getEntity() instanceof DeleteEntity) {
         if (newState != null) checkFinalState(newState);
-      } else {
+      } else { // fresh Entity
         if (newState != null) checkInitialState(newState);
       }
     } catch (Message m) {
@@ -52,6 +78,8 @@ public class CheckStateTransition extends EntityStateJob {
   /**
    * Check if the state belongs to the state model.
    *
+   * <p>In practical terms, throw a Message if the state is invalid.
+   *
    * @param state
    * @throws Message
    */
@@ -65,6 +93,10 @@ public class CheckStateTransition extends EntityStateJob {
   /**
    * Check if state is valid and transition is allowed.
    *
+   * <p>Especially, transitions between {@code null} states are allowed, non-trivial transitions
+   * from or to {@code null} must be initial or final states, respectively ({@link
+   * FORCE_FINAL_STATE} exception applies).
+   *
    * @param oldState
    * @param newState
    * @throws Message if not
@@ -98,6 +130,8 @@ public class CheckStateTransition extends EntityStateJob {
   }
 
   /**
+   * Return the two State's common StateModel, or {@code null} if they don't have one in common.
+   *
    * @param oldState
    * @param newState
    * @return the state model which contains both of the states.
diff --git a/src/main/java/org/caosdb/server/jobs/core/EntityStateJob.java b/src/main/java/org/caosdb/server/jobs/core/EntityStateJob.java
index 83ec96f7..1e536ded 100644
--- a/src/main/java/org/caosdb/server/jobs/core/EntityStateJob.java
+++ b/src/main/java/org/caosdb/server/jobs/core/EntityStateJob.java
@@ -1,3 +1,26 @@
+/*
+ * ** header v3.0
+ * This file is a part of the CaosDB Project.
+ *
+ * Copyright (C) 2020 IndiScale GmbH <info@indiscale.com>
+ * Copyright (C) 2020 Timm Fitschen <t.fitschen@indiscale.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ *
+ * ** end header
+ */
+
 package org.caosdb.server.jobs.core;
 
 import java.util.ArrayList;
@@ -27,24 +50,25 @@ import org.caosdb.server.utils.EntityStatus;
 import org.jdom2.Element;
 
 /**
- * The EntityStateJob is the abstract base class for four EntityJobs.
+ * The EntityStateJob is the abstract base class for four EntityJobs:
  *
- * <p>1. The InitEntityState job reads ClientMessages or StateProperties with tag state and converts
- * them into instances of State. This job runs during WriteTransactions. This job runs during the
- * INIT Phase and does not perform any checks other than those necessary for the conversion.
+ * <p>1. The {@link InitEntityState} job reads ClientMessages or StateProperties with tag state and
+ * converts them into instances of State. This job runs during WriteTransactions. This job runs
+ * during the INIT Phase and does not perform any checks other than those necessary for the
+ * conversion.
  *
- * <p>2. The CheckStateTransition job checks if the attempted state transition is in compliance with
- * the state model. This job runs during the CHECK phase and should do all necessary consistency and
- * permission checks.
+ * <p>2. The {@link CheckStateTransition} job checks if the attempted state transition is in
+ * compliance with the state model. This job runs during the CHECK phase and should do all necessary
+ * consistency and permission checks.
  *
- * <p>3. The MakeStateProperty job constructs an ordinary Property from the State right before the
- * entity is being written to the back-end and after any checks run.
+ * <p>3. The {@link MakeStateProperty} job constructs an ordinary Property from the State right
+ * before the entity is being written to the back-end and after any checks run.
  *
- * <p>4. The MakeStateMessage job converts a state property (back) into State messages and appends
- * them to the entity.
+ * <p>4. The {@link MakeStateMessage} job converts a state property (back) into State messages and
+ * appends them to the entity.
  *
- * <p>Only the 4th job runs during Retrieve transitions. During WriteTransactions all four jobs do
- * run.
+ * <p>Only the 4th job ({@link MakeStateMessage}) runs during Retrieve transitions. During
+ * WriteTransactions all four jobs do run.
  *
  * @author Timm Fitschen (t.fitschen@indiscale.com)
  */
@@ -91,6 +115,10 @@ public abstract class EntityStateJob extends EntityJob {
     private State toState;
     private String name;
 
+    /**
+     * @param transition The transition Entity, from which the Transition is created. Relevant
+     *     Properties are "to" and "from"
+     */
     public Transition(EntityInterface transition) throws Message {
       this.name = transition.getName();
       this.fromState = getFromState(transition);
@@ -167,9 +195,9 @@ public abstract class EntityStateJob extends EntityJob {
   }
 
   /**
-   * The State instance represents a single entity state. This class is used for concrete state (the
-   * state of a stateful entity, say a Record) and abstract states (states which belong to a
-   * StateModel entity).
+   * The State instance represents a single entity state. This class is used for concrete states
+   * (the state of a stateful entity, say a Record) and abstract states (states which are part of a
+   * {@link StateModel}).
    *
    * <p>States are identified via their name and the name of the model to which they belong.
    *
@@ -177,8 +205,8 @@ public abstract class EntityStateJob extends EntityJob {
    * StateModel iff the StateModel RecordType references the State Record. Each State should only
    * belong to one StateModel.
    *
-   * <p>Furthermore, States are the start or end point of Transitions which belong to the same
-   * StateModel. Each State can be part of several transitions at the same time.
+   * <p>Furthermore, States are the start or end point of {@link Transition Transitions} which
+   * belong to the same StateModel. Each State can be part of several transitions at the same time.
    *
    * <p>Note: The purpose of this should not be confused with {@link EntityStatus} which is purely
    * for internal use.
@@ -194,6 +222,7 @@ public abstract class EntityStateJob extends EntityJob {
     private StateModel stateModel;
 
     public State(String stateName, String stateModelName) throws Message {
+      // TODO Make constructors private or protected and outsource to caching factory methods.
       this.stateName = stateName;
       this.stateModelName = stateModelName;
     }
@@ -220,7 +249,12 @@ public abstract class EntityStateJob extends EntityJob {
       return 21364234 + this.getStateName().hashCode() + this.getStateModelName().hashCode();
     }
 
-    /** Serialize this State into XML. */
+    /**
+     * Serialize this State into XML.
+     *
+     * <p>The result looks approximately like this: {@code <State name="My name" model="Model's
+     * name"/>}
+     */
     @Override
     public void addToElement(Element ret) {
       Element e = new Element(STATE_XML_TAG);
@@ -265,7 +299,7 @@ public abstract class EntityStateJob extends EntityJob {
     }
 
     /**
-     * Create a property which represents the current entity state of a stateful entity.
+     * Create a Property which represents the current entity state of a stateful entity.
      *
      * @return stateProperty
      * @throws Message
@@ -295,7 +329,27 @@ public abstract class EntityStateJob extends EntityJob {
 
     @Override
     public String toString() {
-      return "State (name=" + getStateName() + ", model=" + getStateModelName() + ")";
+      String isInitial = null;
+      String isFinal = null;
+      try {
+        isInitial = String.valueOf(isInitial());
+      } catch (Message e) {
+        isInitial = "null";
+      }
+      try {
+        isFinal = String.valueOf(isFinal());
+      } catch (Message e) {
+        isFinal = "null";
+      }
+      return "State (name="
+          + getStateName()
+          + ", model="
+          + getStateModelName()
+          + ", initial="
+          + isInitial
+          + ", final="
+          + isFinal
+          + ")";
     }
   }
 
@@ -323,6 +377,7 @@ public abstract class EntityStateJob extends EntityJob {
 
     public StateModel(EntityInterface stateModelEntity) throws Message {
       long time1 = System.currentTimeMillis();
+      // TODO Maybe check if a parent is STATE_MODEL_RECORD_TYPE_NAME?
       this.name = stateModelEntity.getName();
       this.transitions = getTransitions(stateModelEntity);
       this.states = getStates(transitions, this);
@@ -335,6 +390,7 @@ public abstract class EntityStateJob extends EntityJob {
     }
 
     private State getInitialState(EntityInterface stateModelEntity) throws Message {
+      // TODO maybe check if there is more than one "initial" Property?
       for (Property p : stateModelEntity.getProperties()) {
         if (p.getName().equals(INITIAL_STATE_PROPERTY_NAME)) {
           return createState(p);
@@ -344,6 +400,7 @@ public abstract class EntityStateJob extends EntityJob {
     }
 
     private State getFinalState(EntityInterface stateModelEntity) throws Message {
+      // TODO maybe check if there is more than one "final" Property?
       for (Property p : stateModelEntity.getProperties()) {
         if (p.getName().equals(FINAL_STATE_PROPERTY_NAME)) {
           return createState(p);
@@ -352,6 +409,7 @@ public abstract class EntityStateJob extends EntityJob {
       return null;
     }
 
+    /** Transitions are taken from list Property with name="Transition". */
     private Set<Transition> getTransitions(EntityInterface stateModelEntity) throws Message {
       for (Property p : stateModelEntity.getProperties()) {
         if (p.getName().equals(TRANSITION_RECORD_TYPE_NAME)) {
@@ -372,6 +430,7 @@ public abstract class EntityStateJob extends EntityJob {
       Set<Transition> result = new HashSet<>();
       try {
         if (!(p.getDatatype() instanceof AbstractCollectionDatatype)) {
+          // FIXME raise an exception instead?
           return result;
         }
         p.parseValue();
@@ -402,6 +461,7 @@ public abstract class EntityStateJob extends EntityJob {
      */
     private Set<State> getStates(Set<Transition> transitions, StateModel stateModel)
         throws Message {
+      // TODO Move outside of this class
       Iterator<Transition> it = transitions.iterator();
       Set<State> result = new HashSet<>();
       while (it.hasNext()) {
@@ -452,7 +512,9 @@ public abstract class EntityStateJob extends EntityJob {
       Iterator<Transition> iterator = this.transitions.iterator();
       while (iterator.hasNext()) {
         sb.append(iterator.next().name);
+        sb.append(" -> ");
         sb.append(iterator.next().name);
+        sb.append(", ");
       }
       sb.append("])");
       return sb.toString();
@@ -505,6 +567,7 @@ public abstract class EntityStateJob extends EntityJob {
     return getState(getEntity(), remove);
   }
 
+  /** Return (and possibly remove) the States Properties of `entity`. */
   protected List<Property> getStateProperties(EntityInterface entity, boolean remove) {
     Iterator<Property> it = entity.getProperties().iterator();
     List<Property> result = new ArrayList<>();
@@ -527,6 +590,7 @@ public abstract class EntityStateJob extends EntityJob {
     return getStateProperties(getEntity(), remove);
   }
 
+  /** Get the {@code ClientMessage}s which denote a state. */
   protected List<ClientMessage> getStateClientMessages(EntityInterface entity, boolean remove) {
     Iterator<Message> stateMessages = entity.getMessages(STATE_XML_TAG).iterator();
     List<ClientMessage> result = new ArrayList<>();
@@ -561,13 +625,15 @@ public abstract class EntityStateJob extends EntityJob {
   /**
    * Create a State instance from the value of the state property.
    *
-   * <p>This method also retrieves the state entity from the back-end.
+   * <p>This method also retrieves the state entity from the back-end. The StateModel is deduced
+   * from finding an appropriately referencing StateModel Record.
    *
    * @param p the entity's state property
    * @return The state of the entity
    * @throws Message
    */
   protected State createState(Property p) throws Message {
+    // TODO this should be cached
     try {
       p.parseValue();
       ReferenceValue refid = (ReferenceValue) p.getValue();
@@ -584,6 +650,7 @@ public abstract class EntityStateJob extends EntityJob {
 
   EntityInterface findStateModel(EntityInterface stateEntity) throws Exception {
     // TODO this should be cached
+    // TODO This should throw a meaningful Exception if no matching StateModel can be found.
     TransactionContainer c = new TransactionContainer();
     Query query =
         new Query(
diff --git a/src/main/java/org/caosdb/server/jobs/core/InitEntityStateJobs.java b/src/main/java/org/caosdb/server/jobs/core/InitEntityStateJobs.java
index 8bb1e00a..66d3db12 100644
--- a/src/main/java/org/caosdb/server/jobs/core/InitEntityStateJobs.java
+++ b/src/main/java/org/caosdb/server/jobs/core/InitEntityStateJobs.java
@@ -1,3 +1,26 @@
+/*
+ * ** header v3.0
+ * This file is a part of the CaosDB Project.
+ *
+ * Copyright (C) 2020 IndiScale GmbH <info@indiscale.com>
+ * Copyright (C) 2020 Timm Fitschen <t.fitschen@indiscale.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ *
+ * ** end header
+ */
+
 package org.caosdb.server.jobs.core;
 
 import java.util.ArrayList;
@@ -19,8 +42,8 @@ import org.caosdb.server.utils.Observable;
 import org.caosdb.server.utils.Observer;
 
 /**
- * Initialize the other entity jobs by converting the client message with type "State" into {@link
- * State} instances.
+ * Initialize the other entity jobs by converting the client message with type "State" or
+ * StateProperties into {@link State} instances.
  *
  * <p>This job also needs to initialize the other jobs even if the current entity version does not
  * have a state anymore but the previous version had, because it has to be checked if the stateModel
@@ -105,7 +128,8 @@ public class InitEntityStateJobs extends EntityStateJob implements Observer {
   }
 
   /**
-   * Returns a list of states as the are represented as properties or client messages in the entity.
+   * Return a list of states from their representations as properties or client messages in the
+   * entity.
    *
    * @param entity
    * @return list of state instances for the entity.
diff --git a/src/main/java/org/caosdb/server/jobs/core/MakeStateMessage.java b/src/main/java/org/caosdb/server/jobs/core/MakeStateMessage.java
index 38fd2398..245b90b0 100644
--- a/src/main/java/org/caosdb/server/jobs/core/MakeStateMessage.java
+++ b/src/main/java/org/caosdb/server/jobs/core/MakeStateMessage.java
@@ -1,3 +1,26 @@
+/*
+ * ** header v3.0
+ * This file is a part of the CaosDB Project.
+ *
+ * Copyright (C) 2020 IndiScale GmbH <info@indiscale.com>
+ * Copyright (C) 2020 Timm Fitschen <t.fitschen@indiscale.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ *
+ * ** end header
+ */
+
 package org.caosdb.server.jobs.core;
 
 import java.util.List;
diff --git a/src/main/java/org/caosdb/server/jobs/core/MakeStateProperty.java b/src/main/java/org/caosdb/server/jobs/core/MakeStateProperty.java
index 0d290c0f..56682921 100644
--- a/src/main/java/org/caosdb/server/jobs/core/MakeStateProperty.java
+++ b/src/main/java/org/caosdb/server/jobs/core/MakeStateProperty.java
@@ -1,3 +1,26 @@
+/*
+ * ** header v3.0
+ * This file is a part of the CaosDB Project.
+ *
+ * Copyright (C) 2020 IndiScale GmbH <info@indiscale.com>
+ * Copyright (C) 2020 Timm Fitschen <t.fitschen@indiscale.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ *
+ * ** end header
+ */
+
 package org.caosdb.server.jobs.core;
 
 import org.caosdb.server.entity.Message;
@@ -5,6 +28,10 @@ import org.caosdb.server.jobs.JobAnnotation;
 import org.caosdb.server.jobs.JobExecutionTime;
 import org.caosdb.server.transaction.WriteTransaction;
 
+/**
+ * This job constructs an ordinary Property from the State right before the entity is being written
+ * to the back-end and after any checks run.
+ */
 @JobAnnotation(transaction = WriteTransaction.class, time = JobExecutionTime.PRE_TRANSACTION)
 public class MakeStateProperty extends EntityStateJob {
 
diff --git a/src/main/java/org/caosdb/server/transaction/Update.java b/src/main/java/org/caosdb/server/transaction/Update.java
index 50d7f978..894728cc 100644
--- a/src/main/java/org/caosdb/server/transaction/Update.java
+++ b/src/main/java/org/caosdb/server/transaction/Update.java
@@ -4,6 +4,8 @@
  *
  * Copyright (C) 2018 Research Group Biomedical Physics,
  * Max-Planck-Institute for Dynamics and Self-Organization Göttingen
+ * Copyright (C) 2020 Indiscale GmbH <info@indiscale.com>
+ * Copyright (C) 2020 Timm Fitschen <t.fitschen@indiscale.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
diff --git a/src/main/java/org/caosdb/server/utils/AbstractObservable.java b/src/main/java/org/caosdb/server/utils/AbstractObservable.java
index a19fff9d..abc7f0a0 100644
--- a/src/main/java/org/caosdb/server/utils/AbstractObservable.java
+++ b/src/main/java/org/caosdb/server/utils/AbstractObservable.java
@@ -37,6 +37,7 @@ public abstract class AbstractObservable implements Observable {
     return this.observers.add(o);
   }
 
+  /** @param e A String denoting the notification event. */
   @Override
   public void notifyObservers(final String e) {
     if (this.observers != null) {
diff --git a/src/main/java/org/caosdb/server/utils/Observer.java b/src/main/java/org/caosdb/server/utils/Observer.java
index be89dff4..b4c8f544 100644
--- a/src/main/java/org/caosdb/server/utils/Observer.java
+++ b/src/main/java/org/caosdb/server/utils/Observer.java
@@ -25,6 +25,8 @@ package org.caosdb.server.utils;
 public interface Observer {
 
   /**
+   * Notify this observer that an event {@code e} has happened to the {@code sender}.
+   *
    * @param e
    * @param sender
    * @return true, iff the Observable has to keep it in the list of observers.
-- 
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