diff --git a/src/main/java/ch/ethz/seb/sebserver/gbl/model/Entity.java b/src/main/java/ch/ethz/seb/sebserver/gbl/model/Entity.java
index 07e438e3..be3f84cd 100644
--- a/src/main/java/ch/ethz/seb/sebserver/gbl/model/Entity.java
+++ b/src/main/java/ch/ethz/seb/sebserver/gbl/model/Entity.java
@@ -13,18 +13,29 @@ import com.fasterxml.jackson.annotation.JsonIgnore;
 import ch.ethz.seb.sebserver.gbl.api.API;
 import ch.ethz.seb.sebserver.gbl.api.EntityType;
 
+/** Defines generic interface for all types of Entity. */
 public interface Entity extends ModelIdAware {
 
     public static final String FILTER_ATTR_INSTITUTION = API.PARAM_INSTITUTION_ID;
     public static final String FILTER_ATTR_ACTIVE = "active";
     public static final String FILTER_ATTR_NAME = "name";
 
+    /** Get the type of the entity.
+     *
+     * @return the type of the entity */
     @JsonIgnore
     EntityType entityType();
 
+    /** Get the name of the entity
+     *
+     * @return the name of the entity */
     @JsonIgnore
     String getName();
 
+    /** Get an unique EntityKey for the entity consisting of the model identifier of the entity
+     * and the type of the entity.
+     * 
+     * @return unique EntityKey for the entity */
     @JsonIgnore
     default EntityKey getEntityKey() {
         final String modelId = getModelId();
@@ -34,6 +45,10 @@ public interface Entity extends ModelIdAware {
         return new EntityKey(modelId, entityType());
     }
 
+    /** Creates an EntityName instance from a given Entity.
+     *
+     * @param entity The Entity instance
+     * @return EntityName instance created form given Entity */
     public static EntityName toName(final Entity entity) {
         return new EntityName(
                 entity.entityType(),
diff --git a/src/main/java/ch/ethz/seb/sebserver/gbl/model/EntityKey.java b/src/main/java/ch/ethz/seb/sebserver/gbl/model/EntityKey.java
index 9f6aca6b..636eeb40 100644
--- a/src/main/java/ch/ethz/seb/sebserver/gbl/model/EntityKey.java
+++ b/src/main/java/ch/ethz/seb/sebserver/gbl/model/EntityKey.java
@@ -17,17 +17,25 @@ import com.fasterxml.jackson.annotation.JsonProperty;
 
 import ch.ethz.seb.sebserver.gbl.api.EntityType;
 
+/** A EntityKey uniquely identifies a domain entity within the SEB Server's domain model.
+ * A EntityKey consists of the model identifier of a domain entity and the type of the entity. */
 public class EntityKey implements Serializable {
 
     private static final long serialVersionUID = -2368065921846821061L;
 
+    /** The model identifier of the entity */
     @JsonProperty(value = "modelId", required = true)
     @NotNull
     public final String modelId;
+
+    /** The type of the entity */
     @JsonProperty(value = "entityType", required = true)
     @NotNull
     public final EntityType entityType;
 
+    /** pre-calculated hash value. Since EntityKey is fully immutable this is a valid optimization */
+    private final int hash;
+
     @JsonCreator
     public EntityKey(
             @JsonProperty(value = "modelId", required = true) final String modelId,
@@ -42,31 +50,41 @@ public class EntityKey implements Serializable {
 
         this.modelId = modelId;
         this.entityType = entityType;
+
+        final int prime = 31;
+        int result = 1;
+        result = prime * result + ((this.entityType == null) ? 0 : this.entityType.hashCode());
+        result = prime * result + ((this.modelId == null) ? 0 : this.modelId.hashCode());
+        this.hash = result;
     }
 
     public EntityKey(
             final Long pk,
             final EntityType entityType) {
 
-        this.modelId = String.valueOf(pk);
-        this.entityType = entityType;
+        this(String.valueOf(pk), entityType);
+        if (pk == null) {
+            throw new IllegalArgumentException("modelId has null reference");
+        }
     }
 
+    /** Get the model identifier of this EntityKey
+     *
+     * @return the model identifier of this EntityKey */
     public String getModelId() {
         return this.modelId;
     }
 
+    /** Get the entity type EntityKey
+     *
+     * @return the model identifier of this EntityKey */
     public EntityType getEntityType() {
         return this.entityType;
     }
 
     @Override
     public int hashCode() {
-        final int prime = 31;
-        int result = 1;
-        result = prime * result + ((this.entityType == null) ? 0 : this.entityType.hashCode());
-        result = prime * result + ((this.modelId == null) ? 0 : this.modelId.hashCode());
-        return result;
+        return this.hash;
     }
 
     @Override
diff --git a/src/main/java/ch/ethz/seb/sebserver/gbl/model/ModelIdAware.java b/src/main/java/ch/ethz/seb/sebserver/gbl/model/ModelIdAware.java
index 59d9a61e..9dcafbd1 100644
--- a/src/main/java/ch/ethz/seb/sebserver/gbl/model/ModelIdAware.java
+++ b/src/main/java/ch/ethz/seb/sebserver/gbl/model/ModelIdAware.java
@@ -10,8 +10,12 @@ package ch.ethz.seb.sebserver.gbl.model;
 
 import com.fasterxml.jackson.annotation.JsonIgnore;
 
+/** Interface for all domain model objects that has a model identifier */
 public interface ModelIdAware {
 
+    /** Get the model identifier of the domain model object
+     *
+     * @return the model identifier of the domain model object */
     @JsonIgnore
     String getModelId();
 
diff --git a/src/main/java/ch/ethz/seb/sebserver/gbl/util/Result.java b/src/main/java/ch/ethz/seb/sebserver/gbl/util/Result.java
index fb9cf2d5..ebdc3b5b 100644
--- a/src/main/java/ch/ethz/seb/sebserver/gbl/util/Result.java
+++ b/src/main/java/ch/ethz/seb/sebserver/gbl/util/Result.java
@@ -84,6 +84,12 @@ public final class Result<T> {
         return this.error != null ? errorHandler.apply(this.error) : this.value;
     }
 
+    /** Use this to get the referenced result element or on error case, use the given error handler
+     * to handle the error and use a given supplier to get an alternative element for further processing
+     *
+     * @param errorHandler the error handler to handle an error if happened
+     * @param supplier supplies an alternative result element on error case
+     * @return returns the referenced result element or the alternative element given by the supplier on error */
     public T get(final Consumer<Throwable> errorHandler, final Supplier<T> supplier) {
         if (this.error != null) {
             errorHandler.accept(this.error);
@@ -93,6 +99,9 @@ public final class Result<T> {
         }
     }
 
+    /** Apply a given error handler that consumes the error if there is one.
+     *
+     * @param errorHandler the error handler */
     public void handleError(final Consumer<Throwable> errorHandler) {
         if (this.error != null) {
             errorHandler.accept(this.error);
@@ -120,6 +129,9 @@ public final class Result<T> {
         return this.value;
     }
 
+    /** Get the referenced result element or in error case, throws the referenced error
+     *
+     * @return the referenced result element */
     public T getOrThrow() {
         if (this.error != null) {
             if (this.error instanceof RuntimeException) {
@@ -145,6 +157,9 @@ public final class Result<T> {
         return this.error;
     }
 
+    /** Indicates whether this Result refers to an error or not.
+     *
+     * @return true if this Result refers to an error */
     public boolean hasError() {
         return this.error != null;
     }
@@ -210,9 +225,14 @@ public final class Result<T> {
         }
     }
 
-    public Result<T> onErrorDo(final Consumer<Throwable> block) {
+    /** Uses a given error handler to apply an error if there is one and returning itself again
+     * for further processing.
+     * 
+     * @param errorHandler the error handler
+     * @return self reference */
+    public Result<T> onErrorDo(final Consumer<Throwable> errorHandler) {
         if (this.error != null) {
-            block.accept(this.error);
+            errorHandler.accept(this.error);
         }
         return this;
     }
diff --git a/src/main/java/ch/ethz/seb/sebserver/gbl/util/Tuple.java b/src/main/java/ch/ethz/seb/sebserver/gbl/util/Tuple.java
index 269f004f..ed8b4fa9 100644
--- a/src/main/java/ch/ethz/seb/sebserver/gbl/util/Tuple.java
+++ b/src/main/java/ch/ethz/seb/sebserver/gbl/util/Tuple.java
@@ -8,9 +8,12 @@
 
 package ch.ethz.seb.sebserver.gbl.util;
 
+/** A tuple of two elements of the same type */
 public class Tuple<T> {
 
+    /** The first element of the tuple */
     public final T _1;
+    /** The second element of the tuple */
     public final T _2;
 
     public Tuple(final T _1, final T _2) {
diff --git a/src/main/java/ch/ethz/seb/sebserver/gbl/util/Utils.java b/src/main/java/ch/ethz/seb/sebserver/gbl/util/Utils.java
index 26170478..13fa7245 100644
--- a/src/main/java/ch/ethz/seb/sebserver/gbl/util/Utils.java
+++ b/src/main/java/ch/ethz/seb/sebserver/gbl/util/Utils.java
@@ -29,12 +29,20 @@ import ch.ethz.seb.sebserver.gbl.Constants;
 
 public final class Utils {
 
+    /** Get an immutable List from a Collection of elements
+     *
+     * @param collection Collection of elements
+     * @return immutable List */
     public static <T> List<T> immutableListOf(final Collection<T> collection) {
         return (collection != null)
                 ? Collections.unmodifiableList(new ArrayList<>(collection))
                 : Collections.emptyList();
     }
 
+    /** Get a immutable Collection from a Collection of elements
+     *
+     * @param collection Collection of elements
+     * @return immutable Collection */
     public static <T> Collection<T> immutableCollectionOf(final Collection<T> collection) {
         return (collection != null)
                 ? Collections.unmodifiableCollection(collection)
@@ -53,10 +61,18 @@ public final class Utils {
         return Collections.unmodifiableCollection(Arrays.asList(values));
     }
 
+    /** Get a immutable Set from a Collection of elements
+     *
+     * @param collection Collection of elements
+     * @return immutable Set */
     public static <T> Set<T> immutableSetOf(final Collection<T> collection) {
         return immutableSetOf(new HashSet<>(collection));
     }
 
+    /** Get a immutable Set from a Set of elements
+     *
+     * @param set Set of elements
+     * @return immutable Set */
     public static <T> Set<T> immutableSetOf(final Set<T> set) {
         return (set != null)
                 ? Collections.unmodifiableSet(set)
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/authorization/PermissionDeniedException.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/authorization/PermissionDeniedException.java
index 48a1b721..c27e2d2b 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/authorization/PermissionDeniedException.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/authorization/PermissionDeniedException.java
@@ -15,8 +15,11 @@ public class PermissionDeniedException extends RuntimeException {
 
     private static final long serialVersionUID = 5333137812363042580L;
 
+    /** The EntityType of the denied permission check */
     public final EntityType entityType;
+    /** The PrivilegeType of the denied permission check */
     public final PrivilegeType privilegeType;
+    /** The user identifier of the denied permission check */
     public final String userId;
 
     public PermissionDeniedException(
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/client/ClientCredentials.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/client/ClientCredentials.java
index 652c9a91..dede5a95 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/client/ClientCredentials.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/client/ClientCredentials.java
@@ -1,6 +1,6 @@
 /*
  * Copyright (c) 2019 ETH Zürich, Educational Development and Technology (LET)
- * 
+ *
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
@@ -8,16 +8,20 @@
 
 package ch.ethz.seb.sebserver.webservice.servicelayer.client;
 
+/** Defines a simple data bean holding (encrypted) client credentials */
 public final class ClientCredentials {
+    /** The client id or client name parameter */
     public final String clientId;
+    /** The client secret parameter */
     public final String secret;
+    /** An client access token if supported */
     public final String accessToken;
 
     public ClientCredentials(
-            final String clientId, 
-            final String secret, 
+            final String clientId,
+            final String secret,
             final String accessToken) {
-        
+
         this.clientId = clientId;
         this.secret = secret;
         this.accessToken = accessToken;
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/ActivatableEntityDAO.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/ActivatableEntityDAO.java
index cd47fcff..2b6263db 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/ActivatableEntityDAO.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/ActivatableEntityDAO.java
@@ -16,7 +16,7 @@ import ch.ethz.seb.sebserver.gbl.model.EntityKey;
 import ch.ethz.seb.sebserver.gbl.model.ModelIdAware;
 import ch.ethz.seb.sebserver.gbl.util.Result;
 
-/** Interface of a DAO for an Entity that has activation feature.
+/** Interface of a Data Access Object for an Entity that has activation feature.
  *
  * @param <T> the type of Entity */
 public interface ActivatableEntityDAO<T extends Entity, M extends ModelIdAware> extends EntityDAO<T, M> {
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/EntityDAO.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/EntityDAO.java
index 1b34902a..50c885de 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/EntityDAO.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/EntityDAO.java
@@ -24,6 +24,10 @@ import ch.ethz.seb.sebserver.gbl.model.EntityName;
 import ch.ethz.seb.sebserver.gbl.model.ModelIdAware;
 import ch.ethz.seb.sebserver.gbl.util.Result;
 
+/** Defines generic interface for all Entity based Data Access Objects
+ *
+ * @param <T> The specific type of the Entity domain model
+ * @param <M> The specific type of the Entity domain model to create a new Entity */
 public interface EntityDAO<T extends Entity, M extends ModelIdAware> {
 
     /** Get the entity type for a concrete EntityDAO implementation.
@@ -34,7 +38,7 @@ public interface EntityDAO<T extends Entity, M extends ModelIdAware> {
     /** Use this to get an Entity instance of concrete type by database identifier/primary-key (PK)
      *
      * @param id the data base identifier of the entity
-     * @return Result refer the Entity instance with the specified database identifier or refer to an error if
+     * @return Result referring the Entity instance with the specified database identifier or refer to an error if
      *         happened */
     Result<T> byPK(Long id);
 
@@ -44,7 +48,7 @@ public interface EntityDAO<T extends Entity, M extends ModelIdAware> {
      * but usually they are the same.
      *
      * @param id the model identifier
-     * @return Result refer the Entity instance with the specified model identifier or refer to an error if
+     * @return Result referring the Entity instance with the specified model identifier or refer to an error if
      *         happened */
     @Transactional(readOnly = true)
     default Result<T> byModelId(final String id) {
@@ -53,12 +57,20 @@ public interface EntityDAO<T extends Entity, M extends ModelIdAware> {
         }).flatMap(this::byPK);
     }
 
-    Result<Collection<T>> loadEntities(Collection<EntityKey> keys);
+    /** Get a collection of all entities for the given Set of entity keys.
+     *
+     * @param keys the Set of EntityKey to get the Entity's for
+     * @return Result referring the collection or an error if happened */
+    Result<Collection<T>> byEntityKeys(Set<EntityKey> keys);
 
+    /** Get a collection of all EntityName for the given Set of EntityKey.
+     *
+     * @param keys the Set of EntityKey to get the EntityName's for
+     * @return Result referring the collection or an error if happened */
     @Transactional(readOnly = true)
-    default Result<Collection<EntityName>> loadEntityNames(final Collection<EntityKey> keys) {
+    default Result<Collection<EntityName>> getEntityNames(final Set<EntityKey> keys) {
         return Result.tryCatch(() -> {
-            return loadEntities(keys)
+            return byEntityKeys(keys)
                     .getOrThrow()
                     .stream()
                     .map(entity -> new EntityName(
@@ -69,27 +81,56 @@ public interface EntityDAO<T extends Entity, M extends ModelIdAware> {
         });
     }
 
+    /** Create a new Entity from the given entity domain model data.
+     *
+     * @param data The entity domain model data
+     * @return Result referring to the newly created Entity or an error if happened */
     Result<T> createNew(M data);
 
     /** Use this to save/modify an entity.
      *
      * @param data entity instance containing all data that should be saved
-     * @return A Result of the entity instance where the successfully saved/modified entity data is available or a
+     * @return A Result referring the entity instance where the successfully saved/modified entity data is available or
+     *         a
      *         reported exception on error case */
     Result<T> save(T data);
 
     /** Use this to delete a set Entity by a Collection of EntityKey
      *
      * @param all The Collection of EntityKey to delete
-     * @return Result of a collection of all entities that has been deleted or refer to an error if
+     * @return Result referring a collection of all entities that has been deleted or refer to an error if
      *         happened */
     Result<Collection<EntityKey>> delete(Set<EntityKey> all);
 
+    /** Get a (unordered) collection of all Entities that matches the given filter criteria.
+     * The possible filter criteria for a specific Entity type is defined by the entity type.
+     * 
+     * This adds filtering in SQL level by creating the select where clause from related
+     * filter criteria of the specific Entity type. If the filterMap contains a value for
+     * a particular filter criteria the value is extracted from the map and added to the where
+     * clause of the SQL select statement.
+     * 
+     * @param filterMap FilterMap instance containing all the relevant filter criteria
+     * @return Result referring to collection of all matching entities or an error if happened */
     @Transactional(readOnly = true)
     default Result<Collection<T>> allMatching(final FilterMap filterMap) {
         return allMatching(filterMap, e -> true);
     }
 
+    /** Get a (unordered) collection of all Entities that matches a given filter criteria
+     * and a given predicate.
+     * 
+     * The possible filter criteria for a specific Entity type is defined by the entity type.
+     * This adds filtering in SQL level by creating the select where clause from related
+     * filter criteria of the specific Entity type. If the filterMap contains a value for
+     * a particular filter criteria the value is extracted from the map and added to the where
+     * clause of the SQL select statement.
+     * 
+     * The predicate is applied after the SQL query by filtering the resulting list with the
+     * predicate after on the SQL query result, before returning.
+     * 
+     * @param filterMap FilterMap instance containing all the relevant filter criteria
+     * @return Result referring to collection of all matching entities or an error if happened */
     Result<Collection<T>> allMatching(FilterMap filterMap, Predicate<T> predicate);
 
     /** Context based utility method to extract an expected single resource entry form a Collection of specified type.
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/ExamDAO.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/ExamDAO.java
index dcec75f7..c2e5cd7d 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/ExamDAO.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/ExamDAO.java
@@ -11,10 +11,6 @@ package ch.ethz.seb.sebserver.webservice.servicelayer.dao;
 import ch.ethz.seb.sebserver.gbl.model.exam.Exam;
 import ch.ethz.seb.sebserver.webservice.servicelayer.bulkaction.BulkActionSupportDAO;
 
+/** Concrete EntityDAO interface of Exam entities */
 public interface ExamDAO extends ActivatableEntityDAO<Exam, Exam>, BulkActionSupportDAO<Exam> {
-
-//    Result<Exam> importFromQuizData(Long institutionId, Long lmsSetupId, QuizData quizData);
-//
-//    Result<Exam> byQuizId(String quizId);
-
 }
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/FilterMap.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/FilterMap.java
index 035eb1ab..43c6ca9c 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/FilterMap.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/FilterMap.java
@@ -22,6 +22,12 @@ import ch.ethz.seb.sebserver.gbl.model.institution.SebClientConfig;
 import ch.ethz.seb.sebserver.gbl.model.user.UserInfo;
 import ch.ethz.seb.sebserver.webservice.datalayer.batis.JodaTimeTypeResolver;
 
+/** A Map containing various filter criteria from a certain API request.
+ * This is used as a data object that can be used to collect API request parameter
+ * data on one side and supply filter criteria based access to concrete Entity filtering
+ * on the other side.
+ * 
+ * All text based filter criteria are used as SQL wildcard's */
 public class FilterMap extends POSTMapper {
 
     public FilterMap() {
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/IndicatorDAO.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/IndicatorDAO.java
index caec6323..86da7e9f 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/IndicatorDAO.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/IndicatorDAO.java
@@ -14,8 +14,13 @@ import ch.ethz.seb.sebserver.gbl.model.exam.Indicator;
 import ch.ethz.seb.sebserver.gbl.util.Result;
 import ch.ethz.seb.sebserver.webservice.servicelayer.bulkaction.BulkActionSupportDAO;
 
+/** Concrete EntityDAO interface of Indicator entities */
 public interface IndicatorDAO extends EntityDAO<Indicator, Indicator>, BulkActionSupportDAO<Indicator> {
 
+    /** Get a collection of all Indicator entities for a specified exam.
+     *
+     * @param examId the Exam identifier to get the Indicators for
+     * @return Result referring to the collection of Indicators of an Exam or to an error if happened */
     Result<Collection<Indicator>> allForExam(Long examId);
 
 }
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/InstitutionDAO.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/InstitutionDAO.java
index ccc4a75b..2388ef8f 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/InstitutionDAO.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/InstitutionDAO.java
@@ -11,9 +11,8 @@ package ch.ethz.seb.sebserver.webservice.servicelayer.dao;
 import ch.ethz.seb.sebserver.gbl.model.institution.Institution;
 import ch.ethz.seb.sebserver.webservice.servicelayer.bulkaction.BulkActionSupportDAO;
 
-public interface InstitutionDAO
-        extends ActivatableEntityDAO<Institution, Institution>, BulkActionSupportDAO<Institution> {
-
-    boolean exists(String name);
-
+/** Concrete EntityDAO interface of Institution entities */
+public interface InstitutionDAO extends
+        ActivatableEntityDAO<Institution, Institution>,
+        BulkActionSupportDAO<Institution> {
 }
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/LmsSetupDAO.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/LmsSetupDAO.java
index 39c40170..cfdea8ab 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/LmsSetupDAO.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/LmsSetupDAO.java
@@ -13,7 +13,13 @@ import ch.ethz.seb.sebserver.gbl.util.Result;
 import ch.ethz.seb.sebserver.webservice.servicelayer.bulkaction.BulkActionSupportDAO;
 import ch.ethz.seb.sebserver.webservice.servicelayer.client.ClientCredentials;
 
+/** Concrete EntityDAO interface of LmsSetup entities */
 public interface LmsSetupDAO extends ActivatableEntityDAO<LmsSetup, LmsSetup>, BulkActionSupportDAO<LmsSetup> {
 
+    /** Get the configured ClientCredentials for a given LmsSetup.
+     * The ClientCredentials are still encoded as they are on DB storage
+     * 
+     * @param lmsSetupId the identifier of the LmsSetup to get the ClientCredentials for
+     * @return the configured ClientCredentials for a given LmsSetup */
     Result<ClientCredentials> getLmsAPIAccessCredentials(String lmsSetupId);
 }
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/ResourceNotFoundException.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/ResourceNotFoundException.java
index af2103b1..89069b03 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/ResourceNotFoundException.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/ResourceNotFoundException.java
@@ -14,6 +14,7 @@ import org.springframework.web.bind.annotation.ResponseStatus;
 import ch.ethz.seb.sebserver.gbl.api.EntityType;
 import ch.ethz.seb.sebserver.gbl.model.EntityKey;
 
+/** Thrown by Data Access Object if an requested Entity or other requested resource wasn't found */
 @ResponseStatus(HttpStatus.NOT_FOUND)
 public final class ResourceNotFoundException extends RuntimeException {
 
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/SebClientConfigDAO.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/SebClientConfigDAO.java
index e23be8c3..fe516e50 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/SebClientConfigDAO.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/SebClientConfigDAO.java
@@ -13,10 +13,16 @@ import ch.ethz.seb.sebserver.gbl.util.Result;
 import ch.ethz.seb.sebserver.webservice.servicelayer.bulkaction.BulkActionSupportDAO;
 import ch.ethz.seb.sebserver.webservice.servicelayer.client.ClientCredentials;
 
+/** Concrete EntityDAO interface of SebClientConfig entities */
 public interface SebClientConfigDAO extends
         ActivatableEntityDAO<SebClientConfig, SebClientConfig>,
         BulkActionSupportDAO<SebClientConfig> {
 
+    /** Get the configured ClientCredentials for a given SebClientConfig.
+     * The ClientCredentials are still encoded as they are on DB storage
+     *
+     * @param modelId the model identifier of the SebClientConfig to get the ClientCredentials for
+     * @return the configured ClientCredentials for a given SebClientConfig */
     Result<ClientCredentials> getSebClientCredentials(String modelId);
 
 }
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/TransactionHandler.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/TransactionHandler.java
index e3533537..37812a36 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/TransactionHandler.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/TransactionHandler.java
@@ -10,6 +10,7 @@ package ch.ethz.seb.sebserver.webservice.servicelayer.dao;
 
 import org.springframework.transaction.interceptor.TransactionInterceptor;
 
+/** Defines some static Spring based transaction handling functionality for rollback handling */
 public interface TransactionHandler {
 
     /** Use this to mark the current transaction within the calling thread as "to rollback".
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/UserActivityLogDAO.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/UserActivityLogDAO.java
index 05c574ef..a1e4d21c 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/UserActivityLogDAO.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/UserActivityLogDAO.java
@@ -17,6 +17,7 @@ import ch.ethz.seb.sebserver.gbl.model.user.UserActivityLog;
 import ch.ethz.seb.sebserver.gbl.util.Result;
 import ch.ethz.seb.sebserver.webservice.servicelayer.authorization.SEBServerUser;
 
+/** Concrete EntityDAO interface of UserActivityLog entities */
 public interface UserActivityLogDAO extends
         EntityDAO<UserActivityLog, UserActivityLog>,
         UserRelatedEntityDAO<UserActivityLog> {
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/UserRelatedEntityDAO.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/UserRelatedEntityDAO.java
index 01c101cc..5f0a708e 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/UserRelatedEntityDAO.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/UserRelatedEntityDAO.java
@@ -13,8 +13,7 @@ import java.util.Collection;
 import ch.ethz.seb.sebserver.gbl.model.Entity;
 import ch.ethz.seb.sebserver.gbl.util.Result;
 
-/** Interface for a DAo handling an Entity with relations to an user (account)
- *
+/** Interface for all Data Access Objects handling an Entity with relations to an user (account)
  *
  * @param <T> the concrete type of the Entity */
 public interface UserRelatedEntityDAO<T extends Entity> {
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/ExamDAOImpl.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/ExamDAOImpl.java
index 759914d4..e36b000c 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/ExamDAOImpl.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/ExamDAOImpl.java
@@ -285,7 +285,7 @@ public class ExamDAOImpl implements ExamDAO {
 
     @Override
     @Transactional(readOnly = true)
-    public Result<Collection<Exam>> loadEntities(final Collection<EntityKey> keys) {
+    public Result<Collection<Exam>> byEntityKeys(final Set<EntityKey> keys) {
         return Result.tryCatch(() -> {
             final List<Long> ids = extractPKsFromKeys(keys);
             return this.examRecordMapper.selectByExample()
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/IndicatorDAOImpl.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/IndicatorDAOImpl.java
index e84a0711..0ba770bb 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/IndicatorDAOImpl.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/IndicatorDAOImpl.java
@@ -105,7 +105,7 @@ public class IndicatorDAOImpl implements IndicatorDAO {
 
     @Override
     @Transactional(readOnly = true)
-    public Result<Collection<Indicator>> loadEntities(final Collection<EntityKey> keys) {
+    public Result<Collection<Indicator>> byEntityKeys(final Set<EntityKey> keys) {
         return Result.tryCatch(() -> {
             final List<Long> ids = extractPKsFromKeys(keys);
 
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/InstitutionDAOImpl.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/InstitutionDAOImpl.java
index 90fd402d..3c68e42d 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/InstitutionDAOImpl.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/InstitutionDAOImpl.java
@@ -56,21 +56,6 @@ public class InstitutionDAOImpl implements InstitutionDAO {
         return EntityType.INSTITUTION;
     }
 
-    @Override
-    @Transactional(readOnly = true)
-    public boolean exists(final String name) {
-        if (StringUtils.isBlank(name)) {
-            return false;
-        }
-
-        final Long count = this.institutionRecordMapper.countByExample()
-                .where(InstitutionRecordDynamicSqlSupport.name, isEqualTo(name))
-                .build()
-                .execute();
-
-        return count != null && count.longValue() > 0;
-    }
-
     @Override
     @Transactional(readOnly = true)
     public Result<Institution> byPK(final Long id) {
@@ -248,7 +233,7 @@ public class InstitutionDAOImpl implements InstitutionDAO {
 
     @Override
     @Transactional(readOnly = true)
-    public Result<Collection<Institution>> loadEntities(final Collection<EntityKey> keys) {
+    public Result<Collection<Institution>> byEntityKeys(final Set<EntityKey> keys) {
         return Result.tryCatch(() -> {
             final List<Long> ids = extractPKsFromKeys(keys);
 
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/LmsSetupDAOImpl.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/LmsSetupDAOImpl.java
index 78fdbdd6..88f3344e 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/LmsSetupDAOImpl.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/LmsSetupDAOImpl.java
@@ -252,7 +252,7 @@ public class LmsSetupDAOImpl implements LmsSetupDAO {
 
     @Override
     @Transactional(readOnly = true)
-    public Result<Collection<LmsSetup>> loadEntities(final Collection<EntityKey> keys) {
+    public Result<Collection<LmsSetup>> byEntityKeys(final Set<EntityKey> keys) {
         return Result.tryCatch(() -> {
             final List<Long> ids = extractPKsFromKeys(keys);
 
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/SebClientConfigDAOImpl.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/SebClientConfigDAOImpl.java
index 5ca2aad1..84bc4511 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/SebClientConfigDAOImpl.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/SebClientConfigDAOImpl.java
@@ -223,7 +223,7 @@ public class SebClientConfigDAOImpl implements SebClientConfigDAO {
 
     @Override
     @Transactional(readOnly = true)
-    public Result<Collection<SebClientConfig>> loadEntities(final Collection<EntityKey> keys) {
+    public Result<Collection<SebClientConfig>> byEntityKeys(final Set<EntityKey> keys) {
         return Result.tryCatch(() -> {
             final List<Long> ids = extractPKsFromKeys(keys);
 
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/UserActivityLogDAOImpl.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/UserActivityLogDAOImpl.java
index 56188ea5..48aff299 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/UserActivityLogDAOImpl.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/UserActivityLogDAOImpl.java
@@ -317,7 +317,7 @@ public class UserActivityLogDAOImpl implements UserActivityLogDAO {
 
     @Override
     @Transactional(readOnly = true)
-    public Result<Collection<UserActivityLog>> loadEntities(final Collection<EntityKey> keys) {
+    public Result<Collection<UserActivityLog>> byEntityKeys(final Set<EntityKey> keys) {
         // TODO Auto-generated method stub
         return Result.ofTODO();
     }
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/UserDAOImpl.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/UserDAOImpl.java
index cba6c377..908c1535 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/UserDAOImpl.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/UserDAOImpl.java
@@ -343,7 +343,7 @@ public class UserDAOImpl implements UserDAO {
 
     @Override
     @Transactional(readOnly = true)
-    public Result<Collection<UserInfo>> loadEntities(final Collection<EntityKey> keys) {
+    public Result<Collection<UserInfo>> byEntityKeys(final Set<EntityKey> keys) {
         return Result.tryCatch(() -> {
             final List<Long> ids = extractPKsFromKeys(keys);
 
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/validation/BeanValidationService.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/validation/BeanValidationService.java
index 34b371ab..12d05388 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/validation/BeanValidationService.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/validation/BeanValidationService.java
@@ -22,6 +22,11 @@ import ch.ethz.seb.sebserver.gbl.profile.WebServiceProfile;
 import ch.ethz.seb.sebserver.gbl.util.Result;
 import ch.ethz.seb.sebserver.webservice.servicelayer.dao.ActivatableEntityDAO;
 
+/** This service can be used to 'manually' validate a Bean that is annotated within bean
+ * validation annotations.
+ * 
+ * On validation error BeanValidationException is used to collect all validation issues
+ * and report them within the Result. */
 @Service
 @WebServiceProfile
 public class BeanValidationService {
@@ -41,6 +46,14 @@ public class BeanValidationService {
                         dao -> dao));
     }
 
+    /** Validates a given bean that is annotated with Java bean validation annotations
+     *
+     * On validation error BeanValidationException is used to collect all validation issues
+     * and report them within the Result.
+     *
+     * @param bean the Bean to validate
+     * @return Result referring the Bean if there are no validation issues or to a BeanValidationException
+     *         containing the collected validation issues */
     public <T> Result<T> validateBean(final T bean) {
         final DirectFieldBindingResult errors = new DirectFieldBindingResult(bean, "");
         this.validator.validate(bean, errors);
@@ -51,6 +64,10 @@ public class BeanValidationService {
         return Result.of(bean);
     }
 
+    /** Indicates whether the Entity of a given EntityKey is currently active or not.
+     *
+     * @param entityKey the EntityKey of the Entity to check
+     * @return true if the Entity of a given EntityKey is currently active */
     public boolean isActive(final EntityKey entityKey) {
         final ActivatableEntityDAO<?, ?> activatableEntityDAO = this.activatableDAOs.get(entityKey.entityType);
         if (activatableEntityDAO == null) {
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/weblayer/api/EntityController.java b/src/main/java/ch/ethz/seb/sebserver/webservice/weblayer/api/EntityController.java
index eebff1d2..7021c915 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/weblayer/api/EntityController.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/weblayer/api/EntityController.java
@@ -240,10 +240,10 @@ public abstract class EntityController<T extends GrantEntity, M extends GrantEnt
             return Arrays.asList(StringUtils.split(modelIds, Constants.LIST_SEPARATOR_CHAR))
                     .stream()
                     .map(modelId -> new EntityKey(modelId, this.entityDAO.entityType()))
-                    .collect(Collectors.toList());
+                    .collect(Collectors.toSet());
 
         })
-                .flatMap(this.entityDAO::loadEntities)
+                .flatMap(this.entityDAO::byEntityKeys)
                 .getOrThrow()
                 .stream()
                 .filter(this.authorization::hasReadonlyGrant)
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/weblayer/oauth/RevokeTokenEndpoint.java b/src/main/java/ch/ethz/seb/sebserver/webservice/weblayer/oauth/RevokeTokenEndpoint.java
index bb855b84..3cd3c96a 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/weblayer/oauth/RevokeTokenEndpoint.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/weblayer/oauth/RevokeTokenEndpoint.java
@@ -25,6 +25,7 @@ import org.springframework.web.bind.annotation.ResponseStatus;
 
 import ch.ethz.seb.sebserver.gbl.profile.WebServiceProfile;
 
+/** Spring MVC controller that defines a revoke token endpoint */
 @Controller
 @WebServiceProfile
 public class RevokeTokenEndpoint {
diff --git a/src/main/resources/messages.properties b/src/main/resources/messages.properties
index e81b6294..92ee888d 100644
--- a/src/main/resources/messages.properties
+++ b/src/main/resources/messages.properties
@@ -27,6 +27,7 @@ sebserver.form.validation.fieldError.username.notunique=This Username is already
 sebserver.form.validation.fieldError.password.wrong=Old password is wrong
 sebserver.form.validation.fieldError.password.mismatch=Re-typed password don't match new password
 sebserver.form.validation.fieldError.invalidURL=The input does not match the URL pattern.
+sebserver.form.validation.fieldError.exists=This name already exists. Please choose another.
 sebserver.error.unexpected=Unexpected Error
 sebserver.page.message=Information
 sebserver.dialog.confirm.title=Confirmation