diff --git a/DEPENDENCIES.md b/DEPENDENCIES.md
index 7a8c01251891d47d3aa1b57028719e817843b0bc..63a0678aa601762279c7c46bd71d7582051c4287 100644
--- a/DEPENDENCIES.md
+++ b/DEPENDENCIES.md
@@ -1,7 +1,7 @@
 # GENERAL
 
-* >=conan-1.37.2 (e.g. with `pip install conan`)
-* >=cmake-3.14
+* >=conan-1.37.2
+* >=cmake-3.13
 * >=gcc-10.2.0 | >=clang-11
 
 # OPTIONAL
diff --git a/include/caosdb/connection.h b/include/caosdb/connection.h
index 22bdc6f9f5b524ae895469d25d540f9679e65353..5d7930a0d63e484f01be52dab7749d02b3916c33 100644
--- a/include/caosdb/connection.h
+++ b/include/caosdb/connection.h
@@ -149,6 +149,9 @@ public:
     return ConnectionManager::GetInstance().mGetConnection(name);
   };
 
+  /**
+   * Get the connection marked by the "default" key in the configuration.
+   */
   inline static auto GetDefaultConnection()
     -> const std::shared_ptr<Connection> & {
     return ConnectionManager::GetInstance().mGetDefaultConnection();
diff --git a/include/caosdb/entity.h b/include/caosdb/entity.h
index 911f621b2f5b0be8b939ee42162652166364feba..8d0b14aac7129c9bbb24afebbf7fa4d53f6cb4ab 100644
--- a/include/caosdb/entity.h
+++ b/include/caosdb/entity.h
@@ -258,6 +258,24 @@ public:
   auto Append(const Property &property) -> void;
 
   friend class Entity;
+};
+
+/**
+ * Messages convey information about the state and result of transactions.
+ *
+ * A Message object can be thought of as kinf of a generalized error object in
+ * other frameworks. Please have a look at MessageCodes for more details.
+ */
+class Message {
+public:
+  explicit inline Message(caosdb::entity::v1alpha1::Message *wrapped)
+    : wrapped(wrapped){};
+  [[nodiscard]] inline auto GetCode() const -> MessageCode {
+    return get_message_code(wrapped->code());
+  }
+  [[nodiscard]] inline auto GetDescription() const -> std::string {
+    return wrapped->description();
+  }
 
 private:
   inline Properties(){};
diff --git a/include/caosdb/exceptions.h b/include/caosdb/exceptions.h
index 6dc44cbef4d05345eaab4b00d439967f7c88d89a..d60f7a162b6a36d803a37c1e40dfc43d21a3f172 100644
--- a/include/caosdb/exceptions.h
+++ b/include/caosdb/exceptions.h
@@ -32,9 +32,9 @@ using std::runtime_error;
 /**
  * @brief Generic exception class of the caosdb client library.
  */
-class GenericException : public runtime_error {
+class Exception : public runtime_error {
 public:
-  explicit GenericException(StatusCode code, const std::string &what_arg)
+  explicit Exception(StatusCode code, const std::string &what_arg)
     : runtime_error(what_arg), code(code) {}
   [[nodiscard]] inline auto GetCode() const -> StatusCode { return this->code; }
 
@@ -45,32 +45,32 @@ private:
 /**
  * @brief Exception for authentication errors.
  */
-class AuthenticationError : public GenericException {
+class AuthenticationError : public Exception {
 public:
   explicit AuthenticationError(const std::string &what_arg)
-    : GenericException(StatusCode::AUTHENTICATION_ERROR, what_arg) {}
+    : Exception(StatusCode::AUTHENTICATION_ERROR, what_arg) {}
 };
 
 /**
  * @brief The connection to the CaosDB server is down.
  */
-class ConnectionError : public GenericException {
+class ConnectionError : public Exception {
 public:
   explicit ConnectionError(const std::string &what_arg)
-    : GenericException(StatusCode::CONNECTION_ERROR, what_arg) {}
+    : Exception(StatusCode::CONNECTION_ERROR, what_arg) {}
 };
 
 /**
  * @brief The transaction terminated unsuccessfully.
  */
-class TransactionError : public GenericException {
+class TransactionError : public Exception {
 protected:
   TransactionError(StatusCode code, const std::string &what_arg)
-    : GenericException(code, what_arg) {}
+    : Exception(code, what_arg) {}
 
 public:
   explicit TransactionError(const std::string &what_arg)
-    : GenericException(StatusCode::GENERIC_TRANSACTION_ERROR, what_arg) {}
+    : Exception(StatusCode::GENERIC_TRANSACTION_ERROR, what_arg) {}
 };
 
 class TransactionStatusError : public TransactionError {
@@ -83,19 +83,19 @@ public:
  * @brief Exception for errors of the ConfigurationManager or other components
  * of the configuration.
  */
-class ConfigurationError : public GenericException {
+class ConfigurationError : public Exception {
 public:
   explicit ConfigurationError(const std::string &what_arg)
-    : GenericException(StatusCode::CONFIGURATION_ERROR, what_arg) {}
+    : Exception(StatusCode::CONFIGURATION_ERROR, what_arg) {}
 };
 
 /**
  * @brief The connection isn't known to the ConnectionManager under this name.
  */
-class UnknownConnectionError : public GenericException {
+class UnknownConnectionError : public Exception {
 public:
   explicit UnknownConnectionError(const std::string &what_arg)
-    : GenericException(StatusCode::UNKNOWN_CONNECTION_ERROR, what_arg) {}
+    : Exception(StatusCode::UNKNOWN_CONNECTION_ERROR, what_arg) {}
 };
 
 } // namespace caosdb::exceptions
diff --git a/include/caosdb/log_level.h b/include/caosdb/log_level.h
index af05d3ba11b3d0e6252c889f7c9be1ddd61015f8..c2fcb9b1181dcb86f91dfaf9a4ddecba3ea417cb 100644
--- a/include/caosdb/log_level.h
+++ b/include/caosdb/log_level.h
@@ -19,8 +19,8 @@
  *
  */
 
-#ifndef CAOSDB_LOG_LEVELS_H
-#define CAOSDB_LOG_LEVELS_H
+#ifndef CAOSDB_LOG_LEVEL_H
+#define CAOSDB_LOG_LEVEL_H
 
 #define CAOSDB_LOG_LEVEL_OFF 1000000
 #define CAOSDB_LOG_LEVEL_FATAL 700
diff --git a/include/caosdb/logging.h b/include/caosdb/logging.h
index 26ec1c8465b6805132f66853cea5aa4e384018ed..fcebc6df8b5db2eb9f800893f8d296d6174285ce 100644
--- a/include/caosdb/logging.h
+++ b/include/caosdb/logging.h
@@ -43,6 +43,9 @@ typedef boost::log::sources::severity_channel_logger<int, std::string>
 
 BOOST_LOG_INLINE_GLOBAL_LOGGER_DEFAULT(logger, boost_logger_class)
 
+/**
+ * This class stores the integer log level.
+ */
 class LevelConfiguration {
 public:
   LevelConfiguration(int level) : level(level){};
@@ -54,6 +57,11 @@ private:
 
 class SinkConfiguration;
 
+/**
+ * This class stores the logging level and log sinks.
+ *
+ * Sinks are represented by SinkConfiguration objects.
+ */
 class LoggingConfiguration : public LevelConfiguration {
 public:
   virtual ~LoggingConfiguration() = default;
@@ -69,6 +77,23 @@ private:
 auto initialize_logging_defaults() -> int;
 auto initialize_logging(const LoggingConfiguration &configuration) -> void;
 
+/**
+ * A logging sink is characterized by a name and destination.
+ *
+ * Typical inheriting configurations exist for console, files and syslog.
+ *
+ * When a SinkConfiguration is created from a configuration, the sink
+ * configuration must contain a \p destination key which matches one of the
+ * keywords for implemented sinks.  At the moment of writing this documentation,
+ * valid destinations are:
+ *
+ * \li \p file
+ * \li \p console
+ * \li \p syslog
+ *
+ * A \p level keyword sets the logging level, if it exists at the sink or
+ * logging level of the configuration.
+ */
 class SinkConfiguration : public LevelConfiguration {
 public:
   virtual ~SinkConfiguration() = default;
@@ -104,6 +129,12 @@ private:
   const std::string destination = "Console";
 };
 
+/**
+ * The file name is the destination, the directory can be set separately.
+ *
+ * If there is a `directory` key in the configuration, that will be used as a
+ * default, otherwise it is the current directory.
+ */
 class FileSinkConfiguration : public SinkConfiguration {
 public:
   virtual ~FileSinkConfiguration() = default;
@@ -136,27 +167,27 @@ private:
 };
 
 /**
- * Convenience function for the c-interface.
+ * Convenience function for the C interface.
  */
 void caosdb_log_fatal(const char *channel, const char *msg);
 /**
- * Convenience function for the c-interface.
+ * Convenience function for the C interface.
  */
 void caosdb_log_error(const char *channel, const char *msg);
 /**
- * Convenience function for the c-interface.
+ * Convenience function for the C interface.
  */
 void caosdb_log_warn(const char *channel, const char *msg);
 /**
- * Convenience function for the c-interface.
+ * Convenience function for the C interface.
  */
 void caosdb_log_info(const char *channel, const char *msg);
 /**
- * Convenience function for the c-interface.
+ * Convenience function for the C interface.
  */
 void caosdb_log_debug(const char *channel, const char *msg);
 /**
- * Convenience function for the c-interface.
+ * Convenience function for the C interface.
  */
 void caosdb_log_trace(const char *channel, const char *msg);
 
diff --git a/include/caosdb/message_code.h b/include/caosdb/message_code.h
index 17ec1c1a9fdfb58a512eaa5e7940686ea9ccbaa3..2cc3f516f4e3356d9dfccc9e0435bfdfe2063306 100644
--- a/include/caosdb/message_code.h
+++ b/include/caosdb/message_code.h
@@ -30,6 +30,10 @@
  * In contrast to the status codes, the message codes are part of the CaosDB
  * API. Messages (and their codes) represent the state of the entities in a
  * transaction or the server.
+ *
+ * For a specification of the message codes, look at the protobuf documentation.
+ * The sources and documentation can be found at
+ * https://gitlab.indiscale.com/caosdb/src/caosdb-proto.
  */
 
 namespace caosdb::entity {
diff --git a/include/caosdb/transaction_status.h b/include/caosdb/transaction_status.h
index 8645aceb3749efbbcf8c6cfec5aa96394b029ed7..6c5b7a6ee30c498f15c3c25c5ec5fbc3e1d93ea0 100644
--- a/include/caosdb/transaction_status.h
+++ b/include/caosdb/transaction_status.h
@@ -25,7 +25,12 @@
 /**
  * TransactionStatus indicates the current status of a transaction and, when it
  * has already terminated, whether the transaction has been successful or not.
+ *
+ * A status code of 0 denotes a generic success state, positive values indicate
+ * errors, and negative values indicate other states, such as different stages
+ * of a transaction in process.
  */
+
 #include "caosdb/status_code.h"
 #include "caosdb/exceptions.h"
 #include <memory> // for shared_ptr, unique_ptr
@@ -35,7 +40,7 @@ namespace caosdb::transaction {
 using caosdb::StatusCode;
 using caosdb::exceptions::AuthenticationError;
 using caosdb::exceptions::ConnectionError;
-using caosdb::exceptions::GenericException;
+using caosdb::exceptions::Exception;
 using caosdb::exceptions::TransactionError;
 
 /**
@@ -113,7 +118,7 @@ public:
     case StatusCode::GENERIC_TRANSACTION_ERROR:
       throw TransactionError(this->description);
     default:
-      throw GenericException(StatusCode::GENERIC_ERROR, this->description);
+      throw Exception(StatusCode::GENERIC_ERROR, this->description);
     }
   }
 
@@ -130,7 +135,7 @@ public:
   /**
    * Return a description of the erroneous state.
    *
-   * Returns an empty string if there is no description.
+   * No description yields an empty string.
    */
   inline auto GetDescription() const -> const std::string & {
     return this->description;
diff --git a/include/caosdb/utility.h b/include/caosdb/utility.h
index e1e306e40a82ced49ccefea45a42a9e63a2b04b9..30e21747ec4ce39493e24e10e09d7c53c7ab1308 100644
--- a/include/caosdb/utility.h
+++ b/include/caosdb/utility.h
@@ -43,8 +43,6 @@ using boost::json::value;
 
 /**
  * @brief Read a text file into a string and return the file's content.
- *
- * TODO use boost-filesystem's "load_string_file"!
  */
 inline auto load_string_file(const path &path) -> std::string {
   std::string result;
@@ -52,11 +50,13 @@ inline auto load_string_file(const path &path) -> std::string {
   return result;
 }
 
-inline auto get_env_var(const char *key, const char *fall_back) -> const
-  char * {
+/**
+ * @brief Return the environment variable KEY, or FALLBACK if it does not exist.
+ */
+inline auto get_env_var(const char *key, const char *fallback) -> const char * {
   const char *val = getenv(key);
   if (val == nullptr) {
-    return fall_back;
+    return fallback;
   } else {
     return val;
   }
@@ -64,11 +64,11 @@ inline auto get_env_var(const char *key, const char *fall_back) -> const
 
 /**
  * @brief Return the value of an environment variable or - if undefined - the
- * fall_back value.
+ * fallback value.
  */
-inline auto get_env_var(const std::string &key, const std::string &fall_back)
+inline auto get_env_var(const std::string &key, const std::string &fallback)
   -> const std::string {
-  const char *val = get_env_var(key.c_str(), fall_back.c_str());
+  const char *val = get_env_var(key.c_str(), fallback.c_str());
 
   auto const result = std::string(val);
   return result;
diff --git a/include/ccaosdb.h b/include/ccaosdb.h
index 0df5f0e085d5e012c221491ed8c78c26b4d1c807..bb62a5105db9559444f5b5d178ced583c41c9fcb 100644
--- a/include/ccaosdb.h
+++ b/include/ccaosdb.h
@@ -79,9 +79,9 @@ typedef struct {
 /**
  * Return the environment variable of the given name.
  *
- * If the environment variable is not set, return the fall_back instead.
+ * If the environment variable is not set, return the fallback instead.
  */
-const char *caosdb_utility_get_env_var(const char *name, const char *fall_back);
+const char *caosdb_utility_get_env_var(const char *name, const char *fallback);
 
 /**
  * Return a description of the status code.
diff --git a/src/caosdb/configuration.cpp b/src/caosdb/configuration.cpp
index b3934d31511ced991488cef7f0343294264f0574..eb5465967d2703f5536f9ca3116e695972fabdcc 100644
--- a/src/caosdb/configuration.cpp
+++ b/src/caosdb/configuration.cpp
@@ -358,7 +358,7 @@ auto ConfigurationManager::mReset() noexcept -> int {
     mClear();
     InitializeDefaults();
     return StatusCode::SUCCESS;
-  } catch (const caosdb::exceptions::GenericException &exc) {
+  } catch (const caosdb::exceptions::Exception &exc) {
     return exc.GetCode();
   } catch (const std::exception &exc) {
     CAOSDB_LOG_ERROR(logger_name)
@@ -373,7 +373,7 @@ auto ConfigurationManager::mClear() noexcept -> int {
     json_configuration = value(nullptr);
     ConnectionManager::Reset();
     return StatusCode::SUCCESS;
-  } catch (const caosdb::exceptions::GenericException &exc) {
+  } catch (const caosdb::exceptions::Exception &exc) {
     return exc.GetCode();
   } catch (const std::exception &exc) {
     CAOSDB_LOG_ERROR(logger_name)
@@ -511,6 +511,7 @@ auto ConfigurationManager::InitializeDefaults() -> int { // NOLINT
     mLoadSingleJSONConfiguration(*configuration_file_path);
   }
 
+  // Logging in the configuration leads to additional content.
   if (this->json_configuration.is_object() &&
       this->json_configuration.as_object().contains("logging")) {
     LoggingConfiguration logging_configuration =
diff --git a/src/caosdb/logging.cpp b/src/caosdb/logging.cpp
index 486ab846c4ce43225b9242aceb557775b9632531..3618826a5ed6061f210c393b3429b641293fccae 100644
--- a/src/caosdb/logging.cpp
+++ b/src/caosdb/logging.cpp
@@ -59,6 +59,7 @@ auto LoggingConfiguration::GetSinks() const
 
 SinkConfiguration::SinkConfiguration(std::string name, int level)
   : LevelConfiguration(level), name(std::move(name)) {}
+
 [[nodiscard]] auto SinkConfiguration::GetName() const -> const std::string & {
   return this->name;
 }
@@ -77,6 +78,7 @@ auto SinkConfiguration::Configure(boost::log::settings &settings) const
 ConsoleSinkConfiguration::ConsoleSinkConfiguration(const std::string &name,
                                                    int level)
   : SinkConfiguration(name, level) {}
+
 [[nodiscard]] auto ConsoleSinkConfiguration::GetDestination() const
   -> const std::string & {
   CAOSDB_LOG_TRACE(logger_name)
@@ -93,12 +95,14 @@ auto ConsoleSinkConfiguration::Configure(boost::log::settings &settings) const
 
 FileSinkConfiguration::FileSinkConfiguration(const std::string &name, int level)
   : SinkConfiguration(name, level) {}
+
 [[nodiscard]] auto FileSinkConfiguration::GetDestination() const
   -> const std::string & {
   CAOSDB_LOG_TRACE(logger_name)
     << "Enter FileSinkConfiguration::GetDestination()";
   return this->destination;
 }
+
 auto FileSinkConfiguration::SetDirectory(const std::string &directory) -> void {
   this->directory = std::string(directory);
 }
@@ -114,11 +118,13 @@ auto FileSinkConfiguration::Configure(boost::log::settings &settings) const
 SyslogSinkConfiguration::SyslogSinkConfiguration(const std::string &name,
                                                  int level)
   : SinkConfiguration(name, level) {}
+
 [[nodiscard]] auto SyslogSinkConfiguration::GetDestination() const
   -> const std::string & {
   return this->destination;
 }
 
+// Called if no custom logging settings are specified.
 auto initialize_logging_defaults() -> int {
   // first: turn everything off
   boost::log::settings off_settings;
@@ -148,6 +154,7 @@ auto initialize_logging_defaults() -> int {
   return 0;
 }
 
+// Called if custom logging settings are specified.
 auto initialize_logging(const LoggingConfiguration &configuration) -> void {
   boost::log::settings new_settings;
 
diff --git a/src/ccaosdb.cpp b/src/ccaosdb.cpp
index d21b3bd0aafd9c95488658574ef6c03a044996c1..5f89af16ed3da4de89df1d83e1de0bdecb79592f 100644
--- a/src/ccaosdb.cpp
+++ b/src/ccaosdb.cpp
@@ -56,9 +56,8 @@ const char *caosdb_constants_COMPATIBLE_SERVER_VERSION_PRE_RELEASE() {
   return caosdb::COMPATIBLE_SERVER_VERSION_PRE_RELEASE;
 }
 
-const char *caosdb_utility_get_env_var(const char *name,
-                                       const char *fall_back) {
-  return caosdb::utility::get_env_var(name, fall_back);
+const char *caosdb_utility_get_env_var(const char *name, const char *fallback) {
+  return caosdb::utility::get_env_var(name, fallback);
 }
 
 const char *caosdb_get_status_description(int code) {