diff --git a/src/Dibi/exceptions.php b/src/Dibi/exceptions.php
index 612ca7a1..2eb849f5 100644
--- a/src/Dibi/exceptions.php
+++ b/src/Dibi/exceptions.php
@@ -11,7 +11,7 @@ namespace Dibi;
 
 
 /**
- * Dibi common exception.
+ * A database operation failed.
  */
 class Exception extends \Exception
 {
@@ -44,7 +44,7 @@ class Exception extends \Exception
 
 
 /**
- * database server exception.
+ * The database server reported an error.
  */
 class DriverException extends Exception
 {
@@ -52,7 +52,7 @@ class DriverException extends Exception
 
 
 /**
- * PCRE exception.
+ * Regular expression pattern or execution failed.
  */
 class PcreException extends Exception
 {
@@ -63,18 +63,24 @@ class PcreException extends Exception
 }
 
 
+/**
+ * The requested feature is not implemented.
+ */
 class NotImplementedException extends Exception
 {
 }
 
 
+/**
+ * The requested operation is not supported.
+ */
 class NotSupportedException extends Exception
 {
 }
 
 
 /**
- * Database procedure exception.
+ * A database stored procedure failed.
  */
 class ProcedureException extends Exception
 {
@@ -102,7 +108,7 @@ class ProcedureException extends Exception
 
 
 /**
- * Base class for all constraint violation related exceptions.
+ * A database constraint was violated.
  */
 class ConstraintViolationException extends DriverException
 {
@@ -110,7 +116,7 @@ class ConstraintViolationException extends DriverException
 
 
 /**
- * Exception for a foreign key constraint violation.
+ * The foreign key constraint check failed.
  */
 class ForeignKeyConstraintViolationException extends ConstraintViolationException
 {
@@ -118,7 +124,7 @@ class ForeignKeyConstraintViolationException extends ConstraintViolationExceptio
 
 
 /**
- * Exception for a NOT NULL constraint violation.
+ * The NOT NULL constraint check failed.
  */
 class NotNullConstraintViolationException extends ConstraintViolationException
 {
@@ -126,7 +132,7 @@ class NotNullConstraintViolationException extends ConstraintViolationException
 
 
 /**
- * Exception for a unique constraint violation.
+ * The unique constraint check failed.
  */
 class UniqueConstraintViolationException extends ConstraintViolationException
 {