update README

README.md

@@ -1,6 +1,6 @@
 storage-manger-s3-plugin
 ----
-
+storage-manager-s3-plugin is a Java plugin of storage-manager-core library. It enables to perform CRUD operation on  any S3 compliant object storage. The object-storage credentials are retrieved automatically from a gCube ServiceEndpoint with coordinates DataStorage - StorageManager.
     
 ## Examples of use
 
@@ -12,6 +12,16 @@ Notes about how to deploy this component on an infrastructure or link to wiki do
 ## Documentation
 See storage-manager-core on [Wiki](https://gcube.wiki.gcube-system.org/gcube/Storage_Manager).
 
+Some notes:
+
+ * only the CRUD operations were implemented in this version;
+ * this component is a storage-manager-core plugin so it works only with the storage-manager libraries (wrapper and core): it could be loaded at runtime or it could be included in the pom as a static dependency;
+ * the API are the same used for MongoDB but the new storage-manager-wrapper version (starting from 3.0.0-SNAPSHOT) contains a new constructor that permit to specify the S3 Backend as input parameter;
+ * for the moment there are two different object storage that can be automatically discovered and used: "Zadara" is discovered automatically on NextNext; "VaiSulWeb" is discovered automatically on devVRE;
+ * the S3 object storage is discovered automatically only if the S3 Backend is passed as input parameter;
+ * if the VOLATILE memory is specified as input parameter, the storage-manager will use MongoDB Volatile area even if the S3 backend is specified as input parameter;
+This component can be used with storage-manager-wrapper and core starting from 3.0.0-SNAPSHOT version;
+
 
 
 ## License