diff --git a/src/main/java/it/inaf/oats/vospace/datamodel/NodeProperties.java b/src/main/java/it/inaf/oats/vospace/datamodel/NodeProperties.java
index 2df43ee3f30173b13b01793f50abc98b6a0a6257..2c826fefbcd5cee1b06280bca7398e272a9c3def 100644
--- a/src/main/java/it/inaf/oats/vospace/datamodel/NodeProperties.java
+++ b/src/main/java/it/inaf/oats/vospace/datamodel/NodeProperties.java
@@ -40,6 +40,7 @@ public abstract class NodeProperties {
     public static final String SUBJECT_URI = "ivo://ivoa.net/vospace/core#subject";     // the topic of the resource     
     public static final String TITLE_URI = "ivo://ivoa.net/vospace/core#title";       // a name given to the resource  
     public static final String TYPE_URI = "ivo://ivoa.net/vospace/core#type";        // the nature or genre of the resource
+    public static final String MD5_URI = "ivo://ivoa.net/vospace/core#MD5";        // MD5 of a DataNode. This should be a standard property, however it is currently used only in examples and it is not present in the list of standard properties
     //
     // Non-standard properties
     public static final String ASYNC_TRANS_URN = "urn:async_trans";