diff --git a/docs/specs/protocol-reference.rst b/docs/specs/protocol-reference.rst
--- a/docs/specs/protocol-reference.rst
+++ b/docs/specs/protocol-reference.rst
@@ -273,6 +273,79 @@
 :ref:`metadata deposit specification <spec-metadata-deposit>`
 
 
+.. _deposit-metadata-provenance:
+
+Metadata provenance
+-------------------
+
+To indicate where the metadata is coming from, deposit clients can use a
+``<swhdeposit:metadata-provenance>`` element in ``<swhdeposit:deposit>`` whose content is
+the object the metadata is coming from,
+preferably using the ``https://schema.org/`` namespace.
+
+For example, when the metadata is coming from Wikidata, then the
+``<swhdeposit:metadata-provenance>`` should be the page of a Q-entity, such as
+``https://www.wikidata.org/wiki/Q16988498`` (not the Q-entity
+``http://www.wikidata.org/entity/Q16988498`` itself, as the Q-entity **is** the
+object described in the metadata)
+Or when the metadata is coming from a curated repository like HAL, then
+``<swhdeposit:metadata-provenance>`` should be the HAL project.
+
+In particular, Software Heritage expects the ``<swhdeposit:metadata-provenance>`` object
+to have a ``https://schema.org/url`` property, so that it can appropriately link
+to the original page.
+
+For example, to deposit metadata on GNU Hello:
+
+.. code:: xml
+
+   <?xml version="1.0"?>
+   <entry xmlns="http://www.w3.org/2005/Atom"
+          xmlns:schema="https://schema.org/">
+
+     <!-- ... -->
+
+     <swh:deposit>
+       <swh:metadata-provenance>
+         <schema:url>https://www.wikidata.org/wiki/Q16988498</schema:url>
+       </swh:metadata-provenance>
+     </swh:deposit>
+
+     <!-- ... -->
+
+   </entry>
+
+Here is a more complete example of a metadata-only deposit on version 2.9 of GNU Hello,
+to show the interaction with other fields,
+
+.. code:: xml
+
+   <?xml version="1.0"?>
+   <entry xmlns="http://www.w3.org/2005/Atom"
+          xmlns:swh="https://www.softwareheritage.org/schema/2018/deposit"
+          xmlns:schema="https://schema.org/"
+          xmlns:codemeta="https://doi.org/10.5063/SCHEMA/CODEMETA-2.0">
+
+     <swh:deposit>
+       <swh:reference>
+         <swh:object swhid="swh:1:dir:9b6f93b12a500f560796c8dffa383c7f4470a12f;origin=https://ftp.gnu.org/gnu/hello/;visit=swh:1:snp:1abd6aa1901ba0aa7f5b7db059250230957f8434;anchor=swh:1:rev:3d41fbdb693ba46fdebe098782be4867038503e2" />
+       </swh:reference>
+
+       <swh:metadata-provenance>
+         <schema:url>https://www.wikidata.org/wiki/Q16988498</schema:url>
+       </swh:metadata-provenance>
+     </swh:deposit>
+
+     <codemeta:name>GNU Hello</codemeta:name>
+     <codemeta:id>http://www.wikidata.org/entity/Q16988498</codemeta:id>
+     <codemeta:url>https://www.gnu.org/software/hello/</codemeta:url>
+
+     <!-- is part of the GNU project -->
+     <codemeta:isPartOf>http://www.wikidata.org/entity/Q7598</codemeta:isPartOf>
+
+   </entry>
+
+
 Schema
 ------
 
diff --git a/docs/specs/swh.xsd b/docs/specs/swh.xsd
--- a/docs/specs/swh.xsd
+++ b/docs/specs/swh.xsd
@@ -6,32 +6,41 @@
             >
   <xsd:element name="deposit">
     <xsd:complexType>
-      <xsd:choice>
-        <!-- code deposit on a new origin -->
-        <xsd:element name="create_origin" >
-          <xsd:complexType>
-            <xsd:element ref="swh:origin" />
-          </xsd:complexType>
-        </xsd:element>
+      <xsd:sequence>
+        <xsd:complexType>
+          <xsd:choice>
+            <!-- code deposit on a new origin -->
+            <xsd:element name="create_origin" >
+              <xsd:complexType>
+                <xsd:element ref="swh:origin" />
+              </xsd:complexType>
+            </xsd:element>
 
-        <!-- code deposit on an origin already created by a previous deposit -->
-        <xsd:element name="add_to_origin" >
-          <xsd:complexType>
-            <xsd:element ref="swh:origin" />
-          </xsd:complexType>
-        </xsd:element>
+            <!-- code deposit on an origin already created by a previous deposit -->
+            <xsd:element name="add_to_origin" >
+              <xsd:complexType>
+                <xsd:element ref="swh:origin" />
+              </xsd:complexType>
+            </xsd:element>
+
+            <!-- metadata-only deposit -->
+            <xsd:element name="reference">
+              <xsd:complexType>
+                <xsd:choice>
+                  <xsd:element ref="swh:origin" />
+                  <xsd:element ref="swh:object" />
+                </xsd:choice>
+              </xsd:complexType>
+            </xsd:element>
+
+          </xsd:choice>
+        </xsd:complexType>
 
-        <!-- metadata-only deposit -->
-        <xsd:element name="reference">
-          <xsd:complexType>
-            <xsd:choice>
-              <xsd:element ref="swh:origin" />
-              <xsd:element ref="swh:object" />
-            </xsd:choice>
-          </xsd:complexType>
+        <xsd:element name="metadata-provenance" minOccurs="0" maxOccurs="1" >
+          <xsd:any />
         </xsd:element>
 
-      </xsd:choice>
+      </xsd:sequence>
     </xsd:complexType>
   </xsd:element>