diff --git a/docs/metadata.rst b/docs/metadata.rst
index 52d9cedc..768099e3 100644
--- a/docs/metadata.rst
+++ b/docs/metadata.rst
@@ -1,187 +1,183 @@
 Deposit metadata
 ================
 
 When making a software deposit into the SWH archive, one can add
 information describing the software artifact and the software project.
 
 
 Metadata requirements
 ---------------------
 
 - **the schema/vocabulary** used *MUST* be specified with a persistent url
   (DublinCore, DOAP, CodeMeta, etc.)
 
   .. code:: xml
 
       <entry xmlns="http://www.w3.org/2005/Atom">
       or
       <entry xmlns="http://www.w3.org/2005/Atom"
 	     xmlns:dcterms="http://purl.org/dc/terms/">
       or
       <entry xmlns="http://www.w3.org/2005/Atom"
 	     xmlns:codemeta="https://doi.org/10.5063/SCHEMA/CODEMETA-2.0">
 
-- **the url** representing the location of the source *MUST* be provided under
+- **the name** of the software deposit *MUST* be provided [atom:title,
+   codemeta:name, dcterms:title]
+
+- **the authors** of the software deposit *MUST* be provided
+
+- **the url** representing the location of the source *MAY* be provided under
   the url tag. The url will be used for creating an origin object in the
   archive.
 
   .. code:: xml
 
-      <url>www.url-example.com</url>
-      or
       <codemeta:url>www.url-example.com</codemeta:url>
-      or
-      <dcterms:url>www.url-example.com</dcterms:url>
-
-- **the external\_identifier** *MUST* be provided as an identifier
-
-- **the name** of the software deposit *MUST* be provided [atom:title,
-   codemeta:name, dcterms:title]
 
-- **the authors** of the software deposit *MUST* be provided
+- **the external\_identifier** *MAY* be provided as an identifier
 
 - **the external\_identifier** *SHOULD* match the Slug external-identifier in
   the header
 
 - **the description** of the software deposit *SHOULD* be provided
-  [codemeta:description]: short or long description of the software 
+  [codemeta:description]: short or long description of the software
 
 - **the license/s** of the software
   deposit *SHOULD* be provided [codemeta:license]
 
 - other metadata *MAY* be added with terms defined by the schema in use.
 
 Examples
 --------
 
 Using only Atom
 ~~~~~~~~~~~~~~~
 
 .. code:: xml
 
     <?xml version="1.0"?>
         <entry xmlns="http://www.w3.org/2005/Atom">
             <title>Awesome Compiler</title>
             <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
             <external_identifier>1785io25c695</external_identifier>
             <updated>2017-10-07T15:17:08Z</updated>
             <author>some awesome author</author>
     </entry>
 
 Using Atom with CodeMeta
 ~~~~~~~~~~~~~~~~~~~~~~~~
 
 .. code:: xml
 
     <?xml version="1.0"?>
         <entry xmlns="http://www.w3.org/2005/Atom"
                  xmlns:codemeta="https://doi.org/10.5063/SCHEMA/CODEMETA-2.0">
             <title>Awesome Compiler</title>
             <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
             <external_identifier>1785io25c695</external_identifier>
             <codemeta:id>1785io25c695</codemeta:id>
             <codemeta:url>origin url</codemeta:url>
             <codemeta:identifier>other identifier, DOI, ARK</codemeta:identifier>
             <codemeta:applicationCategory>Domain</codemeta:applicationCategory>
 
             <codemeta:description>description</codemeta:description>
             <codemeta:keywords>key-word 1</codemeta:keywords>
             <codemeta:keywords>key-word 2</codemeta:keywords>
             <codemeta:dateCreated>creation date</codemeta:dateCreated>
             <codemeta:datePublished>publication date</codemeta:datePublished>
             <codemeta:releaseNotes>comment</codemeta:releaseNotes>
             <codemeta:referencePublication>
               <codemeta:name> article name</codemeta:name>
               <codemeta:identifier> article id </codemeta:identifier>
             </codemeta:referencePublication>
             <codemeta:isPartOf>
                 <codemeta:type> Collaboration/Projet </codemeta:type>
                 <codemeta:name> project name</codemeta:name>
                 <codemeta:identifier> id </codemeta:identifier>
             </codemeta:isPartOf>
             <codemeta:relatedLink>see also </codemeta:relatedLink>
             <codemeta:funding>Sponsor A  </codemeta:funding>
             <codemeta:funding>Sponsor B</codemeta:funding>
             <codemeta:operatingSystem>Platform/OS </codemeta:operatingSystem>
             <codemeta:softwareRequirements>dependencies </codemeta:softwareRequirements>
             <codemeta:softwareVersion>Version</codemeta:softwareVersion>
             <codemeta:developmentStatus>active </codemeta:developmentStatus>
             <codemeta:license>
                 <codemeta:name>license</codemeta:name>
                 <codemeta:url>url spdx</codemeta:url>
             </codemeta:license>
             <codemeta:runtimePlatform>.Net Framework 3.0 </codemeta:runtimePlatform>
             <codemeta:runtimePlatform>Python2.3</codemeta:runtimePlatform>
             <codemeta:author>
                 <codemeta:name> author1 </codemeta:name>
                 <codemeta:affiliation> Inria </codemeta:affiliation>
                 <codemeta:affiliation> UPMC </codemeta:affiliation>
             </codemeta:author>
             <codemeta:author>
                 <codemeta:name> author2 </codemeta:name>
                 <codemeta:affiliation> Inria </codemeta:affiliation>
                 <codemeta:affiliation> UPMC </codemeta:affiliation>
             </codemeta:author>
             <codemeta:codeRepository>http://code.com</codemeta:codeRepository>
             <codemeta:programmingLanguage>language 1</codemeta:programmingLanguage>
             <codemeta:programmingLanguage>language 2</codemeta:programmingLanguage>
             <codemeta:issueTracker>http://issuetracker.com</codemeta:issueTracker>
         </entry>
 
 Using Atom with DublinCore and CodeMeta (multi-schema entry)
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 .. code:: xml
 
     <?xml version="1.0"?>
     <entry xmlns="http://www.w3.org/2005/Atom"
            xmlns:dcterms="http://purl.org/dc/terms/"
            xmlns:codemeta="https://doi.org/10.5063/SCHEMA/CODEMETA-2.0">
         <title>Awesome Compiler</title>
         <client>hal</client>
         <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
         <external_identifier>%s</external_identifier>
         <dcterms:identifier>hal-01587361</dcterms:identifier>
         <dcterms:identifier>doi:10.5281/zenodo.438684</dcterms:identifier>
         <dcterms:title xml:lang="en">The assignment problem</dcterms:title>
         <dcterms:title xml:lang="fr">AffectationRO</dcterms:title>
         <dcterms:creator>author</dcterms:creator>
         <dcterms:subject>[INFO] Computer Science [cs]</dcterms:subject>
         <dcterms:subject>[INFO.INFO-RO] Computer Science [cs]/Operations Research [cs.RO]</dcterms:subject>
         <dcterms:type>SOFTWARE</dcterms:type>
         <dcterms:abstract xml:lang="en">Project in OR: The assignment problemA java implementation for the assignment problem first release</dcterms:abstract>
         <dcterms:abstract xml:lang="fr">description fr</dcterms:abstract>
         <dcterms:created>2015-06-01</dcterms:created>
         <dcterms:available>2017-10-19</dcterms:available>
         <dcterms:language>en</dcterms:language>
 
 
         <codemeta:url>origin url</codemeta:url>
 
         <codemeta:softwareVersion>1.0.0</codemeta:softwareVersion>
         <codemeta:keywords>key word</codemeta:keywords>
         <codemeta:releaseNotes>Comment</codemeta:releaseNotes>
         <codemeta:referencePublication>Rfrence interne </codemeta:referencePublication>
 
         <codemeta:relatedLink>link  </codemeta:relatedLink>
         <codemeta:funding>Sponsor  </codemeta:funding>
 
         <codemeta:operatingSystem>Platform/OS </codemeta:operatingSystem>
         <codemeta:softwareRequirements>dependencies </codemeta:softwareRequirements>
         <codemeta:developmentStatus>Ended </codemeta:developmentStatus>
         <codemeta:license>
             <codemeta:name>license</codemeta:name>
             <codemeta:url>url spdx</codemeta:url>
         </codemeta:license>
 
         <codemeta:codeRepository>http://code.com</codemeta:codeRepository>
         <codemeta:programmingLanguage>language 1</codemeta:programmingLanguage>
         <codemeta:programmingLanguage>language 2</codemeta:programmingLanguage>
     </entry>
 
 Note
 ----
 We aim on harmonizing the metadata from different origins and thus
 metadata will be translated to the `CodeMeta
 v.2 <https://doi.org/10.5063/SCHEMA/CODEMETA-2.0>`__ vocabulary if
 possible.