diff --git a/cypress/integration/validation.js b/cypress/integration/validation.js
index 0a26c90..19eb73f 100644
--- a/cypress/integration/validation.js
+++ b/cypress/integration/validation.js
@@ -1,822 +1,856 @@
 /**
  * Copyright (C) 2020  The Software Heritage developers
  * See the AUTHORS file at the top-level directory of this distribution
  * License: GNU Affero General Public License version 3, or any later version
  * See top-level LICENSE file for more information
  */
 
 /*
  * Tests the basic features of the application.
  */
 
 "use strict";
 
 describe('Document validation', function() {
     it('accepts empty document', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#name').should('have.value', '');
         cy.get('#errorMessage').should('have.text', '');
     });
 
     it('accepts all main fields', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "license": "https://spdx.org/licenses/AGPL-3.0",
                 "dateCreated": "2019-10-02",
                 "datePublished": "2020-01-01",
                 "name": "My Test Software",
                 "description": "This is a\ngreat piece of software",
             }))
         );
         cy.get('#validateCodemeta').click();
 
 
         cy.get('#name').should('have.value', '');
         cy.get('#errorMessage').should('have.text', '');
     });
 
     it('accepts anything in non-validated fields', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "programmingLanguage": "foo",
             }))
         );
         cy.get('#validateCodemeta').click();
         cy.get('#errorMessage').should('have.text', '');
 
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "programmingLanguage": 21,
             }))
         );
         cy.get('#validateCodemeta').click();
         cy.get('#errorMessage').should('have.text', '');
 
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "programmingLanguage": {},
             }))
         );
         cy.get('#validateCodemeta').click();
         cy.get('#errorMessage').should('have.text', '');
     });
 
     it('errors on invalid type', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "foo",
                 "name": "My Test Software",
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#name').should('have.value', '');
 
         cy.get('#errorMessage').should('have.text', 'Wrong document type: must be "SoftwareSourceCode"/"SoftwareApplication", not "foo"');
     });
 
     it('errors on invalid field name', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "foobar": "baz",
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#name').should('have.value', '');
 
         cy.get('#errorMessage').should('have.text', 'Unknown field "foobar".');
     });
 });
 
 describe('URLs validation', function() {
     it('accepts valid URL', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "codeRepository": "http://example.org/",
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '');
     });
 
     it('accepts empty list of URLs', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "codeRepository": [],
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '');
     });
 
     it('accepts list of valid URLs', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "codeRepository": ["http://example.org/", "http://example.com/"],
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '');
     });
 
     it('errors on invalid URL', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "codeRepository": "foo",
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', 'Invalid URL in field "codeRepository": "foo"');
     });
 
     it('errors on non-string instead of URL', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "codeRepository": {},
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"codeRepository" must be an URL (or a list of URLs), not: {}');
     });
 
     it('errors on list with an invalid URL at the end', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "codeRepository": ["http://example.org/", "foo"],
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', 'Invalid URL in field "codeRepository": "foo"');
     });
 
     it('errors on list with an invalid URL at the beginning', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "codeRepository": ["http://example.org/", "foo"],
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', 'Invalid URL in field "codeRepository": "foo"');
     });
 
     it('errors on non-string in URL list', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "codeRepository": ["http://example.org/", {}],
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"codeRepository" must be a list of URLs (or a single URL), but it contains: {}');
     });
 });
 
 describe('Texts or URLs validation', function() {
     it('accepts valid Text', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "applicationCategory": "foo",
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '');
     });
 
     it('accepts valid URL', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "applicationCategory": "http://example.org/",
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '');
     });
 
     it('accepts empty list of Texts', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "applicationCategory": [],
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '');
     });
 
     it('accepts list of Texts', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "applicationCategory": ["foo", "bar"],
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '');
     });
 
     it('errors on non-string instead of Text', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "applicationCategory": {},
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"applicationCategory" must be a text/URL (or a list of texts/URLs), not: {}');
     });
 
     it('errors on list with an invalid Text at the beginning', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "applicationCategory": [{}, "foo"],
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"applicationCategory" must be a list of texts/URLs (or a single text/URL), but it contains: {}');
     });
 
     it('errors on list with an invalid Text at the end', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "applicationCategory": ["foo", {}],
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"applicationCategory" must be a list of texts/URLs (or a single text/URL), but it contains: {}');
     });
 });
 
 describe('Text validation', function() {
     it('accepts valid Text', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "description": "foo",
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '');
     });
 
     it('errors on empty list of Texts', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "description": [],
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"description" must be text, not []');
     });
 
     it('errors on list of Texts', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "description": ["foo", "bar"],
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"description" must be text, not ["foo","bar"]');
     });
 
     it('errors on non-string instead of Text', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "description": {},
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"description" must be text, not {}');
     });
 });
 
 describe('Date validation', function() {
     it('accepts valid Date', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "dateCreated": "2020-03-18",
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '');
     });
 
     it('errors on empty list of Dates', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "dateCreated": [],
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"dateCreated" must be a date, not []');
     });
 
     it('errors on list of Dates', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "dateCreated": ["2020-03-18", "2020-03-19"],
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"dateCreated" must be a date, not ["2020-03-18","2020-03-19"]');
     });
 
     it('errors on non-string instead of Date', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "dateCreated": {},
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"dateCreated" must be a date, not {}');
     });
 
     it('errors on non-Date string', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "dateCreated": "foo",
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"dateCreated" must be a date in the format YYYY-MM-DD, not "foo"');
     });
 });
 
 describe('Person validation', function() {
+    it('accepts URI', function() {
+        cy.get('#codemetaText').then((elem) =>
+            elem.text(JSON.stringify({
+                "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
+                "@type": "SoftwareSourceCode",
+                "author": "http://example.org/~jdoe",
+            }))
+        );
+        cy.get('#validateCodemeta').click();
+
+        cy.get('#errorMessage').should('have.text', '');
+    });
+
     it('accepts valid complete Person', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "author": {
                     "@type": "Person",
                     "@id": "http://example.org/~jdoe",
                     "url": "http://example.org/~jdoe",
                     "name": "Jane Doe",
                     "givenName": "Jane",
                     "familyName": "Doe",
                     "email": "jdoe@example.org",
                     "affiliation": {
                         "@type": "Organization",
                         "@id": "http://example.org/",
                     }
                 }
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '');
     });
 
     it('errors on Person with missing type', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "author": {
                 },
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"author" must be a (list of) Person/Organization object(s) or an URI, but is missing a type/@type.');
     });
 
     it('errors on Person with wrong type', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "author": {
                     "type": "SoftwareSourceCode",
                 },
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"author" type must be a (list of) Person/Organization object(s), not "SoftwareSourceCode"');
     });
 
     it('errors on Person with unknown field', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "author": {
                     "type": "Person",
                     "foo": "bar",
                 },
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', 'Unknown field "foo" in "author".');
     });
 
     it('errors on Person with invalid field', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "author": {
                     "type": "Person",
                     "email": 32,
                 },
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"email" must be text, not 32');
     });
 
+    it('accepts URI in list', function() {
+        cy.get('#codemetaText').then((elem) =>
+            elem.text(JSON.stringify({
+                "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
+                "@type": "SoftwareSourceCode",
+                "author": [
+                    "http://example.org/~jadoe",
+                    {
+                        "@type": "Person",
+                        "@id": "http://example.org/~jodoe",
+                        "givenName": "John",
+                        "familyName": "Doe",
+                    },
+                ]
+            }))
+        );
+        cy.get('#validateCodemeta').click();
+
+        cy.get('#errorMessage').should('have.text', '');
+    });
+
     it('accepts list of valid Person', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "author": [
                     {
                         "@type": "Person",
                         "@id": "http://example.org/~jadoe",
                         "givenName": "Jane",
                         "familyName": "Doe",
                     },
                     {
                         "@type": "Person",
                         "@id": "http://example.org/~jodoe",
                         "givenName": "John",
                         "familyName": "Doe",
                     },
                 ]
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '');
     });
 
     it('errors on list with invalid Person at the beginning', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "author": [
                     {
                         "givenName": "Jane",
                         "familyName": "Doe",
                     },
                     {
                         "@type": "Person",
                         "@id": "http://example.org/~jodoe",
                         "name": "John Doe",
                         "givenName": "John",
                         "familyName": "Doe",
                     },
                 ]
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"author" must be a (list of) Person/Organization object(s) or an URI, but is missing a type/@type.');
     });
 
     it('errors on list with invalid Person at the end', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "author": [
                     {
                         "@type": "Person",
                         "@id": "http://example.org/~jadoe",
                         "givenName": "Jane",
                         "familyName": "Doe",
                     },
                     {
                         "givenName": "John",
                         "familyName": "Doe",
                     },
                 ]
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"author" must be a (list of) Person/Organization object(s) or an URI, but is missing a type/@type.');
     });
 });
 
 describe('Organization validation', function() {
     it('accepts valid complete Organization', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "author": {
                     "@type": "Organization",
                     "@id": "http://example.org/",
                     "url": "https://example.org/",
                     "name": "Example Org",
                     "identifier": "http://example.org/",
                     "address": "Nowhere",
                 }
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '');
     });
 
     it('errors on Organization with missing type', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "author": {
                 },
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"author" must be a (list of) Person/Organization object(s) or an URI, but is missing a type/@type.');
     });
 
     it('errors on Organization with wrong type', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "author": {
                     "type": "SoftwareSourceCode",
                 },
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"author" type must be a (list of) Person/Organization object(s), not "SoftwareSourceCode"');
     });
 
     it('errors on Organization with unknown field', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "author": {
                     "type": "Organization",
                     "foo": "bar",
                 },
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', 'Unknown field "foo" in "author".');
     });
 
     it('errors on Organization with invalid field', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "author": {
                     "type": "Organization",
                     "email": 32,
                 },
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"email" must be text, not 32');
     });
 
     it('accepts list of valid Organization', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "author": [
                     {
                         "@type": "Organization",
                         "@id": "http://example.org/",
                         "name": "Example Org",
                     },
                     {
                         "@type": "Organization",
                         "@id": "http://example.org/~jodoe",
                         "name": "Example Org",
                     },
                 ]
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '');
     });
 
     it('errors on list with invalid Organization at the beginning', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "author": [
                     {
                         "name": "Example Org",
                     },
                     {
                         "@type": "Organization",
                         "name": "Example Org",
                     },
                 ]
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"author" must be a (list of) Person/Organization object(s) or an URI, but is missing a type/@type.');
     });
 
     it('errors on list with invalid Organization at the end', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "author": [
                     {
                         "@type": "Organization",
                         "name": "Example Org",
                     },
                     {
                         "name": "Example Org",
                     },
                 ]
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"author" must be a (list of) Person/Organization object(s) or an URI, but is missing a type/@type.');
     });
 });
 
 describe('CreativeWork validation', function() {
     it('accepts valid CreativeWork', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "name": "Small Software",
                 "isPartOf": {
                     "type": "CreativeWork",
                     "name": "Big Creative Work",
                     "author": "http://example.org/~jdoe",
                     "keywords": ["foo", "bar"],
                 }
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '');
     });
 
     it('errors on CreativeWork with missing type', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "isPartOf": {
                 }
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"isPartOf" must be a (list of) CreativeWork/SoftwareSourceCode/SoftwareApplication object(s) or an URI, but is missing a type/@type.');
     });
 
     it('errors on CreativeWork with wrong type', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "isPartOf": {
                     "type": "Person",
                 },
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"isPartOf" type must be a (list of) CreativeWork/SoftwareSourceCode/SoftwareApplication object(s), not "Person"');
     });
 
     it('errors on CreativeWork with unknown field', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "isPartOf": {
                     "type": "CreativeWork",
                     "foo": "bar",
                 },
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', 'Unknown field "foo" in "isPartOf".');
     });
 
     it('errors on CreativeWork with invalid field', function() {
         cy.get('#codemetaText').then((elem) =>
             elem.text(JSON.stringify({
                 "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                 "@type": "SoftwareSourceCode",
                 "isPartOf": {
                     "type": "CreativeWork",
                     "url": 32,
                 },
             }))
         );
         cy.get('#validateCodemeta').click();
 
         cy.get('#errorMessage').should('have.text', '"url" must be an URL (or a list of URLs), not: 32');
     });
 });
diff --git a/js/validation/things.js b/js/validation/things.js
index eac4387..9d61e65 100644
--- a/js/validation/things.js
+++ b/js/validation/things.js
@@ -1,325 +1,309 @@
 /**
  * Copyright (C) 2020  The Software Heritage developers
  * See the AUTHORS file at the top-level directory of this distribution
  * License: GNU Affero General Public License version 3, or any later version
  * See top-level LICENSE file for more information
  */
 
 /*
  * Validators for codemeta objects derived from http://schema.org/Thing.
  */
 
 function getDocumentType(doc) {
     // TODO: check there is at most one.
     // FIXME: is the last variant allowed?
     return doc["type"] || doc["@type"] || doc["codemeta:type"]
 }
 
 function isCompactTypeEqual(type, compactedType) {
     // FIXME: are all variants allowed?
     return (type == `${compactedType}`
         || type == `schema:${compactedType}`
         || type == `codemeta:${compactedType}`
         || type == `http://schema.org/${compactedType}`
     );
 }
 
 function noValidation(fieldName, doc) {
     return true;
 }
 
 
-// Validates subtypes of Thing.
+// Validates subtypes of Thing, or URIs
+//
+// typeFieldValidators is a map: {type => {fieldName => fieldValidator}}
+function validateThingOrId(parentFieldName, typeFieldValidators, doc) {
+    var acceptedTypesString = Object.keys(typeFieldValidators).join('/');
+
+    if (typeof doc == 'string') {
+        if (!isUrl(doc)) {
+            setError(`"${fieldName}" must be an URL or a ${acceptedTypesString} object, not: ${JSON.stringify(doc)}"`);
+            return false;
+        }
+        else {
+            return true;
+        }
+    }
+    else if (!Array.isArray(doc) && typeof doc == 'object') {
+        return validateThing(parentFieldName, typeFieldValidators, doc);
+    }
+    else {
+        setError(`"${fieldName}" must be a ${acceptedTypesString} object or URI, not ${JSON.stringify(doc)}`);
+        return false;
+    }
+}
+
+// Validates subtypes of Thing
 //
 // typeFieldValidators is a map: {type => {fieldName => fieldValidator}}
 function validateThing(parentFieldName, typeFieldValidators, doc) {
-    // TODO: allow an URI instead
-    // TODO: validate id/@id
+    // TODO: check there is either id or @id but not both
     // TODO: check there is either type or @type but not both
+
+    var acceptedTypesString = Object.keys(typeFieldValidators).join('/');
+
     var documentType = getDocumentType(doc);
 
     var id = doc["id"] || doc["@id"];
     if (id !== undefined && !isUrl(id)) {
         setError(`"${fieldName}" has an invalid URI as id: ${JSON.stringify(id)}"`);
         return false;
     }
 
     if (documentType === undefined) {
         if (id === undefined) {
-            setError(`"${parentFieldName}" must be a (list of) ${Object.keys(typeFieldValidators).join('/')} object(s) or an URI, but is missing a type/@type.`);
+            setError(`"${parentFieldName}" must be a (list of) ${acceptedTypesString} object(s) or an URI, but is missing a type/@type.`);
             return false;
         }
         else {
             // FIXME: we have an @id but no @type, what should we do?
             return true;
         }
     }
 
     for (expectedType in typeFieldValidators) {
         if (isCompactTypeEqual(documentType, expectedType)) {
             fieldValidators = typeFieldValidators[expectedType];
             return Object.entries(doc).every((entry) => {
                 var fieldName = entry[0];
                 var subdoc = entry[1];
                 if (fieldName == "type" || fieldName == "@type") {
                     // Was checked before
                     return true;
                 }
                 else {
                     var validator = fieldValidators[fieldName];
                     if (validator === undefined) {
                         // TODO: find if it's a field that belongs to another type,
                         // and suggest that to the user
                         setError(`Unknown field "${fieldName}" in "${parentFieldName}".`)
                         return false;
                     }
                     else {
                         return validator(fieldName, subdoc);
                     }
                 }
             });
         }
     }
 
-    setError(`"${parentFieldName}" type must be a (list of) ${Object.keys(typeFieldValidators).join('/')} object(s), not ${JSON.stringify(documentType)}`);
+    setError(`"${parentFieldName}" type must be a (list of) ${acceptedTypesString} object(s), not ${JSON.stringify(documentType)}`);
     return false;
 }
 
 
 // Helper function to validate a field is either X or a list of X.
 function validateListOrSingle(fieldName, doc, validator) {
     if (Array.isArray(doc)) {
         return doc.every((subdoc) => validator(subdoc, true));
     }
     else {
         return validator(doc, false);
     }
 }
 
 // Validates a CreativeWork or an array of CreativeWork
 function validateCreativeWorks(fieldName, doc) {
     return validateListOrSingle(fieldName, doc, (subdoc, inList) => {
         return validateCreativeWork(fieldName, subdoc);
     });
 }
 
 // Validates a single CreativeWork
 function validateCreativeWork(fieldName, doc) {
-    if (!Array.isArray(doc) && typeof doc == 'object') {
-        var id = doc["id"] || doc["@id"];
-        if (id !== undefined && !isUrl(id)) {
-            setError(`"${fieldName}" has an invalid URI as id: ${JSON.stringify(id)}"`);
-            return false;
-        }
-        return validateThing(fieldName, {
-            "CreativeWork": creativeWorkFieldValidators,
-            "SoftwareSourceCode": softwareFieldValidators,
-            "SoftwareApplication": softwareFieldValidators,
-        }, doc);
-
-    }
-    else if (typeof doc == 'string') {
-        if (!isUrl(doc)) {
-            setError(`"${fieldName}" must be an URI or CreativeWork object, not: ${JSON.stringify(id)}"`);
-            return false;
-        }
-        else {
-            return true;
-        }
-    }
-    else {
-        setError(`"${fieldName}" must be a CreativeWork object or URI, not ${JSON.stringify(doc)}`);
-        return false;
-    }
+    return validateThingOrId(fieldName, {
+        "CreativeWork": creativeWorkFieldValidators,
+        "SoftwareSourceCode": softwareFieldValidators,
+        "SoftwareApplication": softwareFieldValidators,
+    }, doc);
 }
 
 // Validates a Person, Organization or an array of these
 function validateActors(fieldName, doc) {
     return validateListOrSingle(fieldName, doc, (subdoc, inList) => {
         return validateActor(fieldName, subdoc);
     });
 }
 
 // Validates a Person or an array of Person
 function validatePersons(fieldName, doc) {
     return validateListOrSingle(fieldName, doc, (subdoc, inList) => {
         return validatePerson(fieldName, subdoc);
     });
 }
 
 // Validates an Organization or an array of Organization
 function validateOrganizations(fieldName, doc) {
     return validateListOrSingle(fieldName, doc, (subdoc, inList) => {
         return validateOrganization(fieldName, doc);
     });
 }
 
 // Validates a single Person or Organization
 function validateActor(fieldName, doc) {
-    if (!Array.isArray(doc) && typeof doc == 'object') {
-        var id = doc["id"] || doc["@id"];
-        if (id !== undefined && !isUrl(id)) {
-            setError(`"${fieldName}" has an invalid URI as id: ${JSON.stringify(id)}"`);
-            return false;
-        }
-
-        return validateThing(fieldName, {
-            "Person": personFieldValidators,
-            "Organization": organizationFieldValidators,
-        }, doc);
-    }
-    else if (typeof doc == 'string') {
-        if (!isUrl(doc)) {
-            setError(`"${fieldName}" must be an URI or a Person or Organization object, not: ${JSON.stringify(id)}"`);
-            return false;
-        }
-        else {
-            return true;
-        }
-    }
-    else {
-        setError(`"${fieldName}" must be a Person or Organization object or an URI, not ${JSON.stringify(doc)}.`);
-        return false;
-    }
+    return validateThingOrId(fieldName, {
+        "Person": personFieldValidators,
+        "Organization": organizationFieldValidators,
+    }, doc);
 }
 
 // Validates a single Person object
 function validatePerson(fieldName, doc) {
-    return validateThing(fieldName, {"Person": personFieldValidators}, doc);
+    return validateThingOrId(fieldName, {"Person": personFieldValidators}, doc);
 }
 
 // Validates a single Organization object
 function validateOrganization(fieldName, doc) {
-    return validateThing(fieldName, {"Organization": organizationFieldValidators}, doc);
+    return validateThingOrId(fieldName, {"Organization": organizationFieldValidators}, doc);
 }
 
 
 var softwareFieldValidators = {
     "@id": validateUrl,
     "id": validateUrl,
 
     "codeRepository": validateUrls,
     "programmingLanguage": noValidation,
     "runtimePlatform": validateTexts,
     "targetProduct": noValidation, // TODO: validate SoftwareApplication
     "applicationCategory": validateTextsOrUrls,
     "applicationSubCategory": validateTextsOrUrls,
     "downloadUrl": validateUrls,
     "fileSize": validateText,  // TODO
     "installUrl": validateUrls,
     "memoryRequirements": validateTextsOrUrls,
     "operatingSystem": validateTexts,
     "permissions": validateTexts,
     "processorRequirements": validateTexts,
     "releaseNotes": validateTextsOrUrls,
     "softwareHelp": validateCreativeWorks,
     "softwareRequirements": noValidation, // TODO: validate SoftwareSourceCode
     "softwareVersion": validateText, // TODO?
     "storageRequirements": validateTextsOrUrls,
     "supportingData": noValidation, // TODO
     "author": validateActors,
     "citation": validateCreativeWorks, // TODO
     "contributor": validateActors,
     "copyrightHolder": validateActors,
     "copyrightYear": validateNumbers,
     "creator": validateActors, // TODO: still in codemeta 2.0, but removed from master
     "dateCreated": validateDate,
     "dateModified": validateDate,
     "datePublished": validateDate,
     "editor": validatePersons,
     "encoding": noValidation,
     "fileFormat": validateTextsOrUrls,
     "funder": validateActors, // TODO: may be other types
     "keywords": validateTexts,
     "license": validateCreativeWorks,
     "producer": validateActors,
     "provider": validateActors,
     "publisher": validateActors,
     "sponsor": validateActors,
     "version": validateNumberOrText,
     "isAccessibleForFree": validateBoolean,
     "isPartOf": validateCreativeWorks,
     "hasPart": validateCreativeWorks,
     "position": noValidation,
     "identifier": noValidation, // TODO
     "description": validateText,
     "name": validateText,
     "sameAs": validateUrls,
     "url": validateUrls,
     "relatedLink": validateUrls,
 
     "softwareSuggestions": noValidation, // TODO: validate SoftwareSourceCode
     "maintainer": validateActors,
     "contIntegration": validateUrls,
     "buildInstructions": validateUrls,
     "developmentStatus": validateText, // TODO: use only repostatus strings?
     "embargoDate": validateDate,
     "funding": validateText,
     "issueTracker": validateUrls,
     "referencePublication": noValidation, // TODO?
     "readme": validateUrls,
 };
 
 var creativeWorkFieldValidators = {
     "@id": validateUrl,
     "id": validateUrl,
 
     "author": validateActors,
     "citation": validateCreativeWorks, // TODO
     "contributor": validateActors,
     "copyrightHolder": validateActors,
     "copyrightYear": validateNumbers,
     "creator": validateActors, // TODO: still in codemeta 2.0, but removed from master
     "dateCreated": validateDate,
     "dateModified": validateDate,
     "datePublished": validateDate,
     "editor": validatePersons,
     "encoding": noValidation,
     "funder": validateActors, // TODO: may be other types
     "keywords": validateTexts,
     "license": validateCreativeWorks,
     "producer": validateActors,
     "provider": validateActors,
     "publisher": validateActors,
     "sponsor": validateActors,
     "version": validateNumberOrText,
     "isAccessibleForFree": validateBoolean,
     "isPartOf": validateCreativeWorks,
     "hasPart": validateCreativeWorks,
     "position": noValidation,
     "identifier": noValidation, // TODO
     "description": validateText,
     "name": validateText,
     "sameAs": validateUrls,
     "url": validateUrls,
 };
 
 var personFieldValidators = {
     "@id": validateUrl,
     "id": validateUrl,
 
     "givenName": validateText,
     "familyName": validateText,
     "email": validateText,
     "affiliation": validateOrganizations,
     "identifier": validateUrls,
     "name": validateText,  // TODO: this is technically valid, but should be allowed here?
     "url": validateUrls,
 };
 
 
 var organizationFieldValidators = {
     "@id": validateUrl,
     "id": validateUrl,
 
     "email": validateText,
     "identifier": validateUrls,
     "name": validateText,
     "address": validateText,
     "sponsor": validateActors,
     "funder": validateActors, // TODO: may be other types
     "isPartOf": validateOrganizations,
     "url": validateUrls,
 
     // TODO: add more?
 };