use OPTIONAL around given name of person authors

project/dalia/query/items/metadata/authors.py

@@ -5,7 +5,7 @@ from rdflib import RDF, URIRef, Variable
 
 from project.dalia.api_models.api_models import OrganizationAuthor, PersonAuthor
 from project.dalia.query.utils import query_dalia_dataset
-from project.dalia.query_builder.query_builder import GROUP, QueryBuilder, UNION, VALUES
+from project.dalia.query_builder.query_builder import GROUP, OPTIONAL, QueryBuilder, UNION, VALUES
 from project.dalia.rdf.namespace import Jena_ARQ_list, SCHEMA, educor
 
 _VARIABLES = {
@@ -42,7 +42,9 @@ def prepare_query_for_authors_metadata_for_resources(resource_uri_refs: List[URI
         UNION(
             (var_member, RDF.type, SCHEMA.Person),
             (var_member, SCHEMA.familyName, _VARIABLES["family"]),
-            (var_member, SCHEMA.givenName, _VARIABLES["given"])
+            OPTIONAL(
+                (var_member, SCHEMA.givenName, _VARIABLES["given"])
+            )
         )
     ).build()
 

tests/project/dalia/query/items/metadata/test_authors.py

@@ -29,12 +29,15 @@ def test_prepare_query_for_authors_metadata_for_resources():
         UNION { 
         ?member <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <https://schema.org/Person> . 
         ?member <https://schema.org/familyName> ?family . 
+        OPTIONAL { 
         ?member <https://schema.org/givenName> ?given .
+        } .
         } 
         } 
     """)
 
 
+# TODO: add test case with an author without given name
 def test_get_authors_metadata_for_resources(triplestore):
     lr_authors = get_authors_metadata_for_resources([
         URIRef("https://id.dalia.education/learning-resource/1ec1db44-5330-47c5-aae3-6852b11f43a4"),