It is not recommended to use SYS or SYSTEM schema to store/manage RDF graph data.
Can you please try the following from a SQL*Plus terminal?
SQL> conn system/welcome1
SQL> create user graphuser identified by graphuser;
SQL> grant connect, resource, unlimited tablespace to graphuser;
SQL> conn graphuser/graphuser
SQL> create table graph_tpl (triple sdo_rdf_triple_s) compress;
SQL> exec sem_apis.create_sem_model('graph', 'graph_tpl', 'triple');
PL/SQL procedure successfully completed.
SQL> insert into graph_tpl values(sdo_rdf_triple_s('graph','<urn:s>','<urn:p>','<urn:o>'));
1 row created.
SQL> select count(1) from mdsys.rdfm_graph;
Can you see the same output?
Yes, I can see the same output after inputting your sql commands. So, I loaded my data again using the user, and I can create
Thank you very much for your help!