My table and tablespace, and semnetwork have been created successfully, with following SQL:
CREATE TABLESPACE MYONTOLOGY_TBS
DATAFILE 'C:\Oracle\oradata\odb1\myontology_tbs.dat' SIZE 1024M REUSE
AUTOEXTEND ON NEXT 256M MAXSIZE UNLIMITED
SEGMENT SPACE MANAGEMENT AUTO;

EXECUTE SEM_APIS.CREATE_SEM_NETWORK('MYONTOLOGY_TBS');

CREATE TABLE MYASSERTIONS
(
ID NUMBER NOT NULL,
ASSERTION MDSYS.SDO_RDF_TRIPLE_S NOT NULL
)
TABLESPACE "MYONTOLOGY_TBS";


Then, I tried to create two models on that table, as following:

EXECUTE sem_apis.create_sem_model('amodel', 'MYASSERTIONS', 'ASSERTION');
EXECUTE sem_apis.create_sem_model('bmodel', 'MYASSERTIONS', 'ASSERTION');

The result was:
anonymous block completed
anonymous block completed

Error starting at line 2 in command:
EXECUTE sem_apis.create_sem_model('bmodel', 'MYASSERTIONS', 'ASSERTION');
Error report:
ORA-13199: Internal error in SDO_RDF.CREATE_RDF_MODEL: SQLERRM=ORA-55300: model bmodel does not exist dss=
SELECT count("ASSERTION") FROM "MYASSERTIONS"
ORA-06512: at "MDSYS.MD", line 1723
ORA-06512: at "MDSYS.MDERR", line 17
ORA-06512: at "MDSYS.SDO_RDF", line 937
ORA-06512: at "MDSYS.SDO_RDF", line 972
ORA-06512: at "MDSYS.RDF_APIS", line 726
ORA-06512: at line 1
13199. 00000 - "%s"
*Cause:    This is an internal error.
*Action:   Contact Oracle Support Services.


It seems that more than one model can not coexist on one single table, is that right? And is it means that, if I wanna manage a large number of models, I must create and manage the same large number of table? On my case, I have hundreds of models to handle and thousands of predicates in each on average, I don't think managing hundreds of tables is a good approach, is there another way?