How can define an outer join in the where clause of a flowr statement?

Question

Hi- In the sample below I'm joining two views based on username but in this case what I really want to use is an outer join instead. What is the syntax for that? I tried the (+) notation but that didn't seem to work..
CREATE OR REPLACE PROCEDURE proc_ctsi_all is
XMLdoc XMLType;
BEGIN
DBMS_XDB.deleteResource('/public/CTSI/ctsi_all_rpt1.xml',1);
SELECT XMLQuery(
'<Progress_Report>
<Personnel_Roster>
{for $c in ora:view("CTSI_INVEST_NONPHS_SOURCE_V"),
$cphs in ora:view("CTSI_INVEST_PHS_SOURCE_V")
  let $username  := $c/ROW/COMMONS_USERNAME/text(),
$expertise  := $c/ROW/AREA_OF_EXPERTISE/text(),
$phsorg  := $cphs/ROW/PHS_ORGANIZATION/text(),
$activitycode  := $cphs/ROW/ACTIVITY_CODE/text(),
$username2  := $cphs/ROW/COMMONS_USERNAME/text()
where $username eq $username2
     return
  <Investigator>
   <Commons_Username>{$username}</Commons_Username>
<Area_of_Expertise>{$expertise}</Area_of_Expertise>
<Federal_PHS_Funding>
<Organization>{$phsorg}</Organization>
<Activity_Code>{$activitycode}</Activity_Code>
<Six_Digit_Grant_Number>{$grantnumber}</Six_Digit_Grant_Number>
</Federal_PHS_Funding>
</Investigator>}
</Personnel_Roster>
</Progress_Report>'
RETURNING CONTENT) INTO XMLdoc FROM DUAL;
IF(DBMS_XDB.CREATERESOURCE('/public/CTSI/ctsi_all_rpt1.xml', XMLdoc)) THEN
DBMS_OUTPUT.PUT_LINE('Resource is created');
ELSE
DBMS_OUTPUT.PUT_LINE('Cannot create resource');
END IF;
COMMIT;
END;
/

Answer 1

What you could do is use query within an XMLTable syntax. Via the COLUMNS parameter you then pass the "column" as XMLType to the following XMLtable statement.
little bit like the following
select hdjfdf
from xmltable
   ({xquery}
    PASSING
    COLUMNS xmlfrag xmltype path 'xxx'
   ) a
,  xmltable
   ({the other stuff you need}
    PASSING a.xmlfrag
   ...etc
  ...etc                 I guess something simular can be done via XQuery straight away as well