Problem inserting and querying XML data with a recursive XML schema

Question

Hello,
I'm facing a problem with querying XML data that is valid against a recursive XML Schema. I have got a table category that stores data as binary XML using Oracle 11g Rel 2 on Windows XP. The XML Schema is the following:
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:complexType name="bold_type" mixed="true">
          <xs:choice minOccurs="0" maxOccurs="unbounded">
               <xs:element name="bold" type="bold_type"/>
               <xs:element name="keyword" type="keyword_type"/>
               <xs:element name="emph" type="emph_type"/>
          </xs:choice>
     </xs:complexType>
     <xs:complexType name="keyword_type" mixed="true">
          <xs:choice minOccurs="0" maxOccurs="unbounded">
               <xs:element name="bold" type="bold_type"/>
               <xs:element name="keyword" type="keyword_type"/>
               <xs:element name="emph" type="emph_type"/>
               <xs:element name="plain_text" type="xs:string"/>
          </xs:choice>
     </xs:complexType>
     <xs:complexType name="emph_type" mixed="true">
          <xs:choice minOccurs="0" maxOccurs="unbounded">
               <xs:element name="bold" type="bold_type"/>
               <xs:element name="keyword" type="keyword_type"/>
               <xs:element name="emph" type="emph_type"/>
          </xs:choice>
     </xs:complexType>
     <xs:complexType name="text_type" mixed="true">
          <xs:choice minOccurs="0" maxOccurs="unbounded">
               <xs:element name="bold" type="bold_type"/>
               <xs:element name="keyword" type="keyword_type"/>
               <xs:element name="emph" type="emph_type"/>
          </xs:choice>
     </xs:complexType>
     <xs:complexType name="parlist_type">
          <xs:sequence>
               <xs:element name="listitem" minOccurs="0" maxOccurs="unbounded" type="listitem_type"/>
          </xs:sequence>
     </xs:complexType>
     <xs:complexType name="listitem_type">
          <xs:choice minOccurs="0" maxOccurs="unbounded">
               <xs:element name="parlist" type="parlist_type"/>
               <xs:element name="text" type="text_type"/>
          </xs:choice>
     </xs:complexType>
     <xs:element name="category">
          <xs:complexType>
               <xs:sequence>
                    <xs:element name="name"/>
                    <xs:element name="description">
                              <xs:complexType>
                                        <xs:choice>
                                                       <xs:element name="text" type="text_type"/>
                                                       <xs:element name="parlist" type="parlist_type"/>
                                        </xs:choice>
                              </xs:complexType>
                    </xs:element>
                                                            </xs:sequence>
                                                            <xs:attribute name="id"/>
                                        </xs:complexType>
                    </xs:element>
</xs:schema>I registered this schema and created the category table. Then I inserted a new row using the code below:
insert into category_a values
(XMlElement("category",
      xmlattributes('categoryAAA' as "id"),
      xmlforest ('ma categ' as "name"),
      (xmlelement("description", (xmlelement("text", 'find doors blest now whiles favours carriage tailor spacious senses defect threat ope willow please exeunt truest assembly <keyword> staring travels <bold> balthasar parts attach </bold> enshelter two <emph> inconsiderate ways preventions </emph> preventions clasps better affections comes perish </keyword> lucretia permit street full meddle yond general nature whipp <emph> lowness </emph> grievous pedro')))    
The row is successfully inserted as witnessed by the results of row counting. However, I cannot extract data from the table. First, I tried using SqlPlus* which hangs up and quits after a while. I then tried to use SQL Developer, but haven't got any result. Here follow some examples of queries and their results in SQL Developer:
Query 1
select * from category
Result : the whole row is returned
Query 2
select xmlquery('$p/category/description' passing object_value as "p" returning content) from category
Result: "SYS.XMLTYPE"
now I tried to fully respect the nested structure of description element in order to extract the text portion of <bold> using this query
Query 3
select  xmlquery('$p/category/description/text/keyword/bold/text()' passing object_value as "p" returning content) from  category_a
Result: null
and also tried to extract the text portion of element <text> using this query
Query 4
select  xmlquery('$p/category/description/text/text()' passing object_value as "p" returning content) from  category_a
Result: "SYS.XMLTYPE".
On the other hand, I noticed, from the result of query 1, that the opening tags of elements keyword and bold are encoded as the less than operator "&lt;". This explains why query 3 returns NULL. However, query 4 should display the text content of <text>, which is not the case.
My questions are about
1. How to properly insert the XML data while preserving the tags (especially the opening tag).
2. How to display the data (the text portion of the main Element or of the nested elements).
The problem about question 1 is that it is quite unfeasible to write a unique insert statement because the structure of <description> is recursive. In other words, if the structure of <description> was not recursive, it would be possible to embed the elements using the xmlelement function during the insertion.
In fact, I need to insert the content of <description> from a source table (called category_a) into a target table (+category_b+) automatically .
I filled category_a using the Saxloader utility from an flat XML file that I have generated from a benchmark. The content of <description> is different from one row to another but it is always valid with regards to the XML Schema. The data is properly inserted as witnessed by the "select * from category_a" instruction (500 row inserted). Besides, the opening tags of the nested elements under <description> are preserved (no "&lt;"). Then I wrote a PL/SQL procedure in which a cursor extracts the category id and category name into varchar2 variables and description into an XMLtype variable from category_a. When I try to insert the values into a category_b, I get the follwing error:
LSX-00213: only 0 occurrences of particle "text", minimum is 1which tells that the <text> element is absent (actually it is present in the source table).
So, my third question is why are not the tags recognized during the insertion?
Can anyone help please?

Answer 1

Hello,
indded, I was using an old version of Sqlplus* (8.0.60.0.0) because I had a previous installation (oracle 10g XE). Instead, I used the Sqlplus* shipped with the 11g2database (version 11.2.0.1.0). All the queries that I wrote work fine and display the data correctly.
I also used the XMLSERIALIZE function and can now display the description content in SQL Developer.
Thank you very much.
To answer your question Marco, I registered the XML Schema using the following code
declare
  doc varchar2(4000) := '<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:complexType name="bold_type" mixed="true">
          <xs:choice minOccurs="0" maxOccurs="unbounded">
               <xs:element name="bold" type="bold_type"/>
               <xs:element name="keyword" type="keyword_type"/>
               <xs:element name="emph" type="emph_type"/>
          </xs:choice>
     </xs:complexType>
     <xs:complexType name="keyword_type" mixed="true">
          <xs:choice minOccurs="0" maxOccurs="unbounded">
               <xs:element name="bold" type="bold_type"/>
               <xs:element name="keyword" type="keyword_type"/>
               <xs:element name="emph" type="emph_type"/>
               <xs:element name="plain_text" type="xs:string"/>
          </xs:choice>
     </xs:complexType>
     <xs:complexType name="emph_type" mixed="true">
          <xs:choice minOccurs="0" maxOccurs="unbounded">
               <xs:element name="bold" type="bold_type"/>
               <xs:element name="keyword" type="keyword_type"/>
               <xs:element name="emph" type="emph_type"/>
          </xs:choice>
     </xs:complexType>
     <xs:complexType name="text_type" mixed="true">
          <xs:choice minOccurs="0" maxOccurs="unbounded">
               <xs:element name="bold" type="bold_type"/>
               <xs:element name="keyword" type="keyword_type"/>
               <xs:element name="emph" type="emph_type"/>
          </xs:choice>
     </xs:complexType>
     <xs:complexType name="parlist_type">
          <xs:sequence>
               <xs:element name="listitem" minOccurs="0" maxOccurs="unbounded" type="listitem_type"/>
          </xs:sequence>
     </xs:complexType>
     <xs:complexType name="listitem_type">
          <xs:choice minOccurs="0" maxOccurs="unbounded">
               <xs:element name="parlist" type="parlist_type"/>
               <xs:element name="text" type="text_type"/>
          </xs:choice>
     </xs:complexType>
     <xs:element name="category">
          <xs:complexType>
               <xs:sequence>
                    <xs:element name="name"/>
                    <xs:element name="description">
                              <xs:complexType>
                                        <xs:choice>
                                                       <xs:element name="text" type="text_type"/>
                                                       <xs:element name="parlist" type="parlist_type"/>
                                        </xs:choice>
                              </xs:complexType>
                    </xs:element>
                                                            </xs:sequence>
                                                            <xs:attribute name="id"/>
                                        </xs:complexType>
                    </xs:element>
</xs:schema>';
begin
  dbms_xmlschema.registerSchema('/xmldb/category_auction.xsd', doc,     LOCAL      => FALSE, 
        GENTYPES   => FALSE,  GENBEAN    => FALSE,   GENTABLES  => FALSE,
         FORCE      => FALSE,
         OPTIONS    => DBMS_XMLSCHEMA.REGISTER_BINARYXML,
         OWNER      => USER);
end;then, I created the Category table as follows:
CREATE TABLE category_a of XMLType XMLTYPE store AS BINARY XML
    XMLSCHEMA "xmldb/category_auction.xsd" ELEMENT "category";Now, there still remains a problem of how to insert the "description" content which I serialized as a CLOB data into another table as XML. To this purpose, I wrote a view over the Category_a table as follows:
CREATE OR REPLACE FORCE VIEW "AUCTION_XWH"."CATEGORY_V" ("CATEGORY_ID", "CNAME", "DESCRIPTION") AS
  select category_v."CATEGORY_ID",category_v."CNAME",
  XMLSerialize(content ( xmlquery('$p/category/description/*' passing object_value as "p" returning content)) as clob) as "DESCRIPTION"
  from  auction.category_a p, 
xmltable ('$a/category' passing p.Object_Value as "a"
columns  category_id varchar2(15) path '@id',
          cname varchar2(20) path 'name') category_v;Then, I wrote a procedure to insert data into the Category_xwh table (the source and target tables are slightly different: the common elements are just copied wereas new elements are created in the target table). The code of the procedure is the following:
create or replace PROCEDURE I_CATEGORY AS
v_cname VARCHAR2(30);
v_description clob ;
v_category_id VARCHAR2(15);
cursor mycursor is select category_id, cname, description from category_v;
BEGIN
open mycursor;
  loop
  /*retrieving the columns*/
  fetch mycursor into v_category_id, v_cname, v_description ;
  exit when mycursor%notfound;
  insert into category_xwh values
  (XMlElement("category",
      xmlattributes(v_category_id as "category_id"),
      xmlelement("Hierarchies", xmlelement("ObjHierarchy", xmlelement ("H_Cat"),
                                                           xmlelement ("Rollsup",
                                                                              (xmlelement("all_categories",
                                                                               xmlattributes('allcategories' as "all_category_id")))
    xmlforest (
              v_cname as "cat_name",
              v_description as "description")    
end loop;
  commit;
  close mycursor;
END I_CATEGORY;When I execute the procedure, I get the following error:
LSX-00201: contents of "description" should be elements onlyso, I just wonder if this is because v_description is considered as plain text and not as XML text, even if its content is XML. Do I need to use a special function to cast the CLOB as XML?
Thanks for your help.
Doulkifli