Consider the following table, which maps an XML document to a relational database:

Which statement is correct?

a. The above table assumes the presence of a DTD or XSD before the mapping can take place.

b. The table will require extensive querying resources since every single (e.g., XPath) navigation step requires a self-join on this table.

c. Using the above table, every XPath expression can be translated to a corresponding SQL query.

d. The table is not entirely normalized and still contains redundant information.

CREATE TABLE NODE( ID CHAR(6) NOT NULL PRIMARY KEY, PARENT_ID CHAR(6), TYPE VARCHAR(9), LABEL VARCHAR(20), VALUE CLOB, FOREIGN KEY (PARENT_ID) REFERENCES NODE (ID) CONSTRAINT CC1 CHECK(TYPE IN ("element", "attribute")) )