Hibernate

Exception in thread main
org.hibernate.exception.SQLGrammarException: could not get next sequence value

Caused by: org.postgresql.util.PSQLException: ERROR: relation "titulacao_id_titulacao" does not exist

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping 
            PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
    <class name="Titulacao" table="titulcao">
        <id name="id_titulacao">            
            <generator class="increment"></generator>            
        </id>
        <property name="nome"/>
        
    </class>
</hibernate-mapping>