Finally after a few hours of test I found the good XPath syntax.
This is de plan.xml file
<?xml version='1.0' encoding='UTF-8'?> <deployment-plan xmlns="http://xmlns.oracle.com/weblogic/deployment-plan" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.oracle.com/weblogic/deployment-plan http://xmlns.oracle.com/weblogic/deployment-plan/1.0/deployment-plan.xsd" global-variables="false"> <application-name>cs.ear</application-name> <variable-definition> <variable> <name>ucmParamValue</name> <value>UCMJSESSIONID</value> </variable> <variable> <name>ucmParamName</name> <value>IdcSessionKey</value> </variable> </variable-definition> <module-override> <module-name>cs.ear</module-name> <module-type>ear</module-type> <module-descriptor external="false"> <root-element>weblogic-application</root-element> <uri>META-INF/weblogic-application.xml</uri> </module-descriptor> <module-descriptor external="false"> <root-element>application</root-element> <uri>META-INF/application.xml</uri> </module-descriptor> <module-descriptor external="true"> <root-element>wldf-resource</root-element> <uri>META-INF/weblogic-diagnostics.xml</uri> </module-descriptor> </module-override> <module-override> <module-name>cs.war</module-name> <module-type>war</module-type> <module-descriptor external="false"> <root-element>weblogic-web-app</root-element> <uri>WEB-INF/weblogic.xml</uri> <variable-assignment> <name>ucmParamValue</name> <xpath>/weblogic-web-app/session-descriptor/cookie-name</xpath> <operation>add</operation> </variable-assignment> </module-descriptor> <module-descriptor external="false"> <root-element>web-app</root-element> <uri>WEB-INF/web.xml</uri> <variable-assignment> <name>ucmParamName</name> <xpath>/web-app/filter/[filter-name="JpsFilter"]/init-param/param-name</xpath> <operation>add</operation> </variable-assignment> <variable-assignment> <name>ucmParamValue</name> <xpath>/web-app/filter/[filter-name="JpsFilter"]/init-param/[param-name="IdcSessionKey"]/param-value</xpath> <operation>add</operation> </variable-assignment> <variable-assignment> <name>ucmParamName</name> <xpath>/web-app/filter/[filter-name="IdcFilter"]/init-param/param-name</xpath> <operation>add</operation> </variable-assignment> <variable-assignment> <name>ucmParamValue</name> <xpath>/web-app/filter/[filter-name="IdcFilter"]/init-param/[param-name="IdcSessionKey"]/param-value</xpath> <operation>add</operation> </variable-assignment> <variable-assignment> <name>ucmParamName</name> <xpath>/web-app/servlet/[servlet-name="adfAuthentication"]/init-param/param-name</xpath> <operation>add</operation> </variable-assignment> <variable-assignment> <name>ucmParamValue</name> <xpath>/web-app/servlet/[servlet-name="adfAuthentication"]/init-param/[param-name="IdcSessionKey"]/param-value</xpath> <operation>add</operation> </variable-assignment> </module-descriptor> </module-override> <module-override> <module-name>dav.war</module-name> <module-type>war</module-type> <module-descriptor external="false"> <root-element>weblogic-web-app</root-element> <uri>WEB-INF/weblogic.xml</uri> </module-descriptor> <module-descriptor external="false"> <root-element>web-app</root-element> <uri>WEB-INF/web.xml</uri> </module-descriptor> </module-override> <config-root>/home/oracle/</config-root> </deployment-plan>