Sequence does not match type xs:string error Xquery

I am using BDB XML 2.5.16 to store and query my XML documents in Java. The documents are IMDB xml documents containing actors information obtained from INEX website http://ift.tt/15jg33e. One of the document I stored in the database is the following

<?xml version="1.0" encoding="UTF-8"?>
 <persons>
  <person>
      <name>jason angeles
      </name>
      <filmography>
         <act>
            <movie>
               <title>prison planet 3 the revenge 1998
                </title>
              <year>1998
              </year>
             <character>evil ninja
              </character>
           </movie>
         </act>
      </filmography>
     </person>
     </persons>

I want to search (using XQuery ) for filmography element whose title element contains ANY of the following keywords ('planet', 'revenge', '1998') and /act/movie/year or direct/movie/year equals to 1998. Below is the query I used

       // declaring function functx:contains-any-of

       String qryRk = "declare namespace functx = 'http://www.functx.com'; " 
        + "declare function functx:contains-any-of "
        + "( $arg as xs:string?" + " , "  + " $searchStrings as xs:string* )   
        as xs:boolean { " + "some $searchString in $searchStrings "
            +  " satisfies contains($arg,$searchString)} ; ";

         String myQuery101 = qryRk + "for $entity in 
           collection('simpleExampleData2.dbxml')//filmography "
              + "where functx:contains-any-of ( $entity/act/movie/title ,                   
             ('planet', 'revenge', '1998'))"
             + "and (   contains ( $entity/act/movie/year , '1998' ) "
             + "or  contains ( $entity/direct/movie/year , '1998' ))"
             + "return $entity";

When I executed the query, I expect to get at least the following element as my output

                   Document : person_31000.xml:
                <filmography>
                       <act>
                             <movie>
                             <title>prison planet 3 the revenge 1998
                            </title>
                            <year>1998
                            </year>
                           <character>evil ninja
                           </character>
                          </movie>
                       </act>
                     </filmography>

However instead of the above element I got the following Error

    Exception in thread "main" com.sleepycat.dbxml.XmlException: Error:    
    Sequence does not match type xs:string? - the sequence contains more   
    than one item [err:XPTY0004], <query>:1:343, errcode =          
    QUERY_EVALUATION_ERROR at                                    
     com.sleepycat.dbxml.dbxml_javaJNI.XmlManager_query__SWIG_0(Native 
    Method)  at 
     com.sleepycat.dbxml.XmlManager.query(XmlManager.java:544)
                             at   

      com.sleepycat.dbxml.XmlManager.query(XmlManager.java:320)
                             at   

      xmlirsystemstruxplus.XQueryEngine.queryEngine(XQueryEngine.java:269)
                             at 

         xmlirsystemstruxplus.XMLIRSystemStruXplus.main(XMLIRSystemStruXplus.java:109)
                             Java Result: 1

Note that i used contains-any-of() function because the contains () function does not work with 'planet revenge 1998' string may be because the keywords do not appear in the order they appear in the element content.

Please can any body help me to find out (1) why i have the above error ? and solution (2) why the condition contains ( $entity/act/movie/title , 'planet revenge 1998') is not working ? how do i use contains() function w.r.t this

Thank you in advance