json - Cannot update pre indexed data via SOLR/CURL -

i've performed following indexation via solr/curl

  
curl http://localhost:8983/solr/wiki/update -h 'content-type:application/json' -d ' [ {"id" : "book1", "title" : "american gods", "author" : "neil gaiman" } ]' 
  

error appears while updating data

  
curl http://localhost:8983/solr/wiki/update -h 'content-         type:application/json' -d ' [ {"id" : "book1", "cat" : { "add" : "fantasy" }, "pubyear_i" : { "add" : 2001 }, "isbn_s" : { "add" : "0-380-97365-0"} } ]' 
  
  
this error 
  {"responseheader":{"status":400,"qtime":0},"error":{"metadata":["error-class","org.apache.solr.common.solrexception","root-error-class","org.apache.solr.common.solrexception"],"msg":"undefined field: \"cat\"","code":400}} 
  

when delete following "id" json file "cat" : { "add" : "fantasy" }, indexation proceeded. problem ?