When indexing through curl

 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"} } ]' 

The following error occurs

 {"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 I remove "cat": {"add": "fantasy"}, then the indexing is normal. What am I doing wrong ??? PS before that performed this index

 curl http://localhost:8983/solr/wiki/update -H 'Content-type:application/json' -d ' [ {"id" : "book1", "title" : "American Gods", "author" : "Neil Gaiman" } ]' 

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