What's the purpose of 'isDraft' in CubeDesc

[yuzhang]

Hi team:
    The frontend web doesn't pass 'is_draft' field to kylin server when update 
or save CubeDesc and don't use it's value for some change of Web UI. Then the 
backend call setDraft(false) before update or save an CubeDesc in backend and 
then read isDraft(must be false) in CubeDescManager before persist into 
metastore. I don't understand the meaning of those logic. What's the purpose of 
'isDraft' in CubeDesc? 
    The sincerity anticipates your reply.
                                                                                
                                                               
                                                                                
                                                                                
                                                                        Best 
regards
                                                                                
                                                                                
                                                                             
yuzhang