 
    
    
         
<IndexSearchCond>::=IndexSingleCond
  LogicalOperator(<IndexSearchCond>,<IndexSearchCond>)
 
LogicalOperator(<IndexSearchCond>,<IndexSearchCond>)
  compress(Attr_name,<IndexSearchCond>)
 
 compress(Attr_name,<IndexSearchCond>)
IndexSingleCond::=RangeSearch  Attr_name ComparisonOperator Attr_value
 Attr_name ComparisonOperator Attr_value  Attr_name= concat(String,*)
 
Attr_name= concat(String,*)  not_exist(Attr_name)
  not_exist(Attr_name)  is_null(Attr_name)
  is_null(Attr_name)
String::= STRING
Attr_name::= ATOM
ComparisonOperator::= =<  <
 <  >
 >  >=
 >=  =
 =
LogicalOperator::=  and  or
  or  dif
  dif
RangeSearch::=  range(Attr_name,Attr_value1,Attr_value2)  etc.
 etc.
Attr_value::= INTEGER  STRING
  STRING