title: Guide or approval for ANTLR example
body: <p>I have an <code>AlgebraRelacional.g4</code> file with this. I need to read a file with a syntax like a CSV file, put the content in some memory tables and then resolve relational algebra operations with that. Can you tell me if I am doing it right? </p>
  
  <p>Example data file to read:</p>
  
  <pre><code>cod_buy(char);name_suc(char);Import(int);date_buy(date)    
  “P-11”;”DC Med”;900;01/03/14    
  “P-14”;”Center”;1500;02/05/14
  </code></pre>
  
  <p>Current ANTLR grammar:</p>
  
  <pre><code>grammar AlgebraRelacional;
  
  SEL     : '\u03C3'
          ;
  PRO     : '\u220F'
          ;
  UNI     : '\u222A' 
          ;
  DIF     : '\u002D'
          ;
  PROC    : '\u0058' 
          ;
  INT     : '\u2229'
          ;
  
  AND     : 'AND'
          ;
  OR      : 'OR'
          ;
  NOT     : 'NOT'
          ;
  
  EQ          : '='
              ;
  DIFERENTE   : '!='
              ;
  MAYOR       : '&gt;'
              ;
  MENOR       : '&lt;'
              ;
  
  SUMA    : '+'
          ;
  MULTI   : '*'
  ;
  
  
  IPAREN  : '('
          ;
  DPAREN  : ')'
          ;
  COMA    : ','
          ;
  PCOMA   : ';'
          ;
  Comillas: '"'
          ;
  
  file  : hdr row+ ;
  hdr   : row ;
  row   : field (',' field)* '\r'? '\n' ;
  field : TEXT | STRING | ;
  
  TEXT   : ~[,\n\r"]+ ;
  STRING : '"' ('""'|~'"')* '"' ;
  </code></pre>