|  | /*!\page rfc2119 RFC2119 Keywords | 
|  |  | 
|  | The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL | 
|  | NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and | 
|  | "OPTIONAL" in this document are to be interpreted as described in | 
|  | <a href="http://www.ietf.org/rfc/rfc2119.txt">RFC 2119.</a> | 
|  |  | 
|  | Specifically, the following definitions are used: | 
|  |  | 
|  | \section MUST | 
|  | \anchor REQUIRED | 
|  | \anchor SHALL | 
|  | This word, or the terms "REQUIRED" or "SHALL", mean that the | 
|  | definition is an absolute requirement of the specification. | 
|  |  | 
|  | \section MUSTNOT MUST NOT | 
|  | \anchor SHALLNOT | 
|  | This phrase, or the phrase "SHALL NOT", mean that the | 
|  | definition is an absolute prohibition of the specification. | 
|  |  | 
|  | \section SHOULD | 
|  | \anchor RECOMMENDED | 
|  | This word, or the adjective "RECOMMENDED", mean that there | 
|  | may exist valid reasons in particular circumstances to ignore a | 
|  | particular item, but the full implications must be understood and | 
|  | carefully weighed before choosing a different course. | 
|  |  | 
|  | \section SHOULDNOT SHOULD NOT | 
|  | \anchor NOTRECOMMENDED | 
|  | This phrase, or the phrase "NOT RECOMMENDED" mean that | 
|  | there may exist valid reasons in particular circumstances when the | 
|  | particular behavior is acceptable or even useful, but the full | 
|  | implications should be understood and the case carefully weighed | 
|  | before implementing any behavior described with this label. | 
|  |  | 
|  | \section MAY | 
|  | \anchor OPTIONAL | 
|  | This word, or the adjective "OPTIONAL", mean that an item is | 
|  | truly optional.  One vendor may choose to include the item because a | 
|  | particular marketplace requires it or because the vendor feels that | 
|  | it enhances the product while another vendor may omit the same item. | 
|  | An implementation which does not include a particular option \ref MUST be | 
|  | prepared to interoperate with another implementation which does | 
|  | include the option, though perhaps with reduced functionality. In the | 
|  | same vein an implementation which does include a particular option | 
|  | \ref MUST be prepared to interoperate with another implementation which | 
|  | does not include the option (except, of course, for the feature the | 
|  | option provides.) | 
|  |  | 
|  |  | 
|  | */ |