CONTENTS:
  1. ERROR MESSAGE EXPLAINED
  2. LIST CONSTANTS
  3. USAGE

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1. ERROR MESSAGE EXPLAINED

This is a proposed error messages severity indicators list.
Each message string represents a bit field, so transitional levels
could be created.

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2. LIST CONSTANTS

BIT CONSTANT    DESCRIPTION
1   ERROR   Super-severe message, meaning general fault, which could not 
            be recovered, must be taken into account if returned by 
            validation script.
2   WARNING Severe message meaning some serious problem in input data, 
            but script must not terminate if experienced with error of 
            this level. It should be taken into account.
4   NOTICE  Notice might not be a real error, but in some conditions 
            this could indicate a real problem incorrectly captured.
            Could be filtered out, while there are enough of warnings...
8   I_ERROR This is information message. It is a process indicator and 
            ERROR message must follow this one. Process indicators are 
            displayed during normal script execution, if -v (verbose) 
            option is selected. Could be useful for script analysis as 
            well.
16  I_WARNING   This is information message about upcoming warning. As 
            well as I_ERROR is displayed prior to WARNING and only if 
            verbose output is selected.
32  I_NOTICE    Information notice could not be related to NOTICE, but 
            in most situations it should. Exceptions could be made if 
            during script run something s-e-e-m-s as a NOTICE, but after 
            full analysis it appears as normal situation.
64  I_INDICATOR This is not error message entirely. It is progress 
            indicator shown only while in DEBUG mode (or full verbose) 
            and writing messages about current script progress.

65536   ALL Do you think, that higher error levels are possible? 
            Intermediate levels could be used by various scripts and 
            this information should be explicitly written in help 
            messages with detailed description on demand.
            ALL means, that script should output ANY actual information, 
            almost every tick of progress.

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3. USAGE

Every script since the creation of this document must be able to accept 
error level defined (bitfield) with '--show-errors' option.
Scripts could have their own command line options to indicate how 
verbose messages will be printed.
If severity is defined in error message outputed it should adhere to 
this document.
