Objective: MC approval of additional standard values for the HEADER_TYPE keyword.
Date:      2003-08-19
Author:    Steve Joy

Background
==========

Many of our data providers like to include a few lines of header material
prior to the beginning of data in ASCII data files (tables, spreadsheets, 
etc.) because users find them useful. One line headers typically consist of 
column names. More detailed headers may provide additional information 
such as data processing parameters, input file names (such as SPICE
kernel files), and other information. The current method of describing these
headers is to call them tables with one column whose description is "Header
text information". 

The PDS has a HEADER object that could be used to describe headers on ASCII 
files as headers, rather than as tables. In order to use the HEADER object
in this way, we need to add TEXT to the standard value list of the 
required HEADER_TYPE keyword. 

Current Urgency
===============

There is an existing work around to this problem that just confuses users 
and makes data providers complain about silly PDS standards. 

Recommendations
===============

1) Add TEXT to the list of standard values for the keyword HEADER_TYPE

Impact
======

Minimal - PDS data dictionary update.

PDS requires that all non-PDS headers be described by a document. I (S. Joy)
will provide a brief document describing text headers. The document will
state that text headers consist only of printable ASCII characters and are
found attached to ASCII data files. I don't see any reason to be much more 
restrictive or descriptive about the formation and/or use of text headers.

-----------------------------------------------------------------------------
PRODUCT_TYPE Data Dictionary Element Definition
-----------------------------------------------------------------------------

   OBJECT                        = ELEMENT_DEFINITION
     NAME                        = HEADER_TYPE
     STATUS_TYPE                 = APPROVED
     STATUS_NOTE                 = "V1.0 2003-08-19 SPJ
             Standard value update request."
     DESCRIPTION                 = "
         The header_type element identifies a specific type of       
         header data structure.  For example: FITS, VICAR.           
         Note:  In the PDS, header_type is used to indicate non-PDS  
         headers."
     SOURCE_NAME                 = "PDS CN/S. Hess"
     GENERAL_DATA_TYPE           = IDENTIFIER
     UNIT                        = "N/A"
     VALID_MAXIMUM               = "N/A"
     VALID_MINIMUM               = "N/A"
     MAXIMUM_LENGTH              = "12"
     MINIMUM_LENGTH              = "N/A"
     STANDARD_VALUE_SET          = {BVD, FITS, GSFC_ODL, IGPP_FFH, 
               SPREADSHEET, TEXT, VICAR, VICAR2}
     STANDARD_VALUE_TYPE         = "DYNAMIC"
     DEFAULT                     = "N/A"
     FORMATION_RULE_DESC         = "N/A"
     SYSTEM_CLASSIFICATION_ID    = COMMON
     GENERAL_CLASSIFICATION_TYPE = STRUCTURE
     OBJECT                      = ALIAS
       ALIAS_NAME                = "N/A"
       OBJECT_NAME               = "N/A"
       USAGE_NOTE                = "N/A"
     END_OBJECT                  = ALIAS
     OBJECT                      = LOCAL_ENVIRONMENT
       SQL_FORMAT                = "CHAR(12)"
       TERSE_NAME                = "N/A"
     END_OBJECT                  = LOCAL_ENVIRONMENT
   END_OBJECT                    = ELEMENT_DEFINITION