Data Dictionary Specs (***DRAFT***)

Purpose: 
         Convenient place to store and retrieve "metadata" about DB fields
         Used by DBMAN for table creation and indexing 
         Produce clean (rather than generic) data output formatting

Each field in a DB table (e.g., pnt_src) will have a row in its corresponding 
Data Dictionary (e.g., pnt_src_dd) with field attributes listed as follows:

n        - Sequencial ID number for the field [1,2,...,N]; smallint
           Ex: 16
name     - Name of the field; char(18)
           Ex: x_scan
dbtype   - Type of field in Informix 
           [Most used: char(X),smallint,integer,decimal(P,S)],date]; char(18)
           Ex: decimal(5.2)
null     - Can NULL occur in this field? [no, yes]; char(3)
           Ex: no
indexed  - Is the field indexed? [yes, no; N>=2 for composite sets]; char(3)
           Ex: yes
format   - C format codes for output; char(TBD)
           Ex: 8.2f
units    - Units; char(8)
           Ex: arcsec
desc     - Description from SIS; char(MAX?)
           Ex: "x (x-scan) position (U-scan coords)"
tbl_id   - Table/relation number in which this field is stored [1,2,...,n]; smallint
           Table naming convention (details TBC): 
                  _1 ==> primary fields
                  _2 ==> secondary fields
                                          ...
                  _n ==> remaining fields
           Ex: tbl_id=2 ==> The field is in secondary table "pnt_src_2"
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Output "view" (column set) membership:

mini     - Is this field a member of the mini view? [0=no,1=yes]; smallint
standard - Is this field a member of the standard view? [0=no,1=yes]; smallint
NOTE: Other (perhaps user-specific) views are TBD.

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Parameters dependent on an Update Statistics (dbschema) or home-grown processing: 

NOTE: Such parameters may be stored in 1 or more auxillary relations,
      with only pointer(s) in this Data Dictionary.

nnulls   - number of NULLS; integer
           Ex: 0
min      - minimum value; decimal(P,S)
           Ex: 2
max      - maximum value; decimal(P,S)
           Ex: 15768
mean     - mean    value; decimal(P,S)
           Ex: 2345.65
std      - standard deviation; decimal(P,S)
           Ex: 456.4

NOTE: Others will be desired. Details TBD.