Update Readme.md (HydrologicEngineeringCenter#14)

Author: ktarbet

Readme.md

@@ -6,6 +6,21 @@ This repository contains a Python wrapper for the HEC-DSS file database C librar
 
 The HEC-DSS file database is a widely used data storage format for hydrological and environmental data. This repository provides a Python interface to interact with the HEC-DSS files using the provided C DLL. The primary goal is to enable Python applications to read data from and write data to HEC-DSS files. 
 
+## Design 
+
+These are the driving design ideas and goals of the hec-dss-python project (subject to updates)
+
+| Feature |      What     | Why  |
+| ------------- |-------------| -----|
+| hecdss.dll/libhecdss.so  | cross platform (Linux,Windows,Mac), cross language ([.net](https://github.com/HydrologicEngineeringCenter/hec-dss-dotnet), [Python](https://github.com/HydrologicEngineeringCenter/hec-dss-python]), Java)  essential API |decouple from underlying HEC-DSS Fortran/C Library  (allow future DSS versions without C and Fortran backend)  |
+| Support only DSS 7 | encourage migration from version 6  |  HEC is moving to DSS version 7 in 2023-2024. |
+|Easy transition from Jython|HEC products use an existing [Java/Jython API](https://www.hec.usace.army.mil/confluence/dssdocs/dssvueum/scripting/reading-and-writing-to-hec-dss-files).  We will loosely follow that design | simplify porting from Jython|
+| hec_dss_native.py | native binding layer   | isolate interactions with low level library(if performance is an issue this Ctypes layer can be replaced ) |
+| hec_dss.py | Programmer entry point ; Python API  | Hides interactions with hec_dss_native, seek to be simple user experience|
+|Pandas_Series_Utilities.py [future](https://github.com/HydrologicEngineeringCenter/hec-dss-python/issues/8) |NumPy/pandas support |provide features such as dataframes, separate from hec-dss.py; can be developed by different/parallel developers|
+| Easy to get started |nothing to install, just copy python files and shared library   |require minimal privileges to install| 
+
+
 ## Features
 
 - Read and write data from HEC-DSS files using the provided C DLL.