1. Python Driven Sensor Observation Service Benjamin Welton NASA USRP

2. Sensor Observation Service A Sensor Observation Service is a server that is designed to serve multiple different types of Sensor and Observation data in a standardized way. Standard is defined by the Open Geospatial Consortium (OGC SOS)

3. Key Features and Goals Obtain compliance with OGC SOS Version 1.0.0 spec Integrate a Tahoe Distributed File System storage node into the SOS to allow for distribution of data and data redundancy Add E-Authentication into the server to restrict access to only certain certified clients

4. OGC SOS Specification The OGC SOS specification is a web based standard that uses standard HTTP Get and Post request for communication between the client and server. Request are sent ether via Key Value Pair (KVP) get requests or XML post request Server responses are returned in XML format

5. Implementation Apache server using the Python SCGI Module Use of the SCGI python package for handling of incoming request and responses XML responses and parsing was done using ElementTree package KVP request are handled using parse_qs from the CGI package SQLite database is used to store metadata and file location information.

6. Tahoe Distributed File System Tahoe is a distributed and remote file system that can be used to store files in a peer to peer manner Each node host's pieces of the file system which allow clients the ability to download a single file in parts from multiple different sources Highly redundant, on its default distribution settings only 3 out of every 10 storage nodes are required to reassemble a file.

7. Tahoe File Upload Tahoe Storage Node Tahoe Client File Tahoe Storage Node

8. Tahoe File Download Tahoe Storage Node Tahoe Client File Tahoe Storage Node

9. Why Tahoe? High level of redundancy and the ability for nodes to join and leave the network without file availability issues Option to download files via standard html links allowed for integration into a SOS server without requiring any changes be made on the client level. Ability for our SOS to serve data from other SOS's (and vice versa) automatically. Creating a situation where the original posting server is does not need to be available to obtain the data

10. SOS Tahoe File Upload SOS #1SOS #2 Fil e = Tahoe Storage Server

11. SOS Tahoe File Retrieval SOS #1SOS #2 Fil e Client = Tahoe Storage Server

12. Issues Tahoe has no method for verifying who uploads a file onto the network No control over access to the Tahoe network (anyone can join and post at there leisure) No ability to list directory's or files available on the network

13. Possible Solutions Possible solutions to the authentication and authorization issue include checking for properly signed files before allowing the tahoe storage server to store that data or only allowing certain ip address the ability to connect to the network as a node.

14. E Authentication E-Authentication is a US Government mandated intuitive to have a more standardized way for authenticating users across varying government agency's Integration into Python will be done using Sun's Java Access Manager Module for apache webserver

15. Links CGI Package - http://docs.python.org/library/cgi.htmlhttp://docs.python.org/library/cgi.html SCGI Package - http://python.ca/scgi/http://python.ca/scgi/ Tahoe - http://allmydata.org/trac/tahoehttp://allmydata.org/trac/tahoe Element Tree - http://effbot.org/zone/element- index.htmhttp://effbot.org/zone/element- index.htm OGC SOS V1.0 Spec - http://www.opengeospatial.org/standards/sos http://www.opengeospatial.org/standards/sos Twisted - http://twistedmatrix.com/trac/http://twistedmatrix.com/trac/