COWS

CEDA OGC Web Services Framework

Stephen Pascoe

COWS Motivation

Develop lightweight OGC services Don't attempt to implement the specifications in full

Enable integration with custom web applications

Build upon a fully-featured web framework Layered design

Support multiple OGC services in one stack

COWS Architecture

Built on Pylons web-appliction framework

Python Eggs – Automatic download/install of components

WSGI – A protocol for deploying Python web-apps to production HTTP servers

HTTP Server

Pas

te

Pylons

Middleware

WebApplication

COWS

WMS WCS W*S

Data Model

WSGI

WSGI

Apache + mod_wsgi,FastCGI,Python HTTPD

E.g. Authentication

LibraryStandard InterfaceApplication-specific Code

COWS Package Structure

cows: top level package cows.model

Implements toe OWS-common data model cows.service

Provides service interfaces and implementations cows.pylons

OGC service controllers and XML templates OGC parameter and exception handling

due for reorganisation cows.pylons.project_templates

pre-canned application template(s)

WSGI Middleware

Add security to a COWS Application by adding security middleware

Python Paste package enables inclusion of middleware via a config file – no change to COWS code required:

CowsApplication

AnotherFilter

AuthenticationFilter

[pipeline:CowsApplication]pipeline = AuthenticationFilter AnotherFilter CowsApplication

Example middleware chain:

HTTP Request

HTTP Response

Development workflow

Install COWS Create web-application from template Customise Test Package Deploy

Example Applications

IPCC Data Distribution Centre

NDG Discovery Portal

http://www.ipcc-data.org/maps

NERC Portals Project

2 Different Station datasets

Integrate with CSML

Pylons Application plots CSML Features

2 visualisation interfaces

KML references plot service

COWS WMS provides in-browser support.

DEFRA UKCP Portal

Highly Dimensional Dataset

Time Period

Emission Scenario

Percentile (CDF)

Meaning Period

UKMO UM Rotated Grid but we need to plot it on GoogleMaps (Transverse Mercator)

Custom WMS operation to serve Grid-box values as JSON

COWS Future

Clean-up and publicised release for NDG3 cows-0.3 on the way

WFS being developed as part of the C-SEKT project

WPS developed for UKCP portal. Will be included in COWS in the future (post v0.3)