The document discusses creating open data using open source tools. It provides an overview of open data and Tim Berners-Lee's 5 star deployment scheme for open data. The author then describes using Python and the Scrapy framework to crawl websites and extract structured data to create open datasets. Specific examples discussed are the WeatherHK and TCTrack projects, which extract weather data from government websites. The author also proposes the hk0weather open source project to convert Hong Kong weather data into JSON format. The goal is to make more government data openly available in reusable, machine-readable formats.