These are a set of steps to produce a relevant result, whether in data processing, analysis, visualization or application of these to policies and programs.
This is a very interesting post that also gets to issues about how we understand the data we collect.
UNFPA and the International Institute for Environment and Development (IIED) have worked together on case studies on urbanization in the BRICS countries, and each looks into how "urban" is defined within the country. Check them out here:
South Africa, for instance, went through a post-apartheid "unicity" process that merged different municipalities together with rural communities into single local governments for the purpose of applying the tax base of core areas of the cities to impoverished and excluded areas, including townships, informal settlements and large rural expanses.
Also, it's worth reiterating that the UN Population Division does not seek a common urban definition in the World Urbanization Prospects, but instead uses national definitions that vary significantly.
Maybe it could be interesting to point out case studies that differ significatively in the atributes analyzed , other than population and funtionality. That is to say countries that have really different classifications for these areas.
Eventhough, I think it is correct that these definitions are not standardized because rural and urban definition is based in social, political and cultural perceptions, a unique cosmovision about our own land and people. Of course it could help to have common urban definitions for comparative purposes but the problem of categorizing areas is really complex. I would find it more useful to look for " in between " or special categories of socio political areas to identify phenomena and development stages. Also for risky rural-urban areas under the influx of climate change, e.g. landslide prone areas, as we have here in Colombia.
An interesting case is the one of polders in the Netherlands, but I´m afraid they are are quite unique and may not offer other countries much lessons... I don´t know. Maybe I should think about new contents of not-rural-neither-urban areas for geographic analysis purposes..