In that post I described how UK Parish data underpinning my geo-history project came from publicly released Ordnance Survey Boundary Line data. I attributed the data in both figures of that post. And giscloud.com also adds a data source to each webmap, as in the middle map here. Now Mapcentia, whose service is used to post that project, also added a metadata button next to each Table of Contents item, as entered in GeoCloud2 database - and to repeat them, see how it works on my map (thanks for the referral).
So to recap, in increasing levels of complexity and power, metadata are:
- attribution (required by most public sources)
- actual source of the data (web link, author, date)
- description of the data (as it pertains to the topic)
- full metadata servers (as for ex. gptogc.esri.com)