data islands are defunct technique for adding DRY-violating invisible data (an antipattern) to HTML pages (AKA sidecar metadata), first introduced then abandoned by Microsoft as XML Data Islands, and more recently, by Facebook and Google as (different) JSON(LD) embedded in HTML.
- 199x Microsoft introduces XML Data Islands
- 2011-07-06 Microsoft drops support for XML Data Islands (e.g. in IE)
- 2015-01 Google adds support for "embedding" JSON(LD) Data Islands, likely unaware of the history.
- 2015-05-12 Facebook launches Instant Articles, which use a JSON Data Island specifically for embedding GeoJSON data.