When the Open Learning Initiative moved to Stanford University, they wanted to integrate with Open edX. I worked with Ross Strader (now at Lumen Learning) to prototype what content tagging might look like if it were embedded into Studio, the Open edX course authoring tool. We spoke about this at the Open edX Conference in 2015.
Eventually, this concept was made production-ready by Credo Education and merged into the master Open edX platform — a big shout-out to them!