Q:

What are "data-require" "data-semver" in HTML files?

I have seen tags like this in HTML. What are these attributes?
This is NOT a duplicate of the data-* question.
Edit:
I am looking for these two specific attributes, not data-* in general, nor data-required, as Google suggests. If you search the web, you can find these attributes are used in many places. I guess this is some like of dependency management software? 
<link data-require="bootstrap-css@*" data-semver="3.0.0" rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css" />

<script data-require="angular.js@1.1.x" src="https://ajax.googleapis.com/ajax/libs/angularjs/1.1.5/angular.js" data-semver="1.1.5"></script>
<script data-require="ui-bootstrap@0.5.0" data-semver="0.5.0" src="http://angular-ui.github.io/bootstrap/ui-bootstrap-tpls-0.6.0.js"></script>

A:

I was curious about this as well.  These appear to be data- attributes that are created by plunker when including external libraries in its editor. Since plunker is used heavily throughout the development community that is probably why you see it appearing a lot.
By themselves they don't do anything special, unless a library or service decides to use them.  
The 'data-semver' attribute appears to be an implementation of Semantic Versioning 
To the best of my knowledge no libraries actually use them for any sort of dependency checking/loading.

