This is silly and makes things way more complicated than they need to be.

We have HTML tags, to which we can apply attributes directly via blah=blah syntax

Or we can add attributes by making a style attribute, and using css syntax inside of it.

Or we can have a space separated list of class names, and have attributes applied to an element externally by a CSS stylesheet.

Or we can have an ID, and apply attributes using javascript.

We can apply attributes with http headers, and the browser can negotiate the resource with http accepts and quality parameters.

We have video, audio, and object tags that can all have child elements.

We have query parameters and fragment selectors, and path parameters, and post parameters and accept parameters for negotiating and selecting content from a server. (Designed to include ampersands which have to be entity encoded when used in HTML!)

We have all these sophisticated overlapping complicated mechanisms for attaching attributes to elements in a webpage. We have huge pieces of software for parsing through this poorly thought through mess.

But no, not a single one of these is good enough for this problem. LET'S INVENT A NEW SYNTAX AND ADD TO THE HEAP OF IDIOCY.