What defines a heading definition

[marcoscaceres]

According to BS, headings (h1-h6) are definitions, but that seems untrue.

For example, <h2>Abstract</h2> and is not a definition?

Is a heading-based definition maybe something that has an explicit data-export?

@dontcallmedom @tidoust, how does Reffy classify them?

[dontcallmedom]

My reading of https://tabatkins.github.io/bikeshed/#dfn-contract is that headings are only considered if they have data-dfn-type set, per:

data-dfn-type MUST be provided, and set one of the accepted values.
(In an actual Bikeshed document, this can be omitted from dfn elements and it will be inferred from context, usually defaulting to "dfn" type. But non-Bikeshed documents must specify this, or else they’ll get their dfn type inferred heuristically, which may or may not be correct.)