Markdown frontmatter for pub imports?

Many Markdown processing systems allow “frontmatter”, some kind of structured data at the beginning of the document. Often it is YAML delimited with ---, like so:

title: My Wonderful Document
author: Peter Williams

# Introduction

Ever since the dawn of time, mankind has yearned to destroy the Sun.

I heard from @gabestein that in PubPub, if you import a Markdown document with the right frontmatter, the metadata will make their way into the PubPub system. Does anyone know the right field names, formatting, etc, that accomplish this? Some subset of the Pandoc YAML metadata fields?