Simply, the specification for custom data attributes states that any attribute that starts with "data-" will be treated as a storage area for private data (private in the sense that the end user can't see it - it doesn't affect layout or presentation).
This allows you to write valid HTML markup (passing an HTML 5 validator) while, simultaneously, embedding data within your page
Machines, with their rigid information processing capabilities, need everything spelled out for them. To be able to do something useful with this title and byline, a machine would need to be able to parse it correctly. It would need to know that the numbe