Marfeel uses Boilerpipe to detect and extract a publisher's metadata in the article details. Essentially, a customer's page is scraped tag by tag to identify, extract, and store the metadata in the article details.
In Boilerpipe, metadata is a detector. Every time there's a script, Marfeel scans the script to identify and parse relevant elements according to the heuristics in place.
When a metadataProvider is detected, Marfeel extracts the information and stores it at the beginning of an article.
The following is an example of extracting custom dimensions for Google Analytics: