Google Stepping Up Merchant Feed Enforcement

Got some slop in your Google product feed? Now’s the time to revisit all those pesky identifiers and tidy things up. Google is upping its enforcement of product feeds in Google Merchant Center again.Google began this process last year by disapproving products without unique product identifiers such as GTIN (which also must be conform to standard specifications), MPN and brand and demoting products with incorrect usage of the identifier_exists attribute.

Source:http://searchengineland.com/google-stepping-merchant-feed-enforcement-186047