I am looking for documentation for Google content API. First of all how to create feed and submit it into Google Merchant center? I found many pages. I think follow page is better:
http://code.google.com/intl/en/apis/shopping/content/getting-started/requirements-products.html

LitePublisher can generate valid xml documents. I have plan to create shop plugin. Plugin must have specail feeed to submit products to Google.