I have been told by one of my clients that Google must be notified if you intend to remove pages (e.g. discontinued product pages) from a site, because Google will penalize your search results if you remove those pages without notifying them. Is that true? I thought that Google would simply update its search results on the next crawl.
He also says that there is a way to create a diff of the old sitemap file and the new sitemap file, and submit that to Google as the notification of deleted pages. Is any (or all) of this really necessary, and will it affect his SEO either way?
I have control over the website programming (it is an ASP.NET MVC 1.0 site). Should I just mark deleted pages in the database, and make them respond with
410 gone, as described here?