There is a lot of info out there about sitemaps, but I haven't found exactly what I am looking for.
I am building a site which has separate mobile/desktop pages and also english and polish. In other words, every page in the site has four copies:
Example the index.html has m/index.html pl/index.html & m/pl/index.html
I have found that you can make a sitemap for mobile sites, according to google info but the sitemap must only hold urls of the mobile pages.
Then, google developers info says that you place the mobile urls in the same sitemap as the rest.
My question is, which is correct? Or have I missed the point completely.
Tim
that is a great question! The short answer is that in order to maintain control and be better organised, you're best off having 4 separate sitemaps - for English, Polish, English mobile & Polish mobile.
Let me explain this: When you have multiple sub-sites, using 4 different sitemaps allows you to easily organise the URLs for each section together. It also clearly indicates to Google the site organisation, and allows you to uniformly indicate the equivalent alternate versions for the pages.
You should note that the Google Webmaster help doc does not tell you to combine mobile and desktop sitemaps. What they're saying is that you should reference the two versions to each other. So, in the desktop sitemap, you could point out the mobile equivalent pages using a rel="alternate" annotation. If you read the documentation closely, you'll see they call it a "two-way ('bidirectional') annotation"
The same principle applies in the multlingual scenario. You should use hreflang annotations to point out the equivalent English & Polish pages on each of the versions.
If you follow the hreflang and rel="alternate" annotations properly, you're allowing Google to easily determine which version (desktop v mobile and English v Polish) is most suitable for your users.