I just created an XML file of my site for google sitemap but I have some question about it. This is the type that I saw in the example provided in Google sitemap's guidelines
I'm wondering that if I submit first time to google and it shows the Last modify date (as in example above). When google come to download the file next time and the date hasn't been changed, Will Google still index the information in that page?
Or if Google see it's the same date as they came last time, and they will ignore and not index the page?
And what about if I don't put the <lastmod> attribute, just the url only, for example...
Would this be okay?
Please help this out because I'm not quite fully understand on what exactly Google want.
Thank you in advance