A frequently asked question about s is how do they compare to s. Aren't they the same thing? Yes, in some content systems, and no in others. In some systems, is a permalink to a weblog item. However, in other systems, each is a synopsis of a longer article, points to the article, and is the permalink to the weblog entry. In all cases, it's recommended that you provide the guid, and if possible make it a permalink. This enables aggregators to not repeat items, even if there have been editing changes.