Eurogamer is reporting that Half-Life 2: Episode 1, the upcoming first single player expansion pack for Valve's best selling first person shooter sequel, will in fact be a stand alone product and will not require the purchase of Half-Life 2 itself. According to Valve's marketing director Doug Lombardi, "Episode 1's complexion and density is markedly richer than Half-Life 2."
http://www.eurogamer.net/article.php?article_id=63038
http://www.eurogamer.net/article.php?article_id=63038