～ている has a few different meanings.
1) The most basic is "currently doing." 本を読んでいます。I am reading a book.
The second use has to do with a state of being and the results of actions which are tied to the present
2) In the case of being alive or dead:
Bob is alive (current state). ボブは生きています。
Bob was hit by a car (an unfortunate turn of events). 車に轢かれていました。
Bob is dying (he will die). 死にます。(the change of state has not come yet, but WILL)
Bob is dead (his state changed and will be in affect for sometime). 死んでいます。
3) For those representing travel:
日本に行きます。He will go to Japan (which includes the entire trip up until he touches Japanese soil)
日本に行っています。He is in/has gone to Japan (he has traveled to Japan and remains there)
日本から帰ります。He will return from Japan (everything up until he returns home)
日本から帰っています。He is back/has returned from Japan (he has returned home and remains here)
And as a bonus: habitual actions continued through a stretch of time
二年間ぐらい日本語を勉強しています。I've been studying Japanese for about 2 years. (regular activity with perhaps with the suggestion of a schedule)
毎日新聞を読んでいます。I read the newspaper everyday. (personal custom)
金沢に住んでいます。I live in Kanazawa. (continuous action)
池田さんはアメリカの会社に勤めています。Ikeda works for/is employed at an American company. (continuous action with perhaps the suggestion of a schedule)
