This is not a real answer but it is way to long for a comment. I translated to the best I can, the part I suggested in my comment to the original question. Since I think that the whole part about 「Ｖ－ている」 could be useful to a great deal of people I post this answer as a community wiki, if somebody wants to help me provide a full translation of the part concerning 「Ｖ－ている」.
I have read it twice but there might still be some mistakes. Part enclosed in // are where I was not really sure so take them with care.
24.3.6 Another classification: Verbs which express changes
Well, through the classifications of action verbs with respect to their relation with time we've seen the rules of application of 「Ｖ－ている」 and its relation with time. Nevertheless, the concept of "instant verbs" is almost not used anymore.
The reason is that verbs that does not fit the definition of "instantaneous" can express the state of a result (of an action). The word that fit best to express the common points of those verbs would be "change".
For example, the previously given examples of 「ふとる・やせる」gives two verbs that do not describe something instantaneous; nevertheless, it does not mean either that 「太{ふと}っている」express something ongoing, it does show the result (... has grow fat). Let's see,
この湖の水には大量の塩が溶けている。
In this lake, a great bunch of salt is dissolved.
台風の影響で潮位が高まっている。
The typhoon caused the tide level to rise.
Again, it needed quite a bunch of time to reach this state; however, those sentences express the result not the process.
The 「行く」 enclosed in 「デパートへ買物に行く」can show the action of going from home to the department store, the action of going out from home or the action of reaching the store. It is all a matter of context to tell the right interpretation.
８時にデパートへ買い物に行った。
I went to the store for shopping purpose at 8.
９時にデパートに行き、１０時に映画館に行った。
At 9 I went to the store, and at 10 I went to the movie theater.
デパートに行くのに１時間かかる。
To reach the store it takes one hour.
However, 「行っている」 would not express anything but the result of the situation (~ is gone). Here again, it is not possible to tell whether or not the action is instantaneous.
Thus, if we were to think again about the shared features of verbs like 「太る・高まる・行く」we would see that a change either in shape or in location can be observed; we can, thus, say that a change occurred on the subject through the action of the verb.
Even verbs that we previously considered as examples of "instant verbs", all express a meaning of change.
始まる・変わる・死ぬ・出発する・帰る・着く・割れる
From now on, let's rename, "instant verbs" to "change verbs".
/Even "duration verbs", without expressing something that lasts in time contrast with the concept of "change". Let's call those verbs "action verbs" (action can be one of a human being as well as something due to a natural phenomenon)./
However, even from this stand point, some exceptions are still hanging around. This is because, some verbs that express an instantaneous action can express the final state of the action while used in the pattern 「Ｖ－ている」.
彼女はその瞬間を目撃している。
She saw this instant. (She witnessed the scene.)
「目撃する」cannot be seen as a verb which shows something in progress (as it is impossible to witness a scene forever), here 「目撃している」does not express an ongoing action but the state of the situation.
If we were to look at a transitive-intransitive pair of verbs:
紙を燃やしている（燃やす）：紙が燃えている（燃える）
Setting fire to a paper. （燃やす）
Burning paper. （燃える）
In both cases, the action can be said to be in progress but while 「燃やしている」 expresses an action, 「燃えている」 expresses that a change is ongoing. It is not the situation of the result of the change. (In the case 「火が燃える」 we could consider it to be an "action" but no matter how you think of it 「紙が燃える」(the paper is burning) shows a change).
Both methods of classification are not free from exceptions, therefore, it cannot be considered as a definitive explanation. It might be a bit of trouble but remembering both classifications (duration verbs/instant verbs and change verbs/action verbs) could be rewarding. Nevertheless, since the changes between the two versions is subtle, it may be not very important to bother too much.
[The object of "change verbs"]
The verbs 「行く」and 「太る」may show that a change happens to the subject. Let's think again about this kind of verbs which cause changes to the object. For example in the sentence,
彼は部屋の壁に自分の絵を掛けている。
In his room, a picture of him hangs on the wall.
In this sentence, the verb 「かける」 can be interpreted as an action (maintain the picture always in that state). In other words, it could be said that it expresses the state of (the result) "being hung". It would therefore express the change and how the object (the picture here) behaves due to the change.
/Other verbs expressing "changes in the object" can be easily seen as "the situation ensuing from a result"./
学生たちはみな教科書の８ページを開いている。
Students opened theirs books at page 8.
「８ページを開く」is not really an instantaneous action (you've to flip the pages through the right one), it does not carry the meaning of 「いま、開きつつある」( ~ being opening it) either. What it shows is the fact that the book has been opened at the page 8 (the result of the action). There is no other explanation that the verb here focus on expressing the state of the situation of "opening a book" (「本を開く」)
彼はいつも研究室のドアを少し開けている。
He always leaves the door of the lab slightly opened.
This example illustrates the same as above. Indeed, one could have also used 「開けてある」which will be discussed later on.
あの喫茶店はテーブルをいくつか前の歩道に出している。
This coffee shop set some tables on the pedestrian way.
この会社は省エネのため、廊下の電気を半分消している。
For energy savings purposes, this company light the corridor with only a half of the nominal power.
妻は、買い物に出るとき、空き巣よけにテレビをつけている。
When the wife goes to shopping, she let the TV on to drive the thieves away.
