Older editions of music (early 1800s, for instance) frequently have one phrase slurred together by connecting two (or more) shorter slurs. So one note can have a slur coming into it, and another one going out of it again. In the case of a wind player, this note won't be tongued, since it is a continuation of the first slur. In the case of a string player it won't have a change of bow direction or separation of any kind (unless the person doing the bowings decides the phrase is too long for one bow, or alter the direction so some later note comes out in a desired up or down direction, but then this is done even with modern notation, so it doesn't really apply). In other words, in the old system, one phrase could have more than one slur.
This can get visually confusing, so modern notation fixes this by generally requiring one slur to indicate what is in one breath or one bow. Therefore, the phrase has one slur only, and it will go over any ties that are within the phrase; the slur will only end when the breath or bow ends.
So far, so good, and all very visually clear.
The one thing that is generally very inconsistently dealt with, and not even the Read book (bible) on notation covers it adequately, is how grace notes that fall within such a phrase, or (more frequently) start such a phrase are dealt with. Sometimes, the grace note is slurred to the main note and then the main slur starts from the main note, but then we are back at having a note with slurs coming in and out of it, and the note isn't separately articulated. Other times, the main slur starts from the grace note, but there is a second slur, connecting the grace note(s) to the main note, much like a tie under a slur. But since this isn't really a tie, it still amounts to 2 slurs.
If the idea is to get one slur starting at the first note to be tongued, then nothing else (except ties underneath the slur) should be added. So theoretically, the main slur should start at the first grace note and carry over until the last note in that phrase. Similarly, if the grace note(s) are within a slurred phrase, there should be no additional slur added.
I've tried this, and I have to admit it looks odd to me. I don't know if it's because I'm so used to seeing the other systems. I also can't find scores that do it this way, despite the guidelines set down in modern notation for the main slurs. (Admittedly, it's holiday now, and I don't have a full library to go trawl through.)
So the question is: do you have an opinion as to what you would like to see in modern typesets, and should we try to include grace notes in the "only one slur for one phrase" philosophy?
If you don't think we should include them, then choose one of the other 2 options:
a) slur grace note(s) to main note, then start main slur from there, or
b) start the main slur from first note to be tongued, but if that's a grace note, add a second slur just for the grace notes into the main note. In this option, grace notes within a phrase would have a slur to their main notes, and this slur would be additional to the main slur.