The disagreement seems to boil down to whether conceptual splitting of a generic OR type claim can result in different priorities for different parts of a generic claim. Some anonymous commenters have said that this cannot be correct, as it cannot be right to assign a priority to a part of a claim that has not been disclosed. Others, however, have said that conceptual splitting is not even needed, since the only requirement is based on what is disclosed in the priority document. My personal view is that the conceptual splitting approach makes more sense, and avoids problems with Article 4C(4) of the Paris Convention, even though it does result in assigning a priority date to a part of a generic claim that is not literally disclosed in a priority document. It is plausible that the EB could come to a different interpretation, although in my view this interpretation is already covered by the words "at least implicitly" in the order.
The issue can probably be best explained by reference to one of the examples in the FICPI memorandum which, as you will recall, was the basis for the decision on partial priorities in G 2/98 and which was totally ignored by decisions from the boards of appeal that went down on the side of literal interpretation of point 6.7 (the "limited number of clearly defined alternatives" bit). The example reads as follows:
It should be clear from this example that there is no need to have literal basis for the ranges 10-15° and 20-25° in the second priority document (let's call it P2) to allow priority for these portions to be validly claimed in the later filed European application (let's call it EP). This, to me at least, suggests that the conceptual splitting approach is correct, where priority for the narrow range of 15-20° is from the first priority document (P1) and for the other parts of the range from P2.b) Broadening of range (temperature, pressure, concentration, etc.).Let us assume that a first priority document discloses a temperature range of 15-20° and a second priority document discloses a temperature range of 10-25°.If multiple priorities for one and the same claim are allowed, it will suffice in the European patent application to draw up a claim directed to the temperature range 10-25°.If multiple priorities for one and the same claim are not allowed, the applicant will have to draw up two parallel claims, one directed to the temperature range 15-20° and enjoying the first priority, and another claim directed to the temperature ranges 10-15° or 20-25°, which claim will then enjoy the priority of the second priority document which was the first one to disclose these temperature ranges.
I would guess that the reasoning in G 1/15 will need to go over in detail each of the examples in the memorandum (which G 2/98 did not) to establish clearly what they mean by assigning partial priorities. Unless they do, the argument about whether conceptual splitting is allowed or not will continue to rumble on. My prediction, for what it is worth, is that they will go over each of the examples, and find that conceptual splitting is a necessary feature of assigning partial priorities to a generic OR type claim, particularly in cases where priority is claimed from more than one document, such as in the example above. I might, however, be wrong.