Unlike argument optionality, frame alternations always require the independent description of more than one frame to be related at the frame_list level. Let us consider first the case of the causative-inchoative alternation exemplified in (138) and (139). Below, frame_1 (table 4.9) and frame_2 (table 4.10) describe the constructions John broke the vase and the vase broke respectively.
| frame_1 | ([slot_1 | ([slot_real_1(CatLabel: np, Subject: subj)]), |
| slot_2 | ([slot_real_1(CatLabel: np, Subject: comp)])]) |
| frame_2 | ([slot_1 | ([slot_real_1(CatLabel: np, Subject: subj)])]) |
In order to express the fact that, in these examples, vase is associated with two different slots in the two frames, we avail ourselves of the notation in table 4.11, specified at the frame_list level, which encodes the correspondence between slot_2 in frame_1 and slot_1 in frame_2.
| frame_list | ([related_1(FrameIndex: 1, SlotIndex: 2, | FrameIndex: 2, SlotIndex: 1)]) |
There is a number of points which are worth stressing here. This notation departs from the traditional assumption that, given two alternating frames, one is taken to be basic and the other derivative, i.e. derived from the latter by means of lexical rules. EAGLES chose to represent all possible alternating frames of the same verb on a par by explicitly listing them within the lexicon; frame alternation is stated here as a relation between slots belonging to fully specified individual frames. The EAGLES approach is not as descriptively economic as the traditional one. On the other hand, it does not force the lexicographer to decide about the direction of the derivation, i.e., ultimately, about which frame is to be encoded explicitly within the lexicon as the base. Moreover, the EAGLES approach is compatible with the different treatments of frame alternation phenomena put forward in the literature and used in practical NLP lexicons, where alternation can be expressed (Comlex) or not (Eurotra), and in which slot relatedness can be encoded in a number of different ways (e.g. by enforcing identity of syntactic function, as in Comlex, or identity of thematic role, as in Acquilex).
More complex cases of frame alternation, which involve more than one slot pair, can also be found, as shown in examples (146) and (147).
(146) | To give a letter to John |
|
(147) | To give John a letter |
whose corresponding frames are given in tables (4.12) and (4.13).
In this case, relatedness involves two different slot pairs, namely slots_2 and slots_3 in both frames, as shown in table (4.14).
| frame_list | ([related_1(FrameIndex: 1, SlotIndex: 2, | FrameIndex: 2, SlotIndex: 3), |
| related_2(FrameIndex: 1, SlotIndex: 3, | FrameIndex: 2, SlotIndex: 2)]) |
As pointed out above, argument optionality can also be treated as an instance of frame alternation: accordingly, the frames corresponding to the constructions of eat exemplified in (134) and (135) can be listed independently in the lexicon as in tables 4.15 and 4.16. Their relationship can be stated in terms of the correspondence between slots_1, i.e. the subjects, of both frames, as shown in table 4.17.
| frame_1 | ([slot_1 | ([slot_real_1(CatLabel: np, Subject: subj)]), |
| slot_2 | ([slot_real_1(CatLabel: np, Subject: comp)])]) |
| frame_2 | ([slot_1 | ([slot_real_1(CatLabel: np, Subject: subj)])]) |
| frame_list | ([related_1(FrameIndex: 1, SlotIndex: 1, | FrameIndex: 2, SlotIndex: 1)]) |