SBERT: Sentence Embeddings using Siamese BERT-Networks\
Generate sentence embeddings for:
1. the literal input $L$
2. the original gold metaphoric expression $M$
3. the generated output $G$

Distance from Gold Metaphor (dis): $\cos(M, G)$\
Relational distance (rel): $\cos(L, M) - cos(L, G)$\
Percentage of times the model produced the exact gold output.

University of Michigan - Ann Arbor

Conceptual metaphor theory (CMT): uses conceptual mappings between domains (conceptual structures that group related concepts) to generate linguistic metaphors.

Framework: Given a literal input sentence --> evokes a target domain --> generates metaphoric sentences that evoke desired corresponding source domain.

Eg. Three inputs: 
1. a literal input sentence (They argued against the contract)
2. the target domain evoked by the literal input (ARGUMENT)
3. the desired source domain (WAR) for the metaphorical sentence

The output is a metaphorical sentence that evokes the desired corresponding source domain (They fought against the contract).

How? Using an intended conceptual mapping (ARGUMENT - WAR)

Introduction (Metaphor Generation with Conceptual Mappings)

Learn joint embedded representations for domains and lexical items. Then use the linear transformation between two domains as a mapping.

Frames ((Fillmore, 1982)): related systems of concepts, which is exchangeable with the term “domain” used in conceptual metaphor theory

FrameNet (Baker et al., 1998): semantic frames along with the set of lexical units that evoke them

Thus, we consider the transformation from one frame to another as a proxy for a conceptual metaphoric mapping.

CM-Lex (Metaphor Generation with Conceptual Mappings)

Creating Parallel Data: 
1. Identify and mask metaphoric verbs(BERT-based metaphor classification model), (i.e “died” in The house where love had died) and replace them with infilling from a language model(pre-trained BERT).
2. Make sure at least 4 of 5 symbolic beams returned by COMET(Bosselut et al., 2019) are the same.
3. Additionally, tag each sentence with FrameNet frames.(Assume that the relation between the frames for the source and target domains reflects a metaphoric mapping.)

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