Japanese: discussions regarding indexing of specific expressions

In discussions with Dr. Torikai & Dr. Noguchi (@Rei_hub), we've considered a few expressions whose indexing results can be improved. In some of the topics below, we have not reached a conclusion on "what should be the correct implementation to achieve desired outcome". I will update this issue as 1) new observations are made upon experiments; and 2) agreed approach is implemented, on each topic.

# a. とか vs. など in Negation expressions
- とか is a verbal expression but often included in informal text such as doctor's progress notes (as opposed to written expression など, which is more formal)
- it would be preferable if they get indexed the same way, especially in expressions such as 胸痛とかはない. In this example, とか would be NonRelevant and は would be PathRelevant.
- after some investigations, it has been determined that this can be achieved for instances that include とかは and とかが
- we need to extend the Negation span to the Concept before とか in both cases

# b. などの and 等の
- in expressions such as 胸痛などの症状 and 胸痛などの重要所見, it would be preferable to have the entire expression as a long Concept
- this is doable but not appropriate if particle や precedes the Concept before などの - in such cases, などの should still be a Relation
- same implementation should be exercised for 等の
- implementation of this would likely be a relatively large effort.

# c. Sahen+SuruVerb+ことはない vs. Sahen+SuruVerb+ことは無い
- currently, 失神したことはない and 失神したことは無い are indexed differently. they should be identical. Current indexing results for the phrase 失神したことはない is considered correct = Relation+Negation+Sahen
- we've also discussed making 失神したこと as a Concept, but when there's an object for the Sahen verb, it looks better as a Relation. Example: 企業と個人の取引に適用したことはない。これまで天皇の即位前に新元号を公表したことはない。
- one approach maybe to make Sahen+SuruVerb+こと a Concept if Sahen is not preceded by object-indicating particles such as を or に. This approach needs further experimentation.

# d. Concept1+や+Concept2+の+Concept3
(new on October 5, 2021)
- currently, 息切れや胸痛の症状 gets indexed as 3 separate Concepts, with や being PathRelevant and の being a Relation, whereas 胸痛の症状 is a single Concept. This is specifically done because 息切れ is being used parallelly to 胸痛. @Rei-hub and I discussed exploring the possibility of making both や and の as PathRelevant in such case to allow identification of such parallelism. Thorough experiment is required, but it may be a possibility to keep track of a group of entities within a sentence.