It has proved quite difficult to come up with a standard set of roles, and equally difficult to produce a formal definition of roles like AGENT, THEME, or INSTRUMENT. Possible solutions are:
- Define generalized semantic roles that abstract over the specific thematic roles.
- Define semantic roles that are specific to a particular verb or a particular group of semantically related verbs or nouns.

University of Michigan - Ann Arbor

Semantic roles focus about what a word actually means and is actually doing in the semantic context they do not care about the structure of the sentence.

Semantic Roles ( Thematic Roles )

An on-going but a helpful book resource about NLP
https://web.stanford.edu/~jurafsky/slp3/

Speech and Language Processing (3rd ed. draft) 

Commonly Used Semantic Roles

Problems with Thematic Roles

- Sematic Role Labeling(SRL) is the process of finding the semantic role of each argument of each predicate in a sentence.

- Supervised machine learning approaches are used to achieve SRL systems.

- FrameNet and PropBank supplies the train and test datasets to develop SRL models.

Semantic Role Labeling

Primitive Decomposition (Componential Analysis) is the idea of decomposing meaning into sets of primitive semantics elements or features. 

For example, we could represent the meaning of "kill" as:
- KILL(x, y)
- CAUSE(x, BECOME(NOT(ALIVE(y))))

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