Vadim Zaytsev aka @grammarware

GraSs: A Taxonomy of Grammar Smells


Organisation
global problems
Navigation
problems with navigating through the grammar
Structure
harmful relationships among grammar components

Convention
violations of visual policies
Notation
metalanguage-related
Parsing
parsing techniques related smells
Duplication
the same fragment is repeated

Underuse
inferior substitutes are used instead of an available feature
Overspec
the same constraint specified through several means
Priorities
not present or circular
Singleton
trivial choice, sequence or conjunction
Combo
double modifier creates an ambiguity
Chant
comments cover up bad code
Deprecated
the use of a feature that is no longer welcome
Exotic
too idiosyncratic notational features decrease portability

Exotic Edit!

Related smells: Vendor Lockāˆ’In, Golden Hammer

This smell is in contradiction with Underuse, and states that using notational features that are uncommon, obscure or overly exotic, should be limited. Excessive use of features idiosyncratic for one particular notation, will result in a vendor lock-in. For example, if a notation allows context handling (pushing the grammar outside the comfort zone of CFGs), using it is only fully justified when the result is too cumbersome otherwise.


The GraSs taxonomy is a joint effort maintained by Dr. Vadim Zaytsev a.k.a. @grammarware. Page last updated in March 2021.
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