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

Proxy
indirect uses
Dependency
antipatterns in use
Complexity
metric-based smells

TooWide
the width (right hand side length) is too big
TooRamose
too much branching
TooRecursive
too much recursion
TooNested
groups are too deeply nested
TooTall
the height (distance from the root) is too big
Lonely
large non-modular grammar
TooModular
too many modules
Greedy
one module that does too much
Lazy
one module that does not do much
TooCoupled
low cohesion and/or high coupling

Greedy Edit!

Related smells: Insufficient Modularization, Too Large Packages/Subsystems, Large Class, The Blob

Similarly to TooLonely but not quite identical to it, there is a scenario when a grammar is modularised, but still insufficiently: in particular, if there is one module that is much greedier than the rest and does too much compared to any other module. In realistic grammars this smell is quite common, and the culture of proper modularisation with close to uniform distribution of responsibilities among modules, has not yet developed. The harmfulness of this smell has also never been shown, and also not been investigated properly (to the best of our knowledge).


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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