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== Parsimony ==
== Parsimony ==
In the context of variant representation, parsimony means representing a variant in as few nucleotides as possible without reducing the length of any allele to 0. It is a property describing the nature of the length of a variant's alleles and is defined as follows:
A variant is parsimonious if it is represented in as few nucleotides as possible
A variant is parsimonious if it is represented in as few nucleotides as possible
without an allele of length 0.
without an allele of length 0.
Also,
A variant has superfluous nucleotides on its left side if the leftmost nucleotide of each variant is of the same type
and the removal of the nucleotide from each allele will not result in an empty allele.
Taking the example below, the Multi Nucleotide Polymorphism (MNP) is represented superfluously for the first 3 representations and parsimoniously for the 4th representation. When a variant has superfluous nucleotides on the left side, it is defined as not being left parsimonious as there is a need to left trim. The concept is symmetric for right parsimony and trimming. Parsimony applies to Indels too which we shall demonstrate in the left alignment section.
Taking the example below, the Multi Nucleotide Polymorphism (MNP) is represented superfluously for the first 3 representations and parsimoniously for the 4th representation. When a variant has superfluous nucleotides on the left side, it is defined as not being left parsimonious as there is a need to left trim. The concept is symmetric for right parsimony and trimming. Parsimony applies to Indels too which we shall demonstrate in the left alignment section.
