Partial word

A partial word is a string that may contain a number of "do not know" or "do not care" symbols i.e. placeholders in the string where the symbol value is not known or not specified. More formally, a partial word is a partial function $u: \{ 0, \ldots, n-1 \} \rightarrow A$ where $A$ is some finite alphabet. If u(k) is not defined for some $k \in \{ 0, \ldots, n-1 \}$ then the unknown element at place k in the string is called a "hole". In regular expressions (following the POSIX standard) a hole is represented by the metacharacter ".". For example, aab.ab.b is a partial word of length 8 over the alphabet A ={a,b} in which the fourth and seventh characters are holes.^[1]

See also

• String

References

1. ↑ Algorithmic Combinatorics on Words REU