This module contains the sequence datastructure of the
TCS Alignment Toolbox. It defines the possible value sets in the
ValueType enum as well as the different KeywordSpecification classes, namely:
1.) StringKeywordSpecification for string type values.
2.) SymbolicKeywordSpecification for values from a discrete alphabet (also refer to the Alphabet class)
3.) VectorialKeywordSpecification for vectors of some length (or for scalars)
A NodeSpecification is a vector of such KeywordSpecifications and defines
the order of value sets. A node, then, is defined as a vector of values
from these value sets (also refer to the Value interface as well as the
StringValue, SymbolicValue and VectorialValue classes). Finally a
sequence is defined as a list of such nodes.