www.entitylogic.org - entity modelling introduced from first principles
When the parts of a whole have a particular order amongst them then an 'S' shaped symbol (S for sequence) maybe added to the relationship. In this way we can represent a sentence as a sequence of words: (a) and a word as a sequence of letters: (b)
Famously, we can represent a DNA molecule (a chromosome) as a sequence of nucleotides.