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Decorated Stem is terminated by zero, one or many Symbol

Symbol terminates zero, one or many Decorated Stem

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Each end of a Decorated Stem may or may not be adorned by a single Symbol. Keep in mind that a Symbol can be compound and built up from many graphical elements. So each terminal can be as ornate as necessary. This effectively means that at most two Symbols can be associated with a given Decorated Stem. See note in formalization section below to see how the two-ness constraint is addressed.

It is also possible for the same Symbol to be used at both ends of a Decorated Stem. Consequently this relationship is many-associative. (A given pairing of Decorated Stem and Symbol can result in two association class instances, differentiated by the End component of the class identifier).

If neither end of a Decorated Stem features a Symbol, there may be a Label associated with the Stem. If there is no Label either, perhaps the Stem is notated by changing its line stroke pattern. For example, in xUML an associative 1 multiplicity on a class diagram is shown by drawing the stem as a dashed pattern with no other label or symbol.

A Decorated Stem that does not have a special line pattern, Symbol or Label is not decorated and should not be declared as such. No harm can come from falsely declaring a Decorated Stem with no Decoration, it will just be rendered as a linear Stem, but it is bad practice.

A given Symbol can be used in as many Decorated Stems as you like. A solid arrow for example might be used both in a state transition and in a domain diagram dependency. If a Symbol is not used at all, there is no harm as it may become useful in a Diagram Notation defined later.