-> For diagrams as code

In a UML sequence diagram, combined fragments let you show loops, branches, and other alternatives. A combined fragment consists of one or more interaction operands, and each of these encloses one or more messages, interaction uses, or combined fragments.

A sequence fragment is represented as a box called a combined fragment, which encloses a portion of the interactions within a sequence diagram. The fragment operator (in the top left corner) indicates the type of fragment. Fragment types include ref, assert, loop, break, alt, opt and neg, ref, sd.

Alt - Alternative multiple fragments: only the one whose condition is true will execute.

Opt - Optional: the fragment executes only if the supplied condition is true. Equivalent to an alt only with one trace.

Par - Parallel: each fragment is run in parallel.

Loop - Loop: the fragment may execute multiple times, and the guard indicates the basis of iteration.

Critical - Critical region: the fragment can have only one thread executing it at once.

Neg - Negative: the fragment shows an invalid interaction.

Ref - Reference: refers to an interaction defined on another diagram. The frame is drawn to cover the lifelines involved in the interaction. You can define parameters and a return value.

Sd - Sequence diagram.

In addition, it would be useful to generate lifelines with highlighted execution/activation.