Hierarchy classification:

1. top of the aat hierarchies
2. Objects Facet
3. Components (hierarchy name)
4. components (objects parts)
5. [components by specific context]
6. architectural elements
7. [architectural elements by building type]
8. fortification elements
9. outworks

Anotations

Scope note:

Triangular outworks situated in the moats of fortifications, and that resemble bastions with a crescent-shaped gorge, constructed to protect a bastion or curtain. The term is often used interchangeably with 'ravelins'. Historically there may have been distinguishing characteristics between ravelins and demi-lunes in the Italian school of fortification design, but in the modern era these terms are most often used synonymously.