private boolean isOverlayIfOtherSpace() {
		if (startAddr.getAddressSpace().equals(AddressSpace.OTHER_SPACE)) {
			if (!isOverlay) {
				message = "Blocks defined in the " + AddressSpace.OTHER_SPACE.getName() +
					" space must be overlay blocks";
				return false;
			}
		}
		return true;
	}
Model to manage adding a memory block.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/memory/AddBlockModel.java