indexing
	description: "Base Eiffel Vision action sequence."
	status: "See notice at end of file."
	keywords: "event, action, sequence"
	date: "$Date$"
	revision: "$Revision$"

deferred class interface
	EV_ACTION_SEQUENCE [EVENT_DATA -> TUPLE create make end]

feature -- Initialization

	arrayed_list_make (n: INTEGER)
			-- Allocate list with n items.
			-- (n may be zero for empty list.)
			-- (from ARRAYED_LIST)
		require -- from ARRAYED_LIST
			valid_number_of_items: n >= 0
		ensure -- from ARRAYED_LIST
			correct_position: before

	make_filled (n: INTEGER)
			-- Allocate list with n items.
			-- (n may be zero for empty list.)
			-- This list will be full.
			-- (from ARRAYED_LIST)
		require -- from ARRAYED_LIST
			valid_number_of_items: n >= 0
		ensure -- from ARRAYED_LIST
			correct_position: before
			filled: full

	make_from_array (a: ARRAY [PROCEDURE [ANY, EVENT_DATA]])
			-- Create list from array a.
			-- (from ARRAYED_LIST)
		require -- from ARRAY
			array_exists: a /= void
	
feature -- Access

	cursor: CURSOR
			-- Current cursor position
			-- (from ARRAYED_LIST)

	dummy_event_data: EVENT_DATA
			-- Attribute of the generic type.
			-- Useful for introspection and use in like statements.
			-- (from ACTION_SEQUENCE)

	event_data_names: ARRAY [STRING]
			-- Textual description of each event datum.
			-- (from ACTION_SEQUENCE)
		ensure -- from ACTION_SEQUENCE
			equal_to_event_data_names_internal: deep_equal (Result, event_data_names_internal)

	first: PROCEDURE [ANY, EVENT_DATA]
			-- Item at first position
			-- (from ARRAYED_LIST)
		require -- from CHAIN
			not_empty: not is_empty

	has (v: PROCEDURE [ANY, EVENT_DATA]): BOOLEAN
			-- Does v appear in array?
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from ARRAY)
		ensure -- from CONTAINER
			not_found_in_empty: Result implies not is_empty

	index: INTEGER
			-- Index of item, if valid.
			-- (from ARRAYED_LIST)

	index_of (v: like item; i: INTEGER): INTEGER
			-- Index of i-th occurrence of item identical to v.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- 0 if none.
			-- (from CHAIN)
		require -- from LINEAR
			positive_occurrences: i > 0
		ensure -- from LINEAR
			non_negative_result: Result >= 0

	item: like first
			-- Current item
			-- (from ARRAYED_LIST)
		require -- from TRAVERSABLE
			not_off: not off
		require -- from ACTIVE
			readable: readable
		require else -- from ARRAYED_LIST
			index_is_valid: valid_index (index)

	i_th (i: INTEGER): PROCEDURE [ANY, EVENT_DATA]
			-- Entry at index i, if in index interval
			-- Was declared in ARRAY as synonym of @.
			-- (from ARRAY)
		require -- from TABLE
			valid_key: array_valid_index (k)

	last: like first
			-- Item at last position
			-- (from ARRAYED_LIST)
		require -- from CHAIN
			not_empty: not is_empty

	name: STRING
			-- Textual description.
			-- (from ACTION_SEQUENCE)
		ensure -- from ACTION_SEQUENCE
			equal_to_name_internal: Result.is_equal (name_internal)

	sequential_occurrences (v: PROCEDURE [ANY, EVENT_DATA]): INTEGER
			-- Number of times v appears.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from LINEAR)
		ensure -- from BAG
			non_negative_occurrences: Result >= 0

	infix "@" (i: INTEGER): PROCEDURE [ANY, EVENT_DATA]
			-- Entry at index i, if in index interval
			-- Was declared in ARRAY as synonym of item.
			-- (from ARRAY)
		require -- from TABLE
			valid_key: array_valid_index (k)
	
feature -- Measurement

	count: INTEGER
			-- Number of items.
			-- (from ARRAYED_LIST)

	index_set: INTEGER_INTERVAL
			-- Range of acceptable indexes
			-- (from CHAIN)
		ensure -- from INDEXABLE
			not_void: Result /= void
		ensure then -- from CHAIN
			count_definition: Result.count = count

	occurrences (v: like item): INTEGER
			-- Number of times v appears.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from CHAIN)
		ensure -- from BAG
			non_negative_occurrences: Result >= 0

	occurrences (v: like item): INTEGER
			-- Number of times v appears.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from CHAIN)
		ensure -- from BAG
			non_negative_occurrences: Result >= 0
	
feature  -- Measurement

	capacity: INTEGER
			-- Number of available indices
			-- Was declared in ARRAY as synonym of count.
			-- (from ARRAY)
		ensure then -- from ARRAY
			consistent_with_bounds: Result = upper - lower + 1
	
feature -- Comparison

	is_equal (other: like Current): BOOLEAN
			-- Does other contain the same elements?
			-- (from LIST)
		require -- from ANY
			other_not_void: other /= void
		ensure -- from ANY
			symmetric: Result implies other.is_equal (Current)
			consistent: standard_is_equal (other) implies Result
		ensure then -- from LIST
			indices_unchanged: index = old index and other.index = old other.index
			true_implies_same_size: Result implies count = other.count
	
feature -- Status report

	after: BOOLEAN
			-- Is there no valid cursor position to the right of cursor?
			-- (from LIST)

	before: BOOLEAN
			-- Is there no valid cursor position to the left of cursor?
			-- (from LIST)

	Blocked_state: INTEGER is 3
			-- (from ACTION_SEQUENCE)

	call_is_underway: BOOLEAN
			-- Is call currently being executed?
			-- (from ACTION_SEQUENCE)
		ensure -- from ACTION_SEQUENCE
			Result = not is_aborted_stack.is_empty

	changeable_comparison_criterion: BOOLEAN
			-- May object_comparison be changed?
			-- (Answer: yes by default.)
			-- (from CONTAINER)

	exhausted: BOOLEAN
			-- Has structure been completely explored?
			-- (from LINEAR)
		ensure -- from LINEAR
			exhausted_when_off: off implies Result

	Extendible: BOOLEAN is True
			-- May new items be added? (Answer: yes.)
			-- (from DYNAMIC_CHAIN)

	full: BOOLEAN
			-- Is structure filled to capacity?
			-- (from ARRAYED_LIST)

	is_empty: BOOLEAN
			-- Is structure empty?
			-- (from FINITE)

	is_inserted (v: PROCEDURE [ANY, EVENT_DATA]): BOOLEAN
			-- Has v been inserted at the end by the most recent put or
			-- extend?
			-- (from ARRAYED_LIST)

	isfirst: BOOLEAN
			-- Is cursor at first position?
			-- (from CHAIN)
		ensure -- from CHAIN
			valid_position: Result implies not is_empty

	islast: BOOLEAN
			-- Is cursor at last position?
			-- (from CHAIN)
		ensure -- from CHAIN
			valid_position: Result implies not is_empty

	Normal_state: INTEGER is 1
			-- (from ACTION_SEQUENCE)

	object_comparison: BOOLEAN
			-- Must search operations use equal rather than =
			-- for comparing references? (Default: no, use =.)
			-- (from CONTAINER)

	off: BOOLEAN
			-- Is there no current item?
			-- (from CHAIN)

	Paused_state: INTEGER is 2
			-- (from ACTION_SEQUENCE)

	prunable: BOOLEAN
			-- May items be removed? (Answer: yes.)
			-- (from ARRAYED_LIST)

	readable: BOOLEAN
			-- Is there a current item that may be read?
			-- (from SEQUENCE)

	state: INTEGER
			-- One of Normal_state Paused_state or Blocked_state
			-- (from ACTION_SEQUENCE)

	valid_cursor (p: CURSOR): BOOLEAN
			-- Can the cursor be moved to position p?
			-- (from ARRAYED_LIST)

	valid_cursor_index (i: INTEGER): BOOLEAN
			-- Is i correctly bounded for cursor movement?
			-- (from CHAIN)
		ensure -- from CHAIN
			valid_cursor_index_definition: Result = ((i >= 0) and (i <= count + 1))

	valid_index (i: INTEGER): BOOLEAN
			-- Is i a valid index?
			-- (from ARRAYED_LIST)
		ensure then -- from INDEXABLE
			only_if_in_index_set: Result implies ((i >= index_set.lower) and (i <= index_set.upper))
		ensure then -- from CHAIN
			valid_index_definition: Result = ((i >= 1) and (i <= count))

	valid_index (i: INTEGER): BOOLEAN
			-- Is i a valid index?
			-- (from ARRAYED_LIST)
		ensure then -- from INDEXABLE
			only_if_in_index_set: Result implies ((i >= index_set.lower) and (i <= index_set.upper))
		ensure then -- from CHAIN
			valid_index_definition: Result = ((i >= 1) and (i <= count))

	writable: BOOLEAN
			-- Is there a current item that may be modified?
			-- (from SEQUENCE)
	
feature -- Status setting

	abort
			-- Abort the current call.
			-- (The current item.call will be completed.)
			-- (from ACTION_SEQUENCE)
		require -- from ACTION_SEQUENCE
			call_is_underway: call_is_underway
		ensure -- from ACTION_SEQUENCE
			is_aborted_set: is_aborted_stack.item

	block
			-- Ignore subsequent calls.
			-- (from ACTION_SEQUENCE)
		ensure -- from ACTION_SEQUENCE
			blocked_state: state = blocked_state

	compare_objects
			-- Ensure that future search operations will use equal
			-- rather than = for comparing references.
			-- (from CONTAINER)
		require -- from CONTAINER
			changeable_comparison_criterion
		ensure -- from CONTAINER
			object_comparison

	compare_references
			-- Ensure that future search operations will use =
			-- rather than equal for comparing references.
			-- (from CONTAINER)
		require -- from CONTAINER
			changeable_comparison_criterion
		ensure -- from CONTAINER
			reference_comparison: not object_comparison

	flush
			-- Discard any buffered calls.
			-- (from ACTION_SEQUENCE)
		ensure -- from ACTION_SEQUENCE
			call_buffer_empty: call_buffer.is_empty

	pause
			-- Buffer subsequent calls for later execution.
			-- If is_blocked calls will simply be ignored.
			-- (from ACTION_SEQUENCE)
		ensure -- from ACTION_SEQUENCE
			paused_state: state = paused_state

	resume
			-- Used after block or pause to resume normal call
			-- execution.  Executes any buffered calls.
			-- (from ACTION_SEQUENCE)
		ensure -- from ACTION_SEQUENCE
			normal_state: state = normal_state
	
feature -- Cursor movement

	back
			-- Move cursor one position backward.
			-- (from ARRAYED_LIST)
		require -- from BILINEAR
			not_before: not before

	finish
			-- Move cursor to last position if any.
			-- (from ARRAYED_LIST)
		ensure then -- from CHAIN
			at_last: not is_empty implies islast
		ensure then -- from ARRAYED_LIST
			before_when_empty: is_empty implies before

	forth
			-- Move cursor one position forward.
			-- (from ARRAYED_LIST)
		require -- from LINEAR
			not_after: not after
		ensure then -- from LIST
			moved_forth: index = old index + 1

	go_i_th (i: INTEGER)
			-- Move cursor to i-th position.
			-- (from ARRAYED_LIST)
		require -- from CHAIN
			valid_cursor_index: valid_cursor_index (i)
		ensure -- from CHAIN
			position_expected: index = i

	go_to (p: CURSOR)
			-- Move cursor to position p.
			-- (from ARRAYED_LIST)
		require -- from CURSOR_STRUCTURE
			cursor_position_valid: valid_cursor (p)

	move (i: INTEGER)
			-- Move cursor i positions.
			-- (from ARRAYED_LIST)
		ensure -- from CHAIN
			too_far_right: (old index + i > count) implies exhausted
			too_far_left: (old index + i < 1) implies exhausted
			expected_index: (not exhausted) implies (index = old index + i)

	search (v: like item)
			-- Move to first position (at or after current
			-- position) where item and v are equal.
			-- If structure does not include v ensure that
			-- exhausted will be true.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from BILINEAR)
		ensure -- from LINEAR
			object_found: (not exhausted and object_comparison) implies equal (v, item)
			item_found: (not exhausted and not object_comparison) implies v = item

	start
			-- Move cursor to first position if any.
			-- (from ARRAYED_LIST)
		ensure then -- from CHAIN
			at_first: not is_empty implies isfirst
		ensure then -- from ARRAYED_LIST
			after_when_empty: is_empty implies after
	
feature -- Element change

	append (s: SEQUENCE [PROCEDURE [ANY, EVENT_DATA]])
			-- Append a copy of s.
			-- (from SEQUENCE)
		require -- from SEQUENCE
			argument_not_void: s /= void
		ensure -- from SEQUENCE
			new_count: count >= old count

	extend (v: like item)
			-- Add v to end.
			-- Do not move cursor.
			-- Was declared in ARRAYED_LIST as synonym of force.
			-- (from ARRAYED_LIST)
		require -- from COLLECTION
			extendible: extendible
		ensure -- from COLLECTION
			item_inserted: is_inserted (v)
		ensure then -- from BAG
			one_more_occurrence: occurrences (v) = old (occurrences (v)) + 1

	extend_kamikaze (an_item: like item)
			-- Extend an_item and remove it again after it is called.

	fill (other: CONTAINER [PROCEDURE [ANY, EVENT_DATA]])
			-- Fill with as many items of other as possible.
			-- The representations of other and current structure
			-- need not be the same.
			-- (from COLLECTION)
		require -- from COLLECTION
			other_not_void: other /= void
			extendible

	force (v: like item)
			-- Add v to end.
			-- Do not move cursor.
			-- Was declared in ARRAYED_LIST as synonym of extend.
			-- (from ARRAYED_LIST)
		require -- from SEQUENCE
			extendible: extendible
		ensure then -- from SEQUENCE
			new_count: count = old count + 1
			item_inserted: has (v)

	force_extend (an_item: PROCEDURE [ANY, TUPLE])
			-- Extend without checking type of an_item.

	merge_left (other: ARRAYED_LIST [PROCEDURE [ANY, EVENT_DATA]])
			-- Merge other into current structure before cursor.
			-- (from ARRAYED_LIST)
		require -- from DYNAMIC_CHAIN
			extendible: extendible
			not_before: not before
			other_exists: other /= void
		ensure -- from DYNAMIC_CHAIN
			new_count: count = old count + old other.count
			new_index: index = old index + old other.count
			other_is_empty: other.is_empty
		ensure then -- from DYNAMIC_LIST
			other_empty: other.is_empty

	merge_right (other: ARRAYED_LIST [PROCEDURE [ANY, EVENT_DATA]])
			-- Merge other into current structure after cursor.
			-- (from ARRAYED_LIST)
		require -- from DYNAMIC_CHAIN
			extendible: extendible
			not_after: not after
			other_exists: other /= void
		ensure -- from DYNAMIC_CHAIN
			new_count: count = old count + old other.count
			same_index: index = old index
			other_is_empty: other.is_empty
		ensure then -- from DYNAMIC_LIST
			other_empty: other.is_empty

	put_i_th (v: like i_th; i: INTEGER)
			-- Replace i-th entry, if in index interval, by v.
			-- (from ARRAY)
		require -- from TABLE
			valid_key: array_valid_index (k)
		ensure then -- from INDEXABLE
			insertion_done: i_th (k) = v

	put (v: like item)
			-- Replace current item by v.
			-- (Synonym for replace)
			-- (from CHAIN)
		require -- from COLLECTION
			extendible: extendible
		ensure -- from COLLECTION
			item_inserted: is_inserted (v)
		ensure then -- from CHAIN
			same_count: count = old count

	put_front (v: like item)
			-- Add v to the beginning.
			-- Do not move cursor.
			-- (from ARRAYED_LIST)
		ensure -- from DYNAMIC_CHAIN
			new_count: count = old count + 1
			item_inserted: first = v

	put_left (v: like item)
			-- Add v to the left of current position.
			-- Do not move cursor.
			-- (from ARRAYED_LIST)
		require -- from DYNAMIC_CHAIN
			extendible: extendible
			not_before: not before
		ensure -- from DYNAMIC_CHAIN
			new_count: count = old count + 1
			new_index: index = old index + 1

	put_right (v: like item)
			-- Add v to the right of current position.
			-- Do not move cursor.
			-- (from ARRAYED_LIST)
		require -- from DYNAMIC_CHAIN
			extendible: extendible
			not_after: not after
		ensure -- from DYNAMIC_CHAIN
			new_count: count = old count + 1
			same_index: index = old index

	replace (v: like first)
			-- Replace current item by v.
			-- (from ARRAYED_LIST)
		require -- from ACTIVE
			writable: writable
		ensure -- from ACTIVE
			item_replaced: item = v
	
feature -- Removal

	prune (v: like item)
			-- Remove first occurrence of v, if any,
			-- after cursor position.
			-- Move cursor to right neighbor.
			-- (or after if no right neighbor or v does not occur)
			-- (from ARRAYED_LIST)
		require -- from COLLECTION
			prunable: prunable

	prune_all (v: like item)
			-- Remove all occurrences of v.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from ARRAYED_LIST)
		require -- from COLLECTION
			prunable
		ensure -- from COLLECTION
			no_more_occurrences: not has (v)
		ensure then -- from DYNAMIC_CHAIN
			is_exhausted: exhausted
		ensure then -- from ARRAYED_LIST
			is_after: after

	remove
			-- Remove current item.
			-- Move cursor to right neighbor
			-- (or after if no right neighbor)
			-- (from ARRAYED_LIST)
		require -- from ACTIVE
			prunable: prunable
			writable: writable
		ensure then -- from DYNAMIC_LIST
			after_when_empty: is_empty implies after
		ensure then -- from ARRAYED_LIST
			index: index = old index

	remove_left
			-- Remove item to the left of cursor position.
			-- Do not move cursor.
			-- (from ARRAYED_LIST)
		require -- from DYNAMIC_CHAIN
			left_exists: index > 1
		require else -- from DYNAMIC_LIST
			not_before: not before
		ensure -- from DYNAMIC_CHAIN
			new_count: count = old count - 1
			new_index: index = old index - 1

	remove_right
			-- Remove item to the right of cursor position
			-- Do not move cursor
			-- (from ARRAYED_LIST)
		require -- from DYNAMIC_CHAIN
			right_exists: index < count
		ensure -- from DYNAMIC_CHAIN
			new_count: count = old count - 1
			same_index: index = old index

	wipe_out
			-- Remove all items.
			-- (from ARRAYED_LIST)
		require -- from COLLECTION
			prunable
		ensure -- from COLLECTION
			wiped_out: is_empty
		ensure then -- from DYNAMIC_LIST
			is_before: before
	
feature -- Transformation

	swap (i: INTEGER)
			-- Exchange item at i-th position with item
			-- at cursor position.
			-- (from ARRAYED_LIST)
		require -- from CHAIN
			not_off: not off
			valid_index: array_valid_index (i)
		ensure -- from CHAIN
			swapped_to_item: item = old i_th (i)
			swapped_from_item: i_th (i) = old item
	
feature -- Conversion

	linear_representation: LINEAR [PROCEDURE [ANY, EVENT_DATA]]
			-- Representation as a linear structure
			-- (from LINEAR)
	
feature -- Duplication

	copy (other: like Current)
			-- Reinitialize by copying all the items of other.
			-- (This is also used by clone.)
			-- (from ARRAY)
		require -- from ANY
			other_not_void: other /= void
			type_identity: same_type (other)
		ensure -- from ANY
			is_equal: is_equal (other)
		ensure then -- from ARRAY
			equal_areas: area.is_equal (other.area)

	duplicate (n: INTEGER): like Current
			-- Copy of sub-list beginning at current position
			-- and having min (n, count - index + 1) items.
			-- (from ARRAYED_LIST)
		require -- from CHAIN
			not_off_unless_after: off implies after
			valid_subchain: n >= 0
	
feature -- Basic operations

	call (event_data: EVENT_DATA)
			-- Call each procedure in order unless is_blocked.
			-- If is_paused delay execution until resume.
			-- Stop at current point in list on abort.
			-- (from ACTION_SEQUENCE)
		ensure -- from ACTION_SEQUENCE
			is_aborted_stack_unchanged: old is_aborted_stack.is_equal (is_aborted_stack)
	
feature -- Element Change

	prune_when_called (an_action: like item)
			-- Remove an_action after the next time it is called.
			-- (from ACTION_SEQUENCE)
		require -- from ACTION_SEQUENCE
			has (an_action)
	
feature -- Event handling

	empty_actions: ARRAYED_LIST [PROCEDURE [ANY, TUPLE]]
			-- Actions to be performed on transition from not is_empty to is_empty.
			-- (from ACTION_SEQUENCE)

	not_empty_actions: ARRAYED_LIST [PROCEDURE [ANY, TUPLE]]
			-- Actions to be performed on transition from is_empty to not is_empty.
			-- (from ACTION_SEQUENCE)
	
feature -- Iteration

	do_all (action: PROCEDURE [ANY, TUPLE [PROCEDURE [ANY, EVENT_DATA]]])
			-- Apply action to every item.
			-- Semantics not guaranteed if action changes the structure;
			-- in such a case, apply iterator to clone of structure instead.
			-- (from LINEAR)
		require -- from TRAVERSABLE
			action_exists: action /= void

	do_if (action: PROCEDURE [ANY, TUPLE [PROCEDURE [ANY, EVENT_DATA]]]; test: FUNCTION [ANY, TUPLE [PROCEDURE [ANY, EVENT_DATA]], BOOLEAN])
			-- Apply action to every item that satisfies test.
			-- Semantics not guaranteed if action or test changes the structure;
			-- in such a case, apply iterator to clone of structure instead.
			-- (from LINEAR)
		require -- from TRAVERSABLE
			action_exists: action /= void
			test_exits: test /= void

	for_all (test: FUNCTION [ANY, TUPLE [PROCEDURE [ANY, EVENT_DATA]], BOOLEAN]): BOOLEAN
			-- Is test true for all items?
			-- (from LINEAR)
		require -- from TRAVERSABLE
			test_exits: test /= void

	there_exists (test: FUNCTION [ANY, TUPLE [PROCEDURE [ANY, EVENT_DATA]], BOOLEAN]): BOOLEAN
			-- Is test true for at least one item?
			-- (from LINEAR)
		require -- from TRAVERSABLE
			test_exits: test /= void
	
invariant

		-- from ANY
	reflexive_equality: standard_is_equal (Current)
	reflexive_conformance: conforms_to (Current)
		-- from ACTION_SEQUENCE
	is_aborted_stack_not_void: is_aborted_stack /= void
	call_buffer_not_void: call_buffer /= void
	not_has_void: not has (void)
	valid_state: state = normal_state or state = paused_state or state = blocked_state
	call_buffer_consistent: state = normal_state implies call_buffer.is_empty
	not_empty_actions_not_void: not_empty_actions /= void
	empty_actions_not_void: empty_actions /= void
		-- from ARRAYED_LIST
	prunable: prunable
	starts_from_one: lower = 1
	empty_means_storage_empty: is_empty implies all_default
		-- from ARRAY
	area_exists: area /= void
	consistent_size: capacity = upper - lower + 1
	non_negative_count: count >= 0
	index_set_has_same_count: valid_index_set
	index_set_has_same_bounds: ((index_set.lower = lower) and (index_set.upper = lower + count - 1))
		-- from RESIZABLE
	increase_by_at_least_one: minimal_increase >= 1
		-- from BOUNDED
	valid_count: count <= capacity
	full_definition: full = (count = capacity)
		-- from FINITE
	empty_definition: is_empty = (count = 0)
	non_negative_count: count >= 0
		-- from INDEXABLE
	index_set_not_void: index_set /= void
		-- from LIST
	before_definition: before = (index = 0)
	after_definition: after = (index = count + 1)
		-- from CHAIN
	non_negative_index: index >= 0
	index_small_enough: index <= count + 1
	off_definition: off = ((index = 0) or (index = count + 1))
	isfirst_definition: isfirst = ((not is_empty) and (index = 1))
	islast_definition: islast = ((not is_empty) and (index = count))
	item_corresponds_to_index: (not off) implies (item = i_th (index))
	index_set_has_same_count: index_set.count = count
		-- from ACTIVE
	writable_constraint: writable implies readable
	empty_constraint: is_empty implies (not readable) and (not writable)
		-- from BILINEAR
	not_both: not (after and before)
	before_constraint: before implies off
		-- from LINEAR
	after_constraint: after implies off
		-- from TRAVERSABLE
	empty_constraint: is_empty implies off
		-- from DYNAMIC_CHAIN
	extendible: extendible

end -- class EV_ACTION_SEQUENCE