modelverse/models/environment_to_EPN.alc

// Pseudo-code
//    assumption: Activities all have duration (e.g., 0 for parallel)
//    TODO: add link to the ports of the boundary
//    TODO: update MM to reflect the new changes to the structure (everything is an Activity with a Next link, and everything has a duration)

//  init_place = new_place()
//	branches = [(init_place, [(0, topmost_model)]]
//	while branches:
//		prev, options = branches.pop()
//		nr = find_min_time(options)
//		time, cur = options.pop(nr)
//
//		if type(cur) == "Event":
//			// Just add the current node and augment the duration for the next one
//			prev_model = new_element(cur)
//			if (cur.next != None):
//				options.append((time + cur.next.duration, cur.next))
//				branches.append((prev_model, options))
//			else:
//				// recurse upwards until we can follow a link
//				elem = containee(cur)
//				while elem.next_activity == None and containee(elem) != None:
//					elem = containee(elem)
//				if containee(elem) == None:
//					// finished this branch
//					continue!
//				else:
//					cur = elem.next_activity
//					options.append((time + elem.duration, cur.next))
//					branches.append((prev_model, options))
//		elif type(cur) == "Sequence":
//			options.append((time + first.duration, cur.first))
//			branches.append((prev_model, options))
//		elif type(cur) == "Parallel":
//			// Add all starts of the parallel as potential next one
//			// But keep the previous source, as we only expanded
//			for next in cur.start_nodes:
//				options.append((time + next.duration, next))
//			branches.append((prev, options))
//		elif type(cur) == "Alternative":
//			// Expand into new branches, but keep the options as is (add the individual options though)
//			for next in cur.start_nodes:
//				options.append((time + next.duration, next))
//				// Don't rewrite the source, as we effectively want to branch out from this node
//				branches.append(prev, options)

include "primitives.alh"
include "modelling.alh"
include "object_operations.alh"

Element function env_to_EPN(params : Element, output_mms : Element):
	Element result
	Element out_model
	Element in_model
	String init_place
	String current_activity
	Element branches
	Element options
	Element branch
	String previous_place
	Integer i
	Integer cnt
	Integer min_time
	Integer index_min_time
	Element option
	Integer current_time
	String new_transition
	String new_model
	Element containers
	Element new_options
	Element inner_elements
	Element entry
	String type
	String prev_model
	String element

	result = create_node()
	out_model = instantiate_model(output_mms["Encapsulated_PetriNet"])
	in_model = params["Environment_PW"]

	// Create the initial place
	init_place = instantiate_node(out_model, "Place", "")
	instantiate_attribute(out_model, init_place, "tokens", 1)

	// Set current element to the TopActivity, which will be expanded
	current_activity = set_pop(allInstances(in_model, "TopActivity"))

	// Initialize the data structure with the current element and initial place
	branches = create_node()
	options = create_node()
	list_append(options, create_tuple(0, current_activity))
	set_add(branches, create_tuple(init_place, options))

	// Keep going as long as there are branches to resolve
	while (read_nr_out(branches) > 0):
		// Still a branch, so pick one at random
		branch = set_pop(branches)
		previous_place = branch[0]
		options = branch[1]

		// Find the index of the option with the lowest time (first element of tuple)
		i = 0
		cnt = list_len(options)
		min_time = 9999999
		index_min_time = -1
		while (i < cnt):
			entry = list_read(options, i)
			if (integer_lt(entry[0], min_time)):
				min_time = entry[0]
				index_min_time = i
			i = i + 1

		// Pop the minimal option
		option = list_pop(options, index_min_time)
		current_time = option[0]
		current_activity = option[1]

		// Figure out the type
		type = read_type(in_model, current_activity)

		// Now branch based on the type
		if (type == "Event"):
			// Process an event: update the PN and go to the next activity
			new_transition = instantiate_node(out_model, "Transition", "")
			new_model = instantiate_node(out_model, "Place", "")
			instantiate_link(out_model, "P2T", "", prev_model, new_transition)
			instantiate_link(out_model, "T2P", "", new_transition, new_model)

			// Check if there is a Next to this Event, meaning another event
			if (read_nr_out(allOutgoingAssociationInstances(in_model, current_activity, "Next")) > 0):
				// We have a Next, so just push that next event on the options
				current_activity = set_pop(allAssociationDestinations(in_model, current_activity, "Next"))
				list_append(options, create_tuple(integer_addition(current_time, read_attribute(in_model, current_activity, "duration")), current_activity))
				set_add(branches, create_tuple(new_model, options))
			else:
				// No Next in this node, so we recurse up until one of these elements does have a next (or we reach the top)
				while (read_nr_out(allOutgoingAssociationInstances(in_model, current_activity, "Next")) == 0):
					// Recurse up
					containers = allAssociationOrigins(in_model, current_activity, "Contains")
					if (read_nr_out(containers) == 1):
						current_activity = set_pop(containers)
					elif (read_nr_out(containers) == 0):
						// No more containers, so at top element
						break!
				if (read_nr_out(containers) == 0):
					// Nothing left to do, so clear up this branch, but continue with the others
					continue!
				else:
					// Found a node with a Next link: we follow it
					current_activity = set_pop(allAssociationDestinations(in_model, current_activity, "Next"))
					list_append(options, create_tuple(integer_addition(current_time, read_attribute(in_model, current_activity, "duration")), current_activity))
					set_add(branches, create_tuple(new_model, options))

		elif (type == "Sequence"):
			// Process a sequence: just move the current option to the enclosing activity
			inner_elements = allAssociationDestinations(in_model, current_activity, "Contains")
			while (read_nr_out(inner_elements) > 0):
				element = set_pop(inner_elements)
				if (read_nr_out(allIncomingAssociationInstances(in_model, element, "Next")) == 0):
					current_activity = element
					break!
			// current_activity now contains the inner element to execute
			list_append(options, create_tuple(integer_addition(current_time, read_attribute(in_model, current_activity, "duration")), current_activity))
			// keep the current branch alive, as everything is updated by reference
			set_add(branches, branch)

		elif (type == "Parallel"):
			// Process a parallel: create new options for each containing element
			inner_elements = allAssociationDestinations(in_model, current_activity, "Contains")
			while (read_nr_out(inner_elements) > 0):
				current_activity = set_pop(inner_elements)
				// current_activity now contains the inner element to execute in parallel (an option)
				list_append(options, create_tuple(integer_addition(current_time, read_attribute(in_model, current_activity, "duration")), current_activity))
			// keep the current branch alive, as everything is updated by reference
			set_add(branches, branch)

		elif (type == "Alternative"):
			inner_elements = allAssociationDestinations(in_model, current_activity, "Contains")
			while (read_nr_out(inner_elements) > 0):
				current_activity = set_pop(inner_elements)
				// current_activity now contains the inner element to execute in alternative branches (a branch)
				new_options = set_copy(options)
				list_append(options, create_tuple(integer_addition(current_time, read_attribute(in_model, current_activity, "duration")), current_activity))
				set_add(branches, create_tuple(previous_place, new_options))

	dict_add(result, "Encapsulated_PetriNet", out_model)
	return result!