Extensible select and enumeration types

and their elements in schema AP210_ASSEMBLY_PHYSICAL_DESIGN_XIM taking into account BASED_ON types


 action_items - EXTENSIBLE GENERIC_ENTITY SELECT
          action_directive
          characterized_object
          configuration_effectivity
          design_pdm_certification_item
          design_pdm_classification_item
          design_pdm_document_reference_item
          design_pdm_identification_item
          design_pdm_requirement_assigned_item
          organization
          person_and_organization
          product_definition
          product_definition_formation
          product_definition_relationship

 action_method_items - EXTENSIBLE SELECT
          product
          product_definition_formation
          test_method_based_parameter_assignment
          test_method_based_parameter_assignment_armx

 action_request_item - EXTENSIBLE GENERIC_ENTITY SELECT
          assigned_property
          product_definition
          product_definition_formation
          product_definition_relationship
          product_view_definition
          property_definition
          versioned_action_request

 analytical_model_port_assignment_select - EXTENSIBLE GENERIC_ENTITY SELECT
          functional_unit_usage_view_terminal_definition

 application_environment - EXTENSIBLE ENUMERATION
          end_user_application
          manufacturing

 approval_item - EXTENSIBLE GENERIC_ENTITY SELECT
          action
          action_directive
          applied_action_assignment
          applied_usage_right
          certification
          configuration_effectivity
          configuration_item
          contract
          date
          digital_document_definition
          directed_action
          document
          document_definition
          document_definition_relationship
          document_version
          effectivity
          executed_action
          general_property_relationship
          group
          group_relationship
          information_usage_right
          physical_document_definition
          product
          product_definition
          product_definition_formation
          product_definition_formation_relationship
          product_definition_relationship
          product_view_definition
          representation
          requirement_assignment
          security_classification
          shape_aspect_relationship
          supplied_part_relationship_armx
          versioned_action_request

 assembled_feature_select - EXTENSIBLE GENERIC_ENTITY SELECT
          assembly_module_component_terminal
          bare_die_component_terminal
          component_mounting_feature_armx
          interconnect_component_interface_terminal
          interconnect_component_join_terminal
          interconnect_module_component_surface_feature
          interconnect_module_component_terminal
          packaged_component_join_terminal
          packaged_connector_component_interface_terminal

 assembly_module_or_assembly_group_component - EXTENSIBLE GENERIC_ENTITY SELECT
          assembly_group_component_armx
          assembly_module

 assembly_product_design_object_category - EXTENSIBLE ENUMERATION
          assembly_component_category
          assembly_module_component_category
          assembly_module_component_terminal_category
          assembly_module_macro_component_category
          assembly_module_macro_component_join_terminal_category
          bare_die_component_category
          bare_die_component_terminal_category
          buried_via_category
          cable_component_category
          component_feature_category
          component_termination_passage_category
          conductive_interconnect_element_with_pre_defined_transitions_category
          cutout_category
          cutout_edge_segment_category
          dielectric_material_passage_category
          embedded_physical_component_terminal_category
          fiducial_category
          fill_area_category
          inter_stratum_feature_category
          interconnect_component_interface_terminal_category
          interconnect_component_join_terminal_category
          interconnect_module_component_category
          interconnect_module_component_stratum_based_terminal_category
          interconnect_module_component_surface_feature_category
          interconnect_module_component_terminal_category
          interconnect_module_edge_category
          interconnect_module_edge_segment_category
          interconnect_module_macro_component_category
          interconnect_module_macro_component_join_terminal_category
          interface_access_material_removal_laminate_component_category
          interface_access_stratum_feature_template_component_category
          interface_component_category
          interfacial_connection_category
          internal_probe_access_area_category
          laminate_component_category
          minimally_defined_component_terminal_category
          packaged_component_category
          packaged_component_join_terminal_category
          packaged_connector_component_category
          packaged_connector_component_interface_terminal_category
          physical_component_category
          plated_passage_or_unsupported_passage_category
          routed_interconnect_component_category
          routed_physical_component_category
          stratum_feature_category
          via_category

 assembly_spacing_type - EXTENSIBLE ENUMERATION
          centroid
          furthest_boundary
          nearest_boundary

 attribute_classification_item - EXTENSIBLE GENERIC_ENTITY SELECT
          action_directive
          action_method
          action_property
          action_property_representation
          action_relationship
          action_request_solution
          action_request_status
          alternate_product_relationship
          applied_action_assignment
          applied_action_request_assignment
          applied_approval_assignment
          applied_certification_assignment
          applied_document_reference
          applied_document_usage_constraint_assignment
          applied_effectivity_assignment
          applied_event_occurrence_assignment
          applied_external_identification_assignment
          applied_identification_assignment
          applied_organization_assignment
          applied_organizational_project_assignment
          applied_person_and_organization_assignment
          approval
          approval_person_organization
          approval_relationship
          approval_status
          certification
          context_dependent_unit
          contract
          date_and_time_assignment
          date_assignment
          derived_unit
          descriptive_representation_item
          document_file
          document_relationship
          effectivity
          event_occurrence_relationship
          executed_action
          general_property
          general_property_relationship
          group
          group_relationship
          information_right
          information_usage_right
          language
          measure_representation_item
          measure_with_unit
          named_unit
          organization_relationship
          organizational_address
          organizational_project_relationship
          person_and_organization
          person_and_organization_address
          product
          product_category
          product_concept
          product_concept_context
          product_definition
          product_definition_context
          product_definition_formation
          product_definition_formation_relationship
          product_definition_relationship
          property_definition
          property_definition_relationship
          property_definition_representation
          representation
          representation_context
          representation_item
          security_classification
          time_interval_relationship
          uncertainty_measure_with_unit
          usage_association
          versioned_action_request

 attribute_language_item - EXTENSIBLE GENERIC_ENTITY SELECT
          applied_document_reference
          applied_document_usage_constraint_assignment
          applied_external_identification_assignment
          applied_organizational_project_assignment
          approval
          approval_relationship
          approval_status
          attribute_value_assignment
          certification
          certification_type
          contract
          date_role
          date_time_role
          digital_document_definition
          document_armx
          document_assignment
          document_definition_relationship
          document_relationship
          document_usage_role
          document_version
          external_source
          external_source_identification
          file_relationship
          identification_role
          information_right
          information_usage_right
          multi_language_attribute_assignment
          object_role
          organization_relationship
          organizational_project
          organizational_project_relationship
          organizational_project_role
          person_and_organization
          physical_document_definition
          product
          product_category
          product_definition
          product_definition_formation
          product_definition_relationship
          usage_association

 bare_die_component_or_packaged_component - EXTENSIBLE GENERIC_ENTITY SELECT
          bare_die_component_armx
          packaged_component_armx

 bare_die_terminal_or_packaged_part_terminal - EXTENSIBLE GENERIC_ENTITY SELECT
          bare_die_terminal_armx
          packaged_part_terminal_armx

 breakdown_item - EXTENSIBLE SELECT
          breakdown_element_definition
          breakdown_element_usage_armx

 built_in_functions - EXTENSIBLE ENUMERATION
          attr_val

 certification_item - EXTENSIBLE GENERIC_ENTITY SELECT
          alternate_product_relationship
          make_from_usage_option
          product_definition_formation
          product_definition_formation_relationship

 class_system_item - EXTENSIBLE GENERIC_ENTITY SELECT
          characterized_class

 classification_item - EXTENSIBLE GENERIC_ENTITY SELECT
          action
          action_directive
          action_method
          action_property
          action_relationship
          action_request_solution
          action_request_status
          address
          alternate_product_relationship
          applied_action_assignment
          applied_action_request_assignment
          applied_approval_assignment
          applied_certification_assignment
          applied_contract_assignment
          applied_date_and_time_assignment
          applied_date_assignment
          applied_document_reference
          applied_document_usage_constraint_assignment
          applied_effectivity_assignment
          applied_event_occurrence_assignment
          applied_external_identification_assignment
          applied_identification_assignment
          applied_organization_assignment
          applied_organizational_project_assignment
          applied_person_and_organization_assignment
          applied_security_classification_assignment
          approval
          approval_person_organization
          approval_relationship
          approval_status
          assembly_component_usage_substitute
          calendar_date
          certification
          characterized_class
          characterized_object
          class
          classification_item_extended
          configuration_item
          context_dependent_unit
          contract
          conversion_based_unit
          date_and_time
          date_and_time_assignment
          date_assignment
          derived_unit
          descriptive_representation_item
          directed_action
          document_file
          document_relationship
          effectivity
          event_occurrence
          executed_action
          general_property
          general_property_relationship
          group
          identification_assignment
          information_right
          information_usage_right
          language
          material_designation
          measure_representation_item
          measure_with_unit
          multi_language_attribute_assignment
          named_unit
          organization
          organization_relationship
          organizational_address
          organizational_project
          organizational_project_relationship
          person
          person_and_organization_address
          product
          product_category
          product_concept
          product_definition
          product_definition_context
          product_definition_formation
          product_definition_formation_relationship
          product_definition_relationship
          property_definition
          property_definition_representation
          representation
          representation_context
          representation_item
          security_classification
          uncertainty_measure_with_unit
          usage_association
          versioned_action_request

 classified_element_select - EXTENSIBLE GENERIC_ENTITY SELECT
          product
          product_definition_formation
          product_view_definition

 classified_item - EXTENSIBLE GENERIC_ENTITY SELECT
          product
          product_definition
          product_definition_formation

 component_feature_or_stratum_surface - EXTENSIBLE GENERIC_ENTITY SELECT
          component_feature_armx
          stratum_surface_armx

 configured_effectivity_item - EXTENSIBLE GENERIC_ENTITY SELECT
          product_definition

 constants - EXTENSIBLE SELECT
          count_measure
          descriptive_measure
          logical_representation_item

 constructive_element_select - EXTENSIBLE GENERIC_ENTITY SELECT
          axis2_placement
          curve
          point_select
          surface

 contract_item - EXTENSIBLE SELECT
          action_directive
          alternate_product_relationship
          directed_action
          document_version
          information_usage_right
          organization
          person_and_organization
          product
          product_definition_formation

 date_and_time_item - EXTENSIBLE SELECT
          action
          action_directive
          applied_action_assignment
          applied_organization_assignment
          applied_person_and_organization_assignment
          applied_security_classification_assignment
          approval_person_organization
          certification
          contract
          digital_document_definition
          digital_file
          directed_action
          document
          document_definition_relationship
          document_file
          document_version
          event_occurrence
          executed_action
          hardcopy
          information_usage_right
          organizational_project
          physical_document_definition
          product_definition
          product_definition_formation
          product_definition_relationship
          rule_action
          security_classification
          versioned_action_request

 date_item - EXTENSIBLE SELECT
          action
          action_directive
          applied_action_assignment
          applied_organization_assignment
          applied_person_and_organization_assignment
          applied_security_classification_assignment
          approval_person_organization
          certification
          contract
          digital_document_definition
          digital_file
          directed_action
          document
          document_definition_relationship
          document_file
          document_version
          event_occurrence
          executed_action
          hardcopy
          information_usage_right
          organizational_project
          physical_document_definition
          product_definition
          product_definition_formation
          product_definition_relationship
          security_classification
          versioned_action_request

 default_setting_select - EXTENSIBLE SELECT
          general_tolerances

 document_reference_item - EXTENSIBLE SELECT
          action_method
          activity
          analytical_model_definition
          applied_external_identification_assignment
          assembly_component_usage
          characterized_class
          characterized_object
          component_or_component_feature
          configuration_item
          descriptive_representation_item
          dimensional_size
          executed_action
          external_source_identification
          externally_defined_dimension_definition
          externally_defined_item
          externally_defined_size_dimension
          group
          group_relationship
          information_right
          information_usage_right
          inter_stratum_feature
          marking
          material_designation
          measure_representation_item
          model_parameter
          model_parameter_armx
          package_terminal
          part
          part_feature
          part_version
          part_view_definition
          passage_technology
          passage_technology_armx
          physical_connectivity_definition
          physical_connectivity_definition_armx
          physical_connectivity_element
          physical_connectivity_element_armx
          predefined_requirement_view_definition
          predefined_requirement_view_definition_armx
          product
          product_category
          product_definition
          product_definition_formation
          product_definition_formation_relationship
          product_view_definition
          property_definition
          property_value_representation
          protocol_physical_layer_definition
          protocol_physical_layer_definition_armx
          representation
          representation_item
          rule_set
          rule_set_armx
          shape_aspect
          shape_aspect_relationship
          shape_element
          shape_element_relationship
          signal_specification
          stratum
          stratum_armx
          stratum_concept
          stratum_feature
          stratum_surface
          stratum_technology
          stratum_technology_armx
          structured_layout_component
          surface_prepped_terminal
          usage_association
          versioned_action_request

 ee_product_definition_with_annotation_elements - EXTENSIBLE GENERIC_ENTITY SELECT
          part_design_view
          part_usage_view
          stratum_armx
          structured_template_armx
          template_definition

 effectivity_item - EXTENSIBLE SELECT
          configuration
          part_definition_relationship
          product_definition
          product_definition_formation
          product_definition_relationship
          product_definition_substitute

 element_with_dimension_select - EXTENSIBLE GENERIC_ENTITY SELECT
          shape_element

 event_item - EXTENSIBLE GENERIC_ENTITY SELECT
          project

 event_occurrence_item - EXTENSIBLE GENERIC_ENTITY SELECT
          organizational_project

 expression_syntax - EXTENSIBLE ENUMERATION
          express

 extended_value_with_unit - EXTENSIBLE SELECT
          measure_with_unit
          textual_quantity_specification
          value_limit
          value_range

 external_identification_item - EXTENSIBLE GENERIC_ENTITY SELECT
          action_relationship
          action_request_status
          applied_organization_assignment
          applied_person_and_organization_assignment
          approval
          approval_status
          assembly_bond_definition
          assembly_component
          composite_signal_property_relationship
          date_and_time_assignment
          date_assignment
          design_layer_technology
          digital_analytical_model_vector_port
          document_definition
          document_file
          documentation_layer_technology
          external_source
          externally_defined_action_request_assignment
          externally_defined_activity_relationship
          externally_defined_address_assignment__oa
          externally_defined_address_assignment__paoa
          externally_defined_approval
          externally_defined_approval_status
          externally_defined_class
          externally_defined_date_or_date_time_assignment__da
          externally_defined_date_or_date_time_assignment__data
          externally_defined_effectivity_or_ineffectivity_assignment__aea
          externally_defined_general_property
          externally_defined_identification_assignment
          externally_defined_organization_or_person_in_organization_assignment__aoa
          externally_defined_organization_or_person_in_organization_assignment__apaoa
          externally_defined_product_definition
          externally_defined_security_classification
          externally_defined_work_request
          externally_defined_work_request_status
          file
          functional_specification
          land_physical_template
          land_physical_template_armx
          organizational_address
          package
          package_terminal_template_definition
          printed_component
          product_definition
          property_definition
          security_classification
          shape_dimension_representation
          shape_representation
          signal
          stratum
          stratum_feature_based_derived_pattern
          stratum_technology
          trimmed_curve
          versioned_action_request

 externally_versioned_item - EXTENSIBLE GENERIC_ENTITY SELECT
          externally_defined_general_property

 feature_or_non_feature_usage - EXTENSIBLE GENERIC_ENTITY SELECT
          part_template_or_physical_unit_2d_shape_model_select
          part_template_or_physical_unit_3d_shape_model_select

 feature_select - EXTENSIBLE GENERIC_ENTITY SELECT
          component_termination_passage_template_terminal
          land_template_terminal_armx
          part_feature
          part_terminal_external_reference
          printed_part_template_terminal_armx
          via_template_terminal

 ft_terminus_condition - EXTENSIBLE ENUMERATION
          bilateral_bond
          bilateral_complete_removal
          unilateral_bond

 general_tolerance_table_select - EXTENSIBLE SELECT
          general_tolerance_table

 groupable_item - EXTENSIBLE GENERIC_ENTITY SELECT
          assembly_component_usage
          assembly_spacing_requirement_occurrence
          component_feature
          group_relationship
          package_product_concept_feature
          part_connected_terminals_definition
          physical_connectivity_definition
          physical_network
          predefined_requirement_view_definition
          printed_part_template_terminal
          product_concept_feature
          product_definition
          product_definition_formation
          property_definition_representation
          representation
          representation_item
          shape_aspect
          shape_aspect_relationship
          stratum

 identification_item - EXTENSIBLE SELECT
          approval_status
          characterized_class
          class
          configuration_item
          contract
          digital_document_definition
          digital_file
          dimensional_size
          document_armx
          document_file
          document_version
          group
          group_relationship
          hardcopy
          information_right
          information_usage_right
          material_designation
          organization
          person_and_organization
          physical_document_definition
          product
          product_category
          product_class
          product_concept
          product_concept_feature
          product_definition
          product_definition_formation
          product_identification
          requirement
          requirement_version
          requirement_view_definition
          rule_set
          security_classification
          security_classification_level
          shape_aspect_relationship
          shape_representation
          usage_association

 instance_usage_context_select - EXTENSIBLE GENERIC_ENTITY SELECT
          product_definition_relationship
          product_definition_usage

 material_item_select - EXTENSIBLE GENERIC_ENTITY SELECT
          assembly_bond_definition_armx
          bare_die_template_terminal_armx
          bare_die_terminal_armx
          coating_layer
          marking
          package_body_armx
          package_terminal_armx
          package_terminal_template_definition_armx
          packaged_part_armx
          part_view_definition
          passage_technology_armx
          predefined_requirement_view_definition_armx
          stratum_technology_armx
          substance_view_definition
          template_definition

 measuring_gauge_select - EXTENSIBLE GENERIC_ENTITY SELECT
          part_view_definition

 multi_language_attribute_item - EXTENSIBLE GENERIC_ENTITY SELECT
          applied_document_reference
          applied_document_usage_constraint_assignment
          applied_external_identification_assignment
          applied_organizational_project_assignment
          approval
          approval_relationship
          approval_status
          certification
          certification_type
          contract
          date_role
          date_time_role
          document_relationship
          document_usage_role
          external_source
          identification_role
          information_right
          information_usage_right
          object_role
          organization_relationship
          organizational_project
          organizational_project_relationship
          organizational_project_role
          person_and_organization
          product
          product_category
          product_definition
          product_definition_formation
          product_definition_relationship
          usage_association

 name_item - EXTENSIBLE GENERIC_ENTITY SELECT
          assembly_component_usage
          external_class_library
          group
          group_relationship
          product
          product_definition
          product_view_definition

 organization_item - EXTENSIBLE SELECT
          action
          action_directive
          applied_action_assignment
          applied_classification_assignment
          applied_identification_assignment
          applied_security_classification_assignment
          approval
          class
          configuration_item
          contract
          digital_document_definition
          digital_file
          document_armx
          document_file
          document_version
          executed_action
          hardcopy
          information_usage_right
          physical_document_definition
          product
          product_definition
          product_definition_formation
          product_definition_formation_relationship
          rule_action
          security_classification
          versioned_action_request

 part_template_or_physical_unit_2d_shape_model_select - EXTENSIBLE GENERIC_ENTITY SELECT
          part_template_planar_shape_model
          physical_unit_planar_shape_model

 part_template_or_physical_unit_3d_shape_model_select - EXTENSIBLE GENERIC_ENTITY SELECT
          part_template_3d_shape_model
          physical_unit_3d_shape_model

 person_and_organization_item - EXTENSIBLE SELECT
          action
          action_directive
          applied_action_assignment
          applied_classification_assignment
          applied_identification_assignment
          applied_security_classification_assignment
          approval
          configuration_item
          contract
          digital_document_definition
          digital_file
          document_armx
          document_file
          document_version
          executed_action
          hardcopy
          information_usage_right
          person_and_organization
          physical_document_definition
          product
          product_definition
          product_definition_formation
          product_definition_formation_relationship
          rule_action
          security_classification
          versioned_action_request

 physical_feature_or_part_template - EXTENSIBLE GENERIC_ENTITY SELECT
          laminate_component_armx
          part_feature
          physical_component_feature_armx
          shape_element

 physical_unit_shape_model_select - EXTENSIBLE GENERIC_ENTITY SELECT
          part_template_3d_shape_model
          physical_unit_3d_shape_model
          physical_unit_planar_shape_model

 placed_element_select - EXTENSIBLE SELECT
          constructive_element_select
          derived_geometry
          element_with_dimension_select

 product_definition_or_breakdown_element_usage - EXTENSIBLE GENERIC_ENTITY SELECT
          breakdown_element_usage
          product_definition

 product_definition_or_product_definition_relationship - EXTENSIBLE GENERIC_ENTITY SELECT
          product_definition
          product_definition_usage

 product_item - EXTENSIBLE SELECT
          product_definition_usage
          product_view_definition

 project_item - EXTENSIBLE SELECT
          executed_action
          product_concept

 property_assignment_select - EXTENSIBLE SELECT
          assembly_bond_definition_armx
          breakdown_element_realization
          breakdown_element_usage_armx
          characterized_object
          document_definition
          file
          part_view_definition
          passage_technology_armx
          product_definition
          product_definition_relationship
          requirement_view_definition
          shape_element
          stratum_technology_armx

 requirement_assigned_item - EXTENSIBLE GENERIC_ENTITY SELECT
          assembly_component_usage
          assembly_item_number
          assembly_joint
          component_functional_unit
          component_material_relationship
          configuration_item
          descriptive_representation_item
          dielectric_crossover_area
          group
          group_product_definition
          group_relationship
          passage_technology
          physical_connectivity_definition
          physical_unit
          predefined_requirement_view_definition
          product
          product_class
          product_definition
          product_definition_formation
          product_definition_relationship
          property_definition
          representation
          shape_aspect
          shape_aspect_relationship
          shape_representation
          statistical_dimensional_location
          statistical_dimensional_size
          statistical_geometric_tolerance
          stratum_feature_conductive_join
          stratum_technology
          stratum_technology_occurrence
          structured_template
          thermal_isolation_removal_template

 requirement_assignment_item - EXTENSIBLE SELECT
          assembly_component_usage
          assembly_item_number_armx
          assembly_joint_armx
          component_feature_to_layout_feature_relationship
          component_material_relationship_armx
          configuration_item
          dielectric_crossover_area_armx
          functional_unit_armx
          group
          group_relationship
          part_feature
          part_template_keepout_shape_model
          part_view_definition
          passage_technology_armx
          physical_connectivity_definition_armx
          physical_connectivity_definition_relationship
          physical_connectivity_element_armx
          physical_unit_keepout_shape_model
          physical_unit_shape_model
          placement_group_requirement_definition
          product
          product_definition_formation
          product_view_definition
          restraint_condition
          restriction_basis_item
          statistical_dimensional_location_armx
          statistical_dimensional_size_armx
          statistical_geometric_tolerance_armx
          stratum_feature_conductive_join_armx
          stratum_technology_armx
          stratum_technology_occurrence_armx
          structured_template_armx
          template_location_in_structured_template

 requirement_source_item - EXTENSIBLE GENERIC_ENTITY SELECT
          characterized_object
          group
          group_relationship
          product
          product_definition
          product_definition_formation
          product_definition_relationship
          shape_aspect

 restriction_basis_item - EXTENSIBLE GENERIC_ENTITY SELECT
          component_or_component_feature
          part_feature
          predefined_requirement_view_definition_armx
          stratum_armx
          stratum_concept

 security_classification_item - EXTENSIBLE SELECT
          assembly_component_usage
          digital_document_definition
          digital_file
          document
          document_armx
          document_file
          document_version
          hardcopy
          make_from_usage_option
          physical_document_definition
          product
          product_definition
          product_definition_formation

 stratum_concept - EXTENSIBLE GENERIC_ENTITY SELECT
          inter_stratum_feature_armx
          laminate_component_armx
          stratum_armx
          stratum_feature_armx
          stratum_surface_armx
          structured_template_armx

 substance_composition_basis - EXTENSIBLE ENUMERATION
          atoms
          mass
          moles
          volume

 template_definition_select - EXTENSIBLE SELECT
          shape_representation

 termination_or_junction - EXTENSIBLE GENERIC_ENTITY SELECT
          component_terminal_abstract
          explicitly_located_layer_connection_point
          inter_stratum_join_relationship
          topological_junction

 time_interval_item - EXTENSIBLE SELECT
          action

 trace_junction_or_via - EXTENSIBLE SELECT
          explicitly_located_layer_connection_point
          inter_stratum_join_relationship

 usage_concept - EXTENSIBLE GENERIC_ENTITY SELECT
          component_termination_passage_template_terminal
          land_template_terminal_armx
          non_feature_shape_element
          part_feature
          printed_part_template_terminal_armx
          via_template_terminal

 versionable_item - EXTENSIBLE SELECT
          characterized_class
          document_file
          product_class
          product_concept_feature
          product_identification
          shape_representation

 view_shape_select - EXTENSIBLE GENERIC_ENTITY SELECT
          part_template_shape_model
          physical_unit_shape_model