pressures

Unless otherwise specified, data names are accessible in level 3 only.

engineering_type
The engineering type of load. Engineering loads act on set entities. Valid values are:
0 - Classic load
2 - Normal engineering load
3 - Directional engineering load
11 - Detonation
Type: unsigned integer

The following data names are available for both classic and engineering loads:

attributesmax
The number of attributes owned by this entity.
Type: unsigned integer
collector
Pointer to the collector that owns the load.
Type: pointer (levels 2, 3, and 4)
config
The configuration of the entity.
4 - Pressure
Type: unsigned integer
definedentity
True if the entity is defined, false otherwise.
Type: Boolean
entityid
The ID of the entity the load is attached to.
Type: integer
entitytype
The type of the entity to which the load is applied.
  • 2 - elem
  • 3 - comp
  • 5 - surf
  • 10 - set
Type: integer
entitytypename
The string type of the entity to which the load is applied.
  • elems
  • comps
  • surfs
  • sets
Type: string
id
The ID of the entity.
Type: unsigned integer
include
The ID of the include file the entity is organized in.
Type: entity
includeid
The ID of the include file the entity is organized in.
Type: unsigned integer
internalid
The ID of the entity.
Type: unsigned integer
internalname
The internal name of the entity.
Type: string
moduleid
The module ID of the entity.
Type: integer
poolid
The pool number of the entity.
Type: integer
poolname
The pool name of the entity.
Type: string
set
Pointer to the set when the load is applied to a set.
Type: integer
solver_id
The solver ID of the entity.
Type: integer
solverkeyword
The name of the solver keyword.
Type: string
solvername
The solver name of the entity for entities enabled for name pool, otherwise the internal name of the entity.
Type: string
type
The solver dependent type code for the entity.
Type: integer
typename
The solver dependent type name for the entity.
Type: string
vectorx
The x component of the unit vector.
Type: double
vectory
The y component of the unit vector.
Type: double
vectorz
The z component of the unit vector.
Type: double

The following data names are available for classic loads:

baselocation
The coordinates where the load on a component or set should display. Valid for hm_getvalue query only.
Also used to convert the load vector components into local values for non-rectangular coordinate systems.
Type: triple double
baselocationx
The x-coordinate where the load on a component or set should display.
Also used to convert the load vector components into local values for non-rectangular coordinate systems.
Type: double
baselocationy
The y-coordinate where the load on a component or set should display.
Also used to convert the load vector components into local values for non-rectangular coordinate systems.
Type: double
baselocationz
The z-coordinate where the load on a component or set should display.
Also used to convert the load vector components into local values for non-rectangular coordinate systems.
Type: double
center
The coordinates of the element centroid for loads applied to shell element faces. Valid for hm_getvalue query only.
Type: double
centerx
The x-coordinate of the element centroid for loads applied to shell element faces.
Type: double
centery
The y-coordinate of the element centroid for loads applied to shell element faces.
Type: double
centerz
The z-coordinate of the element centroid for loads applied to shell element faces.
Type: double
comp1
The x component of the vector in the global coordinate system.
Type: double
comp2
The y component of the vector in the global coordinate system.
Type: double
comp3
The z component of the vector in the global coordinate system.
Type: double
component
Pointer to the component when the load is applied to a component.
Type: pointer
corner1
The ID of a grid point connected to a corner of the face. Valid for hm_getvalue query only.
Type: double
corner2
The ID of a grid point connected to a corner diagonally opposite to corner1 on the same face. Valid for hm_getvalue query only.
Type: double
curveid
The ID of the curve defining the load magnitude when a curve has been used to define the load.
Type: integer
edgelength
The length of the loaded edge for edge pressures.
Type: double
element
Pointer to the element when the load is applied to an element.
Type: pointer
elementtype
The type of element the load is applied to.
  • 1 - shell
  • 2 - tetra
  • 3 - penta
  • 4 - hexa
Type: integer
face
The element face number for face pressures.
This is most useful for loads applied to solid element faces.
Type: integer
facearea
The area of the loaded face for face pressures.
Type: double
facetype
The type of face for face pressures.
  • 3 - tria
  • 4 - quad
Type: integer
inputsystem
Pointer to the reference system.
Type: pointer
inputsystemid
The ID of the reference system.
Type: integer
local_comp1
The x component of the vector in the local coordinate system.
Type: double
local_comp2
The y component of the vector in the local coordinate system.
Type: double
local_comp3
The z component of the vector in the local coordinate system.
Type: double
local_vector
The load vector in the local coordinate system.
Type: triple double
local_vectorx
The x component of the unit vector in the local coordinate system.
Type: double
local_vectory
The y component of the unit vector in the local coordinate system.
Type: double
local_vectorz
The z component of the unit vector in the local coordinate system.
Type: double
location
The ID of the element where the load is applied. Valid for hm_getvalue query only.
Type: entity
magnitude
The magnitude of the load.
Type: double
mappedid
The ID of the original load on geometry.
Type: integer
node1
The ID of the first face node for face pressures.
Type: integer
node2
The ID of the second face node for face pressures.
Type: integer
node3
The ID of the third face node for face pressures.
Type: integer
node4
The ID of the fourth face node for face pressures.
Only available if facetype is 4.
Type: integer
pressuretype
The type of pressure.
  • 0 - pressure on face
  • 1 - traction on face
  • 2 - pressure on edge
  • 3 - traction on edge
Type: pointer
vector
The component of the unit vector. Valid for hm_getvalue query only.
Type: triple double
xscale
The x scale or time scale of the load curve when a curve has been used to define the load.
Type: double

The following data names are available for engineering loads:

compx
The dot product of the load vector projected on the global x axis.
Type: double
compy
The dot product of the load vector projected on the global y axis.
Type: double
compz
The dot product of the load vector projected on the global z axis.
Type: double
distribution_table_count
The number of rows of a non-uniform engineering load.
Type: unsigned integer
field
The field entity that stores the tabular load data.
Type: entity
location_unit_element
The elements for which the data is stored in the table for a non-uniform engineering load.
Type: entity array
location_unit_facet
The elements for which the data is stored in the table for a non-uniform engineering load.
Type: entity array
orient
The load orientation vector.
Type: triple double
orientx
The x component of the load orientation vector.
Type: double
orienty
The y component of the load orientation vector.
Type: double
orientz
The z component of the load orientation vector.
Type: double
resultant_magnitude
The resultant scalar component of the load vector in the global coordiante system.
Type: double

The following data names are available for Abaqus engineering loads:

boundary_region
The type of boundary region on which pressure is applied.
LAGRANGIAN - Apply the pressure to a Lagrangian boundary region (default)
SLIDING - Apply the pressure to a Sliding boundary region
EULERIAN - Apply the pressure to an Eulerian boundary region
Type: string
curveid
The amplitude curve that defines the variation of the load magnitude during the step.
Type: entity
cyclic_mode
The cyclic symmetry mode number of loads that are applied in the current steady-state dynamics procedure.
Type: integer
distribution
The distribution type:
0 - Uniform
1 - Non-uniform
Type: unsigned integer
dload_type
The distributed load type for DLOAD.
HP - Hydrostatic pressure
HPE - Hydrostatic external pressure
HPI - Hydrostatic internal pressure
P - Pressure
P1 - Line load
P2 - Line load
PE - Uniform external pressure
PENU - Nonuniform external pressure
PI - Uniform internal pressure
PINU - Nonuniform internal pressure
TRSHR - Shear surface traction
TRVEC - General surface traction
VBF - Viscous body force
Type: string
dsload_type
The distributed load type for DSLOAD.
HP - Hydrostatic pressure
P - Pressure
PNU - Nonuniform pressure
TRSHR - Shear surface traction
TRVEC - General surface traction
VP - Viscous pressure
Type: string
entity_select_option
Flag to select reference node set.
Type: Boolean
expanded_form_flag
Flag to export loads on elments.
Type: Boolean
magnitude
Reference load magnitude.
Type: double
matrix_generation
The mutually exclusive parameters for matrix generation and steady-state dynamics analyses.
REAL - Define the real (in-phase) part of the loading
IMAGINARY - Define the imaginary (out-of-phase) part of the loading
Type: string
os_ploadsf_z0
Z-coordinate of zero pressure level in three-dimensional or axisymmetric cases; Y-coordinate of zero pressure level in two-dimensional cases.
Type: double
os_ploadsf_z1
Z-coordinate of the point at which the pressure is defined in three-dimensional or axisymmetric cases; Y-coordinate of the point at which the pressure is defined in two-dimensional cases.
Type: double
pipe_diameter
The effective inner or outer diameter.
Type: double
ref_node
The reference node ID.
Type: entity
ref_set
The node set containing the reference node.
Type: entity
vector
The traction vector direction.
Type: triple double

The following data names are available for ADVC engineering loads:

displayname
The text for the title entry.
Type: string
distribution
The distribution type:
0 - Uniform
1 - Non-uniform
Type: unsigned integer
expanded_form_flag
Flag to export loads on nodes.
Type: Boolean
keyword_name
Flag to specify if the title entry is enabled.
Type: Boolean
load_step_id
The ID of the referred loadstep.
Type: entity
magnitude
The scale factor (default 1.0).
Type: double
prev_bc
Flag to hold previously applied boundary conditions.
Type: Boolean
vector
The direction of the force vector. At lesat one of the vector components must be non-zero.
Type: triple double

The following data names are available for ADVC engineering loads:

displayname
The text for the title entry.
Type: string
distribution
The distribution type:
0 - Uniform
1 - Non-uniform
Type: unsigned integer
expanded_form_flag
Flag to export loads on nodes.
Type: Boolean
keyword_name
Flag to specify if the title entry is enabled.
Type: Boolean
load_step_id
The ID of the referred loadstep.
Type: entity
magnitude
The scale factor (default 1.0).
Type: double
prev_bc
Flag to hold previously applied boundary conditions.
Type: Boolean
reference_position
Specifies whether the initial shape or deformed shape should be considered for boundary conditions. Valid values are:
Deformation – Boundary conditions are applied on the deformed shape
Initial – Boundary conditions are applied on the initial shape
Type: string

The following data names are available for LS-DYNA engineering loads:

activation_time
The arrival or birth time of pressure (default 0.0).
Type: double
beam_axial_dir
The direction of the applied load.
1 – Parallel to the r-axis of beam
2 – Parallel to the s-axis of beam
3 – Parallel to the t-axis of beam
Type: integer
box_region_def
The box ID.
Type: entity
curveid
The load curve ID.
Type: entity
displayname
The description of the loading.
Type: string
element_inclusion_option
Flag for applying pressure to elements inside or outside of projected curve.
0 – Elements with center failing inside the projected curve are considered (default).
1 - Elements with center falling outside the projected curve are considered.
Type: integer
keyword_name
Flag that activates ID option.
Type: Boolean
magnitude
The load curve scale factor (default 1.0).
Type: double
masking_fn_projection_vec
The vector ID used to project the masking curve onto the surface of the part.
Type: entity
motion_vec_dir
The vector ID normal to the surface on which the applied pressure acts.
Type: entity
pressure_lower_limit
The threshold point where pressure loads will be discontinued for LOAD_MASK (type=4) (default 0.0).
Type: double
pressure_mask_fn
The curve ID defining the mask.
Type: entity
rgd_bdy_vel_opt_overwrite
The load curve ID option for LOAD_SEGMENT (type=1).
1 – Select curve entity via curveid.
-1 – Use Brode function to determine the pressure for the segments.
-2 – Use empirical airblast function to determine the pressure for the segments.
Type: integer
shell_part
The part ID which must consist three-dimensional shell elements.
Type: entity
timestep_offset
Number of time steps between updating the list of active elements (default 200).
Type: integer

The following data names are available for Nastran engineering loads:

nas_pload4_ldir
The direction of the line load. Valid values are X, Y, X, NORM (default) and TANG.
Type: string
nas_pload4_sorl
LINE - Consistent edge loads acting on the edges of the element
SURF - Surface load acting on the surface of the element (default)
Type: string

The following data names are available for OptiStruct and Nastran engineering loads:

beam_load_distribution_flag
For PLOAD1, determines whether the load distribution is concentrated (0) or distributed (1).
Type: Boolean
distribution
The distribution type:
0 - Uniform
1 - Non-uniform
Type: unsigned integer
inputsystem
The ID fo the coordinate system.
Type: entity
magnitude
For PLOAD, the pressure.
For PLOAD1, the load factors at positions x1 and x2.
For PLOAD2, the pressure value.
For PLOAD4, the load per unit surface area (pressure) at the corners of the element face.
For PLOADSF, the pressure for normal, directional and shear. For hydrostatic, this is the pressure measured at os_ploadsf_z1.
For PLOADX1, the surface traction at grid point GA.
For PRSPENE, the pressure pool magnitude.
Type: double
os_pload_type
The load type:
FX, FY or FZ - The force in the given direction of the basic coordinate system.
FXE, FYE or FZE - The force in the given direction of the element's coordinate system.
MX, MY or MZ - The moment in the given direction of the basic coordinate system.
MXE, MYE or MZE - The moment in the given direction of the element's coordinate system.
Type: string
os_scale
The scale factor for x1 and x2 for PLOAD1:
FR - Fractional
FRPR - Fractional projected
LE - Length
LEPR - Length projected
Type: string
os_theta
The angle between the surface traction and inward normal to the line segment.
Type: double
p2
For PLOAD1, the load factors at positions x1 and x2.
For PLOAD4, the load per unit surface area (pressure) at the corners of the element face.
For PLOADX1, the surface traction at grid point GA.
Type: double
p3
For PLOAD4, the load per unit surface area (pressure) at the corners of the element face.
Type: double
p4
For PLOAD4, the load per unit surface area (pressure) at the corners of the element face.
Type: double
vector
The vector components in the coordinate system CID. Used to define the direction (but not magnitude) of the load.
Type: triple double
x1
The distances along the CBAR or CBEAM element axis from end A.
Type: double
x2
The distances along the CBAR or CBEAM element axis from end A.
Type: double

The following data names are available for OptiStruct engineering loads:

activation_time
For PRSPENE, time period over which the pressures at newly penetrated areas are to be ramped up to the current level of a regular load (default 0.001).
Type: double
contact_interface
The identification number of the contact interface.
Type: entity
entity_select_option
Flag which indicates that the MGi/MSETi field is identified as a set or a grid point.
Type: Boolean
expanded_form_flag
Flag to export loads on nodes.
Type: Boolean
main_orient
The orientation of the pressure applied on the main surface.
REVNORM - Contact force is oriented opposite to the default vector normal to the main surface (default).
NORM - Contact force is oriented along the vector normal to the main surface
Type: string
main_set
The identification of a SET of grids initially exposed to fluid on the main surface.
Type: entity
os_g1
For PRSPENE, the identification number of a grid initially exposed to fluid on the secondary surface.
Type: entity
os_g2
For PRSPENE, the identification number of a grid initially exposed to fluid on the main surface.
Type: entity
os_ploadsf_z0
The height of the surface of the pressure column measured along the z-axis of the user-specified system.
Type: double
os_ploadsf_z1
The depth at which the pressure of the water column P1 is measured along the z-axis of the user-specified system.
Type: double
pressure_threshold
The critical value of the normal contact pressure below which the fluid can penetrate through (default 0.0).
Type: double
secondary_ent_flag
Flag which indicates that the SGi/SSETi field is identified as a set or a grid point.
Type: Boolean
secondary_orient
The orientation of the pressure applied on the secondary surface.
REVNORM - Contact force is oriented opposite to the default vector normal to the secondary surface (default).
NORM - Contact force is oriented along the vector normal to the secondary surface.
Type: string
secondary_set
The identification of a SET of grids initially exposed to fluid on the secondary surface.
Type: entity

The following data names are available for Radioss engineering loads:

curveid
For DFS/LASER, the ID of the curve defining the laser intensity time function number.
For LOAD/PFLUID, the ID of the curve defining the hydrostatic pressure as a function of the fluid column height above the structural surface.
For PLOAD, the ID of the curve defining the time function identifier.
Type: entity
displayname
The text for the title entry.
Type: string
inputsystem
The frame identifier for the vertical (gravitational) direction of the water column above the structural surface.
Type: entity
magnitude
The ordinate scale factor (default 1.0).
For DFS/DETCORD, it is the detonation velocity.
For DFS/LASER, it is the laser intensity scale factor.
Type: double
rad_afterflow
The afterflow computation.
1 - No
2 - Yes (default)
Type: integer
rad_alpha
The maximum pressure constant.
Type: double
rad_alpha_theta
The pressure decay time constant.
Type: double
rad_ascalex_pc
The abscissa scale factor for rad_fct_pc (default 1.0).
Type: double
rad_ascalex_vel
The abscissa scale factor for rad_fct_vel (default 1.0).
Type: double
rad_det_fct_id_target
The target absorption temperature function number.
Type: entity
rad_det_hn
The plasma parameter.
Type: double
rad_det_iopt
The optional formulation flag:
0 - Set to 3
1 - Piecewise linear using VDET
2 - Instantaneous detination
3 - Default. Ignition from the first node and propagation along the neutral fiber computed with Spline interpoloation. Using JWL DCJ parameter or VDET if defined.
Type: integer
rad_det_iopt_legacy
The formulation flag for 2019 and earlier:
0 - Set to 3
1 - Piecewise linear using VDET
2 - Instantaneous detination
3 - Default. Ignition from the first node and propagation along the neutral fiber computed with Spline interpoloation. Using JWL DCJ parameter or VDET if defined.
Type: integer
rad_det_k0
The inverse Bremsstrahlung coefficient k0.
Type: double
rad_det_ks
The compliment absorption in vapor.
Type: double
rad_det_locationA
The coordinates of point A (default 0.0).
Type: triple double
rad_det_locationB
The coordinates of point B (default 0.0).
Type: triple double
rad_det_materialid
The explosive identifier (default 0). All JWL material laws are included.
Type: entity
rad_det_nc
The target element number.
Type: entity
rad_det_node1
The ID of the node defining point A coordinates.
Type: entity
rad_det_node2
The ID of the node defining point B coordinates.
Type: entity
rad_det_rd
The inverse Bremsstrahlung coefficient.
Type: double
rad_det_s_target
The target absorption scale factor.
Type: double
rad_det_time
The detonation time (default 0.0).
Type: double
rad_det_vcp
The enthalpy of vaporization.
Type: double
rad_det_xa
The point A on a free surface.
Type: triple double
rad_det_xc
The explosive charge point.
Type: triple double
rad_det_xs
The standoff point.
Type: triple double
rad_dir
The vertical (gravitational) direction of the water colum above the structural surface. Valid values are X, Y and Z.
Type: string
rad_dir_vel
The direction of fluid velocity. Valid values are X, Y and Z.
Type: string
rad_ebcs_c
The speed of sound (default 0.0).
Type: double
rad_ebcs_fscale_en
The energy scale factor (default 0.0).
Type: double
rad_ebcs_fscale_pr
The pressure scale factor (default 0.0).
Type: double
rad_ebcs_fscale_rho
The density scale factor (default 0.0).
Type: double
rad_ebcs_lc
The characteristic length (default 0.0).
Type: double
rad_ebcs_r1
The linear resistance (default 0.0).
Type: double
rad_ebcs_r2
The quadratic resistance (default 0.0).
Type: double
rad_ebcs_rho
The initial density (default 0.0).
Type: double
rad_exp_data
The experimental data flag.
1 - TM5-1300 Free Air, Spherical charge of TNT (default)
2 - TM5-1300 Ground Reflection, Hemispherical charge of TNT
Type: integer
rad_fct_en
The function identifier for energy.
Type: entity
rad_fct_idp
The incident pressure function identifier.
Type: entity
rad_fct_pc
The ID of the curve defining the hydrodynamic drag coefficient as a function of time.
Type: entity
rad_fct_pr
The function identifier for pressure.
Type: entity
rad_fct_rho
The function identifier for density.
Type: entity
rad_fct_vel
The ID of the curve defining the fluid velocity as a function of time.
Type: entity
rad_frameid_vel
The frame identifier for the fluid velocity direction.
Type: entity
rad_freesurf
The free surface flag.
1 - No (default)
2 - Yes
Type: integer
rad_fscalep
The ordinate (pressure) scale factor for fct_IDP.
Type: double
rad_fscaley_pc
The ordinate scale factor for rad_fct_pc (default 1.0).
Type: double
rad_fscale_vel
The ordinate scale factor for rad_fct_vel (default 1.0).
Type: double
rad_grav_id
The gravity card identifier used.
Type: entity
rad_iform
The BEM solution flag.
1 - Gauss integration (default)
2 - Analytical integration
Type: integer
rad_integr
The time integer flag.
1 - First order
2 - Second order (default)
Type: integer
rad_ipres
The pressure loading flag.
1 - Pressure computed as Pi(t) = Pm * e^ (-t/Theta).
2 - Input by function
Type: integer
rad_ipri
The printout flag level.
1 - Reduced printout (default)
2 - Full printout
Type: integer
rad_itshift
The time shift flag.
1 - No shift (default)
2 - Shift time to skip computation time from 0 to t * = inf (T_arrival).
Type: integer
rad_itype
The preloading type.
1 - Preload is a force (default)
2 - Preload is a stress
Type: integer
rad_iz
The scaled distance update with time.
1 - Scaled Distance is computed at initial time and does not change with time.
2 - Scaled Distance is updated at each time step (default).
Type: integer
rad_kform
The analysis flag.
1 - DAA1 formulation (default)
2 - High frequency
Type: integer
rad_ndt
The number of intervals for minimal time step (default 100).
Type: integer
rad_pmin
Pressure cutoff (default -10E30).
Type: double
rad_pref
The reference pressure on the reference surface.
Type: double
rad_sect_id
The section identifier to which preloading is applied.
Type: entity
rad_sensor_id
The ID of the sensor entity.
Type: entity
rad_surf_id
The free surface identifier.
Type: entity
rad_theta
The decay time.
Type: double
rad_wtnt
The equivalent TNT mass.
Type: double
xscale
The abscissa scale factor (default 1.0).
Type: double

Version History

2020 - New support for engineering loads. Added new data names beam_load_distribution_flag, compx, compy, compz, corner1, corner2, displayname, distribution, distribution_table_count, engineering_type, field, local_comp1, local_comp2, local_comp3, local_vector, local_vectorx, local_vectory, local_vectorz, location, location_unit_element, location_unit_facet, nas_pload4_ldir, nas_pload4_sorl, orient, orientx, orienty, orientz, os_pload_type, os_ploadsf_z0, os_ploadsf_z1, os_scale, os_theta, p2, p3, p4, rad_ascalex_pc, rad_ascalex_vel, rad_det_fct_id_target, rad_det_hn, rad_det_iopt, rad_det_iopt_legacy, rad_det_k0, rad_det_ks, rad_det_locationA, rad_det_locationB, rad_det_materialid, rad_det_nc, rad_det_node1, rad_det_node2, rad_det_rd, rad_det_s_target, rad_det_time, rad_det_vcp, rad_dir, rad_dir_vel, rad_ebcs_c, rad_ebcs_fscale_en, rad_ebcs_lc, rad_ebcs_fscale_pr, rad_ebcs_fscale_rho, rad_ebcs_r1, rad_ebcs_r2, rad_ebcs_rho, rad_ftc_en, rad_fct_pc, rad_ftc_pr, rad_ftc_rho, rad_fct_vel, rad_frameid_vel, rad_fscaley_pc, rad_fscaley_vel, rad_sensor_id, x1 and x2.

2020.1 - Added new data name solverkeyword.

2021 - Added new data names keyword_name, load_step_id, prev_bc and reference_position. New ADVC support.

2021.1 – Added new data names for LS-DYNA engineering loads: activation_time, beam_axial_dir, box_region_def, curveid, displayname, element_inclusion_option, keyword_name, magnitude, masking_fn_projection_vec, motion_vec_dir, pressure_lower_limit, pressure_mask_fn, rgd_bdy_vel_opt_overwrite, shell_part, and timestep_offset.

2021.1 - Added new data names moduleid, poolid, poolname, and solver_id.

2021.2 - Added new data names for Radioss engineering loads: rad_afterflow, rad_alpha, rad_alpha_theta, rad_det_xa, rad_det_xc, rad_det_xs, rad_exp_data, rad_fct_idp, rad_freesurf, rad_fscalep, rad_grav_id, rad_iform, rad_integr, rad_ipres, rad_ipri, rad_itshift, rad_itype, rad_iz, rad_kform, rad_ndt, rad_pmin, rad_pref, rad_sect_id, rad_surf_id, rad_theta, and rad_wtnt. Added new data names internalname and solvername.

2022.1 - Added new data names for OptiStruct engineering loads activation_time, contact_interface, entity_select_option, main_orient, main_set, os_g1, os_g2, pressure_threshold, secondary_ent_flag, secondary_orient, and secondary_set.

2022.2 - Added new data names for Abaqus engineering loads: boundary_region, cyclic_mode, dload_type, dsload_type, matrix_generation, pipe_diameter, ref_node, and ref_set.