Update ugrid conventions about schism

[josephzhang8]

Thx @veenstrajelmer. Did you do this for OLDIO or new scribed IO? For the latter we have UGRID part added, so we can easily add those changes.
@platipodium @water-e : can u please chime in? Thx,

[veenstrajelmer]

Thanks for your reply. I realized after the creation of this issue that it does not have enough context. At the moment i cannot answer your questions, but I will get back to you after a meeting tomorrow.

[veenstrajelmer]

Hi @josephzhang8. After meeting with @BenjaminJacob86 I realized I used scribedio schism output that was already partly processed. In the below function I have defined the preprocessing that is needed in order for our ugrid reader to read and visualize the raw schism scribedio output. This is a bit more than I communicated before, but I hope this provides useful information to enrich the schism output dataset.

import xarray as xr
import numpy as np
from netCDF4 import default_fillvals
import xugrid as xu # pip install xugrid, adds ugrid and grid accessors to xarray datasets

def preprocess_schism_scribedio(ds):
    """
    This preprocessing function describes the minimal changes that would have to be made 
    in the SCHISM output in order for it to be read via ugrid conventions with xugrid.
    It is probably not a complete overview.
    """
    # set varnames
    gridname = "SCHISM_hgrid"
    fnc_varn = f"{gridname}_face_nodes"
    enc_varn = f"{gridname}_edge_nodes"
    node_x = f"{gridname}_node_x"
    node_y = f"{gridname}_node_y"
    
    # set topology attributes to empty variable
    topo_attrs = {"cf_role": "mesh_topology",
                 "topology_dimension": 2, # has to be int, not str
                 "node_coordinates": f"{node_x} {node_y}",
                 "face_node_connectivity": fnc_varn,
                 "edge_node_connectivity": enc_varn,
                 }
    ds[gridname] = xr.DataArray(np.array(default_fillvals["i4"], dtype=np.int32), attrs=topo_attrs)
    
    # assign necessary attributes to connectivity variables
    fnc_attrs = {"_FillValue":-1, "start_index":1}
    ds[fnc_varn] = ds[fnc_varn].assign_attrs(fnc_attrs)
    ds[enc_varn] = ds[enc_varn].assign_attrs(fnc_attrs)
    
    # set node_x/node_y as coordinate variables instead of data_vars
    ds = ds.set_coords([node_x,node_y])
    
    # to prevent xugrid UserWarning, but this is hardcoded and it should be different for lat/lon models.
    # "UserWarning: No standard_name of ('projection_x_coordinate', 'longitude', 'projection_y_coordinate', 'latitude') in
    # ['SCHISM_hgrid_node_x', 'SCHISM_hgrid_node_y']. Using SCHISM_hgrid_node_x and SCHISM_hgrid_node_y as projected x and y coordinates."
    projected = True
    if projected:
        ds[node_x] = ds[node_x].assign_attrs({"standard_name":"projection_x_coordinate"})
        ds[node_y] = ds[node_y].assign_attrs({"standard_name":"projection_y_coordinate"})
    else:
        ds[node_x] = ds[node_x].assign_attrs({"standard_name":"longitude"})
        ds[node_y] = ds[node_y].assign_attrs({"standard_name":"latitude"})
    
    # add variable with coordinate system, optional but convenient for loading into QGIS and other tools
    # not yet properly read/updated by xugrid: https://github.com/Deltares/xugrid/issues/42
    if projected:
        grid_mapping_name = 'Unknown projected'
        crs_varn = 'projected_coordinate_system'
        crs_num = 25832 #UTM Zone 32N from communication with BJ
    else:
        grid_mapping_name = 'latitude_longitude'
        crs_varn = 'wgs84'
        crs_num = 4326
    crs_str = f'EPSG:{crs_num}'
    crs_attrs = {'epsg': crs_num, # epsg or EPSG_code are required for correct interpretation by QGIS
                  'EPSG_code': crs_str, # epsg or EPSG_code are required for correct interpretation by QGIS
                  'grid_mapping_name': grid_mapping_name,
                  }
    ds[crs_varn] = xr.DataArray(np.array(default_fillvals['i4'],dtype=int),dims=(),attrs=crs_attrs)
    
    # mesh attribute is required for d-ecoimpact
    # valueable other attrs are "location" (node/face/edge), 
    # "standard_name", "long_name", "units", "grid_mapping"
    for varn in ds.data_vars:
        ds[varn] = ds[varn].assign_attrs({'mesh': gridname})
    
    # time requires "units" attribute to be converted by xarray and other tools
    # refdate taken from params.nml
    ds['time'] = ds['time'].assign_attrs({"units":"seconds since 2017-01-02 00:00:00"})
    ds = xr.decode_cf(ds)
    
    #TODO: set _FillValue attribute for data_vars, test dataset did not seem to have nans
    
    return ds

file_nc_pat = r"c:\Users\veenstra\Downloads\example\1_raw_outputs\*_1.nc"

# open the file with xarray, add ugrid conventions with preprocessing function and convert to UgridDataset
# in case of a pre-merged file this oneliner also works: `uds = xu.open_dataset(ds, preprocess=preprocess_schism_scribedio)`
# that would also work if the topology variables would be present in all datasets
ds = xr.open_mfdataset(file_nc_pat)
ds = preprocess_schism_scribedio(ds)
uds = xu.UgridDataset(ds)

# test with a ugrid plot to show the salinity variable was properly connected to the ugrid topology
uds.salinity.isel(time=-1, nSCHISM_vgrid_layers=0).ugrid.plot()

It mostly comes down to creating an empty variable containing the mesh topology and adding some attributes. In the comments some other suggestions or the reasoning behind it is given.

Other suggestions would be:

• Currently the salinity file can only be processed properly by using information from the 2d file. Instead add topology data to all separate datasets, so these files are all self-contained.
• add attributes to all variables so it is clear what it contains
• include global attributes to the dataset with information like the schism version

[platipodium]

Thanks @veenstrajelmer for following up on this. We @josephzhang8 should in any case add the relevant (empty variable) metadata to any output.

@veenstrajelmer Could you attach a netcdf -h header dump of both the original and your desired version of the test file you were using?

We had a discussion previously on your suggestion

Currently the salinity file can only be processed properly by using information from the 2d file. Instead add topology data to all separate datasets, so these files are all self-contained.

Our opinions differ on this issue, as this would require more storage space. @josephzhang8 would you reconsider?

[josephzhang8]

Regarding the comments:

1. Currently the salinity file can only be processed properly by using information from the 2d file. Instead add topology data to all separate datasets, so these files are all self-contained.

Adding this info in all 3D outputs would increase the size by a non-trivial amount for large meshes (e.g. STOFS3D), so it was decided to leave it out. Is there a way to add a note in 3D outputs to point to 2D?

3. add attributes to all variables so it is clear what it contains

In principle this is doable, but since we support A LOT OF outputs, we decided instead to make the output file names as explicit as possible More importantly, this save some communication cost.

[veenstrajelmer]

Thanks for the responses.

I recommend to not add the topology variable if the actual topology is not added, it will result in a corrupt file according to the ugrid conventions since the variables where the topology attributes point to are not present. The current setup is in that case better, so I would recommend to leave that as is.

However, enriching the dataset with the topology variables inside is still beneficial. I do not have netcdf/ncdump installed outside of python, but used this python workaround. I have pasted the entire output of both files below.

Original schism scribedio output (out2d_1.nc):

NetCDF Global Attributes:
NetCDF dimension information:
	Name: nSCHISM_hgrid_node
		size: 515582
		WARNING: nSCHISM_hgrid_node does not contain variable attributes
	Name: nSCHISM_hgrid_face
		size: 1019883
		WARNING: nSCHISM_hgrid_face does not contain variable attributes
	Name: nSCHISM_hgrid_edge
		size: 1535511
		WARNING: nSCHISM_hgrid_edge does not contain variable attributes
	Name: nMaxSCHISM_hgrid_face_nodes
		size: 4
		WARNING: nMaxSCHISM_hgrid_face_nodes does not contain variable attributes
	Name: nSCHISM_vgrid_layers
		size: 21
		WARNING: nSCHISM_vgrid_layers does not contain variable attributes
	Name: one
		size: 1
		WARNING: one does not contain variable attributes
	Name: two
		size: 2
		WARNING: two does not contain variable attributes
	Name: time
		size: 24
		type: dtype('float64')
		i23d: 0
NetCDF variable information:
	Name: minimum_depth
		dimensions: ('one',)
		size: 1
		type: dtype('float64')
	Name: SCHISM_hgrid_node_x
		dimensions: ('nSCHISM_hgrid_node',)
		size: 515582
		type: dtype('float64')
	Name: SCHISM_hgrid_node_y
		dimensions: ('nSCHISM_hgrid_node',)
		size: 515582
		type: dtype('float64')
	Name: depth
		dimensions: ('nSCHISM_hgrid_node',)
		size: 515582
		type: dtype('float32')
	Name: bottom_index_node
		dimensions: ('nSCHISM_hgrid_node',)
		size: 515582
		type: dtype('int32')
	Name: SCHISM_hgrid_face_nodes
		dimensions: ('nSCHISM_hgrid_face', 'nMaxSCHISM_hgrid_face_nodes')
		size: 4079532
		type: dtype('int32')
	Name: SCHISM_hgrid_edge_nodes
		dimensions: ('nSCHISM_hgrid_edge', 'two')
		size: 3071022
		type: dtype('int32')
	Name: dryFlagNode
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: elevation
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: bottomStressX
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: bottomStressY
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: windSpeedX
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: windSpeedY
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: depthAverageVelX
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: depthAverageVelY
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sigWaveHeight
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: meanWavePeriod
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: zeroDowncrossPeriod
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: meanDirSpreading
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: peakPeriod
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: dominantDirection
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: peakSpreading
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: orbitalVelocity
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: rmsOrbitalVelocity
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: bottomExcursionPerio
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: frictionalVelocity
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: rougnessLength
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: waveEnergyDirX
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: waveEnergyDirY
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sedBedloadX_1
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sedBedloadY_1
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sedBedloadX_2
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sedBedloadY_2
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sedBedloadX_3
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sedBedloadY_3
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sedBedloadX_4
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sedBedloadY_4
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sedBedloadX_5
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sedBedloadY_5
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sedBedloadX_6
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sedBedloadY_6
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sedBedloadX_7
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sedBedloadY_7
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sedBedloadX_8
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sedBedloadY_8
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sedBedFraction_1
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sedBedFraction_2
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sedBedFraction_3
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sedBedFraction_4
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sedBedFraction_5
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sedBedFraction_6
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sedBedFraction_7
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: sedBedFraction_8
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		i23d: 1
	Name: dryFlagElement
		dimensions: ('time', 'nSCHISM_hgrid_face')
		size: 24477192
		type: dtype('float32')
		i23d: 4
	Name: dryFlagSide
		dimensions: ('time', 'nSCHISM_hgrid_edge')
		size: 36852264
		type: dtype('float32')
		i23d: 7

Enriched file:

NetCDF Global Attributes:
	Conventions: 'CF-1.9 UGRID-1.0'
NetCDF dimension information:
	Name: nSCHISM_hgrid_face
		size: 1019883
		type: dtype('int64')
	Name: nMaxSCHISM_hgrid_face_nodes
		size: 4
		WARNING: nMaxSCHISM_hgrid_face_nodes does not contain variable attributes
	Name: nSCHISM_hgrid_edge
		size: 1535511
		type: dtype('int64')
	Name: two
		size: 2
		WARNING: two does not contain variable attributes
	Name: nSCHISM_hgrid_node
		size: 515582
		type: dtype('int64')
	Name: time
		size: 24
		type: dtype('float64')
		_FillValue: nan
		i23d: 0
		units: 'seconds since 2017-01-02'
		calendar: 'proleptic_gregorian'
	Name: one
		size: 1
		WARNING: one does not contain variable attributes
NetCDF variable information:
	Name: SCHISM_hgrid
		dimensions: ()
		size: 1
		type: dtype('int32')
		cf_role: 'mesh_topology'
		long_name: 'Topology data of 2D mesh'
		topology_dimension: 2
		node_dimension: 'nSCHISM_hgrid_node'
		edge_dimension: 'nSCHISM_hgrid_edge'
		face_dimension: 'nSCHISM_hgrid_face'
		max_face_nodes_dimension: 'SCHISM_hgrid_nMax_face_nodes'
		edge_node_connectivity: 'SCHISM_hgrid_edge_nodes'
		face_node_connectivity: 'SCHISM_hgrid_face_nodes'
		node_coordinates: 'SCHISM_hgrid_node_x SCHISM_hgrid_node_y'
		name: 'SCHISM_hgrid'
	Name: SCHISM_hgrid_face_nodes
		dimensions: ('nSCHISM_hgrid_face', 'nMaxSCHISM_hgrid_face_nodes')
		size: 4079532
		type: dtype('int32')
		_FillValue: -1
		start_index: 1
		mesh: 'SCHISM_hgrid'
	Name: SCHISM_hgrid_edge_nodes
		dimensions: ('nSCHISM_hgrid_edge', 'two')
		size: 3071022
		type: dtype('int32')
		_FillValue: -1
		start_index: 1
		mesh: 'SCHISM_hgrid'
	Name: SCHISM_hgrid_node_x
		dimensions: ('nSCHISM_hgrid_node',)
		size: 515582
		type: dtype('float64')
		_FillValue: nan
		standard_name: 'projection_x_coordinate'
	Name: SCHISM_hgrid_node_y
		dimensions: ('nSCHISM_hgrid_node',)
		size: 515582
		type: dtype('float64')
		_FillValue: nan
		standard_name: 'projection_y_coordinate'
	Name: minimum_depth
		dimensions: ('one',)
		size: 1
		type: dtype('float64')
		_FillValue: nan
		mesh: 'SCHISM_hgrid'
	Name: depth
		dimensions: ('nSCHISM_hgrid_node',)
		size: 515582
		type: dtype('float32')
		_FillValue: nan
		mesh: 'SCHISM_hgrid'
		coordinates: 'SCHISM_hgrid_node_x SCHISM_hgrid_node_y'
	Name: bottom_index_node
		dimensions: ('nSCHISM_hgrid_node',)
		size: 515582
		type: dtype('int32')
		mesh: 'SCHISM_hgrid'
		coordinates: 'SCHISM_hgrid_node_x SCHISM_hgrid_node_y'
	Name: dryFlagNode
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		_FillValue: nan
		i23d: 1
		mesh: 'SCHISM_hgrid'
		coordinates: 'SCHISM_hgrid_node_x SCHISM_hgrid_node_y'
	Name: elevation
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		_FillValue: nan
		i23d: 1
		mesh: 'SCHISM_hgrid'
		coordinates: 'SCHISM_hgrid_node_x SCHISM_hgrid_node_y'
	Name: bottomStressX
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		_FillValue: nan
		i23d: 1
		mesh: 'SCHISM_hgrid'
		coordinates: 'SCHISM_hgrid_node_x SCHISM_hgrid_node_y'
	Name: bottomStressY
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		_FillValue: nan
		i23d: 1
		mesh: 'SCHISM_hgrid'
		coordinates: 'SCHISM_hgrid_node_x SCHISM_hgrid_node_y'
	Name: windSpeedX
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		_FillValue: nan
		i23d: 1
		mesh: 'SCHISM_hgrid'
		coordinates: 'SCHISM_hgrid_node_x SCHISM_hgrid_node_y'
	Name: windSpeedY
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		_FillValue: nan
		i23d: 1
		mesh: 'SCHISM_hgrid'
		coordinates: 'SCHISM_hgrid_node_x SCHISM_hgrid_node_y'
	Name: depthAverageVelX
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		_FillValue: nan
		i23d: 1
		mesh: 'SCHISM_hgrid'
		coordinates: 'SCHISM_hgrid_node_x SCHISM_hgrid_node_y'
	Name: depthAverageVelY
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		_FillValue: nan
		i23d: 1
		mesh: 'SCHISM_hgrid'
		coordinates: 'SCHISM_hgrid_node_x SCHISM_hgrid_node_y'
	Name: sigWaveHeight
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		_FillValue: nan
		i23d: 1
		mesh: 'SCHISM_hgrid'
		coordinates: 'SCHISM_hgrid_node_x SCHISM_hgrid_node_y'
	Name: meanWavePeriod
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		_FillValue: nan
		i23d: 1
		mesh: 'SCHISM_hgrid'
		coordinates: 'SCHISM_hgrid_node_x SCHISM_hgrid_node_y'
	Name: zeroDowncrossPeriod
		dimensions: ('time', 'nSCHISM_hgrid_node')
		size: 12373968
		type: dtype('float32')
		_FillValue: nan
		i23d: 1
		mesh: 'SCHISM_hgrid'
		coordinates: 'SCHISM_hgrid_node_x SCHISM_hgrid_node_y'
	Name: meanDirSpreading
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[josephzhang8]

Yes I believe there are very simple tools to add this info, e.g. NCL/NCO etc.

[veenstrajelmer]

Sure, but I guess the output is comparable to what I send. Is there any additional information you need from my side? Do you think it would be a valuable update to add the ugrid metadata to schism output?

[josephzhang8]

I'll let @platipodium add the missing meta in SCHISM code. As I explained, we need to be frugal about adding mesh info in all outputs.

[veenstrajelmer]

Yes, understandable, I am not sure if my response was clear. But I think in that case the current setup is good. Plain 3D variables in separate files, that are dependent on the out2d file in the same folder that contains all the connectivity/coordinates (and in the future also the topology metadata). Anyway, happy to be able to contribute something.

[josephzhang8]

Great; thx @veenstrajelmer

@platipodium : can u plz add the missing metadata. Thx