# Clarification about temporal MB or PDC VTKHDF datasets
**URL:** https://discourse.vtk.org/t/clarification-about-temporal-mb-or-pdc-vtkhdf-datasets/16305
**Category:** Development
**Tags:** file-formats
**Created:** [February 25, 2026, 7:03pm UTC](https://discourse.vtk.org/t/clarification-about-temporal-mb-or-pdc-vtkhdf-datasets/16305 "2026-02-25T19:03:03Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@nncarlson](https://discourse.vtk.org/u/nncarlson)
#### Post date: [February 25, 2026, 7:03pm UTC](https://discourse.vtk.org/t/clarification-about-temporal-mb-or-pdc-vtkhdf-datasets/16305/1 "2026-02-25T19:03:03Z")
I had been operating under the assumption that in a MB or PDC VTKHDF dataset some blocks could be temporal and others not (without a `Steps` group). However, I’m getting import errors (with MB) from paraview. Is it required that all blocks have a populated `Steps` group or none do? I’m already aware that there must be a common time line among all (temporal) blocks.
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### Author:  [@nncarlson](https://discourse.vtk.org/u/nncarlson)
#### Post date: [February 25, 2026, 7:49pm UTC](https://discourse.vtk.org/t/clarification-about-temporal-mb-or-pdc-vtkhdf-datasets/16305/2 "2026-02-25T19:49:08Z")
Actually, I read this now in the 2.6 spec:”Not all blocks need to define a `Steps` group, if a block doesn’t have it, a temporal data array will be considered to be a “partial” array.” I’m getting this with MB in both 6.0 and 6.1-RC1. And with PDC too. I’ll submit an issue. The error is “Cannot open Steps/PartOffsets”
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### Author:  [@mwestphal](https://discourse.vtk.org/u/mwestphal)
#### Post date: [February 26, 2026, 8:38am UTC](https://discourse.vtk.org/t/clarification-about-temporal-mb-or-pdc-vtkhdf-datasets/16305/3 "2026-02-26T08:38:01Z")
@Louis_Gombert @lgivord
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### Author:  [@lgivord](https://discourse.vtk.org/u/lgivord)
#### Post date: [February 26, 2026, 9:15am UTC](https://discourse.vtk.org/t/clarification-about-temporal-mb-or-pdc-vtkhdf-datasets/16305/4 "2026-02-26T09:15:59Z")
That’s my fault what I write in the spec isn’t what we test… thanks for the issue : [https://gitlab.kitware.com/vtk/vtk/-/issues/19963](https://gitlab.kitware.com/vtk/vtk/-/issues/19963)
For now, indeed each block need to define the `Step` group, I’ll see what I can do for that and I’ll let you know