PDF-PRC and ISO 10303 (aka STEP)

Yesterday’s announcement about PRC moving its way towards ISO certification generated a lot of excitement and some very good questions. Most notable were 1) Does the PRC format Adobe is releasing include the ‘exact geometry’ definition and 2) if so, does that inclusion of the exact geometry put PRC at odds with ISO 10303 (STEP)?
The short answers are ‘yes’ and ‘not really’. Read on to get the details…

The PRC format Adobe introduced in Acrobat 9 accommodates both precise B-rep and surface tessellation data as well as product structure, Product Manufacturing Information (PMI) and metadata. PDF was released to the ISO process prior to Acrobat 9, and as such the PDF ISO 32000:1 specification does not include the PRC format right now and technically speaking PRC is an Adobe proprietary extension to ISO 32000. We publish the PRC Specification on our website and anyone can read/write it using the spec. As noted in the announcement yesterday by AIIM, Adobe released PRC to ISO and it has been accepted for the standardization process. This will likely take about 2-3 years and become part of ISO 32000:2. The entire PRC format was released to AIIM/ISO, i.e., ‘Yes, the PRC ISO candidate does include topology and exact geometry’.
Which brings us to, “Doesn’t that mean PRC competes with STEP?”. We don’t see PRC replacing the need for STEP today, and if STEP continues to evolve to include other information like design construction history and parametric relationships, there will be even larger gaps between STEP and PRC in the future. As noted in the press release by AIIM, the PRC working group will be coordinating with the STEP ISO technical committee to ensure that there is conformance between the two specs where it makes sense. Given all that, we see very different use cases for PRC and STEP most notably around

  • Design re-use : STEP is more appropriate for pulling data into a CAD system and making modifications, and although there are now direct B-Rep modeling systems that enable using PRC this way, use of STEP will provide much higher fidelity.
  • Visualization : PRC targets this use case squarely while STEP ignores it.
  • Technical Publications like process planning, work instructions, repair operations : PRC is better for this we think as it is lighter weight and includes visualization information.
  • Interrogation of precise geometry for downstream processes : This is the one where there is likely be some overlap as CAM and CAE applications often only need/want the B-REP data and PMI. Today PRC meets these requirements as does STEP AP 203 E2.
  • Archival and Retrieval : here the two formats are complimentary due to the non-overlapping use cases above. We are actually seeing more and more companies archiving 3D PDF along with native CAD and STEP datasets.

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