Author: Jennifer Herron
Semantic PMI is used in commercial and government industries to describe the annotations added to a 3D model. These annotations include information about the product design and the manufacturing processes. Hence, the acronym PMI which stands for Product and Manufacturing Information.
However, I have a few problems with the words traditionally used to describe what we (the industry) want.
- The word semantic is not a good word to describe what we need from connected 3D data. Merriam-Webster includes 2 definitions for semantic. They are 1: of or relating to meaning in language and 2: of or relating to semantics. Semantics is defined as: the study of meanings. Because this doesn’t really describe what we want from digital 3D data, I’d rather drop this word and explain what we want more simply.
- Instead of PMI, we suggest Annotation because it describes information added to the product definition to explain the design intent beyond the shape of the part. The annotations describing dimensions, tolerances, and notes include information intended for machine readability and improved human readability and interpretation. Annotations capture design intent beyond the shape information. The shape and annotation data is called MBD. While I agree with the ASME Y14.47 definition of Annotation, at Action Engineering, we go a step further to define Annotation as: A data element displayed in the 3D Data which includes information about the product, such as dimension, tolerance, or notes, and is associated with a particular feature in the model.
Given these word interpretation challenges, and it is not “just a semantic argument” instead of Semantic PMI, I prefer: annotations digitally associated with the features they represent. Wordier but more straightforward.
The other challenge with how we (the industry) have traditionally defined PMI is that it conflates design, or product definition, with manufacturing definition. Drawings have been the one-stop shop for everything about the product. The document-based medium includes design and manufacturing information layered together. One-stop shopping, but very difficult to interpret and often wrong. The design requirements are incorrectly defined because plus-minus dimensions are used rather than functional geometric tolerancing.
However, 3D Data with digitally associated annotations allows for displaying different information for each role while retaining traceability to the authoritative source. Today, this is feasible, but a human must customize and remaster the information shown. Using 3D Data methods automates the role-based display of information, thereby reducing the cognitive load on the human reader. Automated redaction of 3D Data is also feasible, given the annotations are all machine-readable. Anything authored as drawings run the risk of disconnection from the source authority. With 3D Data, organizations can define what information is published to a specific user, such that they see the information they need for their job and nothing else.
I expect and want the product definition, manufacturing fabrication instructions, and quality results to be connected but displayed separately, depending on the product’s lifecycle and user role.
I propose moving away from the term Semantic PMI and towards an Annotation definition that better describes how we want to do business in the future.
Learn how to apply Semantic PMI, or Annotations, in compliance with ASME Y14.5-2018 in SOLIDWORKS, Creo, and SIEMENS NX in our OSCAR “How To” courses.
References:
- The National Institute for Standards and Technology (NIST) reveals interesting data from their project “PMI Validation and Conformance Testing for Model-based Engineering”.
- In the NIST presentation for the Systems Engineering Conference in Washington DC (SEDC) on April 3, 2014, the concept of SEMANTIC PMI is introduced and researched. This work complies with both ASME Y14.5-1994 – Dimensioning and Tolerancing, and ASME Y14.41-2003 – Digital Product Data Definition Practices standards.