computer science

Model-based definition

Model-based definition is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Model-based definition rather than just read about it. In short: Model-based definition (MBD), sometimes called digital product definition (DPD), is the practice of using 3D models (such as solid models, 3D PMI and associated metadata) within 3D CAD software to define (provide specifications for) individual components and product assemblies. The types of information included are geometric dimensioning and tolerancing (GD&T), component level materials, assembly level bills of mate…

Key takeaways

Model-based definition belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Model-based definition to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Model-based definition from memory before moving on to harder problems.

Reference excerpt

Model-based definition (MBD), sometimes called digital product definition (DPD), is the practice of using 3D models (such as solid models, 3D PMI and associated metadata) within 3D CAD software to define (provide specifications for) individual components and product assemblies. The types of information included are geometric dimensioning and tolerancing (GD&T), component level materials, assembly level bills of materials, engineering configurations, design intent, etc. By contrast, other methodologies have historically required accompanying use of 2D engineering drawings to provide such details.

Use of the 3D digital data set Modern 3D CAD applications allow for the insertion of engineering information such as dimensions, GD&T, notes and other product details within the 3D digital data set for components and assemblies. MBD uses such capabilities to establish the 3D digital data set as the source of these specifications and design authority for the product. The 3D digital data set may contain enough information to manufacture and inspect product without the need for engineering drawings. Engineering drawings have traditionally contained such information. In many instances, use of some information from 3D digital data set (e.g., the solid model) allows for rapid prototyping of product via various processes, such as 3D printing. A manufacturer may be able to feed 3D digital data directly to manufacturing devices such as CNC machines to manufacture the final product.

Limited Dimension Drawing Limited Dimension Drawing (LDD), sometimes Reduced Dimension Drawing, are 2D drawings that only contain critical information, noting that all missing information is to be taken from an associated 3D model. For companies in transition to MBD from traditional 2D documentation a Limited Dimension Drawing allows for referencing 3D geometry while retaining a 2D drawing that can be used in existing corporate procedures. Only limited information is placed on the 2D drawing and then a note is placed to notify manufactures they must build off the 3D model for any dimensions not found on the 2D drawing.

Standardization In 2003, ASME published the ASME Y14.41 Digital Product Definition Data Practices, which was revised in 2012 and again in 2019. The standard provides for the use of many MBD aspects, such as GD&T display and other annotation behaviors within 3D modelling environment. ISO 16792 standardizes MBD within the ISO standards, sharing many similarities with the ASME standard. Other standards, such as ISO 1101 and of AS9100 also make use of MBD. In 2013, the United States Department of Defense released MIL-STD-31000 Revision A to codify the use of MBD as a requirement for technical data packages (TDP).

See also ASME Y14.41 CAD standards

References

External links Model-centric Design, Design World, 2008 Patel, Nikunj (February 2, 2016). "The Argument Against Model-Based Definition". Design News. Ruemler, Shawn P; Zimmerman, Kyle E; Hartman, Nathan W; Hedberg, Thomas; Barnard Feeny, Allison (2016). "Promoting Model-Based Definition to Establish a Complete Product Definition". Journal of Manufacturing Science and Engineering. 139 (5): 051008. doi:10.1115/1.4034625. PMC 5215895. PMID 28070155. Quintana, Virgilio; Rivest, Louis; Pellerin, Robert; Venne, Frédérick; Kheddouci, Fawzi (2010). "Will Model-based Definition replace engineering drawings throughout the product lifecycle? A global perspective from aerospace industry". Computers in Industry. 61 (5): 497–508. doi:10.1016/j.compind.2010.01.005. Miller, Alexander Mcdermott; Alvarez, Ramon; Hartman, Nathan (2018). "Towards an extended model-based definition for the digital twin". Computer-Aided Design and Applications. 15 (6): 880–91. doi:10.1080/16864360.2018.1462569. Zhu, Wenhua; Bricogne, Matthieu; Durupt, Alexandre; Remy, Sébastien; Li, Baorui; Eynard, Benoit (2016). "Implementations of Model Based Definition and Product Lifecycle Management Technologies: A Case Study in Chinese Aeronautical Industry". IFAC-PapersOnLine. 49 (12): 485–90. doi:10.1016/j.ifacol.2016.07.664. Miller, Alexander Mcdermott; Hartman, Nathan W; Hedberg, Thomas; Barnard Feeney, Allison; Zahner, Jesse (2017). "Towards Identifying the Elements of a Minimum Information Model for Use in a Model-Based Definition". Volume 3: Manufacturing Equipment and Systems. V003T04A017. doi:10.1115/MSEC2017-2979. ISBN 978-0-7918-5074-9. Furrer, David U; Dimiduk, Dennis M; Cotton, James D; Ward, Charles H (2017). "Making the Case for a Model-Based Definition of Engineering Materials". Integrating Materials and Manufacturing Innovation. 6 (3): 249–63. doi:10.1007/s40192-017-0102-7. Uski, Pekka; Pulkkinen, Antti; Koskinen, Kari T. (2016). Aaltonen, Jussi; Virkkunen, Riikka; Koskinen, Kari T.; Kuivanen, Risto (eds.). Can a sheet metal product be manufactured without drawings? – Product lifecycle's point of view (PDF). Proceedings of the 1st Annual SMACC Research Seminar 2016. Tampere: Tampere University of Technology. pp. 109–11. ISBN 978-952-15-3832-2. Quintana, Virgilio; Rivest, Louis; Pellerin, Robert; Kheddouci, Fawzi (2012). "Re-engineering the Engineering Change Management process for a drawing-less environment". Computers in Industry. 63 (1): 79–90. doi:10.1016/j.compind.2011.10.003. Hedberg, Thomas D; Hartman, Nathan W; Rosche, Phil; Fischer, Kevin (2016). "Identified research directions for using manufacturing knowledge earlier in the product life cycle". International Journal of Production Research. 55 (3): 819–827. doi:10.1080/00207543.2016.1213453. PMC 5155444. PMID 27990027. Ma, Qin Yi; Song, Li Hua; Xie, Da Peng; Zhou, Mao Jun (2017). "Development of CAD Model Annotation System Based on Design Intent". Applied Mechanics and Materials. 863: 368–72. doi:10.4028/www.scientific.net/AMM.863.368. S2CID 114427127.

Worked examples

Example 1 — a first encounter with Model-based definition

Start with the simplest possible case. Write down what Model-based definition claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Model-based definition before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Model-based definition ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Model-based definition

In research: Model-based definition appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Model-based definition in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Model-based definition is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer-aided design, Computer-aided engineering, Computer-aided manufacturing software, so understanding it makes those chapters shorter.
In everyday life: Look for Model-based definition outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Model-based definition in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Model-based definition means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
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Frequently asked questions

What is Model-based definition in simple terms?

Why does Model-based definition matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Model-based definition?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Model-based definition.