# Custom Predefined Types in bsDD

**URL:** <https://forums.buildingsmart.org/t/custom-predefined-types-in-bsdd/1557>\
**Category:** bSDD\
**Created:** [July 1, 2019, 4:24pm UTC](https://forums.buildingsmart.org/t/custom-predefined-types-in-bsdd/1557 "2019-07-01T16:24:01Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![daviskantor](https://sea2.discourse-cdn.com/flex016/user_avatar/forums.buildingsmart.org/daviskantor/32/1076_2.png) [@daviskantor](https://forums.buildingsmart.org/u/daviskantor)\
**Post date:** [July 1, 2019, 4:24pm UTC](https://forums.buildingsmart.org/t/custom-predefined-types-in-bsdd/1557/1 "2019-07-01T16:24:01Z")

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Hi All,

I would like to define the structure for consistently relating custom IFC Predefined Types to my PDT subjects.

Does anyone recommend a relationship type I should use? Perhaps the custom Predefined Type should be a “subject” concepts type with the relationship `is type of` PDT “subject” concept type? Or should the custom Predefined Type be a “Classification” concept type?

Thanks for the feedback,