# Namespace question when switching from old version (0.13) to latest (2.12)

**URL:** <https://discourse.f2i-consulting.com/t/namespace-question-when-switching-from-old-version-0-13-to-latest-2-12/249>\
**Category:** FESAPI\
**Created:** [June 12, 2025, 5:28pm UTC](https://discourse.f2i-consulting.com/t/namespace-question-when-switching-from-old-version-0-13-to-latest-2-12/249 "2025-06-12T17:28:07Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![sgthomas-github](https://discourse.f2i-consulting.com/user_avatar/discourse.f2i-consulting.com/sgthomas-github/32/12_2.png) [@sgthomas-github](https://discourse.f2i-consulting.com/u/sgthomas-github)\
**Post date:** [June 12, 2025, 5:28pm UTC](https://discourse.f2i-consulting.com/t/namespace-question-when-switching-from-old-version-0-13-to-latest-2-12/249/1 "2025-06-12T17:28:07Z")

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Hi, I recently upgraded across multiple in a huge switch from 0.13 to 2.12.2.1 (latest) and noted that many API changes were there of course as expected. But besides this I noted that we have one `UnstructuredGridRepresentation` under `RESQML2_NS` and another under `RESQML2_0_1_NS` and similarly for properties `DiscreteProperty`, `ContinuousProperty` etc. I have been always following the `example` code closely to import and export `RESQML` files, and I noted even the `example` code has changed since then. Previously where APIs `createUnstructuredGridRepresentation` or `createDiscreteProperty`, `createContinuousProperty`, etc were called, it was returning the object of class type from `RESQML2_0_1_NS` whereas now it returns from `RESQML2_NS`, so I just wanted to confirm whether it is expected to use the one defined in the `RESQML2_NS` as the expected return type just as in the example code? Also, any further comments detailing the difference and when to use the one from `RESQML2_0_1_NS` are much appreciated.

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**Author:** ![philippeVerney](https://discourse.f2i-consulting.com/user_avatar/discourse.f2i-consulting.com/philippeverney/32/29_2.png) [@philippeVerney](https://discourse.f2i-consulting.com/u/philippeVerney)\
**Post date:** [June 12, 2025, 8:00pm UTC](https://discourse.f2i-consulting.com/t/namespace-question-when-switching-from-old-version-0-13-to-latest-2-12/249/2 "2025-06-12T20:00:57Z")

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It is clearly expected to ALWAYS use RESQML2\_NS instead of RESQML2\_0\_1\_NS by default. Use only specializations such as in RESQML2\_0\_1\_NS if you really know what you do.

RESQML2\_NS has appeared with the experimental support of RESQML2.2 in FESAPI. We wanted to provide a way for FESAPI users not to care if the objects would be (de)serialized to/from RESQML2.0.1 or RESQML2.2. RESQML2\_NS is the abstraction of RESQML2.0.1 and RESAML2.2.  
The intent is in consequnce that you code everything possible using RESQML2\_NS. This code will be almost guaranteed to work the same either you work with RESQML2.0.1 files or RESQML2.2. files.  
If you code using RESQML2\_0\_1\_NS, your code would only work for RESQML2.0.1 with, most of time, no advantage.