The R Journal: article published in 2009, volume 1:1

PMML: An Open Standard for Sharing Models
Alex Guazzelli, Michael Zeller, Wen-Ching Lin and Graham Williams , The R Journal (2009) 1:1, pages 60-65.

The PMML package exports a variety of predictive and descriptive models from R to the Predictive Model Markup Language (Data Mining Group, 2008). PMML is an XML-based language and has become the de-facto standard to represent not only predictive and descriptive models, but also data preand post-processing. In so doing, it allows for the interchange of models among different tools and environments, mostly avoiding proprietary issues and incompatibilities.

@article{RJ-2009-010,
  author = {Alex Guazzelli and Michael Zeller and Wen-Ching Lin and
          Graham Williams},
  title = {{PMML: An Open Standard for Sharing Models}},
  year = {2009},
  journal = {{The R Journal}},
  doi = {10.32614/RJ-2009-010},
  url = {https://doi.org/10.32614/RJ-2009-010},
  pages = {60--65},
  volume = {1},
  number = {1}
}