# Interface roadmap - last draft before ratification vote

**URL:** <https://discourse.mc-stan.org/t/interface-roadmap-last-draft-before-ratification-vote/10955>\
**Category:** Developers\
**Created:** [September 12, 2019, 6:25pm UTC](https://discourse.mc-stan.org/t/interface-roadmap-last-draft-before-ratification-vote/10955 "2019-09-12T18:25:53Z")\
**Posts on this page:** 1\
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**Author:** ![bgoodri](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.mc-stan.org/bgoodri/32/4451_2.png) [@bgoodri](https://discourse.mc-stan.org/u/bgoodri)\
**Post date:** [September 12, 2019, 6:52pm UTC](https://discourse.mc-stan.org/t/interface-roadmap-last-draft-before-ratification-vote/10955/8 "2019-09-12T18:52:42Z")

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I think either JSON or something binary is fine, perhaps both. One of the complaints that we get when the summary of a covariance matrix, `Sigma`, is printed is that you see the same summary for `Sigma[1,2]` as for `Sigma[2,1]` because it is a symmetric matrix. So, a better summary would only show that once. Furthermore, there is no need to summarize the fact that the diagonal of a correlation matrix is always 1 or that the upper triangle of a Cholesky factor is always zero. But we need to know what type of matrix the thing is to do that.

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