Horizontal Review - Architecture

## Description

Ask the [TAG](https://www.w3.org/2001/tag/) for review; see [how to work with the TAG](https://tag.w3.org/workmode/). If you are developing javascript APIs you may also want to ask [public-script-coord@w3.org](mailto:public-script-coord@w3.org), a technical discussion list shared by W3C and ECMA's TC 39.