Detail about bbox nesting

[CorentinBrule]

I'm developping a tool to view and edit hOCR files and i'm wondering does the spec include rules about bbox nesting ? Does the parent's rectangle have to be exactly the same size as the children's group bouncing box ? (ex : the bbox of a line is the bbox of its words ?)

Other question (other issue ?) : does it compatible with the specification to wrap all space chars in a or something like this to highlight them and to guarantee their resilience when editing the hOCR file (auto beautify for example)