Nested Blocks including inline Text

Hello,

I am building a rudimentary XSL-FO formatter in C++, initially targeting
only the simpler elements of XSL-FO.

I understand that fo:block can include other fo:block elements, such as the
following:

<fo:block>
  <fo:block>
     Some text
  </fo:block>
</fo:block>

If an fo:block element X contains a nested block, can X also contain inline
elements, for example:

<fo:block>
  Text before a child block.

  <fo:block>
     Some text
  </fo:block>

  Text after a child block.
</fo:block>

In this situation, what is the layout behaviour? I cannot find any explicit
reference to the layout behaviour in the specification under this
circumstance, or even whether the above construct is legal.

If someone can shed light on this I would appreciate it.

Kevin.