Are there any restrictions to XML particle count/size?

Tried to search the XML-DEV archives to see if this was covered previously,
but the search engine is currently inoperable, so please forgive me if this
was already covered.  Are there any restrictions to count or length of XML
documents?  In other words, it seems you can have:

1- infinite number of elements, attribute lists, PI, comments, and entities
of all kinds.
2- the length of names and content is infinite.

The only restriction I found in the XML recommendation is that an XML
document can have only one root element and only one XML declaration.

Is my understanding of the above correct, and are there any other size/count
restrictions to an XML document?

Appreciate your comments,
Ralph