(dsssl) Sibling issues

[tmcd@xxxxxxxxx]

In my XML, an item header (indented out 0.5in) is followed by a
sequence of paragraphs (flush left) and blockquotes (indented, and can
contain multiple paragraphs). I want a "space-before: 0pt" on a
paragraph if either
A: this is the first child of its parent.  It's either the first
   paragraph of an item or the first paragraph of a blockquote.
   Either way, that means it's indented 0.5in more than the preceding
   text, so it doesn't need space-before to set it off visually.
B: the preceding sibling of the current node is a <blockquote>, which
   indents.  Therefore, this paragraph is indented -0.5in from the
   preceding (blockquoted) paragraph, so as with A, it is already
   visually distinguishable.
Otherwise, I want "space-before: 5pt".

Do I understand right that test A is
    (= (child-number (current-node) 1)
(I'm pretty sure of that) and test B is either
    (string=? (gi (ipreced (current-node))) "blockquote")
or
    (match-element? 'blockquote (ipreced (current-node)))
?  I'm weak on sibling issues.

============================================================

While I'm here, can anyone explain the rsiblings function in English?
Note that by "explain ... in English", I exclude the text in the DSSSL
standard, which I can't understand at all.

    (rsiblings nl)

    Returns the mapping over nl of the function on a node that returns
    the reflexive siblings of the node, where the reflexive siblings
    of a node are defined to be the value of the origin-to-subnode
    relationship property of the node(Bs (Borigin, if the node has an
    origin, and otherwise the node itself.  This could be defined as
    follows:

    (define (rsiblings nl)
      (node-list-map (lambda (snl)
                       (let ((rel (origin-to-subnode-rel snl)))
                         (if rel
                             (node-property rel
                                                (origin snl)
                                                default: (empty-node-list))
                                  snl)))
                           nl))

Also, the standard uses "(siblings ...)" in the definition of
functions ipreced, ifollow, preced, and follow.  It doesn't define it
anywhere.  What is the siblings function, and does it differ from
rsiblings?

-- 
Tim McDaniel, tmcd@xxxxxxxxx; tmcd@xxxxxxxxxx is my work address

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