are represented by pointers
of type <tt>DOH *</tt>.  Furthermore, all objects are completely
opaque--that means that the only way to access the internals of an
object is through a well-defined public API.   For convenience, the following
symbolic names are sometimes used to improve readability:

<ul>
<Li><tt>DOHString *</tt>.  A String object.
<li><tt>DOHList *</tt>. A list object.
<li><tt>DOHHash *</tt>. A hash object.
<li><tt>DOHFile *</tt>. A file object.
<li><tt>DOHVoid *</tt>. A void object.
<li><tt>DO