Paragraphing (p and px): element p is the normal paragraph, element px is a restricted paragraph used in the abstract, for example. The restricted paragraph is just like the normal one except that there are a few elements (index, note and draftnote) which may not appear.
The paragraph elements have an `id' attribute, which allows you to refer to them using a ref element (see Appendix C.1.57). This reference will, however, typically be a reference to the section which contains the paragraph rather than to the paragraph specifically. This is an instance of the more general warning that you should make few assumptions about how elements are rendered, when you are authoring a document.
Text style (em, strong, cite, draftnote): em and strong indicate degrees of emphasis; cite refers to the title of something such as a book; and draftnote is a reminder usable whilst drafting a document, which should be prominently displayed in some way.
Verbatim text
(code,
verbatim,
kbd,
linespecific):
The `code' and `kbd' elements are verbatim text, displayed using a
fixed-width font in
the line of a paragraph; the distinction is that kbd text might be
displayed in some way which indicated that it is text a user should
type. Verbatim content is displayed in a fixed-width font, respecting
line-breaks. Note that none of these elements perform any escaping of
their contents - if there are any characters in the content which
would be of significance to the SGML parser (such as & or
<), they should either be escaped with entity references
(& or <) or else the content should be
enclosed in a CDATA marked section as follows (see also
Section 3.5.1).
<verbatim><![ CDATA [ Here is some <em>marked-up</em> text which will be skipped & ignored ]]></verbatim>
The `linespecific' element is slightly different. It is intended to mark up a block of text where the linebreaks are significant, but the text is not otherwise verbatim; the canonical example is that of verse. It consists of a sequence of `line' elements.
Quotations (quote, blockquote, attribution): a short quotation may be enclosed in a quote element, and a longer one in a blockquote element. In both cases, the content may start with an attribution element, which notes the source of the quotation.
Lists (ol, ul, dl, dt, dd, li): These are the ordered, unordered and description lists familiar from HTML. Unlike HTML, however, the dt and dd elements within the description list must be paired.
Angles (angle): as appropriate for a DTD designed to document astronomical software, there is a special element for referring to astronomical angles. This is an empty element, with the components of the angle specified as attributes. See Appendix C.1.2.
For example:
This produces: 45o 30' 10''.0 is an angle in degrees (the default), and 6h 45m is an angle in hours, with the number of seconds and fractions of seconds omitted. An angle like 1000o.10 is syntactically acceptable, but astronomical nonsense.<angle angle=45 minutes=30 seconds=10 fraction=0/> is an angle in degrees (the default), and <angle unit=hours angle=6 minutes=45/> is an angle in hours, with the number of seconds and fractions of seconds omitted. An angle like <angle angle=1000 fraction=10/> is syntactically acceptable, but astronomical nonsense.