THe WWP uses the <opener> element to group together certain kinds of information which typically appear at the beginning of a division. This information is often associated with letters, but may also be found in other kinds of division. It includes:
<argument>: used for an argument (a short section, possibly a single paragraph, summarizing the contents of the division).
<epigraph>: used for a brief quotation (usually from another text)
<dateLine>: used for the date and/or place of writing; includes <placeName> and <date> elements
<respLine>: used for information identifying the writer or the person responsible for the text
<salute>: used for phrases like “To the Reader” or “Dear Sir” or “To my most noble Lord”, phrases addressing the reader.
The WWP always uses <opener> when one or more of these elements is present.
Note that some of this information may also appear in a heading, and it may sometimes be difficult to decide whether a given phrase (such as “To the Reader”) should be encoded with <head> or with <opener> and <salute>. As a guideline, the first textual element within a <div> should be assumed to be a <head> unless there is a strong reason for treating it otherwise. A good example of such a reason might be a collection of letters, where each separate <div type="letter"> might begin with a dateline or with the salute, “Dear ...”, neither of which should be encoded as a heading.
<div type="prefatory"><head>To the Reader</head>
<p>text of div</p></div>
<div type="dedication"><head>To His most Sacred Majesty, <persName>Charles the Second</persName>...</head>
<opener><salute>May it please your Majesty,<salute></opener>
<div type="letter"><head>To Mrs. Rushmore, From Mr. Simpson.</head>
<opener><dateline><placeName>London</placeName>, <date>18 March 1746</date></dateline>
<salute>My dear <persName>Mary</persName>,</salute></opener> ...</div>