The MIME Content-Type to use
for MINSE expressions is
text/x-minse. (The subtype is
"x-minse" because this is an experimental type, as yet unregistered,
while "text" was chosen for the top-level type because the
meaning of an expression can be understood from the plain text,
even if no renderer is available).
I'm considering two ways of inserting mathematics into HTML at this
time. Using the
fits perfectly with existing standards proposals, and avoids adding
another tag to HTML. However, it can be a lot easier to just use a
specialized tag for structured expressions, for which i
<SE> tag, and
To place an expression in an HTML document, you can use the
<OBJECT> tag, as defined by
W3C OBJECT Working Draft. Using the
tag, you can place objects from other files of different types
into your HTML documents.
For mathematical expressions, however, it's quicker
to just specify the expression in the tag itself, which can be
accomplished with the
data: URL scheme (as defined
by the Data:
Internet Draft by Larry Masinter). To represent an expression
with an immediate URL, then, you give the scheme name (
followed by the Content-Type (
text/x-minse), a comma, and then
the text of the expression. Here is an example of such a URL as you
might use it in an
<OBJECT> tag in a document:
The contents of the element (between the<OBJECT DATA="data:text/x-minse,a*'exp(x,2)+b*x+c=0"> (Your browser doesn't support mathematical expressions. Fortunately, you can <a href="http://www.lfw.org/math/nph-pmpm.cgi"> invoke Ping's MINSE polymediator</a> to render this equation for you.) </OBJECT>
</OBJECT>tags) are displayed in browsers that cannot render the content of the OBJECT. It is hoped that this MIME type will eventually be supported by browsers, and so this implementation is designed to let future support work as easily as possible without requiring anyone to change their documents.
Be careful with the characters you use in the OBJECT tag attribute. The set of "safe" characters in a URL is severely restricted by the various ways in which they are transported. According to the standard for URL syntax (Request For Comments 1738), only the following characters are allowed unescaped in URLs, aside from letters of the alphabet and digits:
+ - = . _ / * ( ) , @ ' $ : ; & ! ?
The special characters used in MINSE have been carefully chosen from this set so that you don't have to "escape" them in URLs (using a percent character and a hexadecimal number). After we set aside the parentheses, the comma, and the characters on the left, which are commonly used in expressions, we are left with just six choices for the macro escape character (the ampersand is inconvenient, because it needs to be represented as an entity; but much worse, far too many browsers are broken and will not parse SGML entities in attribute values). The single-quote was chosen for convenience, because it is a non-shifted key on North-American keyboards.
Anything that is not part of the "safe" character set must
always be escaped in a URL. In particular, the percent character
%") and the space must be escaped. Use the following codes:
Sorry about that, but i can't change the standard. There are good reasons for the decisions made in that document.for: space % use: %20 %25
This method is under consideration. Simply insert the expression
between the tags
<SE> a*'exp(x,2)+b*x+c=0 </SE>
How does one justify creating a new tag? First, the notation within
the tag can be understood as text, so this method degrades reasonably
well for browsers that don't support MINSE when the polymediator is not
running. Second, the tag is removed by the polymediator, so what gets
actually served is still quite valid HTML. Third, the expired HTML 3.0
draft suggested a new tag,
<MATH> for mathematical
expressions, but HTML 3.0 math has a much smaller scope of application
than MINSE because it does not support multiple contexts, and is
strongly based on visual, two-dimensional presentation. So it seems fair
to introduce a new tag for structured expressions, which are more general.
The latter method also greatly relieves many of the restrictions of URL characters, but you still have to watch out for the special characters in HTML, in particular the less-than and greater-than signs, which delimit tags, and the ampersand, which invokes SGML entities. Use the following codes:
for: & < > use: & < >
When you give the polymediator a URL to visit (from the form on the launchpad, for instance), your browser is actually making a request to a program instead of retrieving a document. You may notice that, when you browse with the polymediator, the string
is affixed to the beginning of the "real" URL. This passes your URL to a program called
nph-pmpm.cgiat this site.
This program is a CGI script which fetches a requested document,
<OBJECT> elements in the document which
have the Content-Type
text/x-minse, and then sends you the
results. Its job is to choose the appropriate set of macro definitions
based on what it can determine about your client, and to apply them to
the data in these elements. Right now, the only decision it makes is
whether to produce text or an image (the audio link is always inserted).
Even though these lengthened URLs look strange and don't directly refer to real files, you can still treat them the same way as any others. In particular, you can bookmark them and you can link to them. If you want a link which causes a page to be processed by the MINSE polymediator, just add that string to the front of the URL yourself. In order to let people continue to browse sites containing MINSE easily, the polymediator also makes this change to all of the links in the document it fetches.
You may have noticed that the link in the
tag above points to
will be the address of the MINSE polymediator program. When a user
activates the link, their browser will be redirected to a new URL that
invokes the polymediator on the referring URL (the document
that contains the link). So, including a link to
http://www.lfw.org/math/nph-pmpm.cgi is all you need to do to
let people render the expressions on a page with a single hyperlink.
The above example with the quadratic equation both supplies
the expression in the
<OBJECT> tag and provides a
link for users who need to invoke the polymediator.