Held Tuesday, August 31, 1999
Today, we'll consider the details of how one might formally describe
one node in a hypertext system. We'll also visit one system for
describing nodes, HTML, the HyperText Markup Language used for the
- HTML: The HyperText Markup Language
- Computerized representations of formatted texts
- Should computerized representations be in a form that humans can read?
- WYSIWYG vs. markup languages
- Logical vs. physical markup
- Should markup of document elements reflect their underlying purpose,
their intended appearance, or both?
- The evolution of HTML
- The future of Web markup
- Assignment: Web of teaching techniques
- Due: Thursday, September 9
- I'm happy to take a look at the current drafts of your papers
if you'd like further feedback. I'll be in my office until
noon today, but gone in the afternoon.
- While I'd prefer to talk about general ideas in hypertext system
design first and then have you play with HTML, the MathLAN's
schedule dictates that we'll play with HTML first and then talk
about general issues. Let me know how you think this goes.
- How have the readings gone (and did you note that there were
readings that you were supposed to do)?
- The lab is available online.
Follow the instructions as best you can and let me know when
you have difficulties.
- We were all going to think about terminology for today's class.
The three terms we hoped to relate were:
- World-Wide Web
- As you've discovered, hypertext is a way of structuring
- Particulars of the definition differ from person to person.
- The Internet (yes, it's a proper noun) is a network of
- More precisely, it's a network of networks of computers
and other devices.
- The World-Wide Web is a hypertext system that runs on top
of the Internet.
- Note that
- There are other hypertext systems.
- There are other things you can do on the Internet.
- Every hypertext system needs a way to represent the nodes in the
hypertext and the links between those hypertexts.
- Internal representation: how does the system keep track of each
- External representation: how does the system show the pieces to
- Different designers have chosen different mechanisms.
- For example, in some versions of the Talmud, links are represented
by repetitions of text or by small numbers.
- A fundamental decision in designing internal representation
is how to relate the links and the nodes.
- Should links be stored as part of nodes?
- Should links be stored separately from nodes?
- For computerized hypertext, a related decision is what form the nodes
and links are stored in.
- The format can be readable only by computer or by both computer
- If the format need only be read by computers, it might be made more
``efficient'' (smaller, faster to use, etc.)
- If the format must also be read by human, it may be easier for
people to create and modify nodes and links.
- If the format is standardized, then different programs can create
and use it.
- Some of the same questions come up as you consider how the computer
might represent any document. For example, a typical word-processed
document will have different margins, font, and justification at different
parts of the document.
- Should a human be able to tell what's going on; or can it all
be ``computer gibberish''?
- What do you have to represent in a document? Nearly everything:
- The content of the document
- Something about each piece of the document
- General document characteristics (e.g., page margins)
- We say that a language for representing documents includes
``mark up'' symbols that indicate these characteristics.
- In considering markup, there are two general ``philosophies'' for
what you mark: logical markup and physical markup.
- In logical markup, you indicate the role of each
piece of text. For example, you might indicate that
- ``This is a paragraph''
- ``This is an important word or phrase''
- ``This is a quotation''
- ``This is the title of a book''
- ``This is a top-level section heading in a paper''
- In physical markup, you indicate the appearance of
each piece of text. For example, you might indicate that
- ``This should appear in Times Bold 12pt''
- ``This should appear in a box 2 inches each side that is placed
3/4 inch from the top margin and 5 inches from the right margin''
- HTML is a simple markup language created for the World-Wide Web.
- HTML is intended to be human readable.
- Some would dispute that claim.
- HTML is a particular form of SGML, the Standard Generalized
- SGML was designed by a number of scholars for representing
- Full SGML can even describe layout of pages so that one can
precisely represent documents like the Talmud.
- In HTML, parts of the document are surrounded by tags.
- Tags give information about those parts of the document.
- Each tag begins with a less-than sign and ends with a
- End tags have a slash after the less-than sign.
- For example,
- You begin a paragraph with
<P> and end
a paragraph with
- You begin an important word or phrase with
and end it with
- You begin a list of items with
end it with
- You begin an item in that list with
end it with
- You begin a numbered list with
end it with
- You begin a piece of text in a ``typewriter font'' with
<TT> and end it with
- Some tags do not require end tags. Some even disallow end tags.
<BR> is a line break. Since there's not text
that you're marking, it needs no end tag.
<HR> is a horizontal rule.
<LI> tag does not need an end tag
(since the next
<LI> or the ending
<UL> obviously ends it).
- Some tags permit you to enter parameters: more information
about how the text should be displayed. For example, you can write
<P align="right"> for right-justified text
<HR width="75%"> for a less-wide rule
<FONT face="Helvetica" color="Red"> for
red, Helvetica text.
- Now that you've seen some details about markup languages (or at least
a markup language), we can reconsider some of the questions.
- We'll try these in something of discussion format.
- What are the advantages of logical markup? Physical markup?
- Is it useful to have a ``human readable'' markup language?
- How hard is HTML?
Monday, 22 March 1999
- Created as a blank outline. (Can you tell
what I was doing during Spring break?)
Tuesday, 30 August 1999
- Filled in the details (such as they are).