computer science 1611 internet & web technology infrastructure hypertext and the world wide web

Computer Science 1611Internet & Web

Technology Infrastructure

Hypertext and the

World Wide Web


Learning Objectives

• History of the written word (books)

• History of hypertext

• How HTML tags and links work on the World Wide Web


History: Before the Web

• History of the Internet• Before the creation of the World Wide Web (when,

whom?) there was a set of technologies which constituted the internet

– telnet– ftp– Gopher

• History of the Web

• Early browsers for the Web were not as capable as those of today

http://www.netvalley.com/archives/mirrors/davemarsh-timeline-1.htm

http://www.webopedia.com/TERM/T/Telnet.html

ftp://ftp.mta.ca/

http://www.mta.ca/~amiller/cs1611/gopher.htm

http://www.dejavu.org/

http://www.dejavu.org/emulator.htm


Early Writing

• Cuneiform, the earliest writing was on baked clay tablets, since clay was readily available– Tough to transport

– Easily destroyed

– Write once


Wherefore the Web ?

Early Books• Linear Access: The Scroll

Earliest books in the western world were in the form of a “roll”, usually made of sheets of papyrus sewn or glued together. Text could only be written on one side of the scroll (roll), and the reader would roll up the side of the scroll that had already been read, and would unroll the unread side

– “From our modern perspective this seems a most cumbersome way to read, but it was obviously not so considered by the ancient reader.”


The Development of the Modern Book

• The codex (paginated book as we know it) was developed in the first two centuries AD as convenience for travelers and libraries, and by 300 AD the codex had achieve parity with the (sc)roll.


Chained Books (1)

• Chaining books was the most widespread and effective security system in European libraries from the Middle Ages to the 18th century.


Chained Books (2)

Chaining books was the most widespread and effective security system in European libraries from the Middle Ages to the 18th century.

Early codex manuscripts were expensive and scarce, and libraries took “medieval security measures” to protect them from theft or loss, physically chaining them to a shelf in the library.

The system allows a book to be taken from the shelf and read at the desk, but not to be removed from the bookcase. In this environment, the reader was virtually “chained to her desk”, since such books could be read only in the location in which they were stored. (privacy ?)


Demand for Books

It would only be after books could be produced accurately and in sufficient quantity to meet the growing demands of the universities that books could be “freed from their chains”.

Of course, the manual copying methods of the “scriptoria” (book copiers) could meet some of the demand, and the dormant scriptoria of the monasteries found new life in the business of (manually) copying books for the university needs.

But the demand for books far exceeded the capabilities of the manual methods, and needed were mechanical means of mass-producing books.


Books and the Rise of Universities

• It was the rise in the growth of universities in the 12th and 13th centuries in Europe that lead to increasing demands for books.

• Stationers and book copiers began to appear, providing paper and libraries of books that could be (manually) copied.

• When a student needed a book for a class, (s)he would go to a stationer and copy the book by hand, or pay a book copier to do the work.


Copiees of Coppies of Copies ….

• Inaccuracies from the “original” were quite prevalent, due to the human errror of the person doing the (manual) copying, as well as the fact that the book being copied was also likely a “copy” of the “original”. The increasing demand for books, and the slow speed at which they could be “copied”, led to the invention of the printing press.


Gutenberg and Printing

• Johann Gutenberg invented the printing press and the use of movable type in 1445.

• By the 1470s printing presses were functioning in most of the countries of Western Europe, and by the end of the century every major European city boasted of at least one printing establishment.

• The appearance of books changed little in the transition from manuscript to printed book.

http://www.learner.org/exhibits/renaissance/printing.html

http://www.learner.org/exhibits/renaissance/printing.html


Early Printed Books• Early printers more than met the demand for

books, producing far more copies than could be sold.

• Prices for printed books plummeted in relation to those of the equivalent manuscripts, costing 20% of the price of a hand-copied version.

• Printers and publishers concentrated in commercial centers, and the production and sales of books had become a modern business.


Sequential Access to Scrolls

• Early scrolls (rolls) were generally read in a sequential fashion, since it was difficult to move to sections of text because of the necessity to unroll and roll the sections of the scrolled book.

• Additionally, scrolls did not include the concept of “pagination”, so movement within a scroll was generally limited to progressive sequential access.


Pages and Pages and Pages and …

• The invention of the codex (modern format for a book) allowed reasonably easy access to independent pages, subject only to the existence of an indexing mechanism

– table of contents, paged index

• As long as the written word was tied to the physical medium (atoms) in the form of a scroll or a modern codex (pages, index, etc), the reader was bound by the organization imposed by the author. As well, any indexing needed to be done when the book was printed, and was limited by the decisions of the author and the publisher.


Vannevar Bush

• In his 1945 essay, "As We May Think“, Vannevar Bush described a theoretical machine he called a "memex

• The “memex" was intended to enhance human memory by allowing the user to store and retrieve documents linked by associations. This associative linking was very similar to what is known today as hypertext


Memex

• Vannevar Bush’s main purpose in writing “As We May Think” was to influence "thinking regarding science in the modern world" and to "emphasize the opportunity for the application of science in a field which is largely neglected by science“.

• That field was the automation or augmentation of human thought.

• The memex was to be a storage and retrieval device using microfilm. It would consist of

– desk with viewing screens– keyboard– selection buttons and levers– microfilm storage.


Hypertext (1)

• The term "hypertext" was coined by Ted Nelson, who conceived of the concept in 1960 and formally introduced it in his self-published (paper book) Literary Machines as "non-sequential writing".

• Nelson based many of his ideas on the previous work of Vannevar Bush

• Nelson coined the term transclusion, the ability to make a virtual copy of part of one document, for inclusion in a second document and saw this as a way to get around copyright and transcription errors.

• Nelson’s Xanadu project envisioned a mechanism whereby authors would automatically received royalties for “transcluded” copyrighted materials.

http://www.eastgate.com/catalog/LiteraryMachines.html

http://www.eastgate.com/catalog/LiteraryMachines.html


Hypertext (2)

• Although Nelson never was able to implement his ideas, he was one of the first thinkers to suggest a mechanism which would lead to the web as we know it (though he is highly critical of the current World Wide Web as implemented) and to suggest a technology that might deal with the use of copyrighted material.


The Invention of HTML and the Web

• Tim Berners-Lee “invented” the Web during the period 1980 - 1990– Unlike so many of the inventions that have moved the

world, this one was the work of one man.

– Thomas Edison got credit for the light bulb, but he had dozens of people in his lab working on it. The Internet with its protocols and packet switching, was designed by committee

– But the World Wide Web is Berners-Lee's alone. He alone designed it


Hypertext Markup Language

• HTML is a simplified subset of SGML that includes tags defining the format and style of text elements in a document.

• HTML now includes tags for tables, frames, and other features that help Web designers create more complex page layouts.


Markup Languages and the Web


HTML Tags

• An HTML document contains both document text and elements.

• Tags are codes that are used to define where an HTML element starts and (if necessary) where it ends.

• In an HTML document, each tag is enclosed in brackets (<>).

• A two-sided tag set has an opening tag and a closing tag.


Document Tags

• Document tags are those divide up a Web page into its basic sections, such as the header information and the part of the page which contains the displayed text and graphics.

• HTML– The first and last tags in a document should always be

the HTML tags. The absolute most basic of all possible Web documents is:

<HTML> </HTML> – If we load such a page into a Web browser, it will give us

a blank screen, but it is technically a valid Web page.


Document Tags (Head and Body)

<head> ….. </head>

– The HEAD tags contain all of the information describing the document

<title> …. </title>• The TITLE container is placed within the HEAD

structure. Between the TITLE tags, you should have the title of your document. This will appear at the top of the browser's title bar, and also appears in the history list. Finally, the contents of the TITLE container go into your bookmark file, if you create a bookmark to a page.


BODY• BODY

– BODY comes after the HEAD structure. Between the BODY tags, you find all of the stuff that gets displayed in the browser window. All of the text, the graphics, and links, and so on -- these things occur between the BODY tags.

<HTML> <HEAD>

<TITLE>Document Title</TITLE>

</HEAD> <BODY> </BODY>

</HTML>

• Web view of the above


HTML Links

• Hyperlinks are bits of text that connect the current document to:

• another location in the same document

• another document on the same host machine

• another document on the Internet

• Hyperlinks are created using the HTML anchor tag.


Anchors

• The anchor tag <a ….> …. </a> is used to allow a user to move from the present “page” to another location .

• <a href=“anchors.html">Anchor description </a>.

• This “anchor” will be displayed on the web page as

Anchor description and when the user clicks on the “anchor text” the browser will retrieve the hypertext reference (href) associated with the anchor.

computer science 1611 internet & web technology infrastructure hypertext and the world wide web

Documents

internet web books

internet web chained

internet web history

internet web demand

computer science

chaining books

world wide web slide

web early browsers