Tuesday, 15 November 2005

1st bit of literature review

No discussion of the provenance of Asynchronous Javascript and XML techniques (henceforth to be known as AJAX) would be complete without looking at the internet and its development over the past few years.

Licklider is credited with being the "father of the internet". He discussed the concept of the "Galactic Network" in 1962 in a series of memos where he envisioned a globally interconnected set of computers through which users might access data and programs from any machine (Liener & Cerf et al, 2003). Licklider was made the head of the computer research program at the U.S. Department of Defense Advanced Research Projects Agency (DARPA) soon after and it was here that he promoted, and subsequently encouraged his successors to promote, an all-encompassing computer network when he left in 1964. DARPA itself had been created by President Eisenhower in 1958 as a line item in an Air Force appropriations bill in order to pursue research and development of technologies which might be of benefit to the military. It is believed that its creation was a direct response to the launching of the Sputnik satellite by the USSR. Eisenhower later made comments warning about the rising economic, political and spiritual power of what he coined the "military-industrial complex". In a speech he gave before leaving office he listed technological issues as being one of the gravest threats facing the USA, on the one hand he warned about scholars being manipulated by the financial power of the "military-industrial complex", while he was also conscious of "the equal and opposite danger that public policy could itself become the captive of a scientific-technological elite" (1961, 1035-1040).

While Licklider provided the concept of the internet, three teams were working concurrently on the technologies which made the internet possible. Kleinrock had published the first paper on packet switching technology in 1961 (Klienrock, 1961) at the Massachusetts Institute of Technology (MIT) where he continued to work on the technology until 1967. About the same time (1962-1965) the RAND Corporation, sponsored by the United States Air Force, was funding Baran who came up with the concept of robust communications networks through a distributed network rather than the centralized or decentralized networks models popular at the time. Primarily he was concerned with "a communication network which will allow several hundred major communications stations to talk with one another after an enemy attack" (Baran, 1962). He also worked on packet switching techniques. Packet switching was also worked on independently by Davies of the UK's National Physical Lab between 1964 and 1967.

Roberts (convinced by Klienrock's theories about packet switching) succeeded in creating the first ever network of 2 machines over a telephone line at MIT in 1965. In 1966 Roberts was recruited by DARPA and within a year put together a plan for the ARPANET which he presented at the ACM Symposium on Operating Systems Principles conference (Roberts, 1967). There, Davies and his team made him aware of the work of Baran. In 1968 the theories of the three teams were refined into a final specification for the ARPANET which was commissioned by the USA Department of Defense in 1969 for research into networking (PBS Online, 1998) . However, it has been suggested that ARPANET was originally conceived of as a way for DARPA contractors to share computing resources (Griffin, 2000).

More and more computers were added, and more and more networks were connected to ARPANET, making the first internet, or network of networks. It was eventually decommissioned in 1990 but not before many of the protocols which make up the modern internet were tested upon it. ARPANET was demonstrated to the public in 1972 at which time work commenced on a second generation of network protocols based upon the packet switching ideas developed by the three teams above. By 1982 a family of new protocols had been developed. The Transmission Control Protocol - responsible for host communications, and the Internet Protocol - responsible for routing and addressing (more commonly known as TCP/IP) were by far the two most prominent members of this family (Davidson, 1988). TCP/IP has the benefit of being operating system agnostic and though originally developed for large systems it was demonstrated by Clarke that it enabled workstations to be networked as well as the large systems. Asleson and Schutta (2005) see the development of TCP/IP and the personal computing revolution of the 1980s and 1990s as another significant step along the way to the networked world in which we reside today. We can see that the impetus for the creation of the internet came from Licklider, that its architecture was primarily the responsibility of Baran, that the protocols used upon it were developed by Roberts, Davies and Baran, but the final contributer towards todays Internet and World Wide Web is Berners-Lee.

Berners-Lee believes the concept of the internet predated the work of Licklider and notes that Vannevar Bush wrote about a machine called the Memex in 1945, and Ted Nelson wrote of 'Literary Machines' in 1965 (Berners-Lee, 1999). Nelson's machines, once networked, would allow users to share information as equals using a process he termed hypertext. Hypertext was also the basis of a collaborative workspace called On Line System developed in the 1960s by Doug Engelbart at Stanford. But their contributions, while visionary, didn't come to fruition in the way that Licklider's did. Berners-Lee is also conscious of the element of timing in the success of his work. He states, "I happened to come along with time, and the right interest and inclination, after hypertext and the Internet had come of age. The task left to me was to marry them together" (Berners-Lee, 1999, p7).

Handley and Crowcroft (1995) are amongst many who credit Berners-Lee with the creation of the World Wide Web. Berners-Lee used the idea of hypertext as developed by Nelson and Engelbart to link documents together. In much the same way as an academic paper has references to other academic papers Berners-Lee thought that it might be appropriate for references in electronic resources to link to other electronic resources using an addressing scheme. This would allow the reader to directly access the referenced resource by clicking on a link in the document. Initially these links were called URNs (Universal Resource Name), later they were known as URLs (Universal resource Locator), and more recently they are called URIs (Uniform Resource Identifier). More colloquially they are known as web addresses. Berners-Lee wasn't alone in his enthusiasm for hypertext but he was initially alone in his belief in the possibilities of placing hypertext on the internet. After looking at already available hypertext products he decided that a simplified subset of Standardized General Markup Language (SGML) which he called Hypertext Markup Language (HTML) would, combined with a protocol called Hypertext Transport Protocol (HTTP), provide a mechanism by which scientists working on diverse hardware platforms would be able to share data in a universally accessible format over the infant internet.

Charles Goldfarb, the creator of SGML, saw its development as result of the work of a number of individuals active in the late 1960s whose main concern was the presentation of printed material (Goldfarb, 1990). A number of people proposed splitting the data contained in documents from the formatting of documents; the formatting would then be described in specific ways. Goldfarb took these ideas, and with his colleagues at IBM in 1969, created GML in order to allow text-editing, formatting and information retrieval subsystems to share documents in an integrated law office information system.

Goldfarb continued to work with markup languages (Goldfarb & Prescod, 2001) and designed SGML to have: Common data representation allowing different hardware/software combinations to read and write the same document; flexibility to be able to work with any of the myriad different types of document; Rules for the creation of a formal description of documents of the same type.

While Goldfarb started work on SGML almost immediately after his work on GML, it wasn't until 1974 that SGML was properly proven. This was when Goldfarb proved that software could check the validity of a document against its document type definition. SGML was ratified as a standard in 1986, though it had been in use for some time prior to this in industry.

Eisenhower D (1960) "Farewell Radio and Television Address to the American People" (January 17, 1961) IN Public Papers of the Presidents, p. 1035-1040 Washington: GPO Also [WWW] http://millercenter.virginia.edu/scripps/diglibrary/prezspeeches/eisenhower/dde_1961_0116.html
Leiner B & Cerf V et al (2003) A Brief History of the Internet, version 3.32 [WWW] http://www.isoc.org/internet/history/brief.shtml
Klienrock L (1961) Information Flow in Large Communication Nets RLE Quarterly Progress Report
Baran P (1964) Rand Memoranda on Distributed Communication [WWW] http://www.rand.org/publications/RM/RM3420/
Griffin S (2000) Internet Pioneers [WWW] http://www.ibiblio.org/pioneers/index.html
Roberts L (1967) Multiple computer networks and intercomputer communication Proceedings of the first ACM symposium on Operating System Principles
PBS Online (1998) Nerds 2.0.1. Timeline [WWW] http://www.pbs.org/opb/nerds2.0.1/timeline/index.html
Davidson J (1988) An Introduction to TCP/IP New York: Springer-Verlag
Berners-Lee T (1999) Weaving The Web The Past, Present and Future of the World Wide Web by its Inventor London: Orion Business Books
Asleson R & Schutta N (2005) Foundations of Ajax Berkeley: Apress
Handley M & Crowcroft J (1995) The World Wide Web Beneath the Surf London: UCL Press
Goldfarb C (1990) SGML HISTORY [WWW] http://xml.coverpages.org/sgmlhist0.html
Goldfarb C & Prescod P (2001) THE XML HANDBOOK 3rd Ed. Prentice Hall