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77-515: MYCIN led to the EMYCIN expert system shell ("essential MYCIN") for acquiring knowledge, reasoning with it, and explaining the results, without the specific medical knowledge. It can be described as "EMYCIN = Prolog + uncertainty + caching + questions + explanations + contexts - variables". An introduction is in Chapter 16 of Paradigms of Artificial Intelligence Programming (PAIP). MYCIN operated using

154-534: A Request for Quotation (RFQ) was issued for 140 potential bidders. Most computer science companies regarded the ARPA proposal as outlandish, and only twelve submitted bids to build a network; of the twelve, ARPA regarded only four as top-rank contractors. At year's end, ARPA considered only two contractors and awarded the contract to build the network to BBN in January 1969. The initial, seven-person BBN team were much aided by

231-421: A fairly simple inference engine and a knowledge base of ~600 rules. It would query the physician running the program via a long series of simple yes/no or textual questions. At the end, it provided a list of possible culprit bacteria ranked from high to low based on the probability of each diagnosis, its confidence in each diagnosis' probability, the reasoning behind each diagnosis (that is, MYCIN would also list

308-477: A modified and simplified version of MYCIN for pedagogical purposes. A rule, and an English paraphrase generated by the system: Research conducted at the Stanford Medical School found MYCIN received an acceptability rating of 65% on treatment plan from a panel of eight independent specialists, which was comparable to the 42.5% to 62.5% rating of five faculty members. This study is often cited as showing

385-597: A network project. Herzfeld redirected funds in the amount of one million dollars from a ballistic missile defense program to Taylor's budget. Taylor hired Larry Roberts as a program manager in the ARPA Information Processing Techniques Office in January 1967 to work on the ARPANET. Roberts met Paul Baran in February 1967, but did not discuss networks. Roberts asked Frank Westervelt to explore

462-475: A testbed for developing and debugging the 1822 protocol , which was a major undertaking. While they were connected electronically in 1969, network applications were not possible until the Network Control Protocol was implemented in 1970 enabling the first two host-host protocols, remote login ( Telnet ) and file transfer ( FTP ) which were specified and implemented between 1969 and 1973. The network

539-599: A transatlantic satellite link connected ARPANET to the Norwegian Seismic Array (NORSAR), via the Tanum Earth Station in Sweden, and onward via a terrestrial circuit to a TIP at UCL. UCL provided a gateway for interconnection of the ARPANET with British academic networks, the first international resource sharing network, and carried out some of the earliest experimental research work on internetworking. 1971 saw

616-439: A wide variety of application areas. A difficulty that rose to prominence during the development of MYCIN and subsequent complex expert systems has been the extraction of the necessary knowledge for the inference engine to use from the human expert in the relevant fields into the rule base (the so-called " knowledge acquisition bottleneck"). Inference engine In the field of artificial intelligence , an inference engine

693-462: Is a software component of an intelligent system that applies logical rules to the knowledge base to deduce new information. The first inference engines were components of expert systems . The typical expert system consisted of a knowledge base and an inference engine. The knowledge base stored facts about the world. The inference engine applied logical rules to the knowledge base and deduced new knowledge. This process would iterate as each new fact in

770-418: Is more, there is some psychological research that indicates humans also tend to favor IF-THEN representations when storing complex knowledge. A simple example of modus ponens often used in introductory logic books is "If you are human then you are mortal". This can be represented in pseudocode as: A trivial example of how this rule would be used in an inference engine is as follows. In forward chaining ,

847-535: Is somewhat fitting to end on the note that the ARPANET program has had a strong and direct feedback into the support and strength of computer science, from which the network, itself, sprang. Access to the ARPANET was expanded in 1981 when the National Science Foundation (NSF) funded the Computer Science Network (CSNET). The transatlantic connectivity with NORSAR and UCL later evolved into

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924-441: Is true) and existential quantification (there exists some X such that some statement is true). What researchers discovered is that the power of these theorem-proving environments was also their drawback. Back in 1965, it was far too easy to create logical expressions that could take an indeterminate or even infinite time to terminate. For example, it is common in universal quantification to make statements over an infinite set such as

1001-602: Is typically characterized by a high volume of data inputs and real-time processing requirements. The logic that an inference engine uses is typically represented as IF-THEN rules. The general format of such rules is IF <logical expression> THEN <logical expression>. Prior to the development of expert systems and inference engines, artificial intelligence researchers focused on more powerful theorem prover environments that offered much fuller implementations of first-order logic . For example, general statements that included universal quantification (for all X some statement

1078-902: The Honeywell DDP-516 computer, configured with 24 KB of expandable magnetic-core memory , and a 16-channel Direct Multiplex Control (DMC) direct memory access unit. The DMC established custom interfaces with each of the host computers and modems. In addition to the front-panel lamps, the DDP-516 computer also features a special set of 24 indicator lamps showing the status of the IMP communication channels. Each IMP could support up to four local hosts and could communicate with up to six remote IMPs via early Digital Signal 0 leased telephone lines. The network connected one computer in Utah with three in California. Later,

1155-502: The Interface Message Processors (IMPs) for the network to Bolt Beranek & Newman (BBN). The design was led by Bob Kahn who developed the first protocol for the network. Roberts engaged Leonard Kleinrock at UCLA to develop mathematical methods for analyzing the packet network technology. The first computers were connected in 1969 and the Network Control Protocol was implemented in 1970, development of which

1232-502: The Lisp programming language. Lisp was a frequent platform for early AI research due to its strong capability to do symbolic manipulation. Also, as an interpreted language it offered productive development environments appropriate to debugging complex programs. A necessary consequence of these benefits was that Lisp programs tended to be slower and less robust than compiled languages of the time such as C . A common approach in these early days

1309-502: The SATNET . The ARPANET, SATNET and PRNET were interconnected in 1977. The DoD made TCP/IP the standard communication protocol for all military computer networking in 1980. NORSAR and University College London left the ARPANET and began using TCP/IP over SATNET in 1982. On January 1, 1983, known as flag day , TCP/IP protocols became the standard for the ARPANET, replacing the earlier Network Control Protocol. In September 1984 work

1386-654: The Transmission Control Program for internetworking . As this work progressed, a protocol was developed by which multiple separate networks could be joined into a network of networks; this incorporated concepts pioneered in the French CYCLADES project directed by Louis Pouzin . Version 4 of TCP/IP was installed in the ARPANET for production use in January 1983 after the Department of Defense made it standard for all military computer networking. Access to

1463-536: The University of California, Berkeley , and another for Multics at the Massachusetts Institute of Technology . Taylor recalls the circumstance: "For each of these three terminals, I had three different sets of user commands. So, if I was talking online with someone at S.D.C., and I wanted to talk to someone I knew at Berkeley, or M.I.T., about this, I had to get up from the S.D.C. terminal, go over and log into

1540-451: The 1970s, ARPA did emphasize the goal of "command and control". According to Stephen J. Lukasik , who was deputy director (1967–1970) and Director of DARPA (1970–1975): The goal was to exploit new computer technologies to meet the needs of military command and control against nuclear threats, achieve survivable control of US nuclear forces, and improve military tactical and management decision making. The first four nodes were designated as

1617-430: The ARPANET came out of our frustration that there were only a limited number of large, powerful research computers in the country, and that many research investigators, who should have access to them, were geographically separated from them. The ARPANET used distributed computation and incorporated frequent re-computation of routing tables (automatic routing was technically challenging at the time). These features increased

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1694-586: The ARPANET did not exactly share Baran's project's goal, he said his work did contribute to the development of the ARPANET. Minutes taken by Elmer Shapiro of Stanford Research Institute at the ARPANET design meeting of 9–10 October 1967 indicate that a version of Baran's routing method ("hot potato") may be used, consistent with the NPL team's proposal at the Symposium on Operating System Principles in Gatlinburg. Later, in

1771-401: The ARPANET project in 1966 to enable resource sharing between remote computers. Taylor appointed Larry Roberts as program manager. Roberts made the key decisions about the request for proposal to build the network. He incorporated Donald Davies ' concepts and designs for packet switching, and sought input from Paul Baran on dynamic routing. In 1969, ARPA awarded the contract to build

1848-497: The ARPANET was expanded in 1981 when the National Science Foundation (NSF) funded the Computer Science Network (CSNET). In the early 1980s, the NSF funded the establishment of national supercomputing centers at several universities and provided network access and network interconnectivity with the NSFNET project in 1986. The ARPANET was formally decommissioned in 1990, after partnerships with

1925-535: The ARPANET was made between Stanford Research Institute (SRI) and UCLA, by SRI programmer Bill Duvall and UCLA student programmer Charley Kline, at 10:30 pm PST on 29 October 1969 (6:30 UTC on 30 October 1969). Kline connected from UCLA's SDS Sigma 7 Host computer (in Boelter Hall room 3420) to the Stanford Research Institute's SDS 940 Host computer. Kline typed the command "login," but initially

2002-473: The Department of Defense allowed the universities to join the network for sharing hardware and software resources. According to Charles Herzfeld, ARPA Director (1965–1967): The ARPANET was not started to create a Command and Control System that would survive a nuclear attack, as many now claim. To build such a system was, clearly, a major military need, but it was not ARPA's mission to do this; in fact, we would have been severely criticized had we tried. Rather,

2079-549: The IMPs (similar to the later concept of routers ), that functioned as gateways interconnecting local resources. Routing, flow control, software design and network control were developed by the BBN team. At each site, the IMPs performed store-and-forward packet switching functions and were interconnected with leased lines via telecommunication data sets ( modems ), with initial data rates of 50 kbit /s . The host computers were connected to

2156-399: The IMPs via custom serial communication interfaces. The system, including the hardware and the packet switching software, was designed and installed in nine months. The BBN team continued to interact with the NPL team with meetings between them taking place in the U.S. and the U.K. As with the NPL network, the first-generation IMPs were built by BBN using a rugged computer version of

2233-462: The SDS 940 crashed after he typed two characters. About an hour later, after Duvall adjusted parameters on the machine, Kline tried again and successfully logged in. Hence, the first two characters successfully transmitted over the ARPANET were "lo". The first permanent ARPANET link was established on 21 November 1969, between the IMP at UCLA and the IMP at the Stanford Research Institute. By 5 December 1969,

2310-531: The business world, various companies, many of them started or guided by prominent AI researchers created productized versions of inference engines. For example, Intellicorp was initially guided by Edward Feigenbaum . These inference engine products were also often developed in Lisp at first. However, demands for more affordable and commercially viable platforms eventually made personal computer platforms very popular. ClipsRules and RefPerSys (inspired by CAIA and

2387-590: The certainty factor MYCIN combined these weights using the formula below to yield a single certainty factor: Where X and Y are the certainty factors. This formula can be applied more than once if more than two rules draw conclusions about the same parameter. It is commutative , so it does not matter in which order the weights were combined. The combination formula was designed to have the following desirable properties: The following examples come from Chapter 16 of PAIP, which contains an implementation in Common Lisp of

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2464-417: The civil and military networks reduced the 113-node ARPANET by 68 nodes. After MILNET was split away, the ARPANET would continue to be used as an Internet backbone for researchers, but be slowly phased out. In 1985, the NSF funded the establishment of national supercomputing centers at several universities and provided network access and network interconnectivity with the NSFNET project in 1986. NSFNET became

2541-499: The concept of 'inference' has expanded to include the process through which trained neural networks generate predictions or decisions. In this context, an 'inference engine' could refer to the specific part of the system, or even the hardware, that executes these operations. This type of inference plays a crucial role in various applications, including (but not limited to) image recognition , natural language processing , and autonomous vehicles . The inference phase in these applications

2618-691: The concept of the " Intergalactic Computer Network ". Those ideas encompassed many of the features of the contemporary Internet. In October 1963, Licklider was appointed head of the Behavioral Sciences and Command and Control programs at the Defense Department's Advanced Research Projects Agency (ARPA). He convinced Ivan Sutherland and Bob Taylor that this network concept was very important and merited development, although Licklider left ARPA before any contracts were assigned for development. Sutherland and Taylor continued their interest in creating

2695-715: The experts to provide estimates for an unfeasibly large number of conditional probabilities . Subsequent studies later showed that the certainty factor model could indeed be interpreted in a probabilistic sense, and highlighted problems with the implied assumptions of such a model. However the modular structure of the system would prove very successful, leading to the development of graphical models such as Bayesian networks . A context in MYCIN determines what types of objects can be reasoned about. They are similar to variables in Prolog, or environment variables in operating systems. In MYCIN it

2772-400: The fact. So if the system asked the user "Is Socrates human?", the user may wonder why she was being asked that question and the system would use the chain of rules to explain why it was currently trying to ascertain that bit of knowledge: that is, it needs to determine if Socrates is mortal and to do that needs to determine if he is human. At first these explanations were not much different than

2849-493: The greatest problem, and the reason that MYCIN was not used in routine practice, was the state of technologies for system integration, especially at the time it was developed. MYCIN was a stand-alone system that required a user to enter all relevant information about a patient by typing in responses to questions MYCIN posed. The program ran on a large time-shared system, available over the early Internet ( ARPANet ), before personal computers were developed. MYCIN's greatest influence

2926-400: The inference engine would find any facts in the knowledge base that matched Human(x) and for each fact it found would add the new information Mortal(x) to the knowledge base. So if it found an object called Socrates that was human it would deduce that Socrates was mortal. In backward chaining , the system would be given a goal, e.g. answer the question is Socrates mortal? It would search through

3003-542: The initial four-node network was established. Elizabeth Feinler created the first Resource Handbook for ARPANET in 1969 which led to the development of the ARPANET directory. The directory, built by Feinler and a team made it possible to navigate the ARPANET. In 1968, Roberts contracted with Kleinrock to measure the performance of the network and find areas for improvement. Building on his earlier work on queueing theory and optimization of packet delay in communication networks, Kleinrock specified mathematical models of

3080-426: The knowledge base and determine if Socrates was human and, if so, would assert he is also mortal. However, in backward chaining a common technique was to integrate the inference engine with a user interface. In that way, rather than simply being automated the system could now be interactive. In this trivial example, if the system was given the goal to answer the question if Socrates was mortal and it didn't yet know if he

3157-418: The knowledge base could trigger additional rules in the inference engine. Inference engines work primarily in one of two modes either special rule or facts: forward chaining and backward chaining . Forward chaining starts with the known facts and asserts new facts. Backward chaining starts with goals, and works backward to determine what facts must be asserted so that the goals can be achieved. Additionally,

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3234-576: The knowledge base. In backward chaining, the engine looks for antecedents that can satisfy one of the current goals. In the second step, select rules , the inference engine prioritizes the various rules that were matched to determine the order to execute them. In the final step, execute rules , the engine executes each matched rule in the order determined in step two and then iterates back to step one again. The cycle continues until no new rules are matched. Early inference engines focused primarily on forward chaining. These systems were usually implemented in

3311-569: The network, in part, to allow ARPA-sponsored researchers at various corporate and academic locales to utilize computers provided by ARPA, and, in part, to quickly distribute new software and other computer science results. Taylor had three computer terminals in his office, each connected to separate computers, which ARPA was funding: one for the System Development Corporation (SDC) Q-32 in Santa Monica , one for Project Genie at

3388-452: The other terminal and get in touch with them. I said, 'Oh Man!', it's obvious what to do: If you have these three terminals, there ought to be one terminal that goes anywhere you want to go. That idea is the ARPANET". Donald Davies' work caught the attention of ARPANET developers at Symposium on Operating Systems Principles in October 1967. He gave the first public presentation, having coined

3465-597: The performance of packet-switched networks, which underpinned the development of the ARPANET as it expanded rapidly in the early 1970s. Roberts engaged Howard Frank to consult on the topological design of the network. Frank made recommendations to increase throughput and reduce costs in a scaled-up network. By March 1970, the ARPANET reached the East Coast of the United States, when an IMP at BBN in Cambridge, Massachusetts

3542-426: The potential for disagreement about therapeutic decisions, even among experts, when there is no "gold standard" for correct treatment. MYCIN was never actually used in practice. This wasn't because of any weakness in its performance. Some observers raised ethical and legal issues related to the use of computers in medicine, regarding the responsibility of the physicians in case the system gave wrong diagnosis. However,

3619-480: The questions and rules which led it to rank a diagnosis a particular way), and its recommended course of drug treatment. Samuel Clark sparked debate about the use of its ad hoc , but principled, uncertainty framework known as " certainty factors ". Certainty factors were designed to deal with disbelief/belief, but they do not deal with probabilistic dependence/independence, and they are not probabilities. The developers performed studies showing that MYCIN's performance

3696-518: The questions of message size and contents for the network, and to write a position paper on the intercomputer communication protocol including “conventions for character and block transmission, error checking and re-transmission, and computer and user identification." In April 1967, ARPA held a design session on technical standards. The initial standards for identification and authentication of users, transmission of characters, and error checking and retransmission procedures were discussed. Roberts' proposal

3773-433: The rules will often result in new facts or goals being added to the knowledge base, which will trigger the cycle to repeat. This cycle continues until no new rules can be matched. In the first step, match rules , the inference engine finds all of the rules that are triggered by the current contents of the knowledge base. In forward chaining, the engine looks for rules where the antecedent (left hand side) matches some fact in

3850-460: The set of all natural numbers. Such statements are perfectly reasonable and even required in mathematical proofs but when included in an automated theorem prover executing on a computer may cause the computer to fall into an infinite loop. Focusing on IF-THEN statements (what logicians call modus ponens ) still gave developers a very powerful general mechanism to represent logic, but one that could be used efficiently with computational resources. What

3927-413: The standard debugging information that developers deal with when debugging any system. However, an active area of research was utilizing natural language technology to ask, understand, and generate questions and explanations using natural languages rather than computer formalisms. An inference engine cycles through three sequential steps: match rules , select rules , and execute rules . The execution of

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4004-442: The start of the use of the non-ruggedized (and therefore significantly lighter) Honeywell 316 as an IMP. It could also be configured as a Terminal Interface Processor (TIP), which provided terminal server support for up to 63 ASCII serial terminals through a multi-line controller in place of one of the hosts. The 316 featured a greater degree of integration than the 516, which made it less expensive and easier to maintain. The 316

4081-594: The survivability of the network in the event of significant interruption. Furthermore, the ARPANET was designed to survive subordinate network losses. However, the Internet Society agrees with Herzfeld in a footnote in their online article, A Brief History of the Internet : It was from the RAND study that the false rumor started, claiming that the ARPANET was somehow related to building a network resistant to nuclear war. This

4158-461: The technical specificity of their response to the ARPA RFQ, and thus quickly produced the first working system. The "IMP guys" were led by Frank Heart ; the theoretical design of the network was led by Bob Kahn ; the team included Dave Walden , Severo Ornstein , William Crowther and several others. The BBN-proposed network closely followed Roberts' ARPA plan: a network composed of small computers,

4235-400: The telecommunication and computer industry had assured private sector expansion and commercialization of an expanded worldwide network, known as the Internet. Historically, voice and data communications were based on methods of circuit switching , as exemplified in the traditional telephone network, wherein each telephone call is allocated a dedicated end-to-end electronic connection between

4312-573: The term packet switching , in August 1968 and incorporated it into the NPL network in England. The NPL network and ARPANET were the first two networks in the world to implement packet switching. Roberts said the computer networks built in the 1970s were similar "in nearly all respects" to Davies' original 1965 design. In February 1966, Bob Taylor successfully lobbied ARPA's Director Charles M. Herzfeld to fund

4389-652: The theoretical model of distributed adaptive message block switching . However, the telecommunication establishment rejected the development in favor of existing models. Donald Davies at the United Kingdom's National Physical Laboratory (NPL) independently arrived at a similar concept in 1965. The earliest ideas for a computer network intended to allow general communications among computer users were formulated by computer scientist J. C. R. Licklider of Bolt Beranek and Newman (BBN), in April 1963, in memoranda discussing

4466-517: The two communicating stations. The connection is established by switching systems that connected multiple intermediate call legs between these systems for the duration of the call. The traditional model of the circuit-switched telecommunication network was challenged in the early 1960s by Paul Baran at the RAND Corporation , who had been researching systems that could sustain operation during partial destruction, such as by nuclear war. He developed

4543-482: The work of Jacques Pitrat ). The Frama-C static source code analyzer also uses some inference engine techniques. ARPANet Early research and development: Merging the networks and creating the Internet: Commercialization, privatization, broader access leads to the modern Internet: Examples of Internet services: The Advanced Research Projects Agency Network ( ARPANET )

4620-428: Was accordingly its demonstration of the power of its representation and reasoning approach. Rule-based systems in many non-medical domains were developed in the years that followed MYCIN's introduction of the approach. In the 1980s, expert system "shells" were introduced (including one based on MYCIN, known as E-MYCIN (followed by Knowledge Engineering Environment - KEE )) and supported the development of expert systems in

4697-446: Was added in 1970, although considerations of cost and IMP processing power meant this capability was not actively used. Larry Roberts saw the ARPANET and NPL projects as complementary and sought in 1970 to connect them via a satellite link. Peter Kirstein 's research group at University College London (UCL) was subsequently chosen in 1971 in place of NPL for the UK connection. In June 1973,

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4774-464: Was completed on restructuring the ARPANET giving U.S. military sites their own Military Network ( MILNET ) for unclassified defense department communications. Both networks carried unclassified information and were connected at a small number of controlled gateways which would allow total separation in the event of an emergency. MILNET was part of the Defense Data Network (DDN). Separating

4851-591: Was configured with 40 kB of core memory for a TIP. The size of core memory was later increased, to 32 kB for the IMPs, and 56 kB for TIPs, in 1973. The ARPANET was demonstrated at the International Conference on Computer Communications in October 1972. In 1975, BBN introduced IMP software running on the Pluribus multi-processor . These appeared in a few sites. In 1981, BBN introduced IMP software running on its own C/30 processor product. ARPA

4928-545: Was connected to the network. Thereafter, the ARPANET grew: 9 IMPs by June 1970 and 13 IMPs by December 1970, then 18 by September 1971 (when the network included 23 university and government hosts); 29 IMPs by August 1972, and 40 by September 1973. By June 1974, there were 46 IMPs, and in July 1975, the network numbered 57 IMPs. By 1981, the number was 213 host computers, with another host connecting approximately every twenty days. Support for inter-IMP circuits of up to 230.4 kbit/s

5005-606: Was declared operational in 1971. Network traffic began to grow once email was established at the majority of sites by around 1973. The initial ARPANET configuration linked UCLA , ARC , UCSB , and the University of Utah School of Computing . The first node was created at UCLA, where Leonard Kleinrock could evaluate network performance and examine his theories on message delay . The locations were selected not only to reduce leased line costs but also because each had specific expertise beneficial for this initial implementation phase: The first successful host-to-host connection on

5082-453: Was human, it would generate a window to ask the user the question "Is Socrates human?" and would then use that information accordingly. This innovation of integrating the inference engine with a user interface led to the second early advancement of expert systems: explanation capabilities. The explicit representation of knowledge as rules rather than code made it possible to generate explanations to users: both explanations in real time and after

5159-573: Was intended to fund advanced research. The ARPANET was a research project that was communications-oriented, rather than user-oriented in design. Nonetheless, in the summer of 1975, operational control of the ARPANET passed to the Defense Communications Agency . At about this time, the first ARPANET encryption devices were deployed to support classified traffic. The ARPANET Completion Report , written in 1978 and published in 1981 jointly by BBN and DARPA , concludes that:  ... it

5236-475: Was led by Steve Crocker at UCLA and other graduate students, including Jon Postel and others. The network was declared operational in 1971. Further software development enabled remote login and file transfer , which was used to provide an early form of email . The network expanded rapidly and operational control passed to the Defense Communications Agency in 1975. Bob Kahn moved to DARPA and, together with Vint Cerf at Stanford University , formulated

5313-485: Was minimally affected by perturbations in the uncertainty metrics associated with individual rules, suggesting that the power in the system was related more to its knowledge representation and reasoning scheme than to the details of its numerical uncertainty model. Some observers felt that it should have been possible to use classical Bayesian statistics . MYCIN's developers argued that this would require either unrealistic assumptions of probabilistic independence , or require

5390-587: Was more focus on issues such as speed and robustness. One of the first and most popular forward chaining engines was OPS5 , which used the Rete algorithm to optimize the efficiency of rule firing. Another very popular technology that was developed was the Prolog logic programming language. Prolog focused primarily on backward chaining and also featured various commercial versions and optimizations for efficiency and robustness. As expert systems prompted significant interest from

5467-423: Was never true of the ARPANET, but was an aspect of the earlier RAND study of secure communication. The later work on internetworking did emphasize robustness and survivability, including the capability to withstand losses of large portions of the underlying networks. Paul Baran , the first to put forward a theoretical model for communication using packet switching, conducted the RAND study referenced above. Though

5544-416: Was possible that two or more rules might draw conclusions about a parameter with different weights of evidence. For example, one rule may conclude that the organism in question is E. Coli with a certainty of 0.8 whilst another concludes that it is E. Coli with a certainty of 0.5 or even -0.8. In the event the certainty is less than zero the evidence is actually against the hypothesis. In order to calculate

5621-434: Was presented at the inaugural Symposium on Operating Systems Principles in October 1967. Donald Davies' work on packet switching and the NPL network, presented by a colleague ( Roger Scantlebury ), and that of Paul Baran, came to the attention of the ARPA investigators at this conference. Roberts applied Davies' concept of packet switching for the ARPANET, and sought input from Paul Baran on dynamic routing. The NPL network

5698-461: Was that all mainframe computers would connect to one another directly. The other investigators were reluctant to dedicate these computing resources to network administration. After the design session, Wesley Clark proposed minicomputers should be used as an interface to create a message switching network. Roberts modified the ARPANET plan to incorporate Clark's suggestion and named the minicomputers Interface Message Processors (IMPs). The plan

5775-665: Was the first wide-area packet-switched network with distributed control and one of the first computer networks to implement the TCP/IP protocol suite. Both technologies became the technical foundation of the Internet . The ARPANET was established by the Advanced Research Projects Agency (now DARPA) of the United States Department of Defense . Building on the ideas of J. C. R. Licklider , Bob Taylor initiated

5852-438: Was to take an expert system application and repackage the inference engine used for that system as a re-usable tool other researchers could use for the development of other expert systems. For example, MYCIN was an early expert system for medical diagnosis and EMYCIN was an inference engine extrapolated from MYCIN and made available for other researchers. As expert systems moved from research prototypes to deployed systems there

5929-480: Was using line speeds of 768 kbit/s, and the proposed line speed for the ARPANET was upgraded from 2.4 kbit/s to 50 kbit/s. By mid-1968, Roberts and Barry Wessler wrote a final version of the IMP specification based on a Stanford Research Institute (SRI) report that ARPA commissioned to write detailed specifications describing the ARPANET communications network. Roberts gave a report to Taylor on 3 June, who approved it on 21 June. After approval by ARPA,

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