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106-405: As a standard RBAC system, PERMIS's main entities are The PERMIS policy is eXtensible Markup Language ( XML )-based and has rules for user-role assignments and role-privilege assignments, the latter containing optional obligations that are returned to the application when a user is granted access to a resource. A PERMIS policy can be stored as either a simple text XML file, or as an attribute within

212-549: A numeric character reference . Consider the Chinese character "中", whose numeric code in Unicode is hexadecimal 4E2D, or decimal 20,013. A user whose keyboard offers no method for entering this character could still insert it in an XML document encoded either as &#20013; or &#x4e2d; . Similarly, the string "I <3 Jörg" could be encoded for inclusion in an XML document as I &lt;3 J&#xF6;rg . &#0;

318-415: A computer network . It provides better bandwidth utilization than traditional circuit-switching used for telephony, and enables the connection of computers with different transmission and receive rates. It is a distinct concept to message switching. Following discussions with J. C. R. Licklider in 1965, Donald Davies became interested in data communications for computer networks. Later that year, at

424-481: A Credential Validation Service that validates users' roles according to the user-role assignment rules, and the Policy Decision Point (PDP) that evaluates users' access requests according to the role-permission assignment rules (or access control rules). Access to a resource depends upon the roles/attributes assigned to the user, and the role-permission assignments, which can contain constraints based on

530-701: A central role in popularizing the Internet outside the ARPANET. In 1986, the NSF created NSFNET , a 56 kbit/s backbone to support the NSF-sponsored supercomputing centers. The NSFNET also provided support for the creation of regional research and education networks in the United States, and for the connection of university and college campus networks to the regional networks. The use of NSFNET and

636-439: A computer network in his March 1960 paper Man-Computer Symbiosis : A network of such centers, connected to one another by wide-band communication lines [...] the functions of present-day libraries together with anticipated advances in information storage and retrieval and symbiotic functions suggested earlier in this paper In August 1962, Licklider and Welden Clark published the paper "On-Line Man-Computer Communication" which

742-598: A distributed network to the IPTO staff, whom he called "Members and Affiliates of the Intergalactic Computer Network ". Although he left the IPTO in 1964, five years before the ARPANET went live, it was his vision of universal networking that provided the impetus for one of his successors, Robert Taylor , to initiate the ARPANET development. Licklider later returned to lead the IPTO in 1973 for two years. The infrastructure for telephone systems at

848-448: A list of syntax rules provided in the specification. Some key points in the fairly lengthy list include: The definition of an XML document excludes texts that contain violations of well-formedness rules; they are simply not XML. An XML processor that encounters such a violation is required to report such errors and to cease normal processing. This policy, occasionally referred to as " draconian error handling", stands in notable contrast to

954-854: A means to help the state's educational and economic development. With initial support from the State of Michigan and the National Science Foundation (NSF), the packet-switched network was first demonstrated in December 1971 when an interactive host to host connection was made between the IBM mainframe computer systems at the University of Michigan in Ann Arbor and Wayne State University in Detroit . In October 1972 connections to

1060-522: A mechanism whereby an XML processor can reliably, without any prior knowledge, determine which encoding is being used. Encodings other than UTF-8 and UTF-16 are not necessarily recognized by every XML parser (and in some cases not even UTF-16, even though the standard mandates it to also be recognized). XML provides escape facilities for including characters that are problematic to include directly. For example: There are five predefined entities : All permitted Unicode characters may be represented with

1166-473: A method was needed to unify them. Louis Pouzin initiated the CYCLADES project in 1972, building on the work of Donald Davies and the ARPANET. An International Network Working Group formed in 1972; active members included Vint Cerf from Stanford University , Alex McKenzie from BBN , Donald Davies and Roger Scantlebury from NPL , and Louis Pouzin and Hubert Zimmermann from IRIA . Pouzin coined

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1272-555: A more compact non-XML syntax; the two syntaxes are isomorphic and James Clark 's conversion tool— Trang —can convert between them without loss of information. RELAX NG has a simpler definition and validation framework than XML Schema, making it easier to use and implement. It also has the ability to use datatype framework plug-ins ; a RELAX NG schema author, for example, can require values in an XML document to conform to definitions in XML Schema Datatypes. Schematron

1378-489: A result, when the handoff was complete, Sprint and its Washington DC Network Access Points began to carry Internet traffic, and by 1996, Sprint was the world's largest carrier of Internet traffic. The research and academic community continues to develop and use advanced networks such as Internet2 in the United States and JANET in the United Kingdom. The term "internet" was reflected in the first RFC published on

1484-506: A rich datatyping system and allow for more detailed constraints on an XML document's logical structure. XSDs also use an XML-based format, which makes it possible to use ordinary XML tools to help process them. xs:schema element that defines a schema: RELAX NG (Regular Language for XML Next Generation) was initially specified by OASIS and is now a standard (Part 2: Regular-grammar-based validation of ISO/IEC 19757 – DSDL ). RELAX NG schemas may be written in either an XML based syntax or

1590-584: A signed X.509 attribute certificate to provide integrity protection and tampering detection. User roles and attributes may be held in secure signed X.509 attributes certificates, and stored in Lightweight Directory Access Protocol ( LDAP ) directories or Web-based Distributed Authoring and Versioning ( WebDAV ) repositories, or they may be created on demand as Security Assertion Markup Language ( SAML ) attribute assertions. The PERMIS authorisation engine comprises two components:

1696-668: A single point of failure, existing telegraphic techniques were inefficient and inflexible. Beginning in 1965 Donald Davies , at the National Physical Laboratory in the United Kingdom, developed a more advanced proposal of the concept, designed for high-speed computer networking , which he called packet switching , the term that would ultimately be adopted. Packet switching is a technique for transmitting computer data by splitting it into very short, standardized chunks, attaching routing information to each of these chunks, and transmitting them independently through

1802-519: A system designed by professor Norman Abramson and others at the University of Hawaiʻi at Mānoa that transmitted data by radio between seven computers on four islands on Hawaii . Steve Crocker formed the "Network Working Group" in 1969 at UCLA. Working with Jon Postel and others, he initiated and managed the Request for Comments (RFC) process, which is still used today for proposing and distributing contributions. RFC 1, entitled "Host Software",

1908-421: A validity error must be able to report it, but may continue normal processing. A DTD is an example of a schema or grammar . Since the initial publication of XML 1.0, there has been substantial work in the area of schema languages for XML. Such schema languages typically constrain the set of elements that may be used in a document, which attributes may be applied to them, the order in which they may appear, and

2014-527: A vocabulary to refer to the constructs within an XML document, but does not provide any guidance on how to access this information. A variety of APIs for accessing XML have been developed and used, and some have been standardized. Existing APIs for XML processing tend to fall into these categories: Stream-oriented facilities require less memory and, for certain tasks based on a linear traversal of an XML document, are faster and simpler than other alternatives. Tree-traversal and data-binding APIs typically require

2120-461: Is a lexical , event-driven API in which a document is read serially and its contents are reported as callbacks to various methods on a handler object of the user's design. SAX is fast and efficient to implement, but difficult to use for extracting information at random from the XML, since it tends to burden the application author with keeping track of what part of the document is being processed. It

2226-726: Is a language for making assertions about the presence or absence of patterns in an XML document. It typically uses XPath expressions. Schematron is now a standard (Part 3: Rule-based validation of ISO/IEC 19757 – DSDL ). DSDL (Document Schema Definition Languages) is a multi-part ISO/IEC standard (ISO/IEC 19757) that brings together a comprehensive set of small schema languages, each targeted at specific problems. DSDL includes RELAX NG full and compact syntax, Schematron assertion language, and languages for defining datatypes, character repertoire constraints, renaming and entity expansion, and namespace-based routing of document fragments to different validators. DSDL schema languages do not have

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2332-578: Is an XML industry data standard. XML is used extensively to underpin various publishing formats. One of the applications of XML is in the transfer of Operational meteorology (OPMET) information based on IWXXM standards. The material in this section is based on the XML Specification . This is not an exhaustive list of all the constructs that appear in XML; it provides an introduction to the key constructs most often encountered in day-to-day use. XML documents consist entirely of characters from

2438-498: Is better suited to situations in which certain types of information are always handled the same way, no matter where they occur in the document. Pull parsing treats the document as a series of items read in sequence using the iterator design pattern . This allows for writing of recursive descent parsers in which the structure of the code performing the parsing mirrors the structure of the XML being parsed, and intermediate parsed results can be used and accessed as local variables within

2544-442: Is not permitted because the null character is one of the control characters excluded from XML, even when using a numeric character reference. An alternative encoding mechanism such as Base64 is needed to represent such characters. Comments may appear anywhere in a document outside other markup. Comments cannot appear before the XML declaration. Comments begin with <!-- and end with --> . For compatibility with SGML ,

2650-593: The .NET Framework , and the DOM traversal API (NodeIterator and TreeWalker). History of the Internet#Internet Engineering Task Force The history of the Internet has its origin in the efforts of scientists and engineers to build and interconnect computer networks . The Internet Protocol Suite , the set of rules used to communicate between networks and devices on the Internet, arose from research and development in

2756-797: The CDC mainframe at Michigan State University in East Lansing completed the triad. Over the next several years in addition to host to host interactive connections the network was enhanced to support terminal to host connections, host to host batch connections (remote job submission, remote printing, batch file transfer), interactive file transfer, gateways to the Tymnet and Telenet public data networks , X.25 host attachments, gateways to X.25 data networks, Ethernet attached hosts, and eventually TCP/IP and additional public universities in Michigan join

2862-505: The Compatible Time-Sharing System project at Massachusetts Institute of Technology (MIT). Taylor's identified need for networking became obvious from the waste of resources apparent to him. 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

2968-692: The Energy Sciences Network or ESNet. NASA developed the TCP/IP based NASA Science Network (NSN) in the mid-1980s, connecting space scientists to data and information stored anywhere in the world. In 1989, the DECnet -based Space Physics Analysis Network (SPAN) and the TCP/IP-based NASA Science Network (NSN) were brought together at NASA Ames Research Center creating the first multiprotocol wide area network called

3074-590: The International Telegraph and Telephone Consultative Committee (ITU-T) in the form of X.25 and related standards. X.25 is built on the concept of virtual circuits emulating traditional telephone connections. In 1974, X.25 formed the basis for the SERCnet network between British academic and research sites, which later became JANET , the United Kingdom's high-speed national research and education network (NREN). The initial ITU Standard on X.25

3180-509: The Internet . It is a textual data format with strong support via Unicode for different human languages . Although the design of XML focuses on documents, the language is widely used for the representation of arbitrary data structures , such as those used in web services . Several schema systems exist to aid in the definition of XML-based languages, while programmers have developed many application programming interfaces (APIs) to aid

3286-450: The National Physical Laboratory (NPL) in the United Kingdom, Davies designed and proposed a national commercial data network based on packet switching. The following year, he described the use of "switching nodes" to act as routers in a digital communication network. The proposal was not taken up nationally but he produced a design for a local network to serve the needs of the NPL and prove

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3392-580: The Transmission Control Protocol (TCP) and Internet Protocol (IP), two protocols of the Internet protocol suite . The design included concepts pioneered in the French CYCLADES project directed by Louis Pouzin. The development of packet switching networks was underpinned by mathematical work in the 1970s by Leonard Kleinrock at UCLA. In the late 1970s, national and international public data networks emerged based on

3498-639: The U.S. government , the National Aeronautics and Space Administration (NASA), the National Science Foundation (NSF), and the Department of Energy (DOE) became heavily involved in Internet research and started development of a successor to ARPANET. In the mid-1980s, all three of these branches developed the first Wide Area Networks based on TCP/IP. NASA developed the NASA Science Network , NSF developed CSNET and DOE evolved

3604-458: The Unicode repertoire. Except for a small number of specifically excluded control characters , any character defined by Unicode may appear within the content of an XML document. XML includes facilities for identifying the encoding of the Unicode characters that make up the document, and for expressing characters that, for one reason or another, cannot be used directly. Unicode code points in

3710-678: The United States and involved international collaboration, particularly with researchers in the United Kingdom and France . Computer science was an emerging discipline in the late 1950s that began to consider time-sharing between computer users, and later, the possibility of achieving this over wide area networks . J. C. R. Licklider developed the idea of a universal network at the Information Processing Techniques Office (IPTO) of

3816-483: The X.25 protocol, designed by Rémi Després and others. In the United States, the National Science Foundation (NSF) funded national supercomputing centers at several universities in the United States, and provided interconnectivity in 1986 with the NSFNET project, thus creating network access to these supercomputer sites for research and academic organizations in the United States. International connections to NSFNET,

3922-401: The end-to-end principle conceived by Donald Davies and make the hosts responsible for reliable delivery of data, rather than the network itself, using unreliable datagrams . Concepts implemented in this network influenced TCP/IP architecture. Based on international research initiatives, particularly the contributions of Rémi Després , packet switching network standards were developed by

4028-410: The infoset augmentation facility and attribute defaults. RELAX NG and Schematron intentionally do not provide these. A cluster of specifications closely related to XML have been developed, starting soon after the initial publication of XML 1.0. It is frequently the case that the term "XML" is used to refer to XML together with one or more of these other technologies that have come to be seen as part of

4134-824: The NASA Science Internet, or NSI. NSI was established to provide a totally integrated communications infrastructure to the NASA scientific community for the advancement of earth, space and life sciences. As a high-speed, multiprotocol, international network, NSI provided connectivity to over 20,000 scientists across all seven continents. In 1981, NSF supported the development of the Computer Science Network (CSNET). CSNET connected with ARPANET using TCP/IP, and ran TCP/IP over X.25 , but it also supported departments without sophisticated network connections, using automated dial-up mail exchange. CSNET played

4240-543: The NPL network was the first to use high-speed links. Many other packet switching networks built in the 1970s were similar "in nearly all respects" to Davies' original 1965 design. The Mark II version which operated from 1973 used a layered protocol architecture. In 1976, 12 computers and 75 terminal devices were attached, and more were added. The NPL team carried out simulation work on wide-area packet networks, including datagrams and congestion ; and research into internetworking and secure communications . The network

4346-680: The NSFNET was decommissioned in 1995, removing the last restrictions on the use of the Internet to carry commercial traffic, as traffic transitioned to optical networks managed by Sprint, MCI and AT&T in the United States. Research at CERN in Switzerland by the British computer scientist Tim Berners-Lee in 1989–90 resulted in the World Wide Web , linking hypertext documents into an information system, accessible from any node on

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4452-671: The Norwegian Seismic Array ( NORSAR ), via a satellite link at the Tanum Earth Station in Sweden, and to Peter Kirstein 's research group at University College London , which provided a gateway to British academic networks , the first international heterogenous resource sharing network. Throughout the 1970s, Leonard Kleinrock developed the mathematical theory to model and measure the performance of packet-switching technology, building on his earlier work on

4558-714: The S.D.C. terminal, go over and log into 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 where you have interactive computing. That idea is the ARPAnet. Bringing in Larry Roberts from MIT in January 1967, he initiated a project to build such a network. Roberts and Thomas Merrill had been researching computer time-sharing over wide area networks (WANs). Wide area networks emerged during

4664-473: The SECRET-level SIPRNET and JWICS for TOP SECRET and above. NIPRNET does have controlled security gateways to the public Internet. The networks based on the ARPANET were government funded and therefore restricted to noncommercial uses such as research; unrelated commercial use was strictly forbidden. This initially restricted connections to military sites and universities. During the 1980s,

4770-464: The TCP protocol (RFC 675: Internet Transmission Control Program, December 1974) as a short form of internetworking , when the two terms were used interchangeably. In general, an internet was a collection of networks linked by a common protocol. In the time period when the ARPANET was connected to the newly formed NSFNET project in the late 1980s, the term was used as the name of the network, Internet, being

4876-581: The United States Department of Defense (DoD) Advanced Research Projects Agency (ARPA). Independently, Paul Baran at the RAND Corporation proposed a distributed network based on data in message blocks in the early 1960s, and Donald Davies conceived of packet switching in 1965 at the National Physical Laboratory (NPL), proposing a national commercial data network in the United Kingdom. ARPA awarded contracts in 1969 for

4982-465: The United States with connections to the United Kingdom and Norway. Several early packet-switched networks emerged in the 1970s which researched and provided data networking . Louis Pouzin and Hubert Zimmermann pioneered a simplified end-to-end approach to internetworking at the IRIA . Peter Kirstein put internetworking into practice at University College London in 1973. Bob Metcalfe developed

5088-470: The World Wide Web with its discussion forums , blogs , social networking services , and online shopping sites. Increasing amounts of data are transmitted at higher and higher speeds over fiber-optic networks operating at 1 Gbit/s , 10 Gbit/s, and 800 Gbit/s by 2019. The Internet's takeover of the global communication landscape was rapid in historical terms: it only communicated 1% of

5194-429: The XML core. Some other specifications conceived as part of the "XML Core" have failed to find wide adoption, including XInclude , XLink , and XPointer . The design goals of XML include, "It shall be easy to write programs which process XML documents." Despite this, the XML specification contains almost no information about how programmers might go about doing such processing. The XML Infoset specification provides

5300-555: The XML processor inserts in the DTD itself and in the XML document wherever they are referenced, like character escapes. DTD technology is still used in many applications because of its ubiquity. A newer schema language, described by the W3C as the successor of DTDs, is XML Schema , often referred to by the initialism for XML Schema instances, XSD (XML Schema Definition). XSDs are far more powerful than DTDs in describing XML languages. They use

5406-434: The allowable parent/child relationships. The oldest schema language for XML is the document type definition (DTD), inherited from SGML. DTDs have the following benefits: DTDs have the following limitations: Two peculiar features that distinguish DTDs from other schema types are the syntactic support for embedding a DTD within XML documents and for defining entities , which are arbitrary fragments of text or markup that

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5512-531: The application of queueing theory to message switching systems. By 1981, the number of hosts had grown to 213. The ARPANET became the technical core of what would become the Internet, and a primary tool in developing the technologies used. The Merit Network was formed in 1966 as the Michigan Educational Research Information Triad to explore computer networking between three of Michigan's public universities as

5618-621: The base language for communication protocols such as SOAP and XMPP . It is one of the message exchange formats used in the Asynchronous JavaScript and XML (AJAX) programming technique. Many industry data standards, such as Health Level 7 , OpenTravel Alliance , FpML , MISMO , and National Information Exchange Model are based on XML and the rich features of the XML schema specification. In publishing, Darwin Information Typing Architecture

5724-401: The behavior of programs that process HTML , which are designed to produce a reasonable result even in the presence of severe markup errors. XML's policy in this area has been criticized as a violation of Postel's law ("Be conservative in what you send; be liberal in what you accept"). The XML specification defines a valid XML document as a well-formed XML document which also conforms to

5830-423: The case of C1 characters, this restriction is a backwards incompatibility; it was introduced to allow common encoding errors to be detected. The code point U+0000 (Null) is the only character that is not permitted in any XML 1.1 document. The Unicode character set can be encoded into bytes for storage or transmission in a variety of different ways, called "encodings". Unicode itself defines encodings that cover

5936-427: The connections expanded to more educational institutions, and a growing number of companies such as Digital Equipment Corporation and Hewlett-Packard , which were participating in research projects or providing services to those who were. Data transmission speeds depended upon the type of connection, the slowest being analog telephone lines and the fastest using optical networking technology. Several other branches of

6042-429: The data structure and contain metadata . What is within the tags is data, encoded in the way the XML standard specifies. An additional XML schema (XSD) defines the necessary metadata for interpreting and validating XML. (This is also referred to as the canonical schema.) An XML document that adheres to basic XML rules is "well-formed"; one that adheres to its schema is "valid." IETF RFC 7303 (which supersedes

6148-593: The development of prototype software. Testing began in 1975 through concurrent implementations at Stanford, BBN and University College London (UCL). After several years of work, the first demonstration of a gateway between the Packet Radio network (PRNET) in the SF Bay area and the ARPANET was conducted by the Stanford Research Institute . On November 22, 1977, a three network demonstration

6254-573: The development of the ARPANET project, directed by Robert Taylor and managed by Lawrence Roberts . ARPANET adopted the packet switching technology proposed by Davies and Baran. The network of Interface Message Processors (IMPs) was built by a team at Bolt, Beranek, and Newman , with the design and specification led by Bob Kahn . The host-to-host protocol was specified by a group of graduate students at UCLA , led by Steve Crocker , along with Jon Postel and others. The ARPANET expanded rapidly across

6360-442: The direct use of almost any Unicode character in element names, attributes, comments, character data, and processing instructions (other than the ones that have special symbolic meaning in XML itself, such as the less-than sign, "<"). The following is a well-formed XML document including Chinese , Armenian and Cyrillic characters: The XML specification defines an XML document as a well-formed text, meaning that it satisfies

6466-537: The emergence of architecture such as the Domain Name System , and the adoption of TCP/IP on existing networks in the United States and around the world marked the beginnings of the Internet . Commercial Internet service providers (ISPs) emerged in 1989 in the United States and Australia. Limited private connections to parts of the Internet by officially commercial entities emerged in several American cities by late 1989 and 1990. The optical backbone of

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6572-523: The entire repertoire; well-known ones include UTF-8 (which the XML standard recommends using, without a BOM ) and UTF-16 . There are many other text encodings that predate Unicode, such as ASCII and various ISO/IEC 8859 ; their character repertoires are in every case subsets of the Unicode character set. XML allows the use of any of the Unicode-defined encodings and any other encodings whose characters also appear in Unicode. XML also provides

6678-436: The feasibility of packet switching using high-speed data transmission. To deal with packet permutations (due to dynamically updated route preferences) and to datagram losses (unavoidable when fast sources send to a slow destinations), he assumed that "all users of the network will provide themselves with some kind of error control", thus inventing what came to be known as the end-to-end principle . In 1967, he and his team were

6784-443: The first attested use of the term internet , as a shorthand for internetwork. This software was monolithic in design using two simplex communication channels for each user session. With the role of the network reduced to a core of functionality, it became possible to exchange traffic with other networks independently from their detailed characteristics, thereby solving the fundamental problems of internetworking. DARPA agreed to fund

6890-549: The first international packet-switched network, referred to as the International Packet Switched Service (IPSS), in 1978. This network grew from Europe and the US to cover Canada, Hong Kong, and Australia by 1981. By the 1990s it provided a worldwide networking infrastructure. Unlike ARPANET, X.25 was commonly available for business use. Telenet offered its Telemail electronic mail service, which

6996-456: The first service to offer electronic mail capabilities and technical support to personal computer users. The company broke new ground again in 1980 as the first to offer real-time chat with its CB Simulator . Other major dial-in networks were America Online (AOL) and Prodigy that also provided communications, content, and entertainment features. Many bulletin board system (BBS) networks also provided on-line access, such as FidoNet which

7102-482: The first to use the term 'protocol' in a modern data-commutation context. In 1968, Davies began building the Mark I packet-switched network to meet the needs of his multidisciplinary laboratory and prove the technology under operational conditions. The network's development was described at a 1968 conference. Elements of the network became operational in early 1969, the first implementation of packet switching, and

7208-498: The following ranges are valid in XML 1.0 documents: XML 1.1 extends the set of allowed characters to include all the above, plus the remaining characters in the range U+0001–U+001F. At the same time, however, it restricts the use of C0 and C1 control characters other than U+0009 (Horizontal Tab), U+000A (Line Feed), U+000D (Carriage Return), and U+0085 (Next Line) by requiring them to be written in escaped form (for example U+0001 must be written as &#x01; or its equivalent). In

7314-708: The functions performing the parsing, or passed down (as function parameters) into lower-level functions, or returned (as function return values) to higher-level functions. Examples of pull parsers include Data::Edit::Xml in Perl , StAX in the Java programming language, XMLPullParser in Smalltalk , XMLReader in PHP , ElementTree.iterparse in Python , SmartXML in Red , System.Xml.XmlReader in

7420-510: The guys at SRI ...", Kleinrock ... said in an interview: "We typed the L and we asked on the phone, Yet a revolution had begun" .... By December 1969, a four-node network was connected by adding the Culler-Fried Interactive Mathematics Center at the University of California, Santa Barbara followed by the University of Utah Graphics Department. In the same year, Taylor helped fund ALOHAnet ,

7526-444: The information flowing through two-way telecommunications networks in the year 1993, 51% by 2000, and more than 97% of the telecommunicated information by 2007. The Internet continues to grow, driven by ever greater amounts of online information, commerce, entertainment, and social networking services . However, the future of the global network may be shaped by regional differences. J. C. R. Licklider, while working at BBN, proposed

7632-516: The late 1950s and became established during the 1960s. At the first ACM Symposium on Operating Systems Principles in October 1967, Roberts presented a proposal for the "ARPA net", based on Wesley Clark's idea to use Interface Message Processors (IMP) to create a message switching network. At the conference, Roger Scantlebury presented Donald Davies' work on a hierarchical digital communications network using packet switching and referenced

7738-500: The mesh of UUCP hosts forwarding on the Usenet news rapidly expanded. UUCPnet, as it would later be named, also created gateways and links between FidoNet and dial-up BBS hosts. UUCP networks spread quickly due to the lower costs involved, ability to use existing leased lines, X.25 links or even ARPANET connections, and the lack of strict use policies compared to later networks like CSNET and BITNET . All connects were local. By 1981

7844-689: The network being responsible for reliability, as in the ARPANET, the hosts became responsible. Cerf and Kahn published their ideas in May 1974, which incorporated concepts implemented by Louis Pouzin and Hubert Zimmermann in the CYCLADES network. The specification of the resulting protocol, the Transmission Control Program , was published as RFC   675 by the Network Working Group in December 1974. It contains

7950-580: The network to; ARPA's primary mission was funding cutting-edge research and development, not running a communications utility. In July 1975, the network was turned over to the Defense Communications Agency , also part of the Department of Defense . In 1983, the U.S. military portion of the ARPANET was broken off as a separate network, the MILNET . MILNET subsequently became the unclassified but military-only NIPRNET , in parallel with

8056-422: The network. All of this set the stage for Merit's role in the NSFNET project starting in the mid-1980s. The CYCLADES packet switching network was a French research network designed and directed by Louis Pouzin . In 1972, he began planning the network to explore alternatives to the early ARPANET design and to support internetworking research. First demonstrated in 1973, it was the first network to implement

8162-426: The network. The dramatic expansion of the capacity of the Internet, enabled by the advent of wave division multiplexing (WDM) and the rollout of fiber optic cables in the mid-1990s, had a revolutionary impact on culture, commerce, and technology. This made possible the rise of near-instant communication by electronic mail , instant messaging , voice over Internet Protocol (VoIP) telephone calls, video chat , and

8268-592: The number of UUCP hosts had grown to 550, nearly doubling to 940 in 1984. Sublink Network , operating since 1987 and officially founded in Italy in 1989, based its interconnectivity upon UUCP to redistribute mail and news groups messages throughout its Italian nodes (about 100 at the time) owned both by private individuals and small companies. Sublink Network evolved into one of the first examples of Internet technology coming into use through popular diffusion. With so many different networking methods seeking interconnection,

8374-550: The older RFC 3023 ), provides rules for the construction of media types for use in XML message. It defines three media types: application/xml ( text/xml is an alias), application/xml-external-parsed-entity ( text/xml-external-parsed-entity is an alias) and application/xml-dtd . They are used for transmitting raw XML files without exposing their internal semantics . RFC 7303 further recommends that XML-based languages be given media types ending in +xml , for example, image/svg+xml for SVG . Further guidelines for

8480-449: The processing of XML data. The main purpose of XML is serialization , i.e. storing, transmitting, and reconstructing arbitrary data. For two disparate systems to exchange information, they need to agree upon a file format. XML standardizes this process. It is therefore analogous to a lingua franca for representing information. As a markup language , XML labels, categorizes, and structurally organizes information. XML tags represent

8586-676: The recent addition of a controlled natural language interface (in English) for writing simple PERMIS policies. XML Extensible Markup Language ( XML ) is a markup language and file format for storing, transmitting, and reconstructing arbitrary data. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable . The World Wide Web Consortium 's XML 1.0 Specification of 1998 and several other related specifications —all of them free open standards —define XML. The design goals of XML emphasize simplicity, generality, and usability across

8692-485: The regional networks was not limited to supercomputer users and the 56 kbit/s network quickly became overloaded. NSFNET was upgraded to 1.5 Mbit/s in 1988 under a cooperative agreement with the Merit Network in partnership with IBM , MCI , and the State of Michigan . The existence of NSFNET and the creation of Federal Internet Exchanges (FIXes) allowed the ARPANET to be decommissioned in 1990. NSFNET

8798-487: The rules of a Document Type Definition (DTD). In addition to being well formed, an XML document may be valid . This means that it contains a reference to a Document Type Definition (DTD), and that its elements and attributes are declared in that DTD and follow the grammatical rules for them that the DTD specifies. XML processors are classified as validating or non-validating depending on whether or not they check XML documents for validity. A processor that discovers

8904-708: The splitting of the Transmission Control Program into the Transmission Control Protocol (TCP) and the Internet Protocol (IP) in version 3 in 1978. Version 4 was described in IETF publication RFC 791 (September 1981), 792 and 793. It was installed on SATNET in 1982 and the ARPANET in January 1983 after the DoD made it standard for all military computer networking. This resulted in a networking model that became known informally as TCP/IP. It

9010-469: The string "--" (double-hyphen) is not allowed inside comments; this means comments cannot be nested. The ampersand has no special significance within comments, so entity and character references are not recognized as such, and there is no way to represent characters outside the character set of the document encoding. An example of a valid comment: <!--no need to escape <code> & such in comments--> XML 1.0 (Fifth Edition) and XML 1.1 support

9116-433: The term catenet for concatenated network. Bob Metcalfe at Xerox PARC outlined the idea of Ethernet and PARC Universal Packet (PUP) for internetworking . Bob Kahn , now at DARPA , recruited Vint Cerf to work with him on the problem. By 1973, these groups had worked out a fundamental reformulation, in which the differences between network protocols were hidden by using a common internetworking protocol. Instead of

9222-699: The theory behind Ethernet and the PARC Universal Packet . ARPA initiatives and the International Network Working Group developed and refined ideas for internetworking, in which multiple separate networks could be joined into a network of networks . Vint Cerf , now at Stanford University , and Bob Kahn, now at DARPA, published their research on internetworking in 1974. Through the Internet Experiment Note series and later RFCs this evolved into

9328-526: The time was based on circuit switching , which requires pre-allocation of a dedicated communication line for the duration of the call. Telegram services had developed store and forward telecommunication techniques. Western Union 's Automatic Telegraph Switching System Plan 55-A was based on message switching . The U.S. military's AUTODIN network became operational in 1962. These systems, like SAGE and SBRE, still required rigid routing structures that were prone to single point of failure . The technology

9434-474: The use of XML in a networked context appear in RFC 3470 , also known as IETF BCP 70, a document covering many aspects of designing and deploying an XML-based language. XML has come into common use for the interchange of data over the Internet. Hundreds of document formats using XML syntax have been developed, including RSS , Atom , Office Open XML , OpenDocument , SVG , COLLADA , and XHTML . XML also provides

9540-472: The use of much more memory, but are often found more convenient for use by programmers; some include declarative retrieval of document components via the use of XPath expressions. XSLT is designed for declarative description of XML document transformations, and has been widely implemented both in server-side packages and Web browsers. XQuery overlaps XSLT in its functionality, but is designed more for searching of large XML databases . Simple API for XML (SAX)

9646-442: The user attributes/roles and the policy, which guarantees their integrity and protects them from being tampered with. New features are continually being added to it, like a standard eXtensible Access Control Markup Language ( XACML ) interface which allows PERMIS and XACML PDPs to be seamlessly interchanged, the ability to accept SAML attribute assertions, support for dynamic delegation of authority and separation of duty policies, and

9752-402: The user's access request (e.g. "print less than 10 pages") and the environment (e.g. time of day). PERMIS can work in either push mode (the user attribute assignments are sent to PERMIS by the application) or in pull mode (PERMIS fetches the attribute assignments itself from LDAP/WebDAV repositories or SAML attribute authorities). PERMIS is unique with its support for cryptographically protecting

9858-426: The vendor support of XML Schemas yet, and are to some extent a grassroots reaction of industrial publishers to the lack of utility of XML Schemas for publishing . Some schema languages not only describe the structure of a particular XML format but also offer limited facilities to influence processing of individual XML files that conform to this format. DTDs and XSDs both have this ability; they can for instance provide

9964-467: The work of Paul Baran at RAND . Roberts incorporated the packet switching and routing concepts of Davies and Baran into the ARPANET design and upgraded the proposed communications speed from 2.4 kbit/s to 50 kbit/s. ARPA awarded the contract to build the network to Bolt Beranek & Newman . The "IMP guys", led by Frank Heart and Bob Kahn , developed the routing, flow control, software design and network control. The first ARPANET link

10070-508: Was also referred to as the Department of Defense (DoD) model or DARPA model. Cerf credits his graduate students Yogen Dalal, Carl Sunshine, Judy Estrin , Richard Karp , and Gérard Le Lann with important work on the design and testing. DARPA sponsored or encouraged the development of TCP/IP implementations for many operating systems. After the ARPANET had been up and running for several years, ARPA looked for another agency to hand off

10176-458: Was also targeted to enterprise use rather than the general email system of the ARPANET. The first public dial-in networks used asynchronous teleprinter (TTY) terminal protocols to reach a concentrator operated in the public network. Some networks, such as Telenet and CompuServe , used X.25 to multiplex the terminal sessions into their packet-switched backbones, while others, such as Tymnet , used proprietary protocols. In 1979, CompuServe became

10282-726: Was approved in March 1976. Existing networks, such as Telenet in the United States adopted X.25 as well as new public data networks , such as DATAPAC in Canada and TRANSPAC in France. X.25 was supplemented by the X.75 protocol which enabled internetworking between national PTT networks in Europe and commercial networks in North America. The British Post Office , Western Union International , and Tymnet collaborated to create

10388-652: Was conducted including the ARPANET, the SRI's Packet Radio Van on the Packet Radio Network and the Atlantic Packet Satellite Network (SATNET) including a node at UCL. The software was redesigned as a modular protocol stack, using full-duplex channels; between 1976 and 1977, Yogen Dalal and Robert Metcalfe among others, proposed separating TCP's routing and transmission control functions into two discrete layers, which led to

10494-443: Was considered vulnerable for strategic and military use because there were no alternative paths for the communication in case of a broken link. In the early 1960s, Paul Baran of the RAND Corporation produced a study of survivable networks for the U.S. military in the event of nuclear war. Information would be transmitted across a "distributed" network, divided into what he called "message blocks". In addition to being prone to

10600-592: Was established between the Network Measurement Center at the University of California, Los Angeles (UCLA) Henry Samueli School of Engineering and Applied Science directed by Leonard Kleinrock , and the NLS system at Stanford Research Institute (SRI) directed by Douglas Engelbart in Menlo Park , California at 22:30 hours on October 29, 1969. "We set up a telephone connection between us and

10706-536: Was expanded and upgraded to dedicated fiber, optical lasers and optical amplifier systems capable of delivering T3 start up speeds or 45 Mbit/s in 1991. However, the T3 transition by MCI took longer than expected, allowing Sprint to establish a coast-to-coast long-distance commercial Internet service. When NSFNET was decommissioned in 1995, its optical networking backbones were handed off to several commercial Internet service providers, including MCI, PSI Net and Sprint. As

10812-707: Was one of the first descriptions of a networked future. In October 1962, Licklider was hired by Jack Ruina as director of the newly established Information Processing Techniques Office (IPTO) within ARPA, with a mandate to interconnect the United States Department of Defense's main computers at Cheyenne Mountain , the Pentagon, and SAC HQ. There he formed an informal group within DARPA to further computer research. He began by writing memos in 1963 describing

10918-410: Was operating, they argued that the router buffers would quickly run out. After the ARPANET was operating, they argued packet switching would never be economic without the government subsidy. Baran faced the same rejection and thus failed to convince the military into constructing a packet switching network. Early international collaborations via the ARPANET were sparse. Connections were made in 1973 to

11024-403: Was popular amongst hobbyist computer users, many of them hackers and amateur radio operators . In 1979, two students at Duke University , Tom Truscott and Jim Ellis , originated the idea of using Bourne shell scripts to transfer news and messages on a serial line UUCP connection with nearby University of North Carolina at Chapel Hill . Following public release of the software in 1980,

11130-537: Was replaced in 1986. Robert Taylor was promoted to the head of the Information Processing Techniques Office (IPTO) at Defense Advanced Research Projects Agency (DARPA) in 1966. He intended to realize Licklider 's ideas of an interconnected networking system. As part of the IPTO's role, three network terminals had been installed: one for System Development Corporation in Santa Monica , one for Project Genie at University of California, Berkeley , and one for

11236-505: Was written by Steve Crocker and published on April 7, 1969. The protocol for establishing links between network sites in the ARPANET, the Network Control Program (NCP), was completed in 1970. These early years were documented in the 1972 film Computer Networks: The Heralds of Resource Sharing . Roberts presented the idea of packet switching to the communication professionals, and faced anger and hostility. Before ARPANET

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