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Enfilade (Xanadu)
Enfilades are a class of tree data structures invented by computer scientist Ted Nelson and used in Project Xanadu "Green" designs of the 1970s and 1980s. Enfilades allow quick editing, versioning, retrieval and inter-comparison operations in a large, cross-linked hypertext database. The Xanadu "Gold" design starting in the 1990s used a related data structure called the Ent. Structure and properties Although the principles of enfilades can be applied to any tree data structure, the particular structure used in the Xanadu system was much like a B-Tree. What distinguishes enfilades is the use of dsps and wids in the indexing information within tree nodes. Dsps are displacements, offsets or relative keys. A dsp is the difference in key between a containing node and that of a subtree or leaf. For instance, the leaf for a grid square in a map might have a certain longitude and latitude offset relative to the larger grid represented by the subtree the leaf is part of. The key of any leaf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tree (data Structure)
In computer science, a tree is a widely used abstract data type that represents a hierarchical tree structure with a set of connected nodes. Each node in the tree can be connected to many children (depending on the type of tree), but must be connected to exactly one parent, except for the ''root'' node, which has no parent. These constraints mean there are no cycles or "loops" (no node can be its own ancestor), and also that each child can be treated like the root node of its own subtree, making recursion a useful technique for tree traversal. In contrast to linear data structures, many trees cannot be represented by relationships between neighboring nodes in a single straight line. Binary trees are a commonly used type, which constrain the number of children for each parent to exactly two. When the order of the children is specified, this data structure corresponds to an ordered tree in graph theory. A value or pointer to other data may be associated with every node in the tre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Permutation Matrix
In mathematics, particularly in matrix theory, a permutation matrix is a square binary matrix that has exactly one entry of 1 in each row and each column and 0s elsewhere. Each such matrix, say , represents a permutation of elements and, when used to multiply another matrix, say , results in permuting the rows (when pre-multiplying, to form ) or columns (when post-multiplying, to form ) of the matrix . Definition Given a permutation of ''m'' elements, :\pi : \lbrace 1, \ldots, m \rbrace \to \lbrace 1, \ldots, m \rbrace represented in two-line form by :\begin 1 & 2 & \cdots & m \\ \pi(1) & \pi(2) & \cdots & \pi(m) \end, there are two natural ways to associate the permutation with a permutation matrix; namely, starting with the ''m'' × ''m'' identity matrix, , either permute the columns or permute the rows, according to . Both methods of defining permutation matrices appear in the literature and the properties expressed in one representation can be easily converted to th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GiST
In computing, GiST or Generalized Search Tree, is a data structure and API that can be used to build a variety of disk-based search trees. GiST is a generalization of the B+ tree, providing a concurrent and recoverable height-balanced search tree infrastructure without making any assumptions about the type of data being stored, or the queries being serviced. GiST can be used to easily implement a range of well-known indexes, including B+ trees, R-trees, hB-trees, RD-trees, and many others; it also allows for easy development of specialized indexes for new data types. It cannot be used directly to implement non-height-balanced trees such as quad trees or prefix trees (tries), though like prefix trees it does support compression, including lossy compression. GiST can be used for any data type that can be naturally ordered into a hierarchy of supersets. Not only is it extensible in terms of data type support and tree layout, it allows the extension writer to support any query pred ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypermedia
Hypermedia, an extension of the term hypertext, is a nonlinear medium of information that includes graphics, audio, video, plain text and hyperlinks. This designation contrasts with the broader term ''multimedia'', which may include non-interactive linear presentations as well as hypermedia. It is also related to the field of electronic literature. The term was first used in a 1965 article written by Ted Nelson. The World Wide Web is a classic example of hypermedia to access web content, whereas a non-interactive cinema presentation is an example of standard multimedia due to the absence of hyperlinks. The first hypermedia work was, arguably, the Aspen Movie Map. Bill Atkinson's HyperCard popularized hypermedia writing, while a variety of literary hypertext and hypertext works, fiction and non-fiction, demonstrated the promise of links. Most modern hypermedia is delivered via electronic pages from a variety of systems including media players, web browsers, and stand-alone ap ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Docuverse
Docuverse is a global distributed electronic library of interconnected documents, in other words, a global metadocument. The term was coined by Ted Nelson in 1974, as a concept related to the Project Xanadu, and the World Wide Web The World Wide Web (WWW), commonly known as the Web, is an information system enabling documents and other web resources to be accessed over the Internet. Documents and downloadable media are made available to the network through web se ... later nominally fulfilled a subset of the aspects of Nelson's vision. References Further reading * External linksXanadu project webpage Content management systems [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Roger Gregory (programmer)
Roger Everett Gregory is a US computer programmer, technologist, and scientist. Gregory's work in project Xanadu made him one of the earliest pioneers of hypertext technology, which helped lay the foundations for the hyperlink technology that underlies the World Wide Web. Gregory attended the University of Michigan as a mathematics major. In the 1970s, he founded the Ann Arbor Computer Club, similar to the West Coast's Home Brew Computer Club. In 1974 Gregory met Theodore Holm (Ted) Nelson, the author of Computer Lib/Dream Machines, and the thinker who coined the term "hypertext". The pair became friends. In 1979 Nelson convinced Gregory to move from Michigan and join him in Swarthmore, Pennsylvania, the small, sleepy college town outside of Philadelphia where Nelson earned his undergraduate degree, and first conceived the concept of a hypertext. Gregory's first summer in Swarthmore, characterized by Xanadu insiders as the ''"Swarthmore Summer"'', was a productive time, wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stuart Greene
Stuart may refer to: Names *Stuart (name), a given name and surname (and list of people with the name) Automobile * Stuart (automobile) Places Australia Generally * Stuart Highway, connecting South Australia and the Northern Territory Northern Territory *Stuart, the former name for Alice Springs (changed 1933) * Stuart Park, an inner city suburb of Darwin *Central Mount Stuart, a mountain peak Queensland * Stuart, Queensland, a suburb of Townsville *Mount Stuart, Queensland, a suburb of Townsville *Mount Stuart (Queensland), a mountain South Australia *Stuart, South Australia, a locality in the Mid Murray Council *Electoral district of Stuart, a state electoral district *Hundred of Stuart, a cadastral unit Canada *Stuart Channel, a strait in the Gulf of Georgia region of British Columbia United Kingdom *Castle Stuart United States *Stuart, Florida *Stuart, Iowa * Stuart, Nebraska * Stuart, Oklahoma * Stuart, Virginia *Stuart Township, Holt County, Nebras ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mark S
Mark may refer to: Currency * Bosnia and Herzegovina convertible mark, the currency of Bosnia and Herzegovina * East German mark, the currency of the German Democratic Republic * Estonian mark, the currency of Estonia between 1918 and 1927 * Finnish markka ( sv, finsk mark, links=no), the currency of Finland from 1860 until 28 February 2002 * Mark (currency), a currency or unit of account in many nations * Polish mark ( pl, marka polska, links=no), the currency of the Kingdom of Poland and of the Republic of Poland between 1917 and 1924 German * Deutsche Mark, the official currency of West Germany from 1948 until 1990 and later the unified Germany from 1990 until 2002 * German gold mark, the currency used in the German Empire from 1873 to 1914 * German Papiermark, the German currency from 4 August 1914 * German rentenmark, a currency issued on 15 November 1923 to stop the hyperinflation of 1922 and 1923 in Weimar Germany * Lodz Ghetto mark, a special currency for Lodz Ghetto. * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tumbler (Project Xanadu)
In the design of the Xanadu computer system, a tumbler is an address of any range of content or link or a set of ranges or links. According to Gary Wolf in ''Wired'', the idea of tumblers was that "the address would not only point the reader to the correct machine, it would also indicate the author of the document, the version of the document, the correct span of bytes, and the links associated with these bytes." Tumblers were created by Roger Gregory and Mark Miller. They were used in the Xanadu FEBE (Front End - Back End) protocol in a manner similar to the use of URIs between web browsers and servers. Concept and implementation The idea behind tumblers comes from transfinite numbers. A tumbler is a unique numerical address of any interesting artifact. It resembles an IP address, but is much larger and has much more detailed structure. The structure looks like this. 1. .0. .0. .0. The leading "1." is used in order to mark the start of a new address. The individual fields ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Literary Machines
''Literary Machines'' (short title) is a book first published in 1981 by Ted Nelson, and republished nine times by 1993. It offers an extensive overview of Nelson's term "hypertext" as well as Nelson's Project Xanadu. It also includes other theories by Nelson, including "tumblers" for addressing bits in files past and present, "transclusion" as a method for including original work in one's own work, and "micropayments" to pay for the use. The format of the book is nonlinear, as the chapters are arranged in such a way that the text can be read out of order. The preface to the 1993 edition states "''The first edition of ''Literary Machines,'' done on a typewriter, appeared in April of 1981. We printed it on a Saxon copier that filled the house with a vinegar smell. But it had a beautiful cover, its white title silk-screened on mirrored plastic. Since that time the book has gone through various editions with different-colored covers, printed by various people with various degrees ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transclusion
In computer science, transclusion is the inclusion of part or all of an electronic document into one or more other documents by reference via hypertext. Transclusion is usually performed when the referencing document is displayed, and is normally automatic and transparent to the end user. The result of transclusion is a single integrated document made of parts assembled dynamically from separate sources, possibly stored on different computers in disparate places. Transclusion facilitates modular design (using the single source of truth model, whether in data, code, or content): a resource is stored once and distributed for reuse in multiple documents. Updates or corrections to a resource are then reflected in any referencing documents. In systems where transclusion is not available, and in some situations where it is available but not desirable, substitution is often the complementary option, whereby a static copy of the single source of truth is integrated into the relevant ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ted Nelson
Theodor Holm Nelson (born June 17, 1937) is an American pioneer of information technology, philosopher, and sociologist. He coined the terms ''hypertext'' and ''hypermedia'' in 1963 and published them in 1965. Nelson coined the terms ''transclusion'', ''virtuality'', and ''intertwingularity'' (in ''Literary Machines''). According to a 1997 ''Forbes'' profile, Nelson "sees himself as a literary romantic, like a Cyrano de Bergerac, or 'the Orson Welles of software'." Early life and education Nelson is the son of Emmy Award-winning director Ralph Nelson and Academy Award-winning actress Celeste Holm. His parents' marriage was brief and he was mostly raised by his grandparents, first in Chicago and later in Greenwich Village. Nelson earned a B.A. in philosophy from Swarthmore College in 1959. While there, he made an experimental humorous student film, ''The Epiphany of Slocum Furlow'', in which the titular hero discovers the meaning of life. His contemporary at the college, music ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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