Garg, P., `Abstraction mechanisms in hypertext', Communications of the ACM 31(7), (1988) 862--870.  Home/Search   Document Not in Database   Summary   ACM   TOC   Related Articles   Check

....destination node. A person browsing ahypertext traverses the graph and views (or hears) the information fragments as he visits nodes. Some researchers are beginning to realize the need for a more formal substructure for the highly implementation defi, fi eld of hypertext# for example [12] and [16]. Projects are beginning to appear that attempt to construct a more complete and descriptive mathematical basis for documents than directed graphs and annotations can provide. The work described in this report is based on one such mathematical framework that provided byaPetri net. The Trellis ....

....to permit addition of notations and commentary) At issue is howto grant some browsers the right to modify while restricting others to reading only. One approach mightbe Contrast the use of this graphically based model with a non graphical one such as Garg s, which is based in abstract algebra [16], While the non graphical models have certainly demonstrated their utility, the mental shift required to employ their results is significant. See, for example, the proceedings of the 1985 International Workshop on Timed Petri Nets and the proceedings of the 1987 International Workshop on Petri ....

Garg, P. K. Abstraction mechanisms in hypertext. Commun. ACM 31, 7 (July 1988), 862--870, 879.

....next over edges of the graph. This conceptual model is appropriate for knowledge tasks in which one node explains, amplifies, or otherwise elucidates another: a line in an outline leads to a paragraph or chapter; a word leads to its definition; a citation leads to the document cited. In general [GARG88] CAGO88] LANG90] there are exceptions [HASW90] links are binary and often directed, and the nodes that they connect differ in kind from one another. For another kind of knowledge task a different conceptual model is more appropriate, a model based on set theory. This model facilitates ....

....our focus is on the conceptual model that governs the user s interaction with the system, not the mathematical model underlying the implementation. Graph theory itself can be founded in set theory, and several formalizations of conventional graph based hypermedia in fact uge a . qet formali.qm [GARG88] HASW90]. Still, conventional systems all envision the user as moving from one node of a graph to another, not from one set to another by way of a shared node, or from one node to another by way of a common set. Even at the conceptual level, sets can be employed in several ways. Aggregation techniques ....

[Article contains additional citation context not shown here]

P.K. Garg, "Abstraction Mechanisms in Hypertext." CACM 31:7, 862-870.

....An example of the formal model for hypertext databases using hypergraphs is presented by Tompa [16] The model facilitates the separation of structure from the content. Functional modelling of dynamic behaviour is based on the algebraic theory or on description of hypertext functions. In [8], the hypertext is modelled as a set of domain and information objects, a set of predicates and attributes. Tompa s structural model [16] is combined with functional modelling of behaviour by extending a hypergraph with operations. The automaton modelling is based on the automaton theory or on ....

Garg, P.K.: Abstraction Mechanisms in Hypertext. Communications of the ACM, Vol. 31, No. 7, 862-870, July 1988.

.... databases, views present a consistent partition of the database [44, 7] Such mechanisms have been adopted in object oriented databases [98, 2, 19, 94] see [81] for a survey) and semantic data models [26] Moreover, contexts have been proposed as a partitioning scheme of hypertext databases [27, 17, 40], and perspectives as a mechanism for organizing and manipulating groups of nodes and links in a hypertext network [91] 27 HAM [17] is a general purpose abstract machine that supports contexts. In HAM, a graph usually contains all the information regarding a general topic and contexts are used ....

Pankaj K. Garg. Abstraction Mechanisms in Hypertext. Communications of the ACM, 31(7):862--870, July 1988.

.... speci#cation can be employed for navigation modelling: data models extended with built in navigation semantics #Garzotto et al. 1993; Isakowitz et al. 1995; Fraternali and Paolini 1998# or explicitly annotated with behavioral speci#cations #Kesseler 1995; Schwabe and Rossi 1995#, #rst order logic #Garg 1988#, Petri nets #Stotts and Furuta 1989#, #nite state machines #Zheng and Pong 1992#, and formal grammars #Jacob 1982# are among the viable options. Presentation modelling aims at representing the visual elements of the application interfaces in a way that abstracts from the particular language and ....

Garg, P. K. 1988. Abstractions mechanisms in hypertext. Communications of ACM 31,7, 862#870.

....generate infinite link instances. Park [14] also studied dynamic properties of hypertext in terms of readers experience . He proved that the set of link followings in a hypertext, i.e. our hyperconnectivity, is regular. However, he does not investigate more powerful classes of automata. Garg [44], and later Richard and Rizk [45] present models able to describe several hypertext systems. Garg [44] focuses on abstractions in hypertexts, while Richard and Rizk highlight the relationship between objects containing information. Furuta and Stotts [11] formalize hypertext systems in their ....

.... readers experience . He proved that the set of link followings in a hypertext, i.e. our hyperconnectivity, is regular. However, he does not investigate more powerful classes of automata. Garg [44] and later Richard and Rizk [45] present models able to describe several hypertext systems. Garg [44] focuses on abstractions in hypertexts, while Richard and Rizk highlight the relationship between objects containing information. Furuta and Stotts [11] formalize hypertext systems in their Trellis model; their R model [46] is more complete as it includes windows modelisation. Parunak describes ....

Pankaj K. Garg, (1988). Abstraction Mechanisms in Hypertext. Communications of the ACM, 31(7):862-- 870.

....destination node. A person browsing a hypertext traverses the graph and views (or hears) the information fragments as he visits nodes. Some researchers are beginning to realize the need for a more formal substructure for the highly implementation defined field of hypertext; for example [12] and [16]. Projects are beginning to appear that attempt to construct a more complete and descriptive mathematical basis for documents than directed graphs and annotations can provide. The work described in this report is based on one such mathematical framework that provided by a Petri net. The Trellis ....

....permit addition of notations and commentary) At issue is how to grant some browsers the right to modify while restricting others to reading only. One approach might be 8 Contrast the use of this graphically based model with a non graphical one such as Garg s, which is based in abstract algebra [16]. While the non graphical models have certainly demonstrated their utility, the mental shift required to employ their results is significant. 9 See, for example, the proceedings of the 1985 International Workshop on Timed Petri Nets and the proceedings of the 1987 International Workshop on Petri ....

Garg, P. K. Abstraction mechanisms in hypertext. Commun. ACM 31, 7 (July 1988), 862--870, 879.

.... Phi Phi Phi refine 6 enlarge most general most specific Figure 5: Conceptual view of the Hyperindex 6 3 Two Level Hypermedia In the literature there have been a number of papers which focus on formally defining hypermedia at a conceptual level. Several approaches can be recognized; in [Gar88] for example, a model of hypermedia is presented using firstorder logic. In [Tom89] hypermedia is modelled in terms of hypergraphs. We take a different approach, and consider hypermedia as more than just a way of presenting the underlying information (this is also recognized in [Sal89] In our ....

P. Garg. Abstraction mechanisms in hypertext. Communications ACM, 31(7):863--870, July 1988.

....enables the user to navigate through the information base. Furthermore, state of the art hypermedia systems, in contrast to conventional information systems, feature almost no conceptual description of the stored data. The weaknesses of such an approach have been discussed by several authors ( Gar88] SF89] There seems to be a growing need to be able to support a conceptual description with regard to both hypermedia and traditional document information systems. The combination of structured documents with hypermedia applications looks promising. This paper describes a stratified ....

....the concept of evolutionary distance is introduced. Finally, section 6 contains a summary and conclusions. 2 Stratified Hypermedia In the literature there have been a number of papers which focus on formally defining hypermedia at a conceptual level. Several approaches can be recognized; in [Gar88] for example, a model of hypermedia is presented using first order logic. In [Tom89] hypermedia is modelled in terms of hypergraphs. Recently, two level hypermedia architectures have been emerging. See [BvdW90b, Luc90, AAC 89, ACG91, GGP89] Such architectures feature an upper level, the ....

P. Garg. Abstraction mechanisms in hypertext. Communications ACM, 31(7):863--870, July 1988.

....considered as being essential: the classification mechanism, the generalization specialization mechanism and the aggregation mechanism. These three mechanisms are hereby illustrated. Major references for the formulation of a conceptual modelling paradigm are [10,11] in the database area and [12] in the hypertext area. The classification mechanism is one of fundamental and very intuitive nature which permits definition of a class selected from a set of objects with common properties. Each single object is a defined instance of the class; a class and its instance are related by means of ....

P. K. Garg, `Abstraction mechanisms in hypertext', Communications of the ACM, 31(7), 862--870, 879 (1988).

....type, but also could add new documents and links without necessarily specifying their semantics in form of a type. It has now become clear that the above distinction between hypertext systems and DBMS is oversimplified and no longer valid. A first step towards typed hypertexts were formal models [24, 15] based on the semantic data model IFO [1] Subsequent implementations like HDM [16] and MacWeb [22] have then demonstrated that the best way for managing real size hypertexts is by generating them according to a schema describing the hypertext application. Hypertext schemas have therefore been ....

P.K. Garg. Abstraction mechanisms in hypertext. Communications of the ACM, 31(7):862-870, July 1988.

.... documents are such rich sources of structure information, presenting them from various viewpoints is essential for an interactive document retrieval system [3] For example, a typesetter may be interested in a document s physical appearance, while an editor may be more concerned with its contents [4]. While printed text has an inherently linear structure, it is not without other structuring mechanisms, such as aggregation due to section level nesting, and referential relations between spans. 1 Hence, textual documents have (at least) a double structure: one defined by inter span relations, ....

P. K. Garg. Abstraction mechanisms in hypertext. In Proceedings of Hypertext '87 (The University of North Carolina, Chapel Hill, North Carolina; November 13-15, 1987), pages 375--395, November 1987.

....Many systems maintain links as first class objects with attributes and types, just as nodes may have attributes and types. Link attributes can be used for: filtering, as in HAM where possibilities are limited to only those links matching a particular predicate [Campbell 88] search, as in [Garg 88] where keywords are used to produce retrieval sets, context clues for the user, as in NoteCards graphical browser, where various link types are displayed as different arc types [Halasz 88] database computation, as in IBIS where link types have semantic meaning [Conklin 87b] 8 I am ....

P.K. Garg. "Abstraction Mechanisms in Hypertext." Communications of the ACM, 31(7), July, 1988. pp. 856-861.

....of nodes) allows the breaking of a single large hypermedia document into appropriate modules, allows for views over the hypermedia document, and allows the user to make changes at the cluster level without affecting the hypermedia document itself. For more information on clustering see [4] [8]. Current clustering in hypermedia systems is either structurally driven where the connectivity of the nodes delineates the clusters [1] 11] or concept driven where the keywords (either in the nodes themselves or in the meta information about each node) delineate the clusters [2] 6] ....

P. Garg. Abstraction mechanisms in hypertext. Communications of the ACM, 31(7):862--870 (1988).

.... Schutt and Haake 1993) Augment(Engelbart 1984) Telesophy(Caplinger 1987; Schatz 1987) and HAM(Campbell and Goodman 1988; Delisle and Schwartz 1987) Others have been proposed primarily as formal abstractions, e.g. Dexter(Halasz and Schwartz 1990) Lange 1990; Lange 1993) Tompa 1989) and (Garg 1988). The way that a system handles anchors is an important consideration. Intermedia and DGS provide explicit mechanisms for associating links with anchor points within nodes, whereas HyperBase and HAM suggest that applications use attributes to store this information. An advantage of the former ....

Garg, P. K. (1988, July). Abstraction mechanisms in hypertext. Communications of the ACM 31 (7), 862--870.

....link definitions and a hypertext interface on top of existing databases and applications also indicate that architectural design be carefully considered. Abstract models of hypertext systems are not plentiful (see Stotts and Furuta [SF89] Tompa [Tom89] Watters and Sheperd [WS90] and Garg [Gar88]) The work by Stotts and Furuta, using Petri nets as their underlying model, and that of Tompa, who uses hypergraphs, is directed to systems where the link network is predefined. Possibly the lack of references to abstract models comes from the belief that if a system is monolithic, as most still ....

....to be defined under user control, the operations which act on these user definitions 18 must maintain their integrity regardless of the type of relations a user might have in mind. The relevant reported work is described in the following sections. 3.4.1. Mathematical Models Pankaj Garg [Gar88] appears to be the first and, one could argue, the main developer of a robust abstraction mechanism for hypertext. He presents a set theoretical model of hypertext as his abstraction and then goes on to show how the abstractions can be supported in a hypertext. Garg points out some of the ....

Garg, P., Abstraction Mechanisms in Hypertext, CACM(31), 7(1988), 862-870.

....of replacing it. The treatment of composites will be discussed further in chapter 4 in the section on mathematical modelling (section 4. 2) Certainly it is the case that composites can be considered representations of aggregations and generalisations of nodes, and the related treatment by both Garg (1988) and Watters and Sheperd (1990) is worth considering when designing operations on composites (see chapter 4) Virtual Structures for Dealing with Changing Information According to Halasz, by definition, hypermedia encodes information into a collection of independent nodes interconnected into a ....

....also require that architectural design must be carefully considered. This chapter addresses these concerns in order to build a firm foundation for a successful design. Abstract models of hypertext systems are not plentiful (see Stotts and Furuta 1989; Tompa 1989; Watters and Sheperd 1990; and Garg 1988). The work by Stotts and Furuta, using Petri nets as their underlying model, and that of Tompa, who uses hypergraphs, is directed at representing browsing semantics in text based information retrieval systems. Possibly the lack of references to abstract models comes from the belief that if a ....

[Article contains additional citation context not shown here]

Garg, P., Abstraction Mechanisms in Hypertext, CACM(31), 7(1988), 862-870.

....within which to reason about hypertext design. The use of this model in presenting and comparing existing models, as well as its use in developing a new hypertext learning model, is briefly discussed. 1 Introduction Many formal reference models of hypertext have been presented in the literature [1, 12, 17, 20, 21], and whilst these models give valuable theoretical insights into certain aspects of the structure of hypertext, they are not by themselves adequate vehicles for the presentation, evaluation and comparison of different systems. In this paper we describe an approach to the formal specification of ....

P. Garg. Abstraction Mechanisms in Hypertext. Communications of the ACM, 31(7):862--870, 1988.

No context found.

Garg, P., `Abstraction mechanisms in hypertext', Communications of the ACM 31(7), (1988) 862--870.

No context found.

Garg, P. J. "Abstraction Mechanisms in Hypertext" in HT'87 [HT'87+]

No context found.

P. Garg. Abstraction mechanisms in hypertext. Communications ACM, 31(7):863--870, July 1988.

No context found.

Pankaj K. Garg. Abstraction Mechanisms in Hypertext. Communications of the ACM, 31(7):862--870, July 1988.

No context found.

P.K. Garg. "Abstraction Mechanisms for Hypertext". Communications ACM 31, 7 (1988), 862-870.

No context found.

Garg88 P. K. Garg, Abstraction Mechanisms in Hypertext, Communications of the ACM, Vol. 31, No. 7, 862-870, July 1988.

No context found.

P. K. Garg. Abstraction mechanisms in hypertext. Communications of the ACM, 31(7):862--870, July 1988.

First 50 documents

Online articles have much greater impact   More about CiteSeer.IST   Add search form to your site   Submit documents   Feedback  

CiteSeer.IST - Copyright Penn State and NEC