SUMMARY A strategy for document analysis is presented which uses Portable Document Format (PDF — the underlying file structure for Adobe Acrobat software) as its starting point. This strategy examines the appearance and geometric position of text and image blocks distributed over an entire document. A blackboard system is used to tag the blocks as a first stage in deducing the fundamental relationships existing between them. PDF is shown to be a useful intermediate stage in the bottom-up analysis of document structure. Its information on line spacing and font usage gives important clues in bridging the ‘semantic gap’ between the scanned bitmap page and its fully analysed, block-structured form. Analysis of PDF can yield not only accurate page decomposition but also sufficient document information for the later stages of structural analysis and document understanding.
The Portable Document Format (PDF), defined by Adobe Systems Inc. as the basis of its Acrobat product range, is discussed in some detail. Particular emphasis is given to its flexible object-oriented structure, which has yet to be fully exploited. It is currently used to represent not logical structure but simply a series of pages and associated resources. A definition of an Encapsulated PDF (EPDF) is presented, in which EPDF blocks carry with them their own resource requirements, together with geometrical and logical information. A block formatter called Juggler is described which can lay out EPDF blocks from various sources onto new pages. Future revisions of PDF supporting uniquely-named EPDF blocks tagged with semantic information would assist in composite-pagemakeup and could even lead to fully revisable PDF.
SUMMARY Hypermedia has initiated an explosion of application development based on a navigational model of information access. However, many thousands of existing applications continue to operate successfully without hypermedia services, even if they could benefit from a navigational paradigm. One of the reasons why developers of an existing application might choose to ignore the benefits of hypermedia is the cost of converting the application. If this cost could be minimized, would developers convert to or experiment with hypermedia? What is the cost of conversion? How would a conversion impact the structure or data management components of the application? This paper discusses these issues from a developer’s perspective by presenting three methods of retrofitting existing, non-hypermedia applications to provide hypermedia services. Two methods are based on traditional hypermedia data models and architectures. The third method, and focus of the paper, is an approach that is based on a process model of hypermedia. This approach allows developers to experiment with hypermedia as an information access paradigm without incurring the costs of a full conversion. Moreover, this approach establishes an open environment, leading to application integration under a common framework and allowing any application to participate. The basis of this approach is an autonomous process that is completely external to the application. The facility monitors application activity and provides first-generation hypermedia services to all or selected applications running on a user’s display. Thus, even though an application provides no hypermedia services itself, is not aware of and does not depend on a hypermedia model, it can operate as a first-generation hypermedia application as a result of this facility. Implementation details, benefits, and limitations of this approach are discussed.
SUMMARY We present a description system for transformation of structured documents based on Context Free Grammars (CFGs). The system caters to transformations between different document class descriptions, and is presented mainly in terms of logical structure transformation. Two requirements for transformation are proposed: the output document class must be explicitly representable, and inconsistency must be avoidable. First, a grammar for document class descriptions, called a T-CFG (Tree-preserving Context Free Grammar), is introduced, then SDTT (Syntax-Directed Tree Translation) is given for a document transformation. The SDTT transformation is formal, concise, and consistent with the above two requirements.
SUMMARY Most hypertext systems used in the field embed some form of mark-up in each hyperdocument in order to represent the hypertext structure. Indeed, more generally, most document preparation systems use this approach. Hypertext researchers, on the other hand, say that the structure of a hyperdocument should be separate from its content. This paper investigates whether the two approaches, embedded v. separate, are really at odds with one another, and describes a technology for combining some of the benefits of both.
SGML and an object model is studied, many issues arise and only a part of them are solved. We propose a complete and generic object model of SGML which eliminates all the limits. Moreover, this model should stand for a universal model, i.e. it can be used as a standard API to plug any SGML visualizer or editor on top of an object repository. HyTime is also an ISO standard, based on SGML, so that it ensures exchange capabilities, longevity and reusability too. Moreover, HyTime goes beyond the SGML limits concerning the hyperlinking features by offering the semantic to model complex links, such as a link from a document to a very precise location inside another one. We describe how to extend our object model to the hyperlink features of HyTime. We give an overview of the prototype we implemented to validate our approach.
SUMMARY The idea of type as a fixed geometrical object is shown to be inadequate for script types. The method presented creates ligatures between script font glyphs on-the-fly, i.e. as a part of the glyph rasterization process. This is done by manipulation of an existing font. So the process described here can be used to give existing fonts the intelligence to join characters correctly when being interpreted by a standard font rasterizer or print server. Of vital importance to the method is the natural appearance of the curve serving as the ‘ligature backbone’. In this article, a new smoothness criterion for curves is developed. Then, a method is presented that creates a curve connecting two given curves in a natural-looking way — this is done by optimizing a parametric curve by means of the new criterion. With this algorithm being integrated into on-the-fly generation of script font ligatures, these ligatures get the required level of quality.
SUMMARY The connotations of ‘publishing’ are undergoing rapid change as technology itself changes. Placing marks on paper (by whatever means), and distributing the result, are perhaps the first thoughts that the word evokes but nowadays it encompasses an ever-widening range of preparation, presentation and dissemination methods. Video sources, animation, still images and sound samples are now available as methods of imparting knowledge — and all of these are increasingly reliant on technology-dependent delivery systems. The end-user of information contained in such electronic publications has expectations of the delivery and display mechanisms which have been shaped, in the main, by exposure to the broadcast media, whose centrally funded resources are capable of exploiting high-technology solutions. In trying to emulate similar delivery systems at a personal level, the electronic publisher needs to have a general awareness of what present-day technologies can achieve, together with an appreciation of cost and practical issues. This paper gives a brief survey of these newer technologies as seen from today’s perspective.
SUMMARY Active documents result from a combination of some specific features in documents and some mechanisms in a document manipulation system. In this paper we present the possibilities offered by a structured model of documents and a structured editor for making active documents. Several applications are described (annotations, electronic indexes, cooperative editing, documents as user interfaces, etc.), which show how a document’s logical structure may be exploited for developing a variety of active document applications.
Because of the complexity of Khmer script, up to now there has been neither typesetting system nor standard encoding for the Khmer language. In this paper are presented: (a) a complete typesetting system for Khmer based on TEX, and an ANSI C preprocessor, as well as (b) a proposal of 8-bit encoding table for Khmer information interchange. Problems of phonic input, subscript and superscript positioning, collating order, spelling reforms and hyphenation are solved, and their solutions described. Finally an alternative solution using 16-bit output font tables is briefly sketched.
SUMMARY The MHEG standard will define a coded representation of multimedia and hypermedia information objects so as to facilitate exchange of hypermedia applications over various platforms. This standard has been developed entirely independently of existing architectures such as Dexter and ‘Dexter like’ systems such as Multicard, KMS[1 ]e tc. In order for the MHEG standard to succeed, it is important that existing hypermedia systems and applications can be rendered MHEG compatible, rather than these applications having to be rewritten using new MHEG engines. This paper provides a case study of how the MHEG standard could be adopted in one such hypermedia system, namely Multicard. The aim is to highlight the similarities and differences of the MHEG standard and Multicard and to provide an idea of the work required in order for such a system to read MHEG compatible streams. The paper starts with a brief description of the Multicard system, the Dexter model and the MHEG standard.
SUMMARY A commercial structured document processing system has been built with an extensible object system. This system is an excellent platform for the design, implementation, and delivery of active documents. Examples are discussed.
SUMMARY A conceptual design for our architecture centered around the entities of a hypermedia node, link, anchor and document is initially presented. Each entity has a well-defined interface so that the respective instances can cooperate despite the number of different media types. Virtual documents are created as views on other documents borrowing from their content and customizing their behavior during navigation and editing. The system functionality is provided by hypertext document objects, acting as providers of hypermedia services. There are storage and display services which are accessible and consumable by the local and remote clients spanning the operating system and workstation boundaries. Due to the object-based approach taken at design and implementation, the incorporation of new types of services (general and media specific) is straightforward and integrates smoothly with the rest of the system.
SUMMARY The Hypermedia/Time-based Structuring Language (HyTime) is a recently adopted International Standard (ISO/IEC 10744:1992). The paper presents the need and potential for HyTime, provides a brief explanation of its various facilities and shows how it may be applied to good effect in various situations, with particular reference to hypertext interchange from Microcosm (an open hypertext system). It then goes on to explore several alternatives to HyTime and compare their relative strengths and weaknesses.
First, a survey on optical scaling is carried out, both from the traditional point of view and from that of today’s digital typography. Then the special case of large characters, such as braces or integral signs, is considered. It is shown that such variable sized symbols should be computed at print time in order to approach the quality of metal typesetting. Finally, an implementation of such dynamic fonts, still in progress in the Grif editor, is described.
During its first decade, T E X has been at home mainly in the academic world. Therefore it comes as a surprise to find that it has been spreading into industry during the last few years, and we try to outline some highlights of this development first. Then criteria for an industrial environment application area and reasons for using the structured document processing approach are discussed. It is shown what role T E X can play in an integrated document processing environment, and this role is exemplified by a case study from application at EDS
SUMMARY Enhancements have been made to the TEX system to support hypertext and multimedia facilities. A special previewer, hdvi, has been developed to give access to these features. Using TEX’s \special mechanism, the previewer displays images, line graphics, audio, and video, as well as supporting hypertext; it also permits limited interaction with the underlying operating system. AL A T E X style file has been devised to provide access to all these features. Some user feedback with the system is described and the effectiveness of the general approach is assessed.
SUMMARY During the last four years the PaVE department at GMD-IPSI experimented with the Individualized Electronic Newspaper, an active publication that is individualized and composed on demand for a reader, and then delivered electronically. The work concentrated on the user interface design for active electronic publications and, in particular, on the investigation of publishing system architectures supporting the preparation and production of active electronic publications. The paper introduces two alternative interfaces for an electronic publication showing the potential of the electronic medium for publication design. The main part of the paper presents our approach to making such publications possible: a combination of structured documents and knowledge-based techniques based on a sound publishing model. This approach guided the design of an integrated publication environment for the preparation and production of active documents.
SUMMARY This contribution presents a simple method for the automatic recognition and hinting of character structure elements such as horizontal and vertical stems. Stem recognition is based on successive steps such as extraction of straight or nearly straight contour segments, detection of hidden segments, merging of original and hidden segments into larger segments, sorting of segments into classes according to their slopes and, finally, composition of black and white stems. Reference values required for character hinting purposes are obtained by evaluating the regularity of the font through statistical analysis of features such as stem widths and stem angles. Knowledge about the location of stems and analysis of outline parts between stems is used in order to produce automatically appropriate grid constraint rules (hints). The presented outline analysis and stem extraction techniques are very general and may be applied to non-Latin characters as well.
SUMMARY This paper presents an electronic index service that was developed in the Grif editor by taking advantage of the hypertext facilities available in the system. Grif is a structured document editor based on the generic structure concept that supports both hierarchical structures and non-hierarchical links. The active cross-reference within the Grif index makes activation and browsing through indexing more powerful than in other systems: the index tables, helpful as a medium for supporting search by keywords in paper documents, support browsing in electronic documents. These indexes are easy to use as they are displayed in the same form as indexes in a paper document.
