Contemporary Publishing Technology Essentials (1)

SGML and PDF, why do we both need (on)

(SGML and PDF—Why We Need Both)



SGML, the Standard Portable Generalized Markup Language, a standard universal markup language.

PDF, Portable document format, Adobe Acrobat's removable file format.

SGML and PDF are two technologies for book and periodical publishers to produce print and electronic publications. They are different and complementary to each Other. Most publishers should use these two technologies in a comprehensive manner because it will make the entire publication. The process is smoother and more conducive to resource utilization.



First, the basic introduction

There is a common misconception that publishers have shifted from print publishing to electronic publishing. That is to say that SGML and PDF can only be selected in electronic publishing. In fact, the two technologies complement each other. If they truly understand their respective characteristics, they can be better combined and used. First of all, we should start with the steps of electronic publishing and analyze one by one.



(a) Integration of SGML and PDF in an accidental situation

When traditional publishers expanded into the field of electronic publishing, their common practice was to publish manually-labeled content, forms, and text samples in HTML language format to the web-site on-line, while delivering the manuscript as a Postscript file to the printer. publishing. The SGML and PDF synthesis has already been implemented at this time. Because HTML is a derivative of SGML, Postscript is the source of PDF. But the synthesis in this case is entirely accidental, and publishers are not aware of their respective values.



When publishers have provided Postscript files for print editions and are ready for the electronic version, publishers are happy to choose the PDF format because PDF is a byproduct of Postscript. It is very cheap to convert from Postscript to PDF or PDF files. Fast. So at this stage, publishers can easily conclude: "PDF has been able to achieve the electronic version of the conversion, why use SGML?"



(B) SGML makes the file structured and easily adapted

With the increase in the number and complexity of electronic publications, publishers need a way to organize and manage them. At this time, the benefits of SGML are highlighted because SGML language is a very structured language and through this Structures to organize content, so SGML can not only help publishers organize PDF files, but also help readers find the information they need in many documents, so even if readers ultimately need PDF format, they also need SGML as search information. tool.



At the same time, with the advancement of technology, publishers’ electronic documents may be eliminated at any time. When new XML languages ​​are accepted by general browsers, past HTML documents will become obsolete. In this case, most publishers have to go back. Overdue, recode and structure these electronic files. Undoubtedly this will bring a lot of capital investment, publishers need to find a way to reduce this loss, if you choose SGML language at this time, you can minimize the loss of this technology update.



Although electronic publishing has developed rapidly and it has seized the market for some printed publications, in fact, most people still prefer the print media. Printed edition publications are what many people want, and the file formats produced for screen displays are rarely suitable for printing, so there is a need for some conversion between electronic publishing and printed publishing formats. Using SGML can reduce this conversion cost because SGML can make the typesetting process more automated.



It can be seen that the entire publishing process starts with SGML. It can be used to generate HTML (or XML) and PDF, HTML (or OCML) for web publishing, and PPF format electronic pages for printing (whether batch printing or pressing Need to print). Such an ideal workflow may not be immediately recognized, but the actual work will allow publishers to gradually approach it. The more thorough the publisher knows about SGML and PDF, the more likely it is to find ways to use them appropriately.



(III) SGML Generation Structure, PDF Generation Page

In general, SGML and PDF are two complementary technologies and not mutually exclusive, their essential differences can be described in one sentence: SGML is a language about the structure and meaning of documents, and it is basically independent of the form of the page. . In contrast, PDF is about page representations and has nothing to do with file structure and meaning. Understand this is the key to the effective use of these two technologies.



Below, this article will give an exhaustive introduction to SGML and PDF respectively, describe their basic characteristics, compare their advantages and disadvantages, and analyze how to use them more effectively.



Second, about SGML

We often encounter situations where a file cannot be read by other systems and only returns along the same path. Because different systems, different platforms, and different software use their own proprietary tags, they cannot be understood by other systems. Therefore, with the increase of computer systems, it is more and more important to realize the exchange of information between different systems.



There are usually two different directions for this exchange of information: horizontal and vertical. The horizontal direction is to directly transfer files from individuals to individuals and from systems to systems. The vertical direction allows many people to co-author and adapt a part of a file or file, that is, multiple people work together.



Horizontal exchange is the most common way. This method is effective for almost all files. From the system to the system, each time the file is adapted to the requirements of the receiving file system. For example, a document written in a word processing software must generate an electronic page through a typesetting system and generate an electronic version using an electronic publishing system. These systems are incompatible with each other. Therefore, the work under each system must be completed separately, and during this period, you want to reuse it. Data is almost impossible. Even today, files used in one place are used in other places and undergo extensive conversions, which is costly.



Another form of exchange—vertical mode—allows different people to use the same text in common, that is, files can be used repeatedly in different ways. For example, when the author wrote the Buick Maintenance Manual, he could directly select the same part of the Chevrolet Maintenance Manual without rewriting it.



(i) SGML, separate structure from performance

The design idea of ​​SGML language is to describe the logical framework without describing the manifestation of the document. The specific method is to separate the structure of the document from the overall form and leave the final presentation of the document to the final display system. In this way, when files are transferred from one system to another or part of a file is used in other parts, there is no need to recode them.



In 1986, the SGML language became an international standard (ISO 8879). SGML did not define proprietary tags. Instead, each user/user group could generate its own tags on demand. This principle is useful. SGML allows you to mark the title