Object - Oriented Programming , Descriptive Markup , and TEX Arthur

I describe a synthesis withn TEX of descriptive markup and object-oriented programming. An underlying formatting system may use a number of different collections of user-level markup, such as LATEX or SGML. I give an extension of WX's markup scheme that more effectively addresses the needs of a production environment. The implementation of such a system benefits from the use of the model of object-oriented programming. LATEX environments can be thought of as objects, and several environments may share functionality donated by a common, more general object. Ths article is a companion to William Baxter's "An Object-Oriented Programming System in TEX." I believe that the key to cost-effective production of T$ documents in a commercial setting is descriptive markup. That is, the document being processed contains content organized by codes, the latter describing the structure of the document, but not directly mandating the format. The formatting of such a document is embodied in a separate module (usually a file of definitions of formatting procedures) which represents the implementation of a typographc specification (typespec). Thus, descriptive markup achieves the separation of document instance from formatting engine. At the same time, the key to cost-effective generation of document formatters in TEX is found in the paradigms of object-oriented programming (OOP). Typographc elements are treated as objects, with data and methods. The formatter is a collection of code modules with well-defined boundaries and communication pathways. The programmer can take advantage of oop techniques such as object encapsulation, data-hiding, and inheritance to create robust, easy-to-maintain, powerful formatters. For the purposes of this article, FQX and SGML will be used as specific instances of descriptive coding schemes, but other methods that cleave to the standards of descriptive markup are not excluded. In particular, databases are very descriptive in nature , and the processing engine described in ths and the next paper will process such data well. The present article discusses issues of descriptive markup and object-oriented programming as relate to TEX and document processing. The next article gives implementation details of the processing engine. Advantages of WX's Descriptive Markup. The descriptive markup of LATEX bestows numerous advantages on thls document processing system, malung it the predominant TEX macro package.