GenX
GenX is GenCAM, IPC-2510, described in the eXtensible Markup Language (XML). This particular mapping of GenCAM is very useful for Internet applications of GenCAM files. A good example of an one such application is highly-automated Internet accessible analysis, a concept we refer to as the Engineering Service Bureau. An example GenX-driven analysis that an ESB might offer is our Plated Through Hole (PTH) analysis.
GenCAM is a standard being developed by the Institute for Interconnecting and Packaging Electronic Circuits to facilitate the communication of PWA/B manufacturing data from the designer to the fabricator. A recent news release from the IPC underlines how widespread support for the GenCAM standard will be.
The GenCAM standard has been published as GenCAM 1.0 on November 29, 1998. It is available on the GenCAM web site (www.gencam.org).
There are many benefits to an XML version of GenCAM. Some of these benefits are derived from the inherent representational strengths of XML, as outlined below.
The Extensible Markup Lanugage (XML) is a data format for structured document interchange on the Web. XML was developed as a successor to HTML, but it allows the structure of textual data to be expressed, not just its formatting. This means it can extend the domain of what Web data means.
XML is actually a metalanguage to let you design your own markup language. A regular markup language defines a way to describe information in a certain class of documents (e.g. HTML). XML lets you define your own customized markup languages for many classes of document. It can do this because it's written in SGML, the international standard metalanguage for markup languages.
XML can provide more and better facilities for browser presentation and performance. Because authors and providers (such as the IPC!) can design their own document types using XML, document types can be explicitly tailored to an audience. The cumbersome fudging that has to take place with HTML to achieve special effects should become a thing of the past: authors and designers will be free to invent their own markup elements.
Information content can be richer and easier to use, because the hypertext linking abilities of XML are much greater than those of HTML. Existing HREF-style links will remain usable, but the new XML linking technology is based on the lessons learned in the development of other standards involving hypertext, such as TEI and HyTime and in SGML browsers like Panorama and Multidoc Pro. The new linking capabilities let you manage bidirectional and multi-way links, as well as links to a span of text (within your own or other documents) rather than to a single point.
Information will be more accessible and reusable, because the more flexible markup of XML can be used by any XML software instead of being restricted to specific manufacturers as has become the case with HTML. Valid XML files are legal SGML documents also, so they can be used outside the Web as well, in an SGML environment (once SGML software vendors adopt the XML specification).
The inherent structure of XML files makes them easy to parse. XML parsers have been written in less than 26K of Java (http://www.microstar.com/XML/AElfred/) and less than 5k of Javascript (http://www.jeremie.com/Dev/XML/). Microsoft ships a C++-based parser COM component as part of Internet Explorer 4 and has a JAVA implementation at their XML Web site.
XML files have Document Type Definitions (DTDs). A DTD is usually a file (or several files to be used together) which contains a formal definition of a particular type of document. This sets out what names can be used for elements, where they may occur, and how they all fit together. A DTD for GenCAM XML files would be identical to the contents of the IPC-251x series of documents for describing what is legally allowable in GenCAM. The distinction is that the DTD is computer-processable. That is, the DTD is a formal language which lets processors automatically parse a document and identify where every element comes and how they relate to each other, so that stylesheets, navigators, browsers, search engines, databases, printing routines, and other applications can be used. We believe this will be important because it will enable legal file modifications (workarounds) without necessarily having access to the originating application. This is especially important in collaborative design environments.
An XML version of GenCAM will be very easy to view and interact with, possibly even easier to navigate than a plain text file. As both the major Web browser manufacturers, Microsoft and Netscape, have pledged native support for XML in the next generation of web browsers, viewing XML files will become as effortless as viewing HTML files is now. (Netscape's plans for including XML support in Mozilla/Communicator 5 are outlined at http://www.mozilla.org/rdf/doc/xml.html. A preview version of Microsoft's IE Explorer 5.0 with some limited XML support is available at http://www.microsoft.com/sitebuilder/ie/ieonsbn.htm) And browsing an XML file in an intellegent browser will have lots of advantages. Initial versions of XML parsers make the contents of the file navigable by pointing and clicking, much as we navigate through the directory structure on Windows machines now. This makes it easy to support multiple levels of abstraction; viewing only one section, hiding attributes below a certain level, etc.
This functionality is temporarily unavailable due to GT software licensing restrictions. We hope to have this available to the public soon.
The obvious tradeoff is between efficiency and easy use. It is not difficult to imagine that XML, being verbose and highly descriptive (and therefore relatively humanly readable), is not the most compact format for data storage. Comparisons to STEP's Part 21 Format (an ASCII format intended for automated processing) have shown a factor of 10 increase in size! In contrast, informal evaluations of native GenCAM ASCII and GenX have shown that the XML version is from 1.5 to 3 times larger, depending on the mapping strategies employed to produce an XML file.