Code Notes for Xml

Chapter 1: Introduction Orientation What Is XML? Extensible Markup Language (XML) is a globally accepted, vendor- independent standard for representing structured, text-based data. An XML document is a perfect medium in which to encapsulate any kind of information that can be arranged or structured in some way. For example, an XML document can contain a list of personal or business contacts, books in a library's card catalogue, or products in a warehouse. If we looked at any one of these examplessay, the library card cataloguein the more traditional "table-oriented" view with which most developers would be familiar, we would see something like the following: book_isbnbook_genreFirstnamemiddlenameLastnametitle 0812589041Science OrsonScottCardEnder's FictionGame 0883853280biographyWilliamDunhamEuler: The Master of Us All An XML document, on the other hand, would present this information hierarchically, where the column names would become tags or possibly "attributes." For example: 0812589041 science fiction Orson Scott Card Enders Game 1985 0883853280 biography William Dunham Euler The Master of Us All 1999 Listing 1.1 is included to give you a first look at XML, which can be overwhelming compared to a familiar table structure. However, as you become more familiar with XML, you will see that this structure has many important advantages over a traditional table. XML and HTML It can help to think of XML at its most basic level as being very similar to a HyperText Markup Language (HTML) web page. However, the tags in an XML document do not have a fixed meaning the way they do in HTML (e.g., , , etc.) When a developer writes an XML document, he or she decides on the names of the elements (e.g., book, title, year, and author) and the data the elements will contain (e.g., the tags contain the year the book was published). The developer chooses his elements with the expectation that some client application exists that will read the XML file and be written to process those particular elements in some way. Referring back to Listing 1.1, one can imagine that there is a book-search software application running on a computer in the library that reads XML files with this structure (perhaps receiving them via the Web from some central server), allowing library patrons to search for the books they wish to check out. What Is XML Used For? One misconception regarding XML is that it is simply an alternate way of transporting and storing data. However, that is only one small facet of how XML is used today. To give only a few examples, XML can be used to: -invoke methods on a remote server through a firewall (this protocol is called SOAP) -represent relational database data such that it can be easily translated into HTML, viewable by any browser without programming -store configuration and deployment data for applications, providing operating-system-independent formats for initialization/configuration files -create template docuBrill, Gregory is the author of 'Code Notes for Xml', published 2002 under ISBN 9780812991918 and ISBN 0812991915.