Isn't the Web another strong motivator for XML?
Besides the W3C's own stated motivations for XML, the role of the World Wide Web has been dominant. There are two reasons for this.
First, the Web is an arena for dynamic content. No longer limited to hand-crafted pages, the Web is the medium for content undergoing constant and frequent change. Web-based financial information must reflect complex and far-reaching changes that occur on a minute-to-minute basis. Live electronic commerce (e-commerce) by its definition is about commodities whose pricing and terms are likewise in constant flux. The various nontext media items we see and hear on the Web are also constantly updated: video capture of traffic conditions, weather maps, audio files of hourly news. Even static Web sites run rotational substitutions of images in order to capture the visitor's attention. Customers and trading partners now expect their sessions to be personalized, retaining a history of transactions and maintaining a security profile for personalized access. All of these instances of dynamic content are driven by add-on intelligence, the software that Web designers must write and integrate software to manage content. That software demands a notation that (1) is friendly to Web programming languages (typically scripts) and (2) fits in easily with the Internet's layers of transmission protocols (definitions of how to move information across the Internet). XML has proven to be the perfect fit on both counts.
Second, the obvious and dominant front-line player in the Web food chain is the browser. If the out-of-the-box software in the browser could not deliver the text, audio, and video in the way the creators intended, the Web would only be a nice concept. The fact is that every browser product has come with the intelligence to process scripting languages and to recognize structured markup (text with pointy-bracket tags). The on-going question in browser development is how smart the browser must be about content markup. Fortunately, there is a Hypertext Markup Language (HTML) that was invented solely for Web delivery. All browsers are native speakers of HTML. HTML has been a strong determinant in the development of XML as a transformer of its own content. If the vast and growing store of XML content is ever to reach the Web user's screen, printer, telephone, or player it must somehow be transformed into HTML so that standard browsers can deliver it. We call this transformation down translation, because it reduces XML content, no matter how complex, to HTML.
But the dynamic between XML and browsers goes further. XML-based providers continue to express their need for XML-native browsers. They envision a translation-free delivery that preserves all of the intelligence and personalization of the original XML. On the W3C side, there are several instances within the specifications that seek to accommodate browsers as they are. At this moment the issue of delivering XML-as-is, is not totally resolved. But the status is that browsers can accomplish it in only in a very restricted manner. In Chapter 16 we will demonstrate exactly what a browser can do with XML on its own and how XML as a translator of its own content can down translate to HTML.
So there are compelling reasons to say that XML is a Web technology. It is the dominant player in storing, managing, and aggregating Web content. And it is a powerful contributor to preparing that content for delivery. One commonly heard conclusion is: "Since browsers cannot display XML directly, I should not invest in XML for Web delivery." That statement contains both a half-truth and a serious lack of business judgment. XML, aided by its own built-in transforming power, delivers content quite nicely on the browser. And given the progress of browser technologies, the commitment of technology providers, and the specifications emerging from W3C working groups, it seems inevitable that XML on the Web will become even more straightforward and even more of a sound business strategy.