Content Transformations

Structured Content, XSLT, Folio FFF, Print, Other Devices

Getting to Structured Content

Why is structure so important when it comes to information? Why go through the drill of getting information into XML? Using a data base as an example, once information is organized and stored in a data base, it can be queried and extracted in a variety of ways. Structured content, like information with XML descriptors, is very much like a data base. Content can be searched, selected, reorganized, recombined, and most importantly transformed into a variety of other outputs based on the purpose of the presentation.

Since the content, structure and presentation information types are maintained separately, it is truly an environment in which the content only has to be authored once, but can be used over and over, in a variety of different ways.

XSLT Transformations

XSLT (Extensible Stylesheet Language: Transformations) is a declarative language for transforming the structure of an XML document. Although XML is an ideal way to represent structure and content, an XML document will usually need to be transformed into something else to be used. It might be transformed to HTML for use on the Internet; it might be transformed to a PDF file for printing; or it could be transformed into a different XML document so that it can be interpreted by a software application.

XSLT is actually a two phase process: first is a structural transformation in which the source XML is transformed into a result tree that reflects the desired output; and second is a formatting process in which the output is converted to a specific format such as HTML.

An XSLT stylesheet consists of a sequence of template rules (matching patterns - which is a description of the nodes a rule applies to) which describes how a particular element or attribute or like construct should be processed. It is not unlike CSS (Cascading Style Sheets), but the patterns and the actions that can result are much richer in XSLT.

Data Conversions

XSLT can be used to convert one XML data set into another XML data set. In addition, it can be used to extract data selectively, reorder the data, or import data from multiple XML sources. It can be used to transform an XML document into virtually any other text-based format.

Publishing

As we've stated before, a driving force behind the use of XML is the separation of structure and presentation. But that doesn't mean that XML is not applicable to presentation tasks - it is when the presentation framework is itself XML-based. XSL (Formatting Objects) is such a framework and XSLT is an ideal mechanism for converting data without presentation information to data with it.

Folio Infobase Transformation to XML

The Folio Views technology has long been a foundation for many organizations, that publish content in electronic form. Although Views remains a powerful application, its proprietary architecture and the fact that it won't be directly supported in the future means that infobases will need to be converted to other formats. NetLogex specializes in the transformation of Folio Flat Files to XML. See Folio Transformations for more information.

Content Transformation for Print Publication

Once content is housed in XML, the options for the output are virtually limitless. Print output is certainly one option. XSL, the Extensible Stylesheet Language is one of the XML-related technologies used to output XML for print presentation (it can also be used for screen presentations).

XSL actually breaks the XML edict that an XML element describes the meaning of its content, not its appearance. XSL describes a way to specify output styles through formatting instructions known as formatting objects. Formatting objects are themselves represented as XML elements, the attributes of which control the look and behavior of the object and the content of which is the content of the XML element associated with the formatting object. Conceptually, formatting objects are presentation containers into which XML content is placed.

XSL works in conjunction with XSLT and XPath to transform XML documents. It is a large and extremely complex standard. Much of the complexity results from rich formatting objectives it is trying to achieve. It is expected that XSL support will eventually be added to formatting products such as desk top publishing, typesetting engines and document browsers.

XSLT can be used to transform an XML document into other text-based formatting languages such as RTF (Rich Text Format) and Adobe's PDF (Portable Document Format).

Output to Other Devices such as PDA's

Once content is in XML, it can be readily converted to other markup languages for output to other devices. The most common conversion of XML is into HTML for presentation via Web browser such as Internet Explorer and Netscape Navigator. XSLT provides extraordinary flexibility for such conversions so variations of an XSLT conversion routine can be used to present a common XML document on a variety of browsers. Furthermore, since XSLT can be used to reorganize and select content from an XML document, it can be used to tailor content for the specific limitations of devices such as PDA's.

Other markup languages that can be targeted from XSLT conversions are WML, the Wireless Markup Language, which is part of the Wireless Application Protocol (WAP) used for providing content to cellular phones and pagers, and XHTML (the eXtensible Hypertext Markup Language), a variation of HTML that is XML compliant and which is an alternative way to present content via Web browsers.

Finally, XML content can be transformed into the variety of e-book standards such as Microsoft Reader.

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