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Database-driven charting using XSLT and SVG: controlling finer details of data-driven Scalable Vector Graphics.

Article Excerpt
Over the last few years, there have been significant developments in the XML world. Many enterprises have adopted XML for various purposes such as data transfer, reporting, client-tier presentation, server-to-server communication, and so on.

The need for representing data in XML form is greater than ever. Almost all database vendors have ways of extracting data in XML form. XML technology has enabled us to drive enterprise reports based on legacy databases. A previous article, "Using FOP for Industrial Needs" (XML-J, Vol.3, issue 10), discussed how to generate PDF reports based on XML data. Many times, reports are not complete without good graphical presentation. This article discusses how you can generate Scalable Vector Graphics (SVG) based on XML data. You can combine the FOP and SVG processes to generate complete reports.

Scalable Vector Graphics is a markup language for describing two-dimensional graphics in XML. It is a language for presenting rich graphical content, and it allows you to create graphics from XML data using XSLT. Most of the modern devices are raster-oriented, so it comes down to where graphics are rasterized--at the client or server level. SVG is rasterized at the client level, giving more flexibility for presenting graphics. SVG gives the user full control over the rasterization process. SVG documents define graphics as vector graphics rather than a bitmap so you can scale and zoom in and out without losing any detail or blurring the image.

SVG uses a "painters model" of rendering, meaning that paint is applied in successive operations to the output device such that each operation paints over some area of the output device. When the area overlaps a previously painted area, the new paint partially or completely obscures the old.

SVG 1.1, SVG 1.0, and SVG Mobile Profiles are W3C Recommendations. Work continues on SVG 1.2 and future profiles for mobile and printing. The complete Scalable Vector Graphics (SVG) 1.1 specification can be found at www.w3.org/TR/ SVG11. A full list of implementations is available from the W3C pages at www.w3.org/Graphics/SVG/SVG-Implementations. Htm8.

Why XSLT and SVG?

With the help of XSLT, XML data can be transformed into SVG graphics. SVG drawings can be dynamic and interactive, which gives tremendous flexibility when building data-dependent graphics such as charts. The Document Object Model (DOM) for SVG, which includes the full XML DOM, allows for straightforward and efficient vector graphics animation. A set of event...

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