Database Reference
In-Depth Information
Microsoft's Vector Markup Language (VML), which was only supported by
Internet Explorer, and the WebGL standard supported by Google's Chrome
browser—have also been available over the years. These technologies
attempt to bring a standard for 3D rendering to the web browser.
Introduced in the late 1990s, but not well supported until the current
generation of web browsers, the SVG format offers web pages the ability to
render resolution-independent graphics using a model very similar to the
PostScriptandPortableDisplayFormat(PDF)drawingmodels.LikeHTML,
graphical elements are specified using a markup language that can display
rectangles, circles, and arbitrary paths. These can be styled using Cascading
Style Sheets (CSS) and animated using Document Object Model (DOM)
manipulation. Originally only supported through a clunky plug-in interface,
native SVG was added to Firefox 2.0 and early versions of the WebKit
rendering engine used in both the Safari and Chrome browsers. Today it
is supported by the current version of all major browsers and most mobile
browser implementations. This broad support and resolution independence
makes it an ideal choice for graphical rendering across varying platforms.
Originally introduced as part of Apple's Safari browser and subsequently
included in the WHAT-WG proposal that serves as the basis for the HTML5
standard, the Canvas element also enjoys widespread support across
browsers. The Canvas element provides a drawing surface rather than a
Document Object Model for rendering an image. The drawing model itself
is very similar to SVG because it also draws its inspiration from PostScript
and PDF. However, itonlymaintains theactual pixels drawn rather than the
objects used to render the pixels. This allows the canvas element to act more
like the traditional HTML image element as well as conferring performance
benefits relative to SVG in certain situations. In graphics circles, Canvas
would be known as an “immediate mode” implementation while SVG is a
“retained mode” implementation.
Features of a Real-Time Architecture
All of the components of real-time systems discussed in the last section
share three key features that allow them to operate in a real-time streaming
environment: high availability, low latency, and horizontal scalability.
Without these features, the real-time system encounters fundamental
limitations thatpreventitfromscalingproperly.Thissectiondiscusseswhat
each of these features means in the context of real-time applications.
