450 Chapter 25 – Introduction to XMLExamples of XML Technology
Web Design in a Nutshell, eMatter EditionIn XML code, the description of a simple line might include the starting and
ending x,y coordinates with an assigned thickness to the stroke, like this:
<LINE STARTCOORD="x,01 y,01" ENDCOORD="x,50 y,100"
THICKNESS="2"/>
Along with tags defining graphical shapes, an XML language for describing
graphics could include additional information that would travel with the graphic
such as copyright information, author, title, and printing instructions. Not only
would the graphics then be very compact, they would also be more information
rich and multipurpose.Vector standard contendersThere are currently several technologies vying to become the vector graphic stan-
dard of the Web. The W3C has acknowledged the following proposals and is
working on developing a single vector standard that draws its features and func-
tion from the best of the submitted solutions.
PGML (Precision Graphics Markup Language)
This vector standard proposal was developed by Adobe Systems, IBM,
Netscape, and Sun. It is based on the PostScript language and Portable Docu-
ment Format (PDF), a model that has been used for both online viewing and
printing of graphical information. Because the tagging is so complex, PGML
code would be exported by image creation tools, then copied and pasted into
HTML documents. For more information, see the PGML Note submitted to the
W3C athttp://www.w3.org/TR/1998/NOTE-PGML-19980410.html.
VML (Vector Markup Language)
VML is Microsoft’s bid in the vector standards race, with development support
from Hewlett-Packard, Macromedia, Autodesk Inc., and Visio Corporation.
Like PGML, VML would be generated automatically by an image creation
application and exported for use in web pages. VML is likely to be supported
by Microsoft Internet Explorer 5.0, giving it somewhat of an advantage over
competing standards. For more information, seehttp://w3c.org/TR/NOTE-VML.
Web Schematics on the World Wide Web
Proposed by the CCLRC (Council for the Central Laboratory of the Research
Councils), a computer science research organization in the UK, Schematics on
the World Wide Web is a specification for describing simple flow charts and
graphs. Technically, it does not compete with the aforementioned formats, but
has been acknowledged by the W3C as a simplified alternative for displaying
schematic drawings. For more information, seehttp://www.w3.org/TR/1998/
NOTE-WebSchematics/.
Flash (SWF)
The Flash file format (created by Macromedia) brought vector-based anima-
tions and interactive movies to the Web via a plug-in. Macromedia is making
the Flash (SWF) format an open standard in hopes that it will become the
standard vector graphic format for the Web (in the way that GIF has cornered
the bitmap market). Unlike the other vector standards, Flash is not an XML
text-based solution, but is a binary graphics format that needs to be inter-
preted and “played” by software on the computer. Macromedia asserts,