Cryptography Reference
In-Depth Information
flour</ingredient>
<ingredient amount="1" unit="teaspoon" type="heaping">
salt</ingredient>
<ingredient amount="1" unit="cup" type="heaping">
nuts</ingredient>
<ingredient amount="1" unit="cup" type="heaping">
semi-sweet chocolate chips</ingredient>
<instructions>
<step>Mix together.</step>
<step>Pour into pan.</step>
<step>Bake in the oven at 350(degrees)F.</step>
</instructions>
</recipe>
The new version includes attributes describing the type of mea-
surement used for the ingredients and a new tag giving credit to the
creator. Most software tuned to the original package will ignore these
extra tags and find only the data it expects to find.
This is usually the case with XML, but it is not always true. The
specification includes a mechanism for defining the legitimate pat-
tern for the tags and this specification can block the adding of extra
tags. The
Document Type Definition
, or DTD, includes definitions for
which tags should be found and where they can be found.
Many programmers report a fair amount of frustration with rigid
DTDs because they cause incompatibilities between versions of the
software. This is especially true if the software relies on a feature
that allows a DTD to be downloaded from a web site. I know one
open-source project that started crashing after some of the keepers
updated the DTD on a distant web site.
21.3.1 Microformats
One of the more established attempts at building a regular mech-
anism for revising and extending HTML lives at the
www.microfor-
mats.org
web site. The Microformats project includes a number of
additions to HTML that add more semantic meaning to the text. The
extra meaning identifies the context or meaning of the text on a web
page by identifying its role. One type of tag wraps around a zip or
postal code. Nother identifies a telephone number.
Here's an example of an address spelled out in the the
vcard
for-
mat:
<div class="vcard">
<a class="fn org url" href="http://www.munster.com/">
