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Subject:Re: HTML, ASCII, and Homesite From:Mark Baker <mbaker -at- OMNIMARK -dot- COM> Date:Mon, 4 Jan 1999 17:09:07 -0500
Crystol Wigemyr wrote
>I discovered that my eval copy of Homesite 4.0 was automatically changing
>some of my tags based on an option that, by default, was "on".
>
>The option is:
>
>"When characters above ASCII 127 are entered, convert them to their
>corresponding entity name...."
>
>The software kept changing my — to — .
>
>I have a few questions:
>
>What is an "entity" ??
>
>Why would this option be "on" by default? What advantages are there to
using
>"entities" vs. ASCII code?
Not all character sets use the same number to refer to a character. The
ASCII character set ends at 127, and there are several variants on the
meaning of the codes up to 255. For instance, Windows and the Mac assign
different characters to the codes between 128 and 255 so your — would
probably not produce an emdash on a Mac.
Character entities are an SGML mechanism for getting round this problem.
Instead of specifying a character number, which may be different on
different systems, you supply a character name. This name can then be
interpreted to the appropriate character number by an SGML processing
application (such as a web browser) when the file is displayed.
The problem with this is that there then needs to be agreement on character
names, and applications need to support them. Agreement on character names
is provided by standard publicly available sets of entity declarations, but
whether any particular version of a particular SGML tagging language, like
HTML, includes those entity declarations, or whether any particular browser
supports the included declarations is another matter.
I suspect (but I'm not certain) that the difference in behavior between
browser versions may be due to the fact that different versions of the
browsers support different versions of HTML, and later versions of HTML may
support a wider set of entities. It could also be that the earlier browser
did not support the full HTML spec for the version it was based on.
In any case, using character numbers will work across browsers on the same
platform but fail across different platforms. Using character entities will
work across platforms, provided the version of the browser the user has
supports them, but may fail on older browsers. There is no cross-platform
cross-browser way to use any character outside the basic ASCII character
set.
At some time in the future we may or may not see Unicode widely adopted, in
which case a lot of these problems go away.
---
Mark Baker
Manager, Technical Communication
OmniMark Technologies Corporation
1400 Blair Place
Gloucester, Ontario
Canada, K1J 9B8
Phone: 613-745-4242
Fax: 613-745-5560
Email mbaker -at- omnimark -dot- com
Web: http://www.omnimark.com
