Format conversion with NeXTStep 3.0

Tim Berners-Lee (
Thu, 5 Nov 92 09:55:34 +0100

Date: Thu, 5 Nov 92 09:55:34 +0100
From: Tim Berners-Lee <>
Message-Id: <>
Subject: Format conversion with NeXTStep 3.0

Here's an excerpt from the NeXT Nugget news digest, talking about
aspects of NeXTStep 3.0 which developers ought to take into account.
(I don't think WonderFormat is a MIME type ;-)

- Filter services
A Filter service is a new 3.0 type of Service which has no menu item
but supports the ability to convert a piece of data from one type to
another.  Every application can take advantage of filter services
when opening files (via +typesFilterableTo: if it can open a standard
type, like RTF) and when importing data via copy/paste or dragging
(via +imagePasteboardTypes).

Other applications can provide filter services:  for example, if you
have some code which converts your document format [the WonderFormat]
to RTFD, then you should provide this functionality as a filter
service.  Another application which understands RTFD but not
WonderFormat can still import WonderFormat documents and the filter
service will do the work of the conversion.  The other advantage of
providing a filter to ascii is that your documents then become
indexable by Digital Librarian.  See the 3.0 Appkit Release Notes and
the Pasteboard spec sheet for more information on:
+typesFilterableTo:, +newByFilteringFile:, +newByFilteringData:,