From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hans Reiser Subject: Re: silent semantic changes in reiser4 (brief attempt to document the idea of what reiser4 wants to do with metafiles and why Date: Wed, 01 Sep 2004 01:07:34 -0700 Message-ID: <41358346.20507@namesys.com> References: <185110393004-BeMail@cr593174-a> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: list-help: list-unsubscribe: list-post: Errors-To: flx@namesys.com In-Reply-To: <185110393004-BeMail@cr593174-a> List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: "Alexander G. M. Smith" Cc: reiserfs-list@namesys.com Alexander G. M. Smith wrote: >Hans Reiser wrote on Mon, 30 Aug 2004 23:43:13 -0700: > > >>Alexander G. M. Smith wrote: >> >> >>>Are you sneaking in file types there? Just how does a file know which >>>plugins it supports? >>> >>> >>we have plugins with pluginids, is that what you mean by file type? I >>think they are a bit different from file types. >> >> > >>>From your white-paper: "Every file possesses a plugin id, and every >directory possesses a plugin id. This plugin id will identify a set >of methods." > >Functionally this is very close to a file type. > A file type is based on semantics of the contents, and a plugin id is based on methods of the object. > It classifies the >files into related groups, maybe not as finely as a MIME file type >which can distinguish between multiple varieties of text files. > >A file type would tell us that a file is a text file and can be opened >by certain applications (text/e-mail can be opened by e-mail reader, >text editor, etc) and have other properties (lists of standard >attributes, default icon). A plugin ID says that the file can use text >related plugins (like a word count, or XML structure as a subdirectory). > >In both cases there is a global repository (I assume) that associates >the file type or plugin ID with a list of things about it. > >You could combine the two concepts, just have a file type ID that in the >global repository specifies what plugins it can use as well as the >userland properties (MIME string, etc) of that kind of file. Or at least >make the type ID available to userland so it can be used there. > >Or is this binding irrelevant? How often does the file type the user >sees not match the plugins desired for the file? Or can a new subtype >be defined for just that file? Which may mean that we need something >better than MIME strings for types (something which has inheritance). > >- Alex > > > > I think that there may be some good use for a filename/metas/type metafile.