From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,bbd357da6d6d7756 X-Google-Attributes: gid103376,public X-Google-ArrivalTime: 2003-01-06 01:22:04 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!logbridge.uoregon.edu!newsfeed.vmunix.org!newspeer1-gui.server.ntli.net!ntli.net!newsfep1-gui.server.ntli.net.POSTED!53ab2750!not-for-mail From: "chris.danx" User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.3a) Gecko/20021212 X-Accept-Language: en, en-us MIME-Version: 1.0 Newsgroups: comp.lang.ada Subject: Re: How to? Writeable from a readable? References: <3T2S9.721$GU4.33144@newsfep1-gui.server.ntli.net> In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Inktomi-Trace: pc2-bbrg1-4-cust136.renf.cable.ntl.com 1041844921 19722 80.4.70.136 (6 Jan 2003 09:22:01 GMT) Message-ID: Date: Mon, 06 Jan 2003 09:25:39 +0000 NNTP-Posting-Host: 80.1.224.4 X-Complaints-To: abuse@ntlworld.com X-Trace: newsfep1-gui.server.ntli.net 1041844921 80.1.224.4 (Mon, 06 Jan 2003 09:22:01 GMT) NNTP-Posting-Date: Mon, 06 Jan 2003 09:22:01 GMT Organization: ntl News Service Xref: archiver1.google.com comp.lang.ada:32604 Date: 2003-01-06T09:25:39+00:00 List-Id: John R. Strohm wrote: > Maybe I'm way out in left field here. > > In capability-based operating system terms, it sounds as though you are > trying to take a read-only capability and amplify it into a read-write > capability. Every capability system I ever saw was specifically designed to > prevent you from doing precisely that: if the owner of the object wanted you > to have read-write access to the, he would have granted you a read-write > capability for the object in the first place. > > What I think you want to do is go back to the original system, structure it > as a read-write object, and then make a read-only view of it that you give > out to the world. Only the ones who really have a legitimate need for > read-write access get the read-write capability. That was my first idea, but since it will be OO the read only view of the data would inherit the operations of the read-write view and so the client would be able to modify the read-only raster - unless the operations where overridden to throw an exception, but I'd think that'd be a bad design choice in this instance. What I'm considering is Raster is abstract tagged ...; Read_Only_Raster is new Raster with tagged ...; Write_Read_Raster is new Raster with tagged ...; That would enable the client to use a read_only_raster or write_read_raster wherever they could use a raster. Chris -- for personal replies change spamoff to chris