Path: text.usenetserver.com!atl-c01.usenetserver.com!news.usenetserver.com!atl-c05.usenetserver.com!news.usenetserver.com!postnews.google.com!b68g2000cwa.googlegroups.com!not-for-mail From: "Tony D" Newsgroups: comp.databases.theory Subject: Re: What databases have taught me Date: 24 Jun 2006 18:39:24 -0700 Organization: http://groups.google.com Lines: 54 Message-ID: <1151199564.481896.201850@b68g2000cwa.googlegroups.com> References: <1151026488.310207.201890@m73g2000cwd.googlegroups.com> <1151031561.833094.70320@c74g2000cwc.googlegroups.com> <671tm3-m1t.ln1@pluto.downsfam.net> <1151077022.907639.173530@i40g2000cwc.googlegroups.com> <1151105305.728871.260830@p79g2000cwp.googlegroups.com> <1151112682.857645.63800@m73g2000cwd.googlegroups.com> NNTP-Posting-Host: 84.65.183.129 Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable X-Trace: posting.google.com 1151199569 10590 127.0.0.1 (25 Jun 2006 01:39:29 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: Sun, 25 Jun 2006 01:39:29 +0000 (UTC) In-Reply-To: <1151112682.857645.63800@m73g2000cwd.googlegroups.com> User-Agent: G2/0.2 X-HTTP-UserAgent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv:1.8.0.4) Gecko/20060508 Firefox/1.5.0.4,gzip(gfe),gzip(gfe) Complaints-To: groups-abuse@google.com Injection-Info: b68g2000cwa.googlegroups.com; posting-host=84.65.183.129; posting-account=lQ02DQsAAADWoCQBAmE7gtE1ncXplDWA Xref: usenetserver.com comp.databases.theory:155642 X-Received-Date: Sat, 24 Jun 2006 21:39:29 EDT (text.usenetserver.com) Marshall wrote: > Well, some. Lots of thinking. A trial syntax. Some ambitious > ideas. There is an interpreter for it, but it's never fully functional, > as I keep changing my mind about important design decisions. > For example, a few months ago I ripped out default arguments > when I realized they broke associativity of natural join. :-( I have never been a fan of default arguments, since I first encountered them in Ada. A function that needs default arguments is a function that's trying to do too much, it seems to me. > Sadly, I'm not very good with formal methods yet, so I don't > have an operational semantics. But it's something I want to do. > "Pshaw" says I to operational semantics ;) Check out http://www.cis.ksu.edu/~schmidt/text/densem.html for free PDF or Postscript of David Schmidt's most excellent "Denotational Semantics: A Methodology for Language Development". A very good (and when I wanted to buy it in 1987, very *expensive*) book on denotational semantics. Lloyd Allison's introductory book, "A Practical Introduction to Denotational Semantics" (Cambridge Computer Science Texts No. 23) is a short, quick and decent introduction which might get you going quicker, but isn't available on line (it's quite cheap though - =A315 currently). Lloyd Allison has a website at http://www.csse.monash.edu.au/~lloyd, and his list of programming languages contains the excellent joke : "The last good thing written in C was Franz Schubert's Ninth Symphony." - Gregory V. Wilson > Its primitive operators are those of the Tropaskho algebra: > natural join and inner union. The language is pretty much > just: those operators, scope and name binding, the type > system, Just ?! Languages are invented just to play with type systems, never mind anything else :) > the imperative commands, Oh, boo ... > and a few bits of > miscellany, such as aggregates/group-by. High up on > the wanted-feature list is constraints and updatable views. > But the precise semantics of view updatability remain > elusive. > Well, you've got to start *somewhere*. Pick the low-hanging fruit and make sure you've designed the spec in such a way that adding the fun stuff is easier later (even if someone else gets to do it). Design the semantics first - an interpreter will surely follow :)