Designing Xerox Star Software in 400 Pages

I’ve been reading Bringing Design to Software, an ancient tome (published in 1996) that collects interviews with a dozen software practitioners on the subject of software design. In modern parlance, what was called “software design” in 1996 might overlap with what today is called “user experience”, but in any event, it is an activity related to, but separate from, programming, that results in a well-planned specification for what is to be programmed.

The first interview is with David Liddle, who worked on the Xerox Star, an early desktop computer system aimed at business productivity use. How did Liddle and his colleagues go about designing the Star software?

We ended up writing a 400-page functional specification before we ever wrote one line of code. It was long, because it included a screen view of every possible screen that a user would see. But we did not just sit down and write it. We prototyped a little bit, did some testing with users to decide what made sense, and then wrote a spec for that aspect. Then we prototyped a bit more, tested it, and then spec’d it again, over and over until the process was done.

400 pages of software requirements may be commonplace in specialized applications like avionics systems, but it’s a lot more planning than most software gets today. Not even content with that, Liddle’s team hired Bill Verplank, a human-computer interface expert from MIT:

Verplank and his crew did 600 or 700 hours of video, looking at every single feature and function. From all these video recordings, we were able to identify and eliminate many problems. For example, we chose a two-button mouse because, in testing, we found that users demonstrated lower error rates, shorter learning times, and less confusing than when they used either one-button or three-button mice.

Being on the front line of developing early office applications, Liddle also addresses the misconception that the software models of files and folders and desktops was meant to copy a real-world office environment:

It is a mistake to think that either spreadsheets or desktops were intended to imitate accounting pads, office furniture, or other physical objects. The critically important role of these metaphors was as abstractions that users could then relate to their jobs. The purpose of computer computer metaphors, in general, and particularly of graphical or icon-oriented ones, is to let people use recognition rather than recall. People are good at recognition, but tent to be poor at recall. People can see objects and operations on the screen, and can manage them quite well. But when you ask people to remember what string to type to perform some task, you are counting on one of their weakest abilities.

Curiously, a lot of software written for programmers to use puts heavy demands on recalling arbitrary strings of text…

Would it still make sense to write a 400-page specification for office application software today? Would it still make sense to record hundreds of hours of video to research the optimal way to use the software? Maybe not. Thirty-three years have passed since the Xerox Star, and along the way, many good software design concepts have been identified and established as common practice. If you’re building software for an Apple desktop or mobile platform, for example, you can simply follow Apple’s design guidelines and save yourself a great deal of fundamental human-computer interaction research.

Nevertheless, spending time to plan your application up front may still be a good idea. Thinking through the interaction experience and the needed functionality with a pad of paper and a pen can make writing the code more straightforward, and software is easier to test if you have a precise definition of what it’s supposed to do.

Thanks to people like David Liddle, we can draw on years of experience in good software design to get a head start on our own projects!

Canon 300mm/4 Lens from LensRentals

20140808-samantha-1.jpgI needed a camera lens longer than anything I presently own for some event photography, and decided to rent a Canon 300/4 from LensRentals.

One frequently-cited advantage to using either Canon or Nikon SLR cameras is that they are so common that you can easily rent whatever you need that you don’t own. I’ve never been able to enjoy that alleged truth locally, as I’m not aware of any shop that rents camera equipment within a reasonable driving distance from home. But over the past few years, renting camera equipment online has taken off in popularity, with LensRentals being one of the more well-known providers.

I created my account on a Wednesday afternoon and placed the order to receive the lens on the following Monday and to return it the Monday after that. In filling out the shipment form I asked them to send the lens to my customary third-party shipment service provider, who is authorized to sign to receive packages on my behalf. LensRentals contacted me and asked if they could instead ship directly to a FedEx location, with the reason being that once the package leaves the hands of FedEx, regardless of who signed for it, I become personally liable for whatever happens to the package. So they prefer if it goes directly from FedEx to me.

The package was delivered on schedule to a nearby FedEx location. The lens came lightly wrapped in bubble-wrap, placed inside its standard-issue Canon carrying case, with that placed inside a close-fitting block of foam rubber. The lens was very clean; not mint and pristine, but showing only very light signs of use. I would have been thrilled to buy a used lens in such good condition.

Over the next several days I completed my event photography assignment, which concluded on a Friday evening. Per the LensRentals web page, the next day that I could ship the lens back was Monday (no weekend shipments), so over the weekend I enjoyed taking some personal pictures of Samantha the border collie and a full moon.

MoonMonday morning I packed the lens back up the way it came, slapped the prepaid FedEx return postage onto the box, and dropped it off at the same FedEx location that I picked it up at. The entire LensRentals experience went smoothly flawless, and I look forward to using their services again when I have a short-term need for camera equipment.

Oh, and the lens itself? I don’t have much to add to the scores of reviews online already, but in short, it’s a great lens. My main usage was a moderately well-lit indoor environment. The f4 aperture was plenty to sufficiently freeze motion at a shutter speed around 1/160s, and the image stabilization made that slow of a shutter speed quite usable hand-held. Outside, at 300mm I was able to stay far enough away from Samantha that she usually didn’t find the camera objectionable.

The resulting images were clear and as richly contrasty as I have come to expect from Canon prime lenses. If the focal length and aperture match what you need, and you have an extra $1500, buy one today. If you’d rather spend $1400 less than that, and don’t need 300mm all the time, then rent one for a week from LensRentals.

Three FireWire Audio Interfaces in Six Months

Moog Synthesizers at MIT MuseumIn late 2012, I started using an Echo AudioFire 12 to route analog audio into my 2010 Apple MacBook Pro. On paper, the AudioFire 12 was exactly what I wanted: 12 analog inputs and 12 analog outputs converted to digital and sent across FireWire. I’m using outboard preamps, so I’m not particularly needing the A/D interface to offer built-in preamps. The AudioFire 12 didn’t offer anything fancy; it was an A/D interface with FireWire output.

Initially, all seemed well. Very occasionally when recording I got a spurious digital pop noise on a track. I thought I was probably overdriving something somewhere, and investigated possible causes as a background task.

After a few months, the popping noises increased. About a year after acquiring the AudioFire 12, I was using it for a series of recording sessions, some of which turned out flawless, while others were littered with pops, in some places so bountiful that it came across as a crackling noise.

I learned that these noises are called gaps: essentially, a brief lapse in successful transmission of audio data. In the recorded wave file, when you zoom in far enough, you can see that a normal audio wave is a generally smooth, continuous line. A gap introduces a sudden discontinuity; the wave line jumps from one point to another. Once you locate a gap in the wave file, you can manually fix it by repairing the wave line, making it smooth and continuous again. You can also use a number of software tools to repair gaps automatically.

So I was able to salvage my recording session data, but it was obvious that sloshing around with frequent gaps in recorded audio wasn’t an appealing path forward. Research on the web suggested a number of things to try different in configuring my system, but when all of those failed, I resolved that the problem almost certainly was an incompatibility between the FireWire chipset in the AudioFire 12 and the FireWire chipset in my computer. Had it been a full desktop computer instead of a laptop, I could have installed a secondary FireWire interface card that would hopefully be compatible, but that wasn’t an option for me.

MOTU 828

I decided to sell the AudioFire 12 and replace it with another interface. I had had good success in the past with an audio interface from MOTU (Mark of the Unicorn, based in lovely Cambridge, Massachusetts), and, not needing anything fancy, I bought an original MOTU 828 unit, reportedly the very first FireWire-based audio interface, with eight channels of analog inputs, only two of which sported built-in preamps.

The MOTU 828 was something on the order of 12 years old, but it worked perfectly. Its minimal ability for routing and monitoring audio felt a little archaic, and it lacked the convenient MIDI I/O tacked on to nearly every modern FireWire audio interface, but I was able to make do. It chugged away in service of my home recording studio for an astonishing four months before its internal FireWire chipset flaked out, connectivity between it and the computer failed, and it started emitting a high-pitched squeal which gave me a moderate headache as I tried to make it stop.

I read online that MOTU tech support could, as of 2011 anyway, replace the FireWire ship and refurbish an 828 unit for $75, plus shipping charges. I called MOTU the next morning only to learn that they no longer service the ancient original 828.

So I needed to buy another new interface. I ended up selecting a new interface from Focusrite.

Focusrite Saffire Pro 40

The Echo AudioFire 12 is fairly unusual; audio recording professionals favor using outboard preamps, and buy $2000 interface units that have no built-in preamps. For my needs, I wasn’t looking to spend $2000 on an interface, but, apart from the Echo equipment, I’m not aware of another <$1000 interface that isn’t cluttered with its own preamps.

Built-in preamps are not necessarily bad, but they almost certainly will not be as good as standalone preamps. I have a Focusrite ISA two-channel preamp that sells for $900. The Focusrite Saffire Pro 40 audio interface has eight built-in preamps, one on each input channel, and sells for $500. It doesn’t seem credible that these <$60 preamps would be designed and built as well as a $450 preamp from the same manufacturer. This does, though, get usable preamps into the hands of people who might not have bought them otherwise.

I’ve used the Focusrite Saffire Pro for all of about ten minutes and so far it sounds great. Or I suppose I should say, it doesn’t sound like anything in particular; it functions as an audio interace, converting between analog and digital signals. I have some extra built-in preamps should I need them, and the overall design is (not surprisingly) more modern than the old MOTU 828. It lacks clock input, but I don’t need to synchronize it with anything else at the moment. In addition to the eight analog inputs, it also has digital inputs through ADAT, so I could plug up a really nice A/D converter and use the Saffire just to feed the digital data to the computer over FireWire. The front-panel buttons feel cheaply made out of plastic. (The knobs and power switch feel fine.) I imagine that Focusrite could increase the price by $50 and use the same quality of buttons they use on the ISA preamps.

Basically, it’s a lot like many other similarly-priced interface units. I don’t find these extremely interesting in themselves, but rather, just a needful component in recording audio. They do though become very interesting when they don’t work correctly in one way or another. Hopefully this brand new Focusrite Saffire will function well for years to come.