The draw backs of multiple inheritance

[Grampa_of_Oliva_n_Eden]

From my boss...

"

Once upon a time, in a kingdom not far from here, a king summoned two

of his advisors for a test. He showed them both a shiny metal box

with two slots in the top, a control knob, and a lever. "What do

you think this is?"

One advisor, an Electrical Engineer, answered first. "It is a

toaster," he said. The king asked, "How would you design an embedded

computer for it?" The advisor: "Using a four-bit microcontroller, I

would write a simple program that reads the darkness knob and

quantifies its position to one of 16 shades of darkness, from snow

white to coal black. The program would use that darkness level as

the index to a 16-element table of initial timer values. Then it would

turn on the heating elements and start the timer with the initial

value selected from the table. At the end of the time delay, it

would turn off the heat and pop up the toast. Come back next week, and

I'll show you a working prototype."

The second advisor, a software developer, immediately recognized the

danger of such short-sighted thinking. He said, "Toasters don't

just turn bread into toast, they are also used to warm frozen waffles.

What you see before you is really a breakfast food cooker. As the

subjects of your kingdom become more sophisticated, they will demand

more capabilities. They will need a breakfast food cooker that can

also cook sausage, fry bacon, and make scrambled eggs. A toaster

that only makes toast will soon be obsolete. If we don't look to the

future, we will have to completely redesign the toaster in just a

few years."

"With this in mind, we can formulate a more intelligent solution to

the problem. First, create a class of breakfast foods.

Specialize this class into subclasses: grains, pork, and poultry.

The specialization process should be repeated with grains divided into

toast, muffins, pancakes, and waffles; pork divided into sausage, links,

and bacon; and poultry divided into scrambled eggs, hard- boiled eggs,

poached eggs, fried eggs, and various omelette classes."

"The ham and cheese omelette class is worth special attention because

it must inherit characteristics from the pork, dairy, and poultry

classes. Thus, we see that the problem cannot be properly solved

without multiple inheritance. At run time, the program must create

the proper object and send a message to the object that says, 'Cook

yourself.' The semantics of this message depend, of course, on the

kind of object, so they have a different meaning to a piece of toast

than to scrambled eggs."

"Reviewing the process so far, we see that the analysis phase has

revealed that the primary requirement is to cook any kind of

breakfast food. In the design phase, we have discovered some derived

requirements. Specifically, we need an object-oriented language

with multiple inheritance. Of course, users don't want the eggs to get

cold while the bacon is frying, so concurrent processing is

required, too."

"We must not forget the user interface. The lever that lowers the

food lacks versatility, and the darkness knob is confusing. Users

won't buy the product unless it has a user-friendly, graphical

interface. When the breakfast cooker is plugged in, users should

see a cowboy boot on the screen. Users click on it, and the message

'Booting UNIX v.8.3' appears on the screen. (UNIX 8.3 should be out

by the time the product gets to the market.) Users can pull down a

menu and click on the foods they want to cook."

"Having made the wise decision of specifying the software first in

the design phase, all that remains is to pick an adequate hardware

platform for the implementation phase. An Intel Pentium with 48MB

of memory, a 1.2GB hard disk, and a SVGA monitor should be sufficient.

If you select a multitasking, object oriented language that supports

multiple inheritance and has a built-in GUI, writing the program

will be a snap."

The king wisely had the software developer beheaded, and they all

lived happily ever after.

"

Which appears to an mod of this version

I have to wonder if things would have turn out differently if the software developer had not insisted on multipl inheritance.

Ben

[Aristos Queue]

The failure was not in the software developer who spec'd the device, but in the software manager (aka king) who poorly specified design requirements. The software developer actually spec'd out a really nice breakfast food processor. If that wasn't what the king wanted, he should have said so. I hope that the monarchy is overthrown by angry subjects a decade later when they find out that in the republic next door, food replicators are commonplace.

[LogMAN]

I have to wonder if things would have turn out differently if the software developer had not insisted on multiple inheritance.

Ben

Just guessing about multithreading....

That king wasted a great chance, but hey, the developer somehow is alive, check out this page: toaster pc

There is just no space for a toast....

[Daklu]

I've seen that before, but it's still funny.

Although it's meant as a dig against programmers, if you read it closely it highlights one of the main differences between the software world and hardware world--expectations. The potential issues raised by the software developer are patently absurd when applied to a toaster. Nobody expects a toaster to do anything except make toast. It's obviously not well suited to cooking an omelette. That task requires creating an entirely new set of tools from the ground up. (Stove, frying pan, spatula, etc.) Yet software developers are asked--and expected--to make these kinds of changes all the time.

It's kind of like delivering the first Dodge Viper to the CEO and having him say, "everything is perfect, except.... diesel fuel is cheaper than premium unleaded, so we'd like the car to use that instead. The diesel fuel dispensers at the gas stations are 1/2" larger than the unleaded dispensers, so you'll have to make the hole under the gas cap a little bigger. That's an easy change, right? I'll be back tomorrow to give it a test drive."

[Yair]

It's kind of like delivering the first Dodge Viper to the CEO and having him say, "everything is perfect, except.... diesel fuel is cheaper than premium unleaded, so we'd like the car to use that instead. The diesel fuel dispensers at the gas stations are 1/2" larger than the unleaded dispensers, so you'll have to make the hole under the gas cap a little bigger. That's an easy change, right? I'll be back tomorrow to give it a test drive."

Yeah. That, or saying "you know what, we want it to be able to morph into an armored vehicle with rockets and guns and flying cameras. That's an easy change, right?".

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