Sister Kiyou shuffled nervously under the gaze of the one the Abbott had called "The Master Architect"; a monk called Master Torand. "As promised, I presented my completed design to him the day before the new moon, along with the three hundred and sixty one pages of extensive documentation explaining all ways in which the interface could correctly and incorrectly be used," she concluded. "I was particularly proud of the documentation. I went to great pains to ensure that all possible incompatibilities and failure cases were enumerated in detail, but the Abbott did not seem over pleased."
"And then?" asked Torand.
"He said, 'you have toiled long and hard to complete this, but now I would have you work a while with The Master Architect. Perhaps something will be learned.' Thus, I came here," she finished.
Master Torand nodded in understanding. He clearly seemed to know what this was about. "The Abbott has asked me to design a new pagoda for the temple grounds, that the temple's knowledge might be given a fitting home. Before I begin construction, I must ensure the design is perfect. As such, I shall send the Abbott a model; both that he might inspect it, but also to determine if the design is sound."
Kiyou nodded, for this sounded eminently sensible.
"As it happens, I have prepared just such a model. It is over there," the master said, indicating a table in the corner of the room. Kiyou walked to it and found it covered in hundreds of tiny, loose pieces of delicately carved and painted wood.
"This is... can it truly be called a model when it lies unassembled?"
"A fair point, sister. It shall be your task to assemble the model."
"I have laboured for many days with little rest; I believe I shall walk through the gardens to clear my mind. No doubt a talented nun such as yourself shall have no trouble in completing this final formality."
"Master, I am an architect of algorithms, not buildings; I know little of wood and stone."
"There is much to learn, but fortunately, I already know all that need be known for this task, and have built the pieces for you."
"But I do not... in truth, I have but a vague notion of what a pagoda is meant to look like!"
"This should present no difficulty for one of your ability." With that, Master Torand left Kiyou alone in the workshop with the pile of model parts.
Kiyou was dismayed. There was no way she could assemble the model without even knowing what it was meant to look like! Schematics, a blueprint, some general outline... how could a supposed master expect her to construct something so complex without any guidance?
For some time, Kiyou simply stared at the jumble of wooden pieces. Carelessly, she began to examine the pieces. She became fascinated by how many different and unique parts there appeared to be. Even something as simple as the tiny wooden beams appeared to have many slightly different variants. One might have a square joint at one end, the next would be circular. Another would end in a hexagonal shape.
On a whim, she took two likely looking wooden tiles, and found they would not fit together. Putting one down, she tried the next. And the next. And the next. Finally, she found a second piece that would fit.
She now had two tiles. And so, she searched for a third.
Then a fourth.
Then a fifth.
With each step, she found but a single piece that would fit in place. In short order, she realised she had constructed what appeared to be a small floor. The floor had several holes for other pieces to fit. Careful searching of the pile revealed just five beams that would fit. Thus, she put them together.
On and on this went, as the sun crossed the sky outside. The pagoda grew higher and higher, seemingly of its own volition. Floors assembled, walls attached, tiles locked into place. Kiyou felt she had no control over how the model was coming together: it was as though the model knew what shape it needed to be and would not allow her any freedom.
When the sun was hanging low in the sky, Kiyou found the model complete. Every piece had been used. The structure was sound. It was tall, with elegantly curved roofs. Even though she did not understand how it had been done, Master Torand had somehow built a stable and beautiful model of a pagoda though he had not been present for its assembly.
At that moment, Kiyou was enlightened.
"Ah, just in time for me to return from my walk."
Kiyou did not turn to face him. "I trust your exercise was refreshing?"
"Indeed. Now, I would like you to deliver the model to the Abbott, and tell him what has been learned."
"Whereupon, I returned here," she finished, showing the Abbott the completed model.
The Abbott frowned. "And," he asked, "what was learned?"
"I was wrong to be proud of my documentation. Though it came from great effort and care, I should have used that effort to make the interface itself better. I should have endeavoured to make an interface that did not require three hundred pages of explanation. One where the types themselves guide the programmer in their use.
"A perfect interface is one which is impossible to use incorrectly, even by accident."
The Abbott sighed. "I suppose it cannot be helped. Come, let us put it with the others."
Confused, Kiyou followed the Abbott as he led her through the winding corridors of the temple. At last, they came to a long hall with several shelves along each wall.
Each shelf was covered in dozens upon dozens of little model pagodas, each slightly different to the last. Walking to the very end of the room, past the array of little structures, the Abbott indicated an empty place on a shelf, into which Kiyou set her model.
This was a lesson taught and learned many times over, it seemed.
"It is a valuable lesson for you to have learned, but that was not why I sent you to see Master Torand."
"Indeed not. Master Torand was asked to construct a pagoda for this temple some eight years ago. Each time he completes a design, he withdraws it again, claiming it to not yet be perfect." He sighed again.
"I was rather hoping you might teach him the value of pragmatism and compromising perfection for the sake of completion. Even an ugly, rickety shed would be more useful than a hypothetical, flawless pagoda."
At that moment, Kiyou was enlightened.