Why did the system stall when it came across the ID card?

Comprehension:

If the system hadn’t stalled, Antar would never have guessed that the scrap of paper on his screen was the remnant of an ID card. It looked as though it had been rescued from a fire: the plastic laminate was warped and melted along the edge. The lettering was mostly illegible, and the photograph had vanished under a smudge of soot. But a four-inch metal chain had somehow stayed attached to the card: it hung down in a rusty loop from a perforation in the top left-hand corner, like a drooping tail. It was the chain that triggered the system, not the card.

The card turned up in one of those routine inventories that went flashing around the globe with metronome regularity, for no reason that Antar could understand, except that it was what the system did best. Once it got started, it would keep them coming, hour after hour, an endless succession of documents and objects, stopping only when it stumbled on something it couldn’t file: the most trivial things usually. Once it was a glass paperweight, of the kind that rain snowflakes if you turn them upside down; another time it was a bottle of correcting fluid, from an irrigation overseer’s office just south of the Arab Sea. Both times the machine went into a controlled frenzy, firing off questions, one after another.

Antar had met children who were like that: What? Why? When? Where? How? But the children asked because they were curious. With these AVA/IIe systems it was something else - something he could only think of as a simulated urge for self-improvement. He’d been using Ava for a couple of years now, and he was still awed by her eagerness to become herself. Anything she did not recognise, she’d take apart on screen, producing ever greater refinements of details.