<font size="2">We had a bit more time to look at IDNAbis compatibility, and here are some better (and hopefully clearer) results. Out of a significantly large sampling of the web, there were about 800,000 cases where an HTML document contained an href="..." that contained a host name that was valid IDNA2003. We tested those host names to see if they would also be valid under IDNAbis (based on the current working proposals). About 85% were valid, about 8% more would be valid if IDNAbis were changed to also do case and width folding, and about 6% would still be invalid even if case and width foldings were applied. (The width foldings are applying NFKC to just the half-width and full-width characters to get the normal ones.)
<br><br>Here are some more details, where A0-A4 are disjoint categories.<br><br></font><table style="border-collapse: collapse; width: 411pt;" border="0" cellpadding="0" cellspacing="0" width="548"><tbody><tr height="17">
<td style="width: 323pt;" height="17" width="431"><font size="2">A0: Passes IDNAbis</font></td>
<td style="width: 40pt;" align="right" width="53"><font size="2">708,760</font></td>
<td style="width: 48pt;" align="right" width="64"><font size="2">85.26%</font></td>
</tr>
<tr height="17"><td height="17"><font size="2">A1: Passes IDNAbis after case folding</font></td>
<td align="right"><font size="2">22,714</font></td>
<td align="right"><font size="2">2.73%</font></td>
</tr>
<tr height="17"><td height="17"><font size="2">A2: Passes IDNAbis after width folding</font></td>
<td align="right"><font size="2">47,312</font></td>
<td align="right"><font size="2">5.69%</font></td>
</tr>
<tr height="17"><td height="17"><font size="2">A3: Passes IDNAbis after apply width
folding, and then case folding.</font></td>
<td align="right"><font size="2">4</font></td>
<td align="right"><font size="2">0.00%</font></td>
</tr>
<tr height="17"><td height="17"><font size="2">A4: Failed to pass IDNAbis after 3 steps</font></td>
<td align="right"><font size="2">52,456</font></td>
<td align="right"><font size="2">6.31%</font></td>
</tr>
<tr height="17">
<td height="17"><font size="2"><br></font></td>
<td><font size="2"><br></font></td>
<td><font size="2"><br></font></td>
</tr>
<tr height="17">
<td height="17"><font size="2">A5: Passes IDNA = sum(A1-A4)</font></td>
<td align="right"><font size="2">831,246</font></td>
<td align="right"><font size="2">100.00%</font></td></tr></tbody></table><br>This differs from some of our previous data, because we are explicitly testing IDNA vs IDNAbis (not just approximating the latter), and also filtering out invalid URLs. I will be out next week, but we'll try to follow up with more of a breakdown of A4.
<br><br>Mark<br>