1. The ‘www’ domain = No
2. Letter casing in path = Maybe (depends if server’s OS is Windows)
3. Letter casing in domain = No
4. Index.htm vs. Default.aspx = No
5. Trailing slash on domain = Yes
6. Trailing slash on path = No
7. Empty question mark = No
8. Empty parameter = No
9. Port 80 = Yes
10. Port 443 = No
11. Https vs. Port 443 = Yes
12. Ftp vs. Http = No
13. Letter casing in parameter name = No
14. Letter casing in parameter value = No
15. Hash vs. no hash = Maybe
16. Hash vs. Fragment = No
17. Fragment vs. no Fragment = No
18. Plus vs. Space in path = Yes
19. Space vs. Encoded Space in path = No
20. Plus vs. Encoded Plus in path = No
21. Slash vs. Encoded Slash in path = No
22. Ampersand vs. Encoded Ampersand in path = No
23. Ampersand vs. Encoded Ampersand in parameter value = No
24. Equals vs. Encoded Equals in path = No
25. Equals vs. Encoded Equals in parameter value = No
26. Parameter order = Yes

…I’m curious to know how wrong or how right I am. :) this was fun!

For the hash/fragment examples: depends whether you count the client side fragment resolving as “dereferencing” (say, you’re storing fragments only on some client software). But I’ve assumed that is not what was meant.

1. The ‘www’ domain: Maybe
2. Letter casing in path: Maybe
3. Letter casing in domain: Yes
4. Index.htm vs. Default.aspx: Maybe
5. Trailing slash on domain: Yes
6. Trailing slash on path: Maybe
7. Empty question mark: Maybe
8. Empty parameter: Maybe
9. Port 80: Yes
10. Port 443: Maybe
11. Https vs. Port 443: Maybe
12. Ftp vs. Http: Maybe
13. Letter casing in parameter name: Maybe
14. Letter casing in parameter value: Maybe
15. Hash vs. no hash: Yes
16. Hash vs. Fragment: Yes
17. Fragment vs. no Fragment: Yes
18. Plus vs. Space in path: Maybe
19. Space vs. Encoded Space in path: Yes
20. Plus vs. Encoded Plus in path: Yes
21. Slash vs. Encoded Slash in path: Maybe
22. Ampersand vs. Encoded Ampersand in path: Yes
23. Ampersand vs. Encoded Ampersand in parameter value: Maybe
24. Equals vs. Encoded Equals in path: Yes
25. Equals vs. Encoded Equals in parameter value: Maybe
26. Parameter order: Maybe

Some more:
- Plus vs space in querystring
- semicolon vs ampersand in querystring
- semicolon vs encoded semicolon in path

a. no
b. no
c. yes
d. no
e. yes (because of URI syntax, empty path meaning root?)
f. no (but I wish)
g. yes?
h. no
i. yes
j. no
k. no (but https://mysite.foo:443/ yes)
l. no
m. no
n. no
o. no, yes (because fragID shows resource, but doesn’t affect retrieval)
p. no, yes
q. no, yes
r. no (is the URI with space valid?)
s. is the URI with space valid?
t. yes?
u. no
v. yes?
w. no
x. yes?
y. no
z. no (I wish)

I’ll compare with Devon now. 8-)

1. The ‘www’ domain = No
2. Letter casing in path = No
3. Letter casing in domain = Yes
4. Index.htm vs. Default.aspx = No
5. Trailing slash on domain = Yes
6. Trailing slash on path = No
7. Empty question mark = No
8. Empty parameter = No
9. Port 80 = Yes
10. Port 443 = No
11. Https vs. Port 443 = No
12. Ftp vs. Http = No
13. Letter casing in parameter name = No
14. Letter casing in parameter value = No
15. Hash vs. no hash = No (but HTTP is guarenteed to return the same resource)
16. Hash vs. Fragment = No (but HTTP is guarenteed to return the same resource)
17. Fragment vs. no Fragment = No (but HTTP is guarenteed to return the same resource)
18. Plus vs. Space in path = No (spaces aren’t allowed in URIs)
19. Space vs. Encoded Space in path = No (spaces aren’t allowed in URIs)
20. Plus vs. Encoded Plus in path = No
21. Slash vs. Encoded Slash in path = No
22. Ampersand vs. Encoded Ampersand in path = No
23. Ampersand vs. Encoded Ampersand in parameter value = No
24. Equals vs. Encoded Equals in path = No
25. Equals vs. Encoded Equals in parameter value = No
26. Parameter order = No

Good points. I added clarification above to explain where I was looking for ‘No’ vs. ‘Maybe.’

@jacek >> Answers taken according to specs (IIRC), not to practice which may differ to a good effect.

Definitely to specs, not practice as who knows what evil lurks in the hearts of equipment on the web? ;-)

@Dave Risney >> “I have issues with your definitions of what the answers mean. I’d argue that ‘maybe’ will always be a better answer than ‘no’ because any server may choose to return the same resource for two different URIs. Additionally ‘yes’ meaning “Which can be cached as the same URL?” depends on what entity is doing the caching. So I’m answering with ‘yes’ meaning the URIs are equivalent by RFC 3986 and ‘no’ meaning that the URIs aren’t.

As I said to polaar, good points and I (at least attempted) to clarify above.

ALSO, thanks all for participating! I did this to provide a thought exercise and a way to collect enough research to write an article, not to pass for fail anybody! :) I’ll be doing the writeup on this one in the (hopefully near) future.

.test .example .invalid .localhost

There’s also example.{com,org,net}, which is a valid DNS entry to be used for testing.

The domain .foo can’t be far behind the inappropriate (but real) .mobi (^: