uri - Which ones are URLs? Which ones are URNs? -


the following uris. ones urls? ones urns?

ftp://ftp.is.co.za/rfc/rfc1808.txt http://www.ietf.org/rfc/rfc2396.txt ldap://[2001:db8::7]/c=gb?objectclass?one mailto:john.doe@example.com news:comp.infosystems.www.servers.unix tel:+1-816-555-1212 telnet://192.0.2.16:80/ urn:oasis:names:specification:docbook:dtd:xml:4.1.2

from rfc 3986 §1.1.3:

the term "uniform resource locator" (url) refers subset of uris that, in addition identifying resource, provide means of locating resource describing primary access mechanism (e.g., network "location"). term "uniform resource name" (urn) has been used historically refer both uris under "urn" scheme [rfc2141], required remain globally unique , persistent when resource ceases exist or becomes unavailable, , other uri properties of name.

the precise distinction contained within rfc 3305 §2, , can summarised [translated?] follows.

uniform resource identifier (uri)

a uri matching syntax described in rfc 3986 appendix a; identifies sort of resource. resource in question can webpage telephone number street address javascript guid, disambiguated scheme @ start of uri (the part before first :).

as noted, of samples uris.

uniform resource locator (url)

a url uri tells how access whatever resource it's describing. informal concept (see rfc 3305 §2.2), , such difficult define certainty. (it should noted that, in experience, members of public url when mean uri.)

all except last of samples probably url. (the distinction cannot made certain; above, url informal.) more on why last 1 isn't, keep reading,

uniform resource name (urn)

a urn, defined rfc 1737 , rfc 2141, way of giving more-or-less permanent name something. has syntax

urn:<namespace>:<more :-separated parts>

where urn: scheme name (so processor knows it's urn), <namespace> way of telling apart [basically] different peoples' urns, , rest of urn [more :-separated text] identifies within namespace. rfc 1737 §2 mandates urn always points same thing forever. requires urns which have corresponding urls must have way translated url; seem imply urn not url.

your last sample (urn:oasis:names:specification:docbook:dtd:xml:4.1.2) of urn scheme; is, definition, urn.


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