Why identifiers?

• To access resources

• To cite resources

• To unambiguously identify a resource– To register it as intellectual property– To record changes in ownership

How we identify objects now

http://www.library.cornell.edu/dlit/systems.htm

ftp://ftp.is.co.za/rfc/rfc1808.txt

gopher://spinaltap.micro.umn.edu/00/Weather/New%20York/Ithaca

URLs http://www.library.cornell.edu/dlit/systems.htm

• Service instructions for accessing an object

• Oriented toward access/location vs. identification– Essentially, an address

• Most likely ephemeral

service,protocol

machine/host name

local file location

Good Identifiers

• Globally unique

• Persistent | permanent– Even when the identified resource ceases to

exist or is no longer available

• Independent of location

Good Identifier Schemes

• Scalable

• Extensible

• Support for legacy schemes– ISBNs, ISSNs, etc.

Uniform Resource Identifiers

URL

URN

URNs

urn:<Namespace Identifier>:<Namespace Specific String

• Identifies an object• Nothing about access mechanism, little

about location• Requires resolution services and registries

– Indirection

URNs

urn:issn:0003-486X

urn:dwr:myOrganizations:theirMembers

Naming schemes

• Handle System– cnri.dlib/june98-powell

• DOI– 10.1045/october2002-hitchcock

• ARK– ark://some.host/1234/98765432– ark:1234/98765432

As (potential) URNs

urn:hdl:cnri.dlib/june98-powell

urn:doi:10.1045/october2002-hitchcock

urn:ark://some.host 1234/98765432

PURLs

• A persistent URL– Using indirection

• Temporary solution?

• Still identify a service, not an object– Not an actual “name”– Dependent on that service (HTTP)

In the interim

• Likely depend on proxy services for resolution to Cornell’s “doorstep”– urn:cul:...– urn:hdl:cul.rmc:...

• But inside our doors?– How do we manage identifiers within Cornell

and/or Cornell University Library?

Identifiers and semantics

• Semantic identifiers– Perhaps intelligent to people– cnri.dlib/june98-powell

• Non-semantic identifiers– Not meaningful to people– 10.1045/abc123456