2. UNIQUELY IDENTIFY THE
RESOURCE
There is the problem of naming, identifiers and persistence.
Naming is required to uniquely identify digital objects thus it should be permanent, lasting indefinitely.
These cannot be bound with specific locations. A global scheme of unique identifier is required.
Three schemes proposed to get over the problems of persistent naming are PURLs, URNs, and digital
object identifiers:
PURLs – are persistent URLs, a scheme developed by OCLC to separate document name from its a
location.
URN – Uniform Resource Name have been developed by Internet Engineering Task Force (IETF).
Digital Object Identifier (DOI) – Developed by Association of American Publishers and Corporation for
National Research Initiatives to provide a method by which digital object can be reliably identified and
DR. IRFAN UL HAQ AKHOON
3. UNIFORM RESOURCE IDENTIFIER
A Uniform Resource Identifier (URI) is a unique sequence of characters that identifies a
logical or physical resource used by web technologies.
URIs may be used to identify anything, including real-world objects, such as people and
places, concepts, or information resources such as web pages and books.
Some URIs provide a means of locating and retrieving information resources on a network
(either on the Internet or on another private network, such as a computer file system or an
Intranet).
There are two types of URIs:
Uniform Resource Name (URN):
Uniform Resource Locator (URL): DR. IRFAN UL HAQ AKHOON
5. UNIFORM RESOURCE NAME
URIs which provide only a unique name, without any means of locating or
retrieving the resource or information about it, these are Uniform Resource
Names (URNs).
A Uniform Resource Name (URN) is a persistent and location-independent
identifier that follows the “urn” scheme.
In this context, “persistent” means that the URN persists in identifying the same
resource over time.
DR. IRFAN UL HAQ AKHOON
6. UNIFORM RESOURCE LOCATOR
(URL)
It is an address of the resource located anywhere over the web.
Uniform: Unique.
Resource: Anything that has entity
Locator: A tool that can act as a reference/address to an object that has an identity
DR. IRFAN UL HAQ AKHOON
7. COMPONENT OF URL
Syntax: <scheme>:<host-specific-part>:<domain>
The scheme may be :
FTP :File Transfer protocol
HTTP: Hypertext Transfer Protocol
HTTPS: Hypertext Transfer Protocol Secured
File: Host-specific file names
Domain: region, area, specialty etc.
Example: http://www.kashmiruniversity.ac.in DR. IRFAN UL HAQ AKHOON
8. PROBLEM ASSOCIATED WITH URL
URL are not persistence and resource can lost, if
The server moves to a new computer
Server moves to a new port on the same computer
Name of the computer the server runs on changes
Resource's name changes
Resource moves to a new server
DR. IRFAN UL HAQ AKHOON
10. PERSISTENT UNIFORM RESOURCE
LOCATOR
PURLs are Web addresses that act as permanent identifiers in the changing Web infrastructure.
PURLs provide a level of indirection that allows the underlying Web addresses of resources to change
over time without negatively affecting systems that depend on them.
This capability provides continuity of references to network resources that may migrate from
machine to machine for business, social or technical reasons.
PURL was introduced by OCLC in 1995 and managed for over 20 years.
In 2015, OCLC and the Internet Archive engaged in a cooperative effort to build a new sustainable
service.
All previous PURL definitions have been transferred to the Internet Archive and can continue to be
maintained by their owners through a new web-based interface located at http://www.archive.org/
DR. IRFAN UL HAQ AKHOON
11. PERSISTENT URL
PURL (Persistent Uniform Resource Locator)
Three Component :
Protocol
Resolver address
Name
DR. IRFAN UL HAQ AKHOON
12. SOME PURL SERVERS
purl.org - The PURLs sites hosted at OCLC.
purl.bioontology.org Bioinformatics community project hosted at the National Center for
Biomedical Ontology.
demo.sharedname.org - Bioinformatics community project hosted at Shared Names.
purl.zepheira.com - PURL service for Zepheira and its customers.
purl.access.gpo.gov - Access to US government documents via the Government Printing
Office.
purl.fcla.edu - PURL service of The Florida Center for Library Automation.
The Callimachus Project implements PURLs as of December 2012.
DR. IRFAN UL HAQ AKHOON
14. DIGITAL OBJECT IDENTIFIER (DOI)
A DOI, is a string of numbers, letters and symbols used to permanently identify an article or
document and link to it on the web.
Developed by the International DOI Foundation in 2000
A DOI is a standardized system for identifying an electronic or digital object on the web.
Provides a persistent identification number to each resource registered with DOI registration
agencies.
A DOI looks like this:
DOI: 10.1037/15575330903279630
DR. IRFAN UL HAQ AKHOON
15. USES OF DOI
An identification system for intellectual property in the digital environment.
DOIs are in wide use mainly to identify web resources either academic, professional or
government on the web which include:
Journal articles,
Research reports,
Data sets,
Official publications,
DOI is also used to identify other types of information resources, such as commercial
videos, audios etc..
DR. IRFAN UL HAQ AKHOON
16. COMPONENT OF DOI
DOI Prefix:
Two component:
10.<organization assigned number>
1000 < the registrant> DOI Foundation
DOI Suffix
Identification for the entity, it may be a number, ISBN, item ID etc.
DR. IRFAN UL HAQ AKHOON
17. BENEFITS OF DOI SYSTEMS
Globally accepted unique identifier of electronic
resources;
Persistence !!!
DOIs are easy to use.
Provides multiple instances;
Extensible namespace;
International organizational support;
Works under distributed service model;
Works with secured name service;
Part of distributed administration service; and
Provides efficient resolution service.
Interoperability with other data from other sources
DR. IRFAN UL HAQ AKHOON
