1. The DOI System The DOI System
Resolution
Resolution Resolution
DOI SYSTEM: RESOLUTION
Workshop on the DOI System
International DOI Foundation 1

2. The DOI System The DOI System
Resolution
Resolution Resolution
doi>
Outline / Key concepts in this section
Internet resolution
The Handle System®
Implementation tools: Web browsers, proxies, plug-ins
Appropriate resolution
Data typing
Multiple resolution
Handle System developments 2

3. The DOI System The DOI System
Resolution
Resolution Resolution
doi>
Further reading on key concepts in this section
DOI Handbook Chapter 3, “Resolution Numbering”
“DOI System and the Handle System” Factsheet: 3

4. The DOI System The DOI System
Resolution Resolution
Resolution 4

5. The DOI System The DOI System
Resolution
Resolution Resolution
doi>
DOI Resolution
Resolution: the process of submitting a DOI name to a network service and receiving in return one or more pieces of current information related to the identified object. e.g., a location (URL) of the object or metadata.
DNS is the best known type of resolution: resolve the IP address to route to a computer location
This may involve one or more intermediate mapping operations. The resolution may or may not return an instance of the object.
Multiple resolution is the simultaneous return as output of multiple pieces of current information related to the object, in defined data structures.
The DOI System uses the Handle System to provide resolution
See handle.net for detail e.g. advantages over DNS 5

6. The DOI System The DOI System
Resolution
Resolution Resolution
doi>
The Handle System
The Handle System is “a general purpose distributed information system that provides efficient, extensible, and secure identifier and resolution services for use on networks such as the Internet.”
A non-commercial, openly available protocol and reference implementation.
Met the needs of DOI System development aim: do not re-invent the wheel.
Can utilise existing or new schemes, many advantages that map to DOI System needs.
Developed at Corporation for National Research Initiatives (US) by Robert Kahn, one of the “fathers of the Internet” (TCP/IP). 6

7. The DOI System The DOI System
Resolution
Resolution Resolution
doi>
The Handle System: rationale
“Digital information needs to be a first class citizen in the networked environment”
First class = one that has an identity independent of any other item
Current Internet less than optimal for security, privacy, mobility.
Original Internet design conflated addresses to serve two purposes: an indication of the location of the end point, and an indication of its identity – now recognised as a limitation (see e.g. NewArch*, FIND**)
*Future generation Internet architecture
**Future Internet network design
The fundamental characteristic of digital information is that it is processable data, enabling re-use and hence new forms of electronic commerce, creativity and social benefit.
Managing these units of digital information, the “citizens” in the network, requires that they have unique names (or “identifiers”) denoting a specific referent, and the ability to manage their attributes.
Objects (“citizens”) may be representations of content, people, parties, resources, licences, avatars, sensors, etc. 7

8. The DOI System The DOI System
Resolution
Resolution Resolution
doi>
Part of Digital Object Architecture
Handle System is part of a wider architecture (but entirely separable and usable alone): focus on objects not packets.
Managing information on the Net over very long periods of time – e.g. centuries or more.
Dealing with very large amounts of information on the Net over time.
When information, its location(s) and even the underlying systems may change dramatically over time.
Respecting and protecting rights, interests and value.
Robert Kahn/Robert Wilensky “A Framework for Distributed Digital Object Services”, 1995. 8

9. The DOI System The DOI System
Resolution
Resolution Resolution
doi>
Terminology
Identifier: unique persistent string (“number”, “name”, “identifier”) assigned to a referent
Unique: one to many: an identifier specifies one and only one referent (but a referent may have more than one identifier)
Persistent: once assigned, does not change referent
Resolution: process by which an identifier is input to a network service which returns some information
Referent: the object to which the identifier is assigned, whether or not resolution returns that object.
may be abstract, physical or digital, since all these forms of object are of relevance in identifier management (e.g. creations, resources, agreements, people, organisations) – classical ontology issues
Digital object: an instance of an abstract data type
(Objects are often compound and contain several referents) 9

10. The DOI System The DOI System
Handle System overview
Resolution
Resolution Resolution
doi>
Basic Internet resolution system: identify objects, not servers.
Optimized for speed, reliability, scaling
Open defined protocol and data model (IETF RFC 3650,1,2)
free protocol; service at low cost (non-profit);
freely available to be used as engine underneath other named identifiers.
Separation of control of the handle and who runs the servers
distributed administration, granularity at the handle level
Any Unicode character set
internationalisation
All transactions can be secure and certified
Both registration and resolution
Not all data public: individual values within a handle can be private
No semantics necessary in the identifier
Logically centralized, physically distributed and highly scalable
Does not need DNS, but can work with DNS:
deployed via tools e.g http proxies, client plug-ins, server software, etc 10

11. The DOI System The DOI System
Resolution
Resolution Resolution
Handle syntax
doi>
A Handle consists of a prefix and suffix
e.g. 123/4567
Prefix and suffix may be any length
e.g /456-mydoc
Suffix may incorporate another identifier numbering scheme
e.g /ISBN
Thereby adds functionality to that numbering scheme
Shorter prefixes (1-3 digits) reserved for major projects, countries, etc. 11

12. The DOI System The DOI System
Handles resolve to typed data
Resolution
Resolution Resolution
doi>
Schematic (simplified) representation of a handle record
Handle
Handle value(s)
Data type
Index
Data value
10.123/456
URL 1
Prefix
Suffix
URL 2
DLS 3
acme/repository
HS_ADMIN
100
acme.admin/jsmith
XYZ 12
One or more Handle values (type:value)
Resolution can return all values, or all values of one type 12

13. The DOI System The DOI System
Resolution Resolution
Resolution
doi>
Handles resolve to typed data
Fuller representation of a handle record:
e.g. the handle " /may99-payette" has a set of three handle values:
<index>:
<index>:
<type>: HS_ADMIN
<data>: acme.admin/jsmith
<index>:
<type>: URL
<data>:
<TTL>: {Relative: 24 hours}
<permission>: PUBLIC_READ, ADMIN_WRITE
<timestamp>:
<reference>: {empty} 13

14. The DOI System The DOI System
Resolution Resolution
Resolution
Handles resolve to typed data
The Handle System
is a collection of
handle services,
Client
GHR
LHS
each of which
consists of one or
more replicated sites,
Site 1
Site 2
Site 3
…...
Site n
each of which may
have one or more
servers.
/abc
URL 4 8 #1 #2 #n #4 #3
... 14

15. The DOI System The DOI System
Resolution Resolution
Resolution
Handle clients
Request to Client:
Resolve hdl: /1
1. Sends request to Global to
resolve 0.NA/
(naming authority
handle for )
Client
Global Handle
Registry 15

16. The DOI System The DOI System
Resolution Resolution
Resolution
Handle clients
Request to Client:
Resolve hdl: /1
Client
2. Global Responds with
Service Information for
Service Information
Acme Local Handle Service
xcccxv xc ..
...
xccx
Global Handle
Registry 16

17. The DOI System The DOI System
Resolution Resolution
Resolution
Handle clients
Request to Client:
Resolve hdl: /1
Client
Global Handle
Registry
3. Client queries Server 3
in Secondary Site A
for /1 #1
Acme Local
Handle Service #1 #2
Secondary Site B #2 #1 #3
Primary Site
Secondary Site A 17

18. The DOI System The DOI System
Resolution Resolution
Resolution
Handle clients
Request to Client:
Resolve hdl: /1
Client
Global Handle
Registry
4. Server responds with
handle data #1
Acme Local
Handle Service #1 #2
Secondary Site B #2 #1 #3
Primary Site
Secondary Site A 18

19. The DOI System The DOI System
Resolution Resolution
Resolution
Handle clients
Web Client
Handle Administration
Client
HTTP Redirect
HTTP Get
Proxy/
Web Server
Handle Data
Resolve
Handle
LHS
GHR
Handle System 19

20. The DOI System The DOI System
Resolution Resolution
Resolution
Handle clients
Client
Handle Administration
Client
Client
Plug-In
Handle Data
Resolve Handle
Request
hdl:/ /abc
LHS
GHR
Handle System 20

21. The DOI System The DOI System
Resolution Resolution
Resolution
Handle clients
Web
Handle Administration
Client
HTTP
Admin Forms
Web Server
Handle Admin API
LHS
GHR
Handle System 21

22. The DOI System The DOI System
Resolution Resolution
Resolution
Handle clients
Web
Handle Administration
Client
Custom
Client
LHS
GHR
Handle System 22

23. The DOI System The DOI System
Resolution Resolution
Resolution
Handle clients
Handle Administration
embedded in another
process
Web
LHS
GHR
Handle System 23

24. The DOI System The DOI System
Resolution Resolution
Resolution
Handle clients
Handle Resolution
embedded in another
process
Handle Administration
embedded in another
process
LHS
GHR
Handle System 24

25. The DOI System The DOI System
Handle System: typing
Resolution
Resolution Resolution
doi>
A handle has a set of values assigned to it
= a record that consists of a group of fields
<type> field defines the syntax and semantics of a value’s data
e.g. URL (resolving to current location)
pre-defined set of handle data types for administrative use
registered handle data types for non-administrative use (URL, , and DESC): others being added*
Types may include:
HS_PUBKEY: public key used to authenticate entities in the Handle System
HS_SECKEY: secret key password to access some service
DESC: UTF8-encoded descriptions of the object identified by the handle
Full list at
*Handle System Advisory Committee is defining a recommended practice process 25

26. The DOI System The DOI System
Handle System usage (1)
Resolution
Resolution Resolution
doi>
Provides infrastructure for application domains, e.g. digital libraries & publishing, network management, id management ...
International DOI Foundation
Federation of several independent applications
Defense Virtual Information Architecture
Defense Technical Information Center (DTIC), DARPA, CNRI
context sensitive distribution of data and metadata: resolution result depends on who you are
GRID computing
Shared computing resources
Handle System - Globus Toolkit Integration Project 26

27. The DOI System The DOI System
Handle System usage (2)
Resolution
Resolution Resolution
doi>
DSpace - Digital Repository System
MIT Libraries/Hewlett-Packard
stable, long-term storage of intellectual output of faculty, researchers, centers and labs
National Digital Library Program (NDLP)
Library of Congress. Collections of historic materials converted to digital formats. LoC use handles to identify material in the library's own collections
Los Alamos National Labs
internal doc management (600m+)
Several Digital Library projects
e.g. ARROW
Others who may adopt RFCs:
e.g. Fedmark: independent commercial implementation of Handle protocols for digital rights system 27

28. The DOI System The DOI System
Handle System projects
Resolution
Resolution Resolution
doi>
Some others of particular relevance to identity management...
Transient Network Architecture
Pervasive transient mobile network in which all communications occur between persistently identified entities.
CNRI/University of New Mexico, under NSF’s FIND (Future Internet Network Design) project
Using PKI capability for persistent trustworthy identity, separating:
Transport trustworthy (name/attribute is binding)
Administration trustworthy (attribute is issued by attribute holder)
Attribute credential (attribute value is true)
Representing Value as Digital Objects: Transferability and Anonymity
Deeds of trust, mortgages, bills of lading, digital cash etc.
“Transferable records" structured as digital objects
Possible Application of Handles to licences and parties
See separate talk on content industry identifiers 28

29. The DOI System The DOI System
Handle System statistics
Resolution
Resolution Resolution
doi>
Assigned namespaces (“prefix”)
DOI
D-Space
Others
Individual “Handles” (identifiers within each namespace)
DOI M
Other: 600?? millions
total per namespace known only to namespace manager; e.g. LANL adding 600M but privately
Global Handle System
Core three service sites (added locations being considered)
c. 60 million direct resolutions per month
c. 50 million proxy server resolutions per month 29

30. The DOI System The DOI System
Handle System: security
Resolution
Resolution Resolution
doi>
Integrity of the Global Handle Registry service.
Protected service information and public key pair used to sign global service information.
Handle protocol allows handle servers to authenticate their clients and to provide data integrity service on client request.
Handle servers can be explicitly asked to generate or return a digital signature for every service response (but normally don’t).
Public key and/or secret key cryptography may be used.
Server authentication may be used to prevent eavesdroppers from forging client requests or tampering with server responses.
Client applications can (if wished) only accept information from the authoritative Global Handle Registry (not any mirrors) and check its integrity on each update. 30

31. The DOI System The DOI System
Handle System and DNS (1)
Resolution
Resolution Resolution
doi>
Similarities and differences in both the design and intended use.
Naming
DNS naming hierarchy reflects a control hierarchy, Handle System need not.
Handle System separates control of handle (id) from control of server (location).
Distributed Administration
Handle administrators can add/delete identifier and identifier values securely over the public Internet.
Proxies
Technical advantages regarding resolution work behind SOCKS or HTTP proxies, both supported in Handle client library (whereas DNS resolution from behind proxies is difficult/impossible).
Unicode
Full native Unicode is supported by the Handle System. There are hacks to make DNS support 8-bit character sets, but they are not widely implemented.
Replication
In DNS, if a single record is updated all records must be copied to mirror servers. The Handle System has finer granularity: if a single record is updated, the server will copy only that record to the mirror servers. 31

32. The DOI System The DOI System
Handle System and DNS (2)
Resolution
Resolution Resolution
doi>
Certification
DNS has to be fast, especially at the root. Not very good for alternative uses, e.g. certificates. Handle System has more flexible and robust certification support.
Access Control
Handle System has support for access control and authentication. DNS does not.
Record Size
Technical advantages regarding UDP and TCP handling: more efficient request handling; much larger storage in a record (DNS 64KB, Handle System 4GB).
Examples of integration with DNS:
CNNIC Handle implementation offers secured DNS resolution via a Handle protocol interface. Further work will package the Handle-DNS software for public release; deploy the Handle-DNS server in “.cn” TLD registry and its subsidiaries; and establish an ENUM service and client software based on the Handle-DNS interface.
Client library and proxies for use with http etc. 32

33. The DOI System The DOI System
Handle System and granularity
Resolution
Resolution Resolution
doi>
Functional Granularity: “it should be possible to identify an entity whenever it needs to be distinguished”
First class naming: “Digital objects should have first class names”
Naming hierarchy independent of control hierarchy:
DNS: who runs acme.com controls who runs branch.acme.com
Handle System separates control of handle (id) from control of server (location)
Handles are first class names:
URLs: grouped by domain name and then by some sort of hierarchical structure, originally based on file trees
Handles: each name stands on its own, unconnected to any DNS or other hierarchy Can avoid broken URLs when control changes
Ownership. The prefix administrator is considered the owner of the data (whereas in DNS, the system administrator is considered the owner):
Each Handle identifier and prefix can have its own set of administrators independent from the system administrator
Relationships between objects can be expressed:
If you want to build a hierarchy you can – but on any basis
Handles can refer to other handles (some applications have introduced a detailed data model to allow this – e.g DOI) 33

34. The DOI System The DOI System
Handle System and standards
Resolution
Resolution Resolution
doi>
Specification
RFC 3650: Overview
RFC 3651: Namespace and Service Definition
RFC 3652: Protocol
Application areas
DoD Instruction 1322
Mandates Handle System use as part of Advanced Distributed Learning
ISO standards track for DOI System
A Handle application for the content sector
ISO TC46/SC9 (home of ISBN etc)
Governance: HSAC - Handle System Advisory Committee
Approx 15 members representing big users or interest groups
Goal: evolve to oversee the system, autonomous (cf. IETF etc)
Currently by invitation; interest welcomed 34

35. The DOI System The DOI System
Handle System home page
Resolution
Resolution Resolution 35

36. The DOI System The DOI System
Resolution
Resolution Resolution
DOI name appropriate (contextual) resolution
doi>
Resolve DOI name with some additional information to give results depending on context
Open URL: see e.g.
Resolve to same content at different location (by user)
Full contextual resolution: Handle System can do this (DVIA)
Resolve to different content (by user)
Of interest re licensing etc
Steps in evolution:
URLs: not useful for long term management
naming and resolution: “get me the right thing”
contextual resolution: “get me the thing that is right for me” (e.g. “that I have access rights for”) 36

37. The DOI System The DOI System
Resolution
Resolution Resolution
doi>
DOI tools: example (1)
Adobe Acrobat plug-in
Concept announced and “mock-up” shown 2002
Now fully developed and licensed, available for Acrobat 8.0
Builds on Acrobat SDK
Early adopters needed
Potential for more work
Examples:
1. CrossRef data
2. “New version” functionality 37

38. The DOI System The DOI System
Resolution Resolution
Resolution 38

39. The DOI System The DOI System
Resolution Resolution
Resolution 39

40. The DOI System The DOI System
Resolution Resolution
Resolution 40

41. The DOI System The DOI System
Resolution Resolution
Resolution 41

42. The DOI System The DOI System
Resolution
Resolution Resolution
doi>
DOI tools: example (1)
Adobe Acrobat plug-in
2. “New version” functionality 42

43. The DOI System The DOI System
Resolution Resolution
Resolution 43

44. The DOI System The DOI System
Resolution Resolution
Resolution 44

45. The DOI System The DOI System
Resolution
Resolution Resolution
doi>
DOI tools: example (2)
Firefox Handle Extension
Displays a toolbar with Handle System features
Tool to create additional handles, bookmark handles, etc
Bring up a web page and assign a Handle
Recent work: possible addition to “Firefox Add-ons” 45

46. The DOI System The DOI System
Resolution Resolution
Resolution 46

47. The DOI System The DOI System
Resolution Resolution
Resolution 47

48. The DOI System The DOI System
Resolution
Resolution Resolution
doi>
DOI multiple resolution
Significant benefit of Handle System:
Resolve from one DOI name to several different things
One-to-many linkage
Resolution request would give:
all results, or
all results of one type
Need a framework to build these applications on: group similar uses so that the results are predictable and can be used across applications
DOI Application Profile framework
Handle System “data value typing”
CrossRef use for e.g. location-dependent resolution
Other business cases?
Could express relationships (ISTC to ISBNs etc) 48

49. The DOI System The DOI System
Resolution
Resolution Resolution
doi>
DOI Application Profiles
Referents are
identified by DOIs
The properties of groups of
DOIs are defined as APs
APs have one or more
Services
Services have
definitions
Entity
Application Profile
965
Service Instance
Service Definition
Entity
876
Entity
456
453
453
784
Service Instance
Application Profile
Entity
Service Definition
Application Profile
Service Instance
Entity
784
Entity
369
908
Service Instance
Service Definition
Entity
APs and services are themselves identified by Handles (DOIs) 49

50. Other related tools for resolution
The DOI System
The DOI System The DOI System
Resolution
Resolution Resolution
doi>
NISO = National Information Standards Organization (under ANSI, the US national body of ISO)
Open URL
NISO standard Z A syntax to create web-transportable packages of metadata and/or identifiers about an information object.
Not an identifier, but a complementary technology for appropriate redirection of an identifier resolution.
In use with Digital Object Identifiers (DOI names) and handles.
e.g.
"info" URI Registry
IETF RFC 4452: The "info" URI Scheme for Information Assets with Identifiers in Public Namespaces.
Turn legacy identifiers into URLs (e.g. info:lccn/ ).
DOI and Handle are both registered as info URI schemes.
Now formalizing policies for the "info" URI registry.
“This identifier and its registry could serve as a focal point for NISO's identifier activity, creating a trusted brand and a starting point for community members doing work that requires identifiers.” (NISO workshop on identifiers 2006) 50

51. The DOI System The DOI System
Resolution
Resolution Resolution
New features in recent Handle releases: server side
Berkeley DB JE support
Increased performance
Increased scalability
Template resolution, a.k.a. virtual handles
All handles that match a given pattern, e.g., 123/456*, will resolve to the same data, e.g., a single URL at which all objects are found
Currently a fixed value per pattern, but could be extended to be a function of the handle presented for resolution (think limited regular expressions), e.g.,
123/456.abc, resolved by any client, would resolve to the pattern
and the server would return 51

52. The DOI System The DOI System
Resolution
Resolution Resolution
New features in recent Handle releases: client side
‘Choose by’ facility - currently being deployed in the proxy service
Pack alternatives into a single handle value using XML.
Include criteria for selecting among them, to be evaluated by the client.
Example: alternatives = geographic locations, criteria = incoming IP, proxy matches incoming IP to IP tables and picks best location, other clients could be configured to select country in some other way.
Detail: For some handle, the value of type CNRI.RSRC_LOC
<locations chooseby="locatt,country,weighted">
<location id=0 href=“ country="gb” weight=0 />
<location id=1 href=“ weight=1 />
<location id=2 href=“ weight=1 />
</locations> 52

53. The DOI System The DOI System
Resolution
Resolution Resolution
New features in recent Handle releases: client side
Extended Handle client library to provide higher level API
Creation:
handleValue = hsClient.createHandleValue(1,”URL”,"
hsClient.createHandle(handle, new HandleValue[] {handleValue});
Deletion
hsClient.deleteHandle(handle);
Resolver.xml
Local file containing override or default values for specific handles
If override, local client never goes to Handle System for that handle, but just uses the given value
If default, local client uses that value if it cannot resolve the handle for whatever reason, e.g., on an airplane
Web services interface to Handle System at multiple levels
Added to current set of proxies
Released as a stand-alone interface that could employed by other organizations as needed
Handle plug-in for Acrobat Reader re-released for Reader 8 53

54. The DOI System The DOI System
Handles resolve to typed data
Resolution Resolution
Resolution
doi>
Handle
Data type
Index
Handle data
10.123/456
URL 1
URL 2
DLS 9
acme/repository
HS_ADMIN
100
acme.admin/jsmith
XYZ 12
Rules for data type construction: 54

55. The DOI System The DOI System
Resolution
Resolution Resolution
Handles resolve to typed data
How to define these types? (not types of referents)
Handle Records may be thought of as sets of handle triples: handle:type:value
Clients rely on types in order to interpret the values
All of this is transparent to HS servers – servers simply store and deliver type:value pairs - type is completely open, no type police
A few standard types already exist:
Admin types - what the HS itself needs to operate
Common types, e.g., URL
They are themselves registered as handles, e.g., 0.TYPE/URL
Lots of projects using the Handle System invent types for their own purposes
Two issues coming to the fore:
What can a client do with a type it doesn’t know about ahead of time?
What sort of synergies across projects are we missing through wheel re-invention? 55

56. The DOI System The DOI System
Resolution
Resolution Resolution
Proposed Registry of Handle types
Keep the 0.TYPE mechanism in place
Encourage registration, with low barriers
Is it in use?
Is it understandable?
Is it harmful to the overall HS?
Expand the required type/values under the 0.TYPE handle
Human-readable description
Responsible party
Dates of creation and last revision
Related handle types
Searchable registry in which the type is registered
Introduce a searchable Registry of Handle Types
Publicly available for searching
Searchable version of the complete set of 0.TYPE records
Added fields and examples?
Issues
Ontologies: are two types really the same but using different descriptions or languages?
Trial vs accepted types 56

57. The DOI System The DOI System
Resolution
Resolution Resolution
Outline / Key concepts in this section
Internet resolution
The Handle System
Implementation tools: Web browsers, proxies, plug-ins
Appropriate resolution
Data typing
Multiple resolution
Handle System developments 57

58. The DOI System The DOI System
Resolution
Resolution Resolution
DOI SYSTEM: RESOLUTION
Workshop on the DOI System
International DOI Foundation 58