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2008 Handle SystemWorkshop
Handle Value Types
17 June 2008
Larry LannomCorporation for National Research Initiatives
http://www.cnri.reston.va.us/http://www.handle.net/
Approved for Public Release © 2008 CNRI.
Corporation for National Research Initiatives
Handle Types
• Every handle record consists of one or more typed values: HDL:Type:Value
• Handle clients rely on types to understand the value and determine the correct action
• The Handle System per se never validates any type/value pair, although applications may.
• Handle creators are free to use or create whatever handle value types are needed for their needs
• Very flexible, works well, BUT - how do you understand the intended meaning of a given type?
Corporation for National Research Initiatives
Interpreting Handle Types
• Every handle value type (HVT) should itself be a registered handle− Currently a few registered under 0.Type but it
has been a cumbersome process− New types should be complete handles, e.g.,
10320/loc− Legacy, e.g., URL, assumed to be 0.Type
• Handle Value Type Registry (HVT-R) − Search for types− Open to whoever has a type to register (policies
TBD)
Corporation for National Research Initiatives
Handle Value Type Registry (HVT-R)
• Provides a comprehensive list of all registered HVTs.
• Provides a search/list capability for users to look for any existing type that may address their needs
• Service to be accessible to application frameworks for acquiring relevant information about a specific HVT
• Acquires data from value type handles in the handle system
• Every value type handle contains a description of type 10320/hvt-desc with a value of a defined XML schema− 0.Type/URL : 10320/hvt-desc : <xml description>
Corporation for National Research Initiatives
Handle Value Type Registry (HVT-R)
Corporation for National Research Initiatives
HVT Definition Schema
• Provides all of the information needed to sufficiently define a given HVT so as to promote its interoperable use with the Handle System.
• The schema consists of 13 top level fields• Most fields are simple:
– Handle used as the Type– Title– Contact information
• Some fields require more thought:– Value Description. This field can be complex since it contains all the
information that a developer/admin would need to be able to create a valid instance of that HVT.
• All humanly readable fields accommodate multiple languages.• Some fields can be defined in-line or by-reference.
– References are to existing HVT types: RFC, MIME types etc…
Corporation for National Research Initiatives
Use Case: 10320/loc
HVT-R
10320/loc description
4Handle System
3
Resolve 10320/loc
Is there a servicethat can do location
specific URL redirection?1
HVT: 10320/loc
2
5
Create handles that properlyspecify 10320/loc handle
values to leverage its standardservice implementation.
10320/locenabledService,
e.g., proxy6
Resolve a handlefrom Handle AdminA
Handle AdminA
User
9
Return properly Computed results for
HVT 10320/loc
7
Resolve Handle
8
Return 10320/locHandle values
Corporation for National Research Initiatives
Handle Value Type (HVT) Characteristics
• An HVT should unambiguously identify the nature of a specific handle value.
• A pragmatic classification of Handle Value Types:– HVTs recognized by the Handle System itself, for system
operation. Most of these types are defined within the RFCs. • HS_ADMIN, HS_SITE, HS_PUBKEY, HS_VLIST.
– HVTs recognized and acted upon by the Handle to Web proxy.• URL (0.TYPE/URL), 10320/loc
– User defined HVTs. Application specific• 100.3/GROUP (ADL)
• Strong recommendation: new HVTs should themselves be resolvable handles, to facilitate interoperability across handle applications
Corporation for National Research Initiatives
Beyond Handle Value Types
• Registered “Non HVT Types” are needed to support the development of HVTs.
• HVT descriptions can reference other HVTs as well as non-handle value types. (e.g. MIME types, services etc…)
• Non-handle value types can also be identified using a handle and registered in order to be consistently referenced.
• The current HVT definition schema can be used to describe these non-HVT type definitions.
• The HVT registry will allow for those types to be registered, indexed and searchable.
Corporation for National Research Initiatives
HVT-R Roadmap
• Make accessible to a controlled set of beta testers.– Operational version for CNRI developers - May 08– Volunteers solicited
• Expand the HVT-R to include non-handle value types, e.g., handle aliased MIME types.
• Produce final documentation and schema spec.• Provide public access to the registry.• Open up the registration of HVTs to the larger
Handle System community.