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?

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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)

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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>

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Handle Value Type Registry (HVT-R)

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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…

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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

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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

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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.

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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.