Page History

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	HDL	PURLz
Supports billions of identifiers	Don't know; limited to the practical capacity of the underlying database.	Don't know – mention of 1996 tests resolving 50 resolutions/sec with a database of 500,000 PURLS in Long Introduction to PURLs
Robust architecture	Yes	PURLz is just a simple HTTP server using MySQL
Robust implementation	Yes	No - alpha stage
ability to request metadata about the identifier	Yes	Yes
lightweight understanding of identifier equivalence	Yes	Cloning an existing PURL and chaining a PURL
should be easily discoverable by Google	Yes; the resolvers can't be crawled without providing a dump	Yes; the resolvers can't be crawled without providing a dump
integrate well with the "web architecture"	Yes	Yes
vitality checking	?	not built in
Need to avoid unbounded generation of surrogate persistent identifiers	?	?
PID corresponding to every Cornell NetID	? ?	Depends on the Partial Redirect working – e.g., http://resolver.cornell.edu/netid/bdc34

Governance Issues

	HDL	PURLz
Requires payment to external organization	one-time $50 payment per named resolver (not mirrors)	no
Can continue resolve IDs in absence of external organization	Yes	Yes

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