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Middleware development notes

Middleware development notes. Result set/accumulator improvements Collection hierarchies Collection monitoring Ingest/management services Vocabulary refinements. Result sets and accumulators. Result accumulator now: craps out on first error new: runs until all threads finish or time out

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Middleware development notes

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  1. Middleware development notes • Result set/accumulator improvements • Collection hierarchies • Collection monitoring • Ingest/management services • Vocabulary refinements

  2. Result sets and accumulators • Result accumulator • now: craps out on first error • new: runs until all threads finish or time out • Result set • tracks middleware and per-collection errors • maintains per-collection counts • still merges & ranks results • maintains mapping between results & collections? • interaction with collection hierarchies?

  3. Collection hierarchies • The problem: • flat namespace • people want hierarchies • aggregation • logical grouping • grouping & easy importing of remote collections

  4. Kinds of collections • From implementation perspective: two kinds of collections • leaf collections • “real,” have items • non-leaf collections • pure aggregations • may or may not expose sub-collections • collection-level metadata • static: custom or auto-generated • dynamic: auto-generated • independent of collection location • proxies act like symlinks or NFS mounts • forms a logical namespace of distributed content • From client perspective: all collections look alike*

  5. Exposing the hierarchy • Configuration service • reports hierarchy, collection statuses • Query results • Aggregates with hidden contents act like leaf collections • Result sets?

  6. Identifiers • Now: • collection:local-id • New: • collection/path/...:local-id • collection/path/...:hidden/path/...:local-id • Someday: GUID prefixes • Implementation note: identifier renamers must be uniformly employed

  7. Collection monitoring • New collection-level service: status • possible answers: up, down, partially up • aggregates return info on sub-collections • bucket99 driver: executes test query • Separate thread polls collections, maintains global map

  8. Ingest/management services • Add item • 3 ADL views plus other, arbitrary views • returns collection-local identifier • Replace view • Delete item • Create collection • name, static metadata • Replace collection static metadata • Delete collection • New: these are “lc” (local collection) specific

  9. generic webclient (JSP) ingest tools (JSP) middleware (Java/HTTP/RMI) middleware webapp directory (local file system) Ingest big picture

  10. Vocabulary refinements • Definition: a thesaurus C is a refinement of a thesaurus P if it has the following properties: • every preferred term in C is (transitively) narrower than one or more preferred terms in P • every non-preferred term in C has a use-instead relationship to one or more preferred terms in P and/or in C • Thesaurus protocol must support cross-thesaurus references • Hierarchical bucket is still associated with a root thesaurus • refinements support per-collection customization

  11. adl:types • Base: DCMI Type Vocabulary • http://dublincore.org/documents/dcmi-type-vocabulary/ • MIL extension: • DCMI:Dataset • digital elevation model • DCMI:Image • map • remote-sensing imagery • satellite image • aerial photograph

  12. adl:formats • Offline • digital • physical • Online • text • image • video • audio • application

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