alexandria digital earth prototype architectural directions for distributed geolibraries greg janée...
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Alexandria Digital Earth ProtoType
Architectural Directionsfor
Distributed Geolibraries
Greg Jané[email protected]
Alexandria Digital Earth ProtoType
2Greg Janée JISC/CNI Stratford-upon-Avon June 14, 2000
Outline
(Previous) testbed design and experiences Vision & goals Architecture: foundation
CRADDL FEDORA
Architecture: additions Standard thesaurus interface Two standard metadata models Core index/search service Tile-based browse/aggregation service Collection discovery service Gazetteer service
Goals, revisited
Alexandria Digital Earth ProtoType
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Testbed: Concepts
a distributed catalog system
Library– set of collections– client (public) services
Collection– set of holdings– metadata reports– library (internal) services
Holding– unique identifier
Holdings have footprints Earth surface location(s)
– point– bounding box– polygon(s)
Gazetteer convertsnames footprints
Services accessible via HTTP Methods = URLs
Metadata encoded in XML Queries Reports
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Testbed: Metadata
“Search Buckets”(generic query metadata)
Geographic locations Dates Types Formats Originators Subject-related text
– Assigned terms Identifiers
Reports(descriptive metadata)
Collection
Scan Full Browse Access
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Testbed: Services
Clients
Configuration {collection-id} Collection(collection-id) report Query(query) query-id Results(query-id) {holding-id} Metadata(collection-id, holding-id, view) report
Libraries
Collection report Query(query, accumulator) query-thread Metadata(holding-id, view) report
Collections
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Testbed: Implementation
webclient intermediary
ADL middleware server
collection driver
web browser
Java + XML
servlet engine JDBC
collection metadata(complete)
HTTP + HTML
renderer(offline)
coverage/statisticsscripts
collection metadata(static)
XML
XML
XML
HTML + GIF
map/footprint service
HTTP server
HTTP + GIF
map server
vectormap data
local file cacheBerkeley/DBM databases(multiple per series)
collection databaseindexed search buckets +basic holding metadata
HTTP servermetadata accessors
(one per series)data accessors
(one per series)
XML
RDBMS
HTTP +XML
HTTP
SRB
to SDSC
collection
middleware
client
Java + XML
configurationscripts
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Testbed: CDL Web Client
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Testbed: ContentsSeries # Items Size (GB)
Geodex map index 322,000 -
Landsat 1,514,000 -
DOQQ 10,000 600
DRG 1:24,000 3,000 66
DRG 1:100,000 250 6
NASA air photos 502,000 -
MIL air photos 15,000 450
SPOT 200 6
DEM 3,000 1
ADL Gazetteer 4,000,000 -
UCSB AVHRR 15,000 750
TOTAL 6,385,450 1,879
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9Greg Janée JISC/CNI Stratford-upon-Avon June 14, 2000
Vision
Fundamental organization of information Self-contained, georeferenced digital objects... ...aggregated into collections... ...networked into libraries The Library constitutes a “Digital Earth”
Static and dynamic content Personal, customizable collections Collaborative use of distributed resources Component-based approach
Specify interfaces and protocols Build representative services
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Goals
Find Find appropriate collections Find items within collections
– Using simplified, uniform methods– Using more refined, perhaps collection-specific methods
Assemble, structure, publish Create and populate new collections Structure collections using domain-specific thesauri Make available to others
Use Invoke operations on items Integrate library into user application environment
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CRADDL
D-Lib Magazine, Nov. 1998
client
index/search
naming
repository
update index
submit query;retrieve results
retrieve,deposit, andoperate ondigital objects
resolvename
collection
get configuration,characteristics
updatesummaryinformation
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3.141592.71828
identifier
FEDORA
crop(x,y,w,h)
subsample(factor)
getThumbnail()
type “image”
implementation“image”
apologies to Christophe Blanchi
Type
signature
implementation
attachments
crop(x,y,w,h)subsample(factor)getThumbnail()
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Greg Janée JISC/CNI Stratford-upon-Avon June 14, 2000
Architecture: additions
Standard thesaurus interface Two standard metadata models
ADL-Basic: supports uniform description & search ADL-Full: supports XML-based querying on entire metadata
Standard index/search services Core index/search service Tile-based browse/aggregation service
Collection metadata Characterizes collection Supports collection discovery
Gazetteer service
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getTopTerms()
getDefinition(term)
getBroaderTerm(term)
etc.
getNarrowerTerms(term)
Standard thesaurus interface
ridgeA long and narrow upland
with steep sides.
physiographic feature
mountain
drumlin
cliff
summit
arête
hogback
broader narrower
related preferred
broader narrower
broader narrower
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ADL-Basic fields & subfields
Originator Subject-related text
Title Assigned terms
Type Format Spatial domain Date
Time period of content Identifier
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FGDC 2.5.1.4DOQ 3.11FGDC 1.1/8.2
Semantics
Source image dateSource DEM dateProduction date
Name
RepeatableOptionalAlways present
CharacteristicsDATEcollectionmetadata
ADL-Basic general structure
FGDC 2.5.1.4DOQ 3.11FGDC 1.1/8.2
Semantics
Source image dateSource DEM dateProduction date
Name
1972-03-051966-01-011982-12-19
ValueDATE
digitalobject
client index/search service
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ADL-Basic field definition
Semantics identifies the nature, genre, meaning, or intellectual content of the item
Content zero or more terms drawn from identified thesauri XML representation <!ELEMENT ...> Collection metadata implications collection metadata
lists all referenced thesauri Query value single term from an identified thesaurus Query operator “is a”
{(“Object Types”, “aerial photograph”), (“Geology Concepts”, “erosion”)}
Type is a (“Object Types”, “image”)
Type
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ADL-Full
Encodes the full, native metadata in a standard syntactic representation RDF ADL’s generic encoding
<source prefix=“MARC”>http://lcweb.loc.gov/marc</source>...<group name="Data quality"> <field name="Accuracy" source="MARC:514g"> <value type="number" unit="meters">25</value> </field> <field name="Contour interval" source="MIL-B:06200a"> <value type="number" unit="meters">10</value> </field></group>
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Greg Janée JISC/CNI Stratford-upon-Avon June 14, 2000
Index/search services
Core index/search service Based on ADL-Basic Boolean combinations of constraints on ADL-Basic fields and
subfields (only) Support for other, more refined search services
Utilizing ADL-Basic metadata mappings Based on ADL-Full
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Browse/aggregation service
Aggregate statistics Digital objects (scale-dependent) By type, format, and date
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Collection metadata
Static Scope and purpose, maintaining agency, etc.
Derived Referenced thesauri Referenced metadata standards Native ADL-Basic metadata mappings
Statistical summarization via browse/aggregation service
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Stratford-upon-Avon Variant names Stratford upon Avon; Stratford Location N 52° 11’, W 1° 42’ Feature type populated place (NIMA); town (local) Time period 1196–present
805 Feature type U.S. telephone area code
37T Feature type UTM zone
Mississippi Feature type drainage basin
Gazetteer service (1/3)
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postal codes
2nd orderadministrative areas
1st orderadministrative areas
Gazetteer service (2/3)
Geographic namespace: spatial partition of a region into uniquely named subregions
countries
time zones
U.S.A.
U.K.
states
counties
ZIP codes
postal codes
national parks
continental plates
California
Louisiana parishes
counties
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map service
client
Gazetteer service (3/3)
browse/aggregationservice
gazetteer
placenames
Yogi
Cabbage Patch
Pancake
Bamm-Bamm
Barnacle Bill
Wedge
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Greg Janée JISC/CNI Stratford-upon-Avon June 14, 2000
Goals, revisited
Find Discovery service based on rich collection metadata Uniform searching based on ADL-Basic More refined searching based on ADL-Basic and ADL-Full Browse/aggregation service
Assemble, structure, publish Uniform use of collections Thesauri and inheritance of collections and digital objects
support customization & structure Collections designed to span gamut big small
Use FEDORA-like extensible digital object model