Alexandria Digital Library Project Goals and Challenges in Georeferenced Digital Libraries Greg Janée

Alexandria Digital Library Project

Goals and Challengesin

Georeferenced Digital Libraries

Greg Janée


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Goals

Digital library: “an integrated set of services for capturing, cataloging,

storing, searching, protecting, and retrieving information”

ADL: a lightweight, distributed digital library for heterogeneous,

georeferenced information a system and an infrastructure

– supports personal collections ... institutions– provides interoperability across spatial data providers


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Adjectives

Heterogeneous remotely-sensed imagery; textual documents multimedia instructional materials; executable models gazetteer placenames

Georeferenced generalizes to “scientific data”: any highly-structured, metadata-

rich information

Distributed for scalability

Lightweight accommodate small, cheap (i.e., free) implementations include non-traditional spatial data sources


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Where we are today

Downloadable server software, two clients

In operational use by MIL

Other (potential) users: Bren/ESSW Scripps DLESE Norwegian National Library Auckland University of Technology


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Challenges

Discovery Gazetteers Ranking Scalability Context Client integration

More at http://www.dlib.org/


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Challenge 1: discovery

Can’t beat word search when it works I want a map of Boulder “Downtown street map of Boulder, Colorado”

But there are so many names for a place... Boulder, Arapahoe County, Colorado Chautauqua, Mapleton Hill, Pearl Street Mall Area code 303, ZIP code 80305, UTM grid 13S Flatirons, Rocky Mountains, Front Range Landers earthquake, hurricane Hugo


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If you’re still not convinced...

Remote-sensing imagery is nameless “AVHRR NOAA-13 2002-06-03 14:33 UTC”

Challenge: exactly which two words will find a USGS map of the Flatirons in the Rocky Mountains behind Boulder, Arapahoe County, Colorado?

Eldorado Springs


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ADL approach

Coordinate-based representation and discovery generic lat/lon coordinates rich geometry

– polygons, polylines spatial operators

– overlaps, contains

Gazetteer defines representation of

places maps placenames

coordinates

client

gazetteer

library

coordinates

placenames


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Challenge 2: gazetteers: necessary evil

Few (public) sources of gazetteer data

Lousy quality digitized from maps

Difficult problems conflation classification boundary determination change over time

Conclusion gazetteer-based spatial reasoning seems unlikely interaction will likely remain client-centric


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Final thoughts on discovery

Coordinate-based approach is costly burden on users and catalogers limits potential collections relies on gazetteer’s weakest aspect: footprints continuous coordinate space adds complexity

Gazetteer improvements federated gazetteers new gazetteer models: topological as opposed to metric

Other coordinate spaces, grids, etc.


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Challenge 3: ranking

Observed phenomenon: World Map is first result of every query

Idea: rank by spatial similarity to query region

query

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Challenge 4: scalability

Easy to accumulate lots of data satellites image continuously 1 m resolution, Earth’s surface area = 5 1014 m2

Support for scalability text: amazingly good spatial: not so good

– indexing becomes unwieldy at 106 items combining spatial with other constraint types is difficult


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ADL approach

Partition and distribute the problem

Multiple levels of discovery find relevant collections search just those collections

Support multiple implementation strategies spatial engine relational database home-grown


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Challenge 5: context

Context is critical for evaluation Textual context:

poem

software


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Geospatial context

Does this answer your question?

Flatirons 1-5

Flagstaff Rd.

Green Mountain


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Challenge 6: client integration

“Click here” approach places large burden on users navigate interpret evaluate download

Service-based access will become predominant just as the WWW replaced FTP

Needed: description/access standards, protocols integration with search constraints

Documents

Alexandria Digital Library Project Goals and Challenges in Georeferenced Digital Libraries Greg Janée