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

Alexandria Digital Library Project 2 Goals o Digital library:  “an integrated set of services for capturing, cataloging, storing, searching, protecting, and retrieving information” o 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

Alexandria Digital Library Project 3 Adjectives o Heterogeneous  remotely-sensed imagery; textual documents  multimedia instructional materials; executable models  gazetteer placenames o Georeferenced  generalizes to “scientific data”: any highly-structured, metadata- rich information o Distributed  for scalability o Lightweight  accommodate small, cheap (i.e., free) implementations  include non-traditional spatial data sources

Alexandria Digital Library Project 4 Where we are today o Downloadable server software, two clients o In operational use by MIL o Other (potential) users:  Bren/ESSW  Scripps  DLESE  Norwegian National Library  Auckland University of Technology

Alexandria Digital Library Project 5 Challenges o Discovery o Gazetteers o Ranking o Scalability o Context o Client integration o More at

Alexandria Digital Library Project 6 Challenge 1: discovery o Can’t beat word search when it works  I want a map of Boulder   “Downtown street map of Boulder, Colorado” o 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

Alexandria Digital Library Project 7 If you’re still not convinced... o Remote-sensing imagery is nameless  “AVHRR NOAA :33 UTC” o Challenge: exactly which two words will find a USGS map of the Flatirons in the Rocky Mountains behind Boulder, Arapahoe County, Colorado? Eldorado Springs

Alexandria Digital Library Project 8 ADL approach o Coordinate-based representation and discovery  generic lat/lon coordinates  rich geometry –polygons, polylines  spatial operators –overlaps, contains o Gazetteer  defines representation of places  maps placenames  coordinates client gazetteer library coordinates placenames

Alexandria Digital Library Project 9 Challenge 2: gazetteers: necessary evil o Few (public) sources of gazetteer data o Lousy quality  digitized from maps o Difficult problems  conflation  classification  boundary determination  change over time o Conclusion  gazetteer-based spatial reasoning seems unlikely  interaction will likely remain client-centric

Alexandria Digital Library Project 10 Final thoughts on discovery o 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 o Gazetteer improvements  federated gazetteers  new gazetteer models: topological as opposed to metric o Other coordinate spaces, grids, etc.

Alexandria Digital Library Project 11 Challenge 3: ranking o Observed phenomenon:  World Map is first result of every query o Idea: rank by spatial similarity to query region query

Alexandria Digital Library Project 12 Challenge 4: scalability o Easy to accumulate lots of data  satellites image continuously  1 m resolution, Earth’s surface area = 5  m 2 o Support for scalability  text: amazingly good  spatial: not so good –indexing becomes unwieldy at 10 6 items  combining spatial with other constraint types is difficult

Alexandria Digital Library Project 13 ADL approach o Partition and distribute the problem o Multiple levels of discovery  find relevant collections  search just those collections o Support multiple implementation strategies  spatial engine  relational database  home-grown

Alexandria Digital Library Project 14 Challenge 5: context o Context is critical for evaluation o Textual context: poem software

Alexandria Digital Library Project 15 Geospatial context o Does this answer your question? Flatirons 1-5 Flagstaff Rd. Green Mountain

Alexandria Digital Library Project 16 Challenge 6: client integration o “Click here” approach places large burden on users  navigate  interpret  evaluate  download o Service-based access will become predominant  just as the WWW replaced FTP o Needed:  description/access standards, protocols  integration with search constraints