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A Hybrid Declarative/Procedural Metadata Mapping Language Based on Python

A Hybrid Declarative/Procedural Metadata Mapping Language Based on Python. Greg Janée & James Frew University of California at Santa Barbara. metadata store. XML metadata. ADL. Federated digital library system general framework for distributing queries

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A Hybrid Declarative/Procedural Metadata Mapping Language Based on Python

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  1. A Hybrid Declarative/ProceduralMetadata Mapping LanguageBased on Python Greg Janée & James Frew University of California at Santa Barbara

  2. metadata store XML metadata ADL • Federated digital library system • general framework for distributing queries • specific support for geospatial queries, data ADL query mediator Z39.50 gateway RDBMS Z39.50 server

  3. ADL metadata views • Bucket • mappings of native metadata to high-level search indices • comparable to Dublin Core • but strongly typed • Browse • image thumbnails, abstracts, etc. • Access • describes how item can be accessed • 4 different types of access points • 2 hierarchy mechanisms: decomposition, alternatives

  4. Problem statement • Metadata mapping • largely declarative in nature • “A  B” • need recourse to arbitrary computation • e.g., conversion of geographic coordinates • deal with pervasive quality problems • but problems are often consistent for given collection or provider • Goal • simple, concise way of specifying mappings • that is executable

  5. Related work • Crosswalks • simplistic (“A is equivalent to B”) • no formal way to describe more complex mappings • not executable • Many ad hoc solutions • Perl, XSLT • XSLT • difficult to program • low-level, verbose • computationally hamstrung

  6. Language for metadata mapping • Mapping is an executable Python script • from ADL_mapper import *input()...statements...output() • ~25 language statements • procedure calls • but are declarative in nature • Query language • form tuples from Xpath expressions • Inheritance mechanism

  7. Two examples  map("adl:titles", "/itemRecord/general/title") def convertPresentKeyword (v): if v[1].lower() == "present" return (v[0], "9999") else: return v map("adl:dates", ["/itemRecord/temporalCoverages/timeInfo/timeAD" "begin@date", "end@date"], prefilters=convertPresentKeyword) 

  8. Partial equivalent in XSLT <xsl:template match="itemRecord/temporalCoverages/timeInfo/timeAD"> <temporal-value> <range> <begin><xsl:value-of select="begin/@date"/></begin> <end> <xsl:choose> <xsl:when test="translate(end/@date, 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz')='present'"> <xsl:text/>9999<xsl:text/> </xsl:when> <xsl:otherwise> <xsl:value-of select="end/@date"/> </xsl:otherwise> </xsl:choose> </end> </range> </temporal-value> </xsl:template>

  9. Maya case study • Maya: thematic collection of GIS and other materials with FGDC metadata • Mapping problems: • poor titles, e.g., “mex250kr” • missing originator • misused FGDC field • Solution • generic FGDC mapping • 23 statements • Maya mapping derived from FGDC • 3 statements

  10. Actual Maya mapping from ADL_mapper import * input() import FGDC_mapping def constructNewTitle (v): form = get("/metadata/idinfo/citation/citeinfo/geoform") ... return ... appendPostfilter("adl:titles", constructNewTitle) unmap("adl:formats", id=2) mapConstant("adl:originators", "Anabel Ford, ISBER/MesoAmerican Research Center") output()   

  11. intrinsic contextual Future work • Mapping access-related metadata is problematic • poorly supported by metadata standards • only partially intrinsic to the item • Need to add library context as an input http://host.com/path/P32499.jpg http://host.com/path/P32499.thumb.jpg http://host.com/path/P32499.sid

  12. Summary • Problem • create executable specifications • largely, but not entirely declarative • need ability to do arbitrary computation • Solution • work within a high-level, procedural language • procedure calls act like declarations • resulting hybrid declarative/procedural language • http://www.alexandria.ucsb.edu/mm/

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