1. 1 Mapping and Crosswalking “Absolute Crosswalking” “Relative Crosswalking” “Switching-across”

2. 2 A LOM record (partial) hierarchical structure (not flat) many more elements than DC several elements correspond to one DC element Think of mapping between a DC record and a LOM record

3. 3 Common Crosswalking Approaches Contributor Coverage ----------Location.Current Repository Format----------Technique Dublin Core VAR Core (3.0) Relative crosswalking Absolute crosswalking Contributor Coverage ----------Location.Current Repository Format----------Technique Dublin Core VAR Core (3.0) Relative crosswalking Absolute crosswalking target source

4. 4 Pros and Cons -- Absolute Crosswalking ensures the equivalency (or closely-equivalent matches) of elementsensures the equivalency (or closely-equivalent matches) of elements does not work well for data conversiondoes not work well for data conversion data values in non-mappable space will be left out, especially when a source schema has a richer structure than that of the target schema.data values in non-mappable space will be left out, especially when a source schema has a richer structure than that of the target schema. –E.g., from LOM records to DC records vra:title = dc:title vra:technique = xxx

5. 5 Pros and Cons -- Relative Crosswalking When data conversion is conducted, at least the values in the fields of a source database will find a place to reside in the target database.When data conversion is conducted, at least the values in the fields of a source database will find a place to reside in the target database. Appears to work better when mapping from complex to simpler schema, e.g., from MARC to DC, but not vice versa. http://www.loc.gov/marc/marc2dc.htmlAppears to work better when mapping from complex to simpler schema, e.g., from MARC to DC, but not vice versa. http://www.loc.gov/marc/marc2dc.html http://www.loc.gov/marc/marc2dc.html The problem is that mapped elements are not really equivalent.The problem is that mapped elements are not really equivalent. vra:title = dc:title vra:technique = dc:format

6. 6 Problems exist in direct mapping when: converting from a less inclusive format to a more inclusive format,converting from a less inclusive format to a more inclusive format, converting from an uncontrolled vocabulary content to a controlled vocabulary content,converting from an uncontrolled vocabulary content to a controlled vocabulary content, converting to fields where there are indirect impacts on the corresponding fields and values, (e.g., 043 and 6xx #z),converting to fields where there are indirect impacts on the corresponding fields and values, (e.g., 043 and 6xx #z), data contents using different controlled vocabularies,data contents using different controlled vocabularies, data being converted into non-searchable fields.data being converted into non-searchable fields.

7. 7 missed?! missing keywords OPTIONS mapped to SUBJECT, missing all KEYWORDS Incorrect element mapping after … before …

8. 8 AUTHOR mapped to DESCRIPTION 3357 records ! no CREATOR before … after …

9. 9 If re-generate records based on the embedded metadata, all can be corrected. Incorrect values after … before …

10. 10 CLASSIFICATION mapped to SUBJECT and missed all the KEYWORDs. Inappropriate mapping missed? before … after …

11. 11 Missed Data Values When a group of elements map to a single one, there could be missed data values.When a group of elements map to a single one, there could be missed data values. dc:rights

12. 12 WHY do some data sets have 100% inaccessible IDs in a repository after a few years? The IDENTIFIER only provided the information of the record, such as a local access number ID. When data were migrated or moved around in these collections’ servers, these IDs became obsolete. Missed Data Values which may cause in-accessible IDs

13. 13 When crosswalking, there should be multiple elements mapped to dc:identifier element 3 identifiers From a LOM record:

14. 14 Switching-across when multiple schemas are involved.

15. 15 Mapping Process One of the schemas is used as the switching mechanism among multiple schemas.One of the schemas is used as the switching mechanism among multiple schemas. Instead of mapping between every pair in the group, each of the individual metadata schemas is mapped to the switching schema only.Instead of mapping between every pair in the group, each of the individual metadata schemas is mapped to the switching schema only. Example: http://www.getty.edu/research/conducting_research/s tandards/intrometadata/metadata_element_sets.htmlExample: http://www.getty.edu/research/conducting_research/s tandards/intrometadata/metadata_element_sets.html http://www.getty.edu/research/conducting_research/s tandards/intrometadata/metadata_element_sets.html http://www.getty.edu/research/conducting_research/s tandards/intrometadata/metadata_element_sets.html

16. 16 Common properties in crosswalks definition of each metadata element mandatory, optional, or mandatory based on certain conditions may occur multiple times constraints due to the structure e.g., hierarchical parent-child relationships e.g., hierarchical parent-child relationships constraints imposed on the value e.g., free text, numeric range, date, or a controlled vocabulary locally defined metadata element (s) - Based on St. Pierre and Jr. William. 1998. Issues in Crosswalking Content Metadata Standards. Bethesda, MD: NISO Press.