Mapping of German subject headings to the Dewey Decimal Classification
In CrissCross the subject headings of the German subject headings authority file (SWD) are mapped to notations of the Dewey Decimal Classification (DDC) based on the document-independent connotation scopes of the concepts. The method chosen for the mapping procedure is a directional one: the German subject headings function as initial vocabulary, the DDC as target classification. The mapping data is added directly to the particular SWD data record.
The conceptual mapping is carried out as specific as possible (Deep level mapping); if necessary, institutional notations are built according to the DDC number building instructions. Due to the referential polysemy of many subject headings, one subject heading can be assigned to several DDC classes (One-to-many mapping). The strength of correspondence of SWD terms and DDC classes is expressed by a code, the so-called "Degree of Determinacy". In future retrieval systems the Degrees of Determinacy shall be used for ranking as well as for regulation of recall and precision of search results. A time stamp provides information about the period of validity of the created intersystem relations.