YAZ supports facets for in Solr, SRU 2.0 and Z39.50 protocols.
Like Type-1/RPN, YAZ supports a string notation for specifying
facets. For the API this is performed by
yaz_pqf_parse_facet_list.
For ZOOM C the facets are given by option "facets" For yaz-client it is used for the facets command.
The grammar of this specification is as follows:
facet-spec ::= facet-list
facet-list ::= facet-list ',' attr-spec | attr-spec
attr-spec ::= attr-spec '@attr' string | '@attr' string
The notation is inspired by PQF. The string following '@attr'
may not include blanks and is of the form
type=value,
where type is an integer and
value is a string or an integer.
The Facets specification is not Bib-1. The following types apply:
Table 7.4. Facet attributes
| Type | Description |
|---|---|
| 1 | Field-name. This is often a string, eg "Author", "Year", etc. |
| 2 | Sort order. Value should be an integer. Value 0: count descending (frequency). Value 1: alpha ascending. |
| 3 | Number of terms requested. |
| 4 | Start offset. |