From 8c2a7ff624c3b415f20b1676d7cf15b777941bc2 Mon Sep 17 00:00:00 2001 From: Marc Cromme Date: Mon, 1 May 2006 12:59:33 +0000 Subject: [PATCH] added section on static and dynamic ranking, versus sorting --- doc/administration.xml | 211 +++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 191 insertions(+), 20 deletions(-) diff --git a/doc/administration.xml b/doc/administration.xml index 6cfaa2b..4619e67 100644 --- a/doc/administration.xml +++ b/doc/administration.xml @@ -1,5 +1,5 @@ - + Administrating Zebra Those are in the zebra config file enabled by a directive like (use only one of these a time!): - rank: rank-1 # default - rank: rank-static # dummy - rank: zvrank # TDF-IDF like + rank: rank-1 # default TDF-IDF like + rank: rank-static # dummy do-nothing + rank: zvrank # configurable, experimental TDF-IDF like Notice that the rank-1 and zvrank do not use the static rank @@ -1020,7 +1052,146 @@ function, which is left as an exercise for the reader. - + + + + Invoking dynamic ranking is done in query time (this is why we + call it 'dynamic ranking' in the first place ..). One has to add + the Bib-1 relation attribute with + value "relevance" to the PQF query (that is, @attr + 2=102, see also + + The BIB-1 Attribute Set Semantics). + To find all articles with the word 'Eoraptor' in + the title, and present them relevance ranked, one issues the PQF query: + + Z> f @attr 2=102 @attr 1=4 Eoraptor + + + + + The default rank-1 ranking module implements a + TF-IDF (Term Frequecy over Inverse Document Frequency) like algorithm. + + + + It is possible to apply dynamic ranking on parts of the PQF query + allone: + + Z> f @and @attr 2=102 @attr 1=1010 Utah @attr 1=1018 Springer + + searches for all documents which have the term 'Utah' on the + body of text, and which have the term 'Springer' in the publisher + field, and sort them in the order of the relvance ranking made on + the body of text index only. + + + Rank weight is a way to pass a value to a ranking algorithm - so that + one APT has one value - while another as a different one. For + example, we can + search for 'utah' in use attribute set 'title' with weight 30, as + well as in use attribute set 'any' with weight 20. + + Z> f @attr 2=102 @or @attr 9=30 @attr 1=4 utah @attr 9=20 utah + + + + + The rank weight feature is experimental. It may change in future + releases of zebra, and is not production mature. + + + + + Notice that dynamic ranking can be enabled in + sever side CQL query expansion by adding @attr + 2=102 to the CQL config file. For example + + relationModifier.relevant = 2=102 + + invokes dynamik ranking each time a CQL query of the form + + Z> querytype cql + Z> f alvis.text =/relevant house + + is issued. Dynamic ranking can be enabled on specific CQL indexes + by (for example) setting + + index.alvis.text = 1=text 2=102 + + which then invokes dynamik ranking each time a CQL query of the form + + Z> querytype cql + Z> f alvis.text = house + + is issued. + + + + + + + Sorting + + Sorting is enabled in the configuration of record indexing. For + example, to enable sorting according to the BIB-1 + Date/time-added-to-db field, one could add the line + + xelm /*/@created Date/time-added-to-db:s + + to any .abs record indexing config file, or + similarily, one could add an indexing element of the form + + + + ]]> + to any alvis indexing rule. + + + To trigger a sorting on a pre-defined sorting index of type + s, we can issue a sort with BIB-1 + embedded sort attribute set 7. + The embedded sort is a way to specify sort within a query - thus + removing the need to send a Z39.50 Sort + Request separately. + + + The value after attribute type 7 is + 1 (=ascending), or 2 + (=descending). + The attributes+term (APT) node is separate from the rest of the + PQF query, and must be @or'ed. + The term associated with this attribute is the sorting level, + where + 0 specifies the primary sort key, + 1 the secondary sort key, and so on. + + For example, a search for water, sort by title (ascending), + is expressed by the PQF query + + Z> f @or @attr 1=1016 water @attr 7=1 @attr 1=4 0 + + whereas a search for water, sort by title ascending, + then date descending would be + + Z> f @or @or @attr 1=1016 water @attr 7=1 @attr 1=4 0 @attr 7=2 @attr 1=30 1 + + + + Notice the fundamental differences between dynamic + ranking and sorting: there can only + be one ranking function defined and configured, but there can be + specified multiple sorting indexes dynamically at search + time. Ranking does not need to use specific indexes, which means, + dynamic ranking can be enabled and disabled without + re-indexing. On the other hand, sorting indexes need to be + defined before indexing. + + + + + -- 1.7.10.4