[Solr Wiki] Update of "UserTagDesign" by YonikSeeley

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The following page has been changed by YonikSeeley:
http://wiki.apache.org/solr/UserTagDesign

The comment on the change is:
user tagging design, usecases + flat schema

New page:
= User Tagging Design =
== Data Set ==
{{{
A10: title = Lucene in Action (LIA)
A11: title = Lucene in Action Deux
A12: title = Solr Flare in Action
A13: title = Practical Perl 

erik tagged 
  A10 with "lucene"
  A11 with "lucene","solr"
  A12 with "ruby","solrflare"
  A13 with

yonik tagged
  A10 with
  A11 with "lucene","solr","excellent"
  A12 with "solr"
  A13 with "foo"
}}}

== Use Cases ==
===== U-addUserTag =====
Allow a user to tag a book
 * Example: Allow erik to tag A10 with "lucene"

===== U-delUserTag =====
Allow a user to remove a tag from a book, or all instances of a tag they have used.

===== U-delUser =====
Remove all tags that were added by a specific user

===== U-tagFacet =====
Show number of books tagged with each tag, restricted by users current search results and filters.
 * Example: user submits a search of "title:lucene", and the resulting tag counts are "lucene(2), solr(2), excellent(1)"
  Notice that the count is number of books with that tag, not the number of tags... there are 3 "lucene" tags on the books, but only 2 books are tagged "lucene".

===== U-userFacet =====
Show number of books tagged tagged by each user.
 * Example: user submits a search of "title:lucene", and the resulting tag counts are "erik(2), yonik(1)"
  Notice that the count is number of books tagged, not the number of tags on books.

===== U-tagSuggest =====
When a user is tagging a book, allow them to type in
the first few letters and then give a dropdown list of existing tags to
choose from.  Sort by tag popularity, optionally show counts.
  Tag popularity: number of users using that tag, or number of books
  with that tag?  Either could work if neccesary, 
 * Example1:  user types in "so" into the textbox when tagging a book, and
they are automatically shown "solr(2), solrflare(1)"  (uses #books tagged)
 * Example2:  user types in "so" into the textbox when tagging a book, and
they are automatically shown "solr(3), solrflare(1)"  (uses #tag instances)

===== U-tagNarrow =====
User selects an existing tag to narrow their search results by.
  Any displayed results (including facet counts) must have all tags that
  have been selected by the user.
 * Example: narrow search results by the tag "solr"

===== U-userTagNarrow =====
Show all books a specific user tagged with a specific tag, or restrict search results by the same.
 * Example: restrict matches to books with erik's "solr" tag => restricts to A11

===== U-tagNarrowSuggest =====
Allow the user to narrow their search results by typing in
  a tag instead of selecting it from a list.  When the user has typed
  one or two letters, automatically pop up a list of tags starting
  with that prefix.  Optionally sort tags by number of books it applies to
  in the current search results.
 * Example: search "title:lucene", user types "so" and is presented with solr(1)

===== U-userNarrow =====
Restrict books to those tagged by a specific user.
 * Example: search "title:*" restrict to books tagged by erik => A10,A11,A12
 * Example2: search "title:*", facet by tag, restrict to books tagged by erik:
    facet counts={lucene(2),solr(2),ruby(1),solrflare(1),excellent(1)}
    (note that this does *not* restrict shown tag counts to erik's tags)

===== U-userTagsNarrow =====
Restrict *tags* to those of a specific user.
 * Example: search "lucene", facet by tag, restrict to erik's tags:
    facet counts={lucene(2),solr(1)}

===== U-userNarrowMulti =====
Restrict books to those tagged by a specific users.
 * Example: search "title:*" restrict to books tagged by erik or yonik => A10,A11,A12,A13
 * Example2: search "title:*" restrict to books tagged by erik and yonik => A10,A11,A12

===== U-tagRelevance =====
When searching for a specific tag, increase the
relevance of books that have more instances of that tag.
 * Example: search for tag "lucene" and show A11 before A10

===== U-tagTimeliness =====
Restrict to tags added in the last year (or time period)

 
===== Machine Tags or Triple Tags =====
http://www.flickr.com/groups/api/discuss/72157594497877875

===== Tag Hierarchies =====

== Implementations ==
=== Flat Schema #1 ===
Add tags directly to the documents.

===== U-addUserTag =====
{{{
add to A10, field utag="~erik#lucene"   // single token
add to A10, field utag2="~erik #lucene  // tokenized by whitespace
}}}
utag2 could be added via copyField

===== U-delUserTag =====
  remove A10.utag="~erik#lucene"

===== U-delUser =====
  q="utag:~erik*", get set of documents, remove all tags starting with ~erik

===== U-tagFacet =====
  q="title:lucene" facet.field=utag2 facet.prefix=#

===== U-userFacet =====
  q="title:lucene" facet.field=utag2 facet.prefix=~

===== U-tagSuggest =====
 * Example1: facet.field=utag2 facet.prefix=#so
 * Example2: not easily doable... would require more work within solr to count up tf's

===== U-tagNarrow =====
  fq=utag2:#solr

===== U-userTagNarrow =====
  * fq=utag:~erik#solr
  * OR fq="utag2:"~erik #solr"

===== U-tagNarrowSuggest =====
  q=title:lucene facet.field=utag2 facet.prefix=#so

===== U-userNarrow =====
  q=title:* fq=utag2:~erik

===== U-userTagsNarrow =====
 q=lucene fq=utag2:~erik facet.field=utag facet.prefix=~erik

===== U-userNarrowMulti =====
 * Example: q=title:* fq=utag2:(~erik OR ~yonik)
 * Example2: q=title:* fq=utag2:(+~erik +~yonik)

===== U-tagRelevance =====
  q=utag2:#lucene

===== U-tagTimeliness =====
??? reserve another prefix for fields like time