created: 20130827080000000 modified: 20150221225414000 tags: Reference Concepts title: Filters type: text/vnd.tiddlywiki list: [[Introduction to filter notation]] [[Filter Syntax]] You can think of TiddlyWiki as a database in which the records are tiddlers. A database typically provides a way of discovering which records match a given pattern, and in ~TiddlyWiki this is done with filters. A <<.def filter>> is a concise notation for selecting a particular [[set of tiddlers|Title Selection]], known as its <<.def "output">>. Whenever ~TiddlyWiki encounters a filter, it calculates the output. Further work can then be done with just those tiddlers, such as [[counting|CountWidget]] or [[listing|ListWidget]] them. The following example passes a filter to the <<.mlink list-links>> macro to display a list of all tiddlers whose titles start with the letter H: > `<>` A filter's output can change as tiddlers are added and deleted in the wiki. ~TiddlyWiki recalculates on the fly, automatically updating any filter-based counts or lists as well. [[Advanced Search|$:/AdvancedSearch]] has a <<.advancedsearch-tab Filter>> tab that makes it easy to experiment with filters. ;Find out more: * [[Introduction to filter notation]] -- a step-by-step walkthrough * [[Filter Syntax]] -- the detailed technical rules * [[Filter Operators]] -- the available methods of filtering