https://dokuwiki.grogra.de/ 2026-05-16T10:24:29+00:00 https://dokuwiki.grogra.de/ https://dokuwiki.grogra.de/lib/exe/fetch.php?media=wiki:dokuwiki.svg text/html 2025-08-22T10:48:49+00:00 Anonymous (anonymous@undisclosed.example.com) https://dokuwiki.grogra.de/doku.php?id=01_user_documentation:07_rgg_xl:02_xl:03_query:01_predicate&rev=1755859729&do=diff Predicate This section present the query predicates. (aka what you can put on the left hand side of rules). Node pattern Node predicates represent patterns applied on the Nodes in the graph. They are the base of XL queries, as it is required to have at least one node predicate in a query. text/html 2025-08-21T10:44:23+00:00 Anonymous (anonymous@undisclosed.example.com) https://dokuwiki.grogra.de/doku.php?id=01_user_documentation:07_rgg_xl:02_xl:03_query:02_query_variable&rev=1755773063&do=diff Variables Query variables are variables declared in a query. They are either explicitly (in a declaration) or implicitly declared. To be used manually, the variable need to be given an identifier. Indeed, all node pattern declare a query variable, used in the pattern matching, but only the one with an identifier are accessible manually. text/html 2025-09-04T08:26:23+00:00 Anonymous (anonymous@undisclosed.example.com) https://dokuwiki.grogra.de/doku.php?id=01_user_documentation:07_rgg_xl:02_xl:03_query:04_context&rev=1756974383&do=diff Context The notion of context in the rule-based paradigm refers to some structure which has to exist within the current host structure and which is related in some way with the match, but which is not replaced on rule application. Thus, in a query, marking context on some predicate enable to use these patterns to match and ensure that the Nodes bounded by these patterns will not be removed or replaced. text/html 2025-09-04T10:07:35+00:00 Anonymous (anonymous@undisclosed.example.com) https://dokuwiki.grogra.de/doku.php?id=01_user_documentation:07_rgg_xl:02_xl:03_query:05_query_expression&rev=1756980455&do=diff Query expression A query can be used as an expression if it is enclosed in asterisked parentheses (* and *). Theses symbols are also used to declare context in a query but the concept is different. A query expression enables to execute the query in an imperative context (e.g. in a text/html 2025-10-13T08:16:30+00:00 Anonymous (anonymous@undisclosed.example.com) https://dokuwiki.grogra.de/doku.php?id=01_user_documentation:07_rgg_xl:02_xl:03_query:08_extent_visibility&rev=1760343390&do=diff Extent visibility When looking for matches, queries only consider Node that are in their set of visible extents. An extent collects its nodes not by a single list, but by a number of (doubly linked) lists. Currently, 16 lists are used, but this can easily be changed. This feature is used to partition the extents. The 16 lists are called the extent indexes.