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--- tutorials:rgg-code-structure [2025/10/21 11:52] – MH
+++ tutorials:rgg-code-structure [2026/04/24 11:45] (current) – [XL Blocks - Rules] Tim
@@ Line 143: / Line 143: @@
 While using XL queries mainly three rules are used:
-  * Graph rules (''%%==>>%%'')
+  * SPO rules (''%%==>>%%'')
-  * String replacement rules (''%%==>%%'')
+  * Linendmeyer rules (''%%==>%%'')
   * Update or Execution rules (''%%::>%%'')
@@ Line 150: / Line 150: @@
-=== Graph rules ===
+=== SPO rules ===
-Graph rules are indicated by the rule arrow ''%%==>>%%''.
+SPO rules are indicated by the rule arrow ''%%==>>%%''.
 The right hand side is a semicolon-terminated list of graph statements building the replacing graph for the matched graph. While the left hand side represents a fixed graph pattern, the graph statements can build the replacing graph dynamically, including loops and conditional execution. Thus it is not always possible to find a graphical representation of the right hand side.
@@ Line 161: / Line 161: @@
-=== String rules ===
+=== Lindenmeyer rules ===
-The concept of an replacement rule is basically that all part of the project string that are similar to the left part (before ''%%==>%%'') are replaced by the right part( behind ''%%==>%%'').
+The concept of an replacement rule in XL follows the 'Lindenmayer-form' where basically all parts of the project that are similar to the left part (before ''%%==>%%'') are replaced by the right part ( behind ''%%==>%%'').
 The left part can thereby be any [[tutorials:common_graph_queries|xl-query]].
 The right part (the production) is a collection of Nodes ( instances of either turtle commands, 3d objects or modules) which are linked by different edges. In the example below only successor- and branch-edges are used. A node that is separated to its predecessor by only a white space is added as a sucessor to the predecessor. A Node or a set of nodes framed by square brackets in that is added to the predecessor with a branch-edge.