XL-Operators are designed to simplify the usage of XL queries and rewriting rules. Moreover these operators can improve the performance of a query due to there deep integration into the model. In the following the operators a separated into Analytical and selection operators to either get a value for analysis or a node/ a collection of nodes for rewriting.
| Command | description | example |
| min((*query*)[value]) | returns the smallest value | min((*F*)[length]) |
| max((*query*)[value]) | returns the largest value | max((*F*)[length]) |
| sum((*query*)[value]) | calculate the sum of the values | sum((*F*)[length]) |
| prod((*query*)[value]) | calculates the product of the values | prod((*F*)[length]) |
| count((*query*) ) | returns the number of pattern matching the query | count((*F*) ) |
| empty((*query*) ) | returns true if no pattern matches the query | empty((*F*) ) |
| forall((*query*)[value]condition) | checks if a condition is true for the all results of the query | forall((*f:F*)[length]==1) |
| exist((*query*)[value]condition) | checks if a condition is true for at least one result of the query | exist((*f:F*)[length]==1) |
| command | description | example |
| first((*query*) ) | get the first element found with the query | first((*F*) ) |
| last((*query*) ) | get the last element found with the query | last((*F*) ) |
| slice((*query*),s,e) | return the subset(form s to e) of the result | slice((*F*),2,4), slice((*F*)[length],2,4) |
| selectWhere((*query*),condition) | Select a node of the query that fits the condition | selectWhere((*f:F*),f[length]==1) |
| selectWhereMin((*query*),parameter) | Select a node of the query where the parameter is the smallest | selectWhereMin((*f:F*),f[length]) |
| selectWhereMax((*query*),parameter) | Select a node of the query where the parameter is the largest | selectWhereMax((*f:F*),f[length]) |
| selectRandomly((*query*) ) | select a Random node from the query | selectRandomly((*F*) ) |
| selectRandomly((*query*),prob) | ??? | ??? |
| command | description | example |
| array((*query*) ) | creates an java array of the items or values | array((*F*) ), array((*F*)[length]) |
| string((*query*) ) | creates an comma separated string of the items or values | string((*F*) ), string((*F*)[length]) |
additional information can be found in the javadoc