Theory

ADOxx Development Language: AQL

Extended Backus Naur Form (EBNF) notation is used for describing the AQL syntax.

Terminal symbols are symbols which cannot be split up further and are included by inverted commas   '

Non-terminal symbols are included by < ... >
Symbols ... }... ] and | serve to formulate rules in a more compact form :

  • {...}    arbitrary number of iterations (even 0-times)   
  • [...]    optional (0- or 1-time)
  • |        alternative

Rules start with a non-terminal symbol, followed by "::=" and the symbol's definition

Keep in mind that AQL is cAse sEnsiTivE

AQL Terminal symbols

<‘ and ‘>‘  in this order are used to represent a class, a relation, a model, a model type, etc. (e.g. <"A"> ,<"My Model 01"> , <"My Model Type">)

:‘  is used for specifying the class of a certain object, or the model where a specific class is included (e.g. <"A":"My Model 01":"My First Model Type">)

>‘ and ‘<‘  in this order are used for filtering the results of a query by a specified class (e.g.: <"A"> <<- "Relation" >"B"<  has as results all objects  that fullfill the query criteria <"A"><<-"Relation" AND are of class B)

->‘ , ‘<-‘ , ‘->>‘, ‘<<-‘ , ‘-->‘ , ‘-->>‘ , ‘<--‘   are used for creating AQL expressions that involve relations in the query critera (will be detailed in the future slides)

{‘  and  ‘}‘  are used to represent the object with the specified name (e.g.: {"A01"})

[‘  and  ‘]‘  are used to introduce a criteria to an AQL expression ([?"Radius">"10"])

(‘  and  ‘)‘  are used for deciding the order in which logical operators are evaluated i.e. ‘a OR b AND c‘ and ‘ (a OR b) AND c ‘ return different results.

?‘  is used for imposing a condition on an attribute in the query criteria (e.g.: <"A">[?"Description" like "*OK*"] returns all objects of class A, whose attribute „Description" contains the word „OK")

!‘  is used for imposing a condition on a variable during the simulation (e.g.: (<"A">[!"objectCount">"10"]) OR (<"B">[!"objectCount"<="10"]) returns all objects of class A, if the variable objectCount is higher than 10 and all objects of class otherwise.

AQL Non-Terminal Symbols and Key Words

Names of classes, names of objects, names of relations, names of attributes, names of variables and constants are denoted by inverted commas  (e.g.: "A" , "B" , "requires" , "Colour")

<Class> ::= ‘<‘class_name‘>‘

  • Represents a class (e.g. <"A">)

  • If the class is not included in the current model, the class has to be denoted explicitly through model name and model type: <Class>':'<ModelName>':'<ModelType> (e.g. <"A":"My Model 01":"My First Model Type">)

<Object> :: = ‘<‘object_name‘>‘

Represents an object within a concrete model  (e.g. <"A01">)

  • Should the name of the objects be ambiguous, the name of the class has to be appended to the object's name:<Object>':'<Class> (e.g. <"A01" : "A">)

  • If the object referenced is not part of the current model, the object has to be denoted explicitly through model name and model type: 
    <Object>':'<Model name>':'<Model type> (e.g.: <"A01":"My Model 01":"My First Model Type">) or <Object>':'<Class>':'<Model name>':'<Model type> (e.g.: <"A01":"A":"My Model 02">:<"My First Model Type">)

<Relation> ::= ‘<‘relation_name‘>‘

  • Represents a relationclass (e.g. <"Relation">)

<Attribute> ::= ‘<‘attribute_name‘>‘

  • represents the name of an attribute (e.g. <"Color">, <"Description">)

<Value> ::= <Constant> | '!' <Variable> | '?' <Attribute>

  • a value is either a constant, a variable preceded by the symbol ‘!‘ or an attribute preceded by the symbol ‘?‘

<Operator> ::= '>' | '>=' | '=>' | '=' | '<=' | '=<' | '<' |'!='| 'like' | 'unlike'

  • 'like' and 'unlike' are used for alphanumerical signs
  • ? and * are wildcards:„*" substitutes for any zero or more characters and „?" substitutes for any one character or less (123??? will match 12313 or 1233, but not 1239919991)
  • the other operators are used for comparing numerical values

<LogicalOperator> ::= 'AND' | 'OR' | 'DIFF‘

  • 'AND‘ : the result is the intersection set of the two expressions
  • 'OR‘   : the result is the union set of the two expressions
  • 'DIFF' : the result is the difference of the two expressions
  • 'AND' links more strongly than 'OR' and 'OR' more strongly than 'DIFF'


<AQL expression> ::= '{' [<Object>] [ ',' <Object> ] '}'

  • the result of an AQL expression is a set of objects (0,1 or more)

<AQL expression> ::= '(' <AQL expression> ')'

  • expressions may contain parentheses

<AQL expression> ::= <AQL expression> {<LogicalOperator> <AQL expression>}

  • expressions can be linked to one or more expressions by logical operators

<AQL expression> ::= <AQL expression> '>'<Class>'<'

  • expression results can be filtered by a specific class

AQL Statements

'<' <class> '>'

  • the result is all objects of the specified class
  • Examples:
    • <"A">

    • <"Square":"SecondModel001":"My Second Model Type">

    • <"A"> [?"Name" like "????e?"]

    • <"B"> <- "requires"


<AQL expression> '->' | '<-' | '->>' | '<<-' <Relation>

  • The result contains all objects which are linked through the he given relation with at least one object from the AQL expression
  •  '->'    returns all direct targets of the relation
  •  '<-'    returns all direct start objects of the relation
  • '->>'   returns all transitive targets of the relation
  • '<<-'   returns all transitive start objects of the relation
  • Examples:
    •  {"A1"}->"rel_out"

    •  {"A4"}<-"rel_in"     

    •  <"A">->"rel_out"

    •  <"A"><-"rel_in"

    •  {"A01"}<-"rel_in"

    •  ({"A2"}->>"trans_rel_out") -> "rel_out"

    •  {"A4"}<<-"trans_rel_in"

    •  <"A"><<-"trans_rel_in"

    •  <"A">->"rel_out" >"B"<

 

<AQL expression>    '->' | '<-'   '<' <Relation> '>'

  • The result contains all connectors of the specified relation which have as start or target object one of the objects in the AQL expression
  • '->' returns all connectors originating from the objects of the AQL expression
  • '<-' returns all connectors ending in the objects of the AQL expression
  • Please note similarities and differences with before: if you use the '<' and '>' symbols, the result contains the connectors and if you don't use them, it contains the objects
  • Examples:
    •  <"B">-><"rel_out">

    •  <"A"><-<"rel_in">

    •  {"B3"} <- <"rel_in">

    •  {"A1"} -> <"rel_in">


<AQL expression> '-->' | '-->>' <InterRef_Attribute>

  • The result contains all objects which are referenced in the specified attribute of any of the objects in the AQL expression
  • The ‘-->>' operator returns is all objects which are transitively referenced in the specified attribute of any of the objects in the AQL expression
  • Examples:
    •  <"A"> --> "IsRunBy"

    •  <"A"> -->> "IsRunBy"

    •  {"A5"} --> "IsRunBy"

    •  {"A5"} -->> "IsRunBy"

    •  {"A5"} -->> "IsRunBy" >"Rectangle"<


<AQL expression> '<--'

  • The result contains all objects which refer any of the objects in the AQL expression
  • Example:
    •  <"Rectangle"> <--


<AQL expression> '[' <Value> <Operator> <Value> ']'

  • The result contains all objects, whose attributes fulfill the defined criteria
  • Constants (numbers, strings) can only be at the right of the operator
  • To the left of the operator there are only attributes or variable references
  • Note: Queries with variable references as dynamic components in the performer assignment are only allowed in the simulation
  • Examples:
    • (<"A">[?"attr_name" like "a*"]) AND (<"A">[?"a1" >= 0]) 

    • (<"A">[?"attr_name" = "a1"]) AND (<"A">[?"attr_name" >= 0]) 

    • <"A">[?"Name" like "????a?"]

<AQL expression> '['<Value>']' '['<Value> <Operator> <Value>']'

  • The result contains all objects of the start query where their record attribute or attribute profile fulfills the defined criteria
  • The first value specifies the name of the record attribute or attribute profile.
  • See above the rules for the second expression
  • Note: In case of a record attribute, the criteria is always fulfilled, if at least a table row of the record attribute meets the defined criteria.
  • Examples:
    • record attribute: <"A">[?"attr_name"][?"column_name" = "column_value"]

    • attribute profile: <"A"> [?"attr_name"][?"AP_attr_name" >= 0]

       

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