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research:jtransformer:api:meta:meta-model:ast_relation [2011/02/15 15:29]
Günter Kniesel
research:jtransformer:api:meta:meta-model:ast_relation [2018/05/09 01:59] (current)
Line 1: Line 1:
 +{{page>​languageMetamodelHeader&​fullpage&​nofooter}}
 +
 + -> [[..:​..:​notation|Notation used in the following]]
 +
 +----
 +**ast_relation**(?​Language,​ ?​AstRelLabel : atom, ?​AstNodeArguments : list)  is nondet
 +  * The nodes in the Abstract Syntax Tree (AST) for the language arg1 are linked by relations with
 +    type (label / functor) arg2 and arguments conforming to the [[argument descriptors]] in arg3.
 +    //Relations do not have own identities//​. This is what distinguishes them from AST nodes. ​
 +    All identities occuring as arguments in a relation fact are references to other facts, which represent AST  nodes. ​
 +    Example (excerpt from Java AST definition):​
 +<​Code> ​  ​ast_relation('​Java',​extendsT,​[
 +     ​ast_arg(sub, ​  ​mult(1,​1,​no ), id,   ​[classT]),​
 +     ​ast_arg(super,​ mult(1,1,no ), id,   ​[classT])
 +   ]).
 +</​Code>​
 +
 +  * Relations can degenerate to simple attributes. Then they take the form of binary predicates with 
 +    one argument being the id of some AST node and the other argument being the attribute value 
 +    attached to that node. This makes sense if such arguments can be optional or multi-valued but unordered ​
 +    (Ordered multi-valued arguments are represented as lists). For instance, in the Java AST definition ''​modifierT''​
 +    adds various modifiers to elements such as classes, methods and fields:
 +<​Code> ​  ​ast_relation('​Java',​modifierT,​[
 +     ​ast_arg(id, ​      ​mult(1,​1,​no ), id,   ​[classT,​ fieldT, methodT, constructorT,​ classInitializerT]),​
 +     ​ast_arg(modifier,​ mult(1,1,no ), attr, [atom])
 +   ]).
 +</​Code>​
 +
 +  * Relations can further degenerate to flags. Then they take the form of unary predicate with 
 +    one single argument being the id of some AST node. For instance, in the Java AST definition ​
 +    ''​externT''​ marks classes available only as byte-code:
 +<​Code> ​   ast_relation('​Java',​externT,​[
 +     ​ast_arg(id, ​    ​mult(1,​1,​no ), id,   ​[classT])
 +   ]).
 +</​Code>​
  
research/jtransformer/api/meta/meta-model/ast_relation.txt · Last modified: 2018/05/09 01:59 (external edit)

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