Reuseware - Adding Modularity to Your Language of Choice

syntax grammar Concrete syntax grammar Metamodel (result from mapping) Generate code Extend grammar automatically Figure 1: Grammar of Xcerpt in Reuseware The abstract and concrete syntax grammars of Xcerpt can be derived by separating concrete from abstract elements in the grammar from Listing 2. Additionally, each reference to a production rule in the abstract syntax grammar is tagged with a role name (rolename : ProductionRule). These names are then used to annotate the concrete syntax on top of the abstract structure. The production rule for GoalQueryRule (Line 5 in Listing 2), for instance, is split into an abstract and a concrete form. The abstract syntax production rule looks as follows: GoalQueryRule = goal:ConstructTerm, query:QueryTerm?; VOL 0, NO. 0 JOURNAL OF OBJECT TECHNOLOGY 13 REUSEWARE – ADDING MODULARITY TO YOUR LANGUAGE OF CHOICE This abstract syntax rule is then annotated with its concrete syntax using the notion of role names in the following manner: GoalQueryRule ::= "GOAL" goal ("FROM" query)? "END"; The Xcerpt grammars as they are used in the tool are shown in Figure 1. After the grammars of the original language have been defined in the tool, they can be extended for reuse. This extension can be done automatically or by manually adding production rules. Additional production rules are annotated to enable the tooling to identify variation points as such and address them during composition. In any case, the extended grammar is a context-free reuse grammar and the extension itself conforms to the transformation function τ (defined in Definition 3). Figure 2 visualizes the extended grammars of Xcerpt that use annotations to identify non-terminals that describe variation points. Such annotations are done in the abstract syntax grammar by repeating the rule name followed by a ==> and a predefined marker. Such markers are “componentmodel.Slot” and “componentmodel.Hook”. Abstract syntax reuse grammarsyntax reuse grammar Concrete syntax reuse grammar Separate files for core and reuse grammar Refinement of a rule defined elsewhere Generated code Figure 2: Grammar of ReuseXcerpt in Reuseware Additional production rules may be placed in a separate file. The completed extended grammar will then consist of the original grammar as modified by these additional production rules. Non-terminals defined elsewhere can be referred to using the Language.NonTerminal notation. Thus a separation between core language and reuse extension is reflected on the grammar files. Note that a concrete syntax definition has to be provided for the reuse language. However, such definitions do not have to care about which are original and which are additional rules, since the parsers handle all rules alike. 14 JOURNAL OF OBJECT TECHNOLOGY VOL 0, NO. 0 4 COMPOSITION FRAMEWORK IMPLEMENTATION