M.Sc. Thesis Developing Interacting Domain Specific Languages November 2007 Sander Mak [email protected] Supervising professor : Prof. Dr. S. D. Swierstra Center for Software Technology, Supervisor UU : Dr. B.J. Heeren Dept. of Information and Computing Sciences, Supervisor TUD : Dr. E. Visser Universiteit Utrecht, INF/SCR-07-20 Utrecht, The Netherlands. Abstract Domain specific languages (DSLs) and model driven software development (MDSD) both aim at rais- ing the abstraction level for programmers, thereby enhancing both quality and productivity in software development. Many approaches exist to create and use DSLs. Unfortunately, almost all of these DSL based solutions depend on having a single, monolithic model of the domain as basis. From a software engineering point of view, this approach does not scale very well. In this thesis project, we explore a road less travelled. Instead of starting from a monolithic model, we propose to improve this practice by splitting up different concerns over different domain specific languages. Consequently, the models expressed in these languages must together form a complete ap- plication, and therefore need to interact. This cross-language modularity provides more possibilities for reuse and allows DSLs to be narrower and more focused. Examples of this idea are occasionally found in model driven software development approaches. However, the interaction is often implicitly handled and poorly formalized. We have studied these issues from a more traditional programming language and compiler based point of view. A case study was performed, entailing the creation of two textual domain specific languages for technical domains (and the design for a third). The first language, DomainModel, is geared towards modeling persistent data models, and targets the existing Java Persistence Architecture framework. The second language, WebLayer, is concerned with creating a web-application around such a data model, and targets the JBoss Seam framework. This prototype forms the basis of our study on the interaction amongst those languages. Through this case study, we investigate whether such DSL interaction is feasible and practical, and what the design issues are. i ii Contents 1 Introduction 1 1.1 Setting the scene . 2 1.2 Models and abstraction . 3 1.3 Challenges in DSL development . 5 1.4 Research questions . 6 2 Modeling software 7 2.1 Libraries and frameworks . 7 2.2 4GL languages . 8 2.3 Embedded DSLs . 8 2.3.1 Language assimilation . 9 2.3.2 Natural embedding . 10 2.3.3 Syntax macros . 10 2.3.4 Concluding remarks . 11 2.4 Language oriented programming . 11 2.4.1 Intentional programming . 11 2.4.2 Language workbenches . 12 2.5 Model Driven Architecture . 13 2.6 Our approach . 14 3 DomainModel DSL 15 3.1 Language description . 15 3.1.1 Syntax . 15 3.1.2 Types and annotations . 16 3.2 Implementation . 19 3.2.1 Java Persistence Architecture . 19 3.2.2 Translating concepts . 20 3.2.3 Translating concept members . 22 3.2.4 Equals and hashCode implementation . 25 3.2.5 Semantic checks . 26 3.3 Concluding remarks . 27 4 WebLayer DSL 29 4.1 Target libraries . 30 4.2 Language Description . 31 4.2.1 Text elements . 33 4.2.2 Iterative constructs . 34 4.2.3 Input elements . 35 4.2.4 Actions and forms . 36 4.2.5 Page and session variables . 37 4.3 Implementation . 38 4.3.1 Semantic checking . 39 4.3.2 Specializing generic constructs . 40 4.3.3 Translating pages . 41 4.3.4 Page navigation and data-flow . 44 4.3.5 Translating page elements . 45 iii Contents 4.3.6 Action language . 48 4.3.7 Session variables and validators . 49 4.4 Issues . 50 4.5 Concluding remarks . 51 5 Interaction aspects 55 5.1 Interaction between DSLs . 55 5.1.1 Motivation . 56 5.1.2 Intended usage scenario . 57 5.1.3 Separate compilation and interface files . 58 5.1.4 Interface characteristics . 61 5.1.5 Issues . 62 5.1.6 Dependencies . 63 5.2 Interaction between DSL and user-written code . 63 5.2.1 Motivation . 64 5.2.2 Extended types . 64 5.2.3 Comparison . 67 5.2.4 Inlined Java annotations . 68 5.3 Concluding remarks . 69 6 BusinessRules DSL 71 6.1 Language Description . 71 6.2 Interface . 73 6.3 Concluding remarks . 74 7 Related work 75 7.1 Model composition . 75 7.2 Ordina Software Factory . 76 7.3 openArchitectureWare . 79 7.4 DSLs for the web . 80 7.4.1 Links . 81 7.4.2 bigwig/JWIG . 82 7.4.3 WASH/WebFunctions . 82 7.4.4 WebObjects . 82 7.5 Active Libraries . 83 8 Conclusion 85 8.1 Reflection . 85 8.2 Future work . 87 Bibliography 87 A Implementation details 89 A.1 Syntax definitions . 89 A.2 Generated code . 91 A.2.1 DomainModel . 91 A.2.2 WebLayer . 94 B Model driven development environments 99 B.1 JetBrains Meta Programming System . 99 B.2 OptimalJ . 101 iv Chapter 1 Introduction Software engineering as a discipline finds itself in a permanent state of flux. Especially when it comes to programming languages, their design and application are subject to numerous studies in both academic and corporate environments. Programming languages can be categorized into two large groups: general purpose languages (GPLs) and domain specific languages (DSLs). The former are languages that can be used to create arbitrary computer programs, whereas the latter are focussed on expressing programs on a single, smaller domain. It is the latter group that is of prime interest in this thesis. We observe a surge of interest in high-level software development. Whether it is touted as Model Driven Software Development, Model Driven Architecture, Domain Specific Languages, or using an- other fashionable term, many companies are willing to invest. Mainly, the industry’s need for faster turnaround times on software is the driving force behind this heightened awareness. However, often- times these initiatives.