The problem of software language extension and composition drives much of the research in Software Language Engineering (SLE). Although various solutions have already been proposed, there is still little understanding of the specific ins and outs of this problem, which hinders the comparison and evaluation of existing solutionsIn this SoSyM Expert Voice, we introduce the Language Extension Problem as a way to better qualify the scope of the challenges related to language extension and compositionThe formulation of the problem is similar to the seminal Expression Problem introduced by Wadler in the late 1990s and lifts it from the extensibility of single constructs to the extensibility of groups of constructs, i.e., software languages. We provide a comprehensive definition of the actual constraints when considering language extension and believe the Language Extension Problem will drive future research in SLE, the same way the original Expression Problem helped to understand the strengths and weaknesses of programming languages and drove much research in programming languages.

中文翻译：

---

软件语言扩展问题

软件语言扩展和组合的问题推动了软件语言工程（SLE）的许多研究。尽管已经提出了各种解决方案，但对该问题的具体来龙去脉仍然知之甚少，这妨碍了对现有解决方案的比较和评估。在此SoSyM Expert Voice中，我们介绍了语言扩展问题，以此作为更好地限定该问题的一种方法。与语言扩展和写作有关的挑战范围问题的表述类似于精髓的表达问题由Wadler在1990年代后期提出，将其从单一结构的可扩展性提升到结构组（即软件语言）的可扩展性。我们在考虑语言扩展时提供了对实际约束的全面定义，并相信语言扩展问题将推动SLE的未来研究，就像原始表达问题有助于理解编程语言的优缺点和推动编程语言的大量研究一样。