This special issue contains extended versions of four selected papers from the 12th International Conference on Graph Transformation (ICGT 2019). The articles cover a method for graph pattern matching, the use of graph hierarchies for knowledge representation, the construction of constraint preserving transformation rules, and the definition of a formal framework, extending the theory DPO rewriting to categories of structured objects.

中文翻译：

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第十二届国际图变换会议特刊的序言

本期特刊包含来自第十二届国际图变换大会（ICGT 2019）的四篇论文的扩展版本。文章涵盖了图模式匹配的方法，使用图层次结构进行知识表示，构造约束保留转换规则以及定义正式框架的方法，将DPO理论重写扩展到结构化对象的类别。