Property graphs have reached a high level of maturity, witnessed by multiple robust graph database systems as well as the ongoing ISO standardization effort aiming at creating a new standard Graph Query Language (GQL). Yet, despite documented demand, schema support is limited both in existing systems and in the first version of the GQL Standard. It is anticipated that the second version of the GQL Standard will include a rich DDL. Aiming to inspire the development of GQL and enhance the capabilities of graph database systems, we propose PG-Schemas, a simple yet powerful formalism for specifying property graph schemas. It features PG-Types with flexible type definitions supporting multi-inheritance, as well as expressive constraints based on the recently proposed PG-Keys formalism. We provide the formal syntax and semantics of PG-Schemas, which meet principled design requirements grounded in contemporary property graph management scenarios, and offer a detailed comparison of its features with those of existing schema languages and graph database systems.

翻译：地产图已达到很高的成熟度,这体现在多个稳健的图形数据库系统以及标准化组织正在进行的标准化努力,旨在创建一个新的标准查询语言(GQL),然而,尽管有记录的需求,但在现有系统和GQL标准第一版中,Schema支持有限,预计GQL标准第二版将包括丰富的DDL。 我们提出PG-Schemas,这是用于指定地产图系统的一种简单而有力的形式主义,它具有灵活的型定义,支持多重继承,以及基于最近提议的PG-Keys正式主义的明示限制。我们提供了PG-Schemas的正式语法和语义,它符合当代地产图管理假设中的原则设计要求,并详细比较了它与现有的Schema语言和图表数据库系统的特征。