ISO 19155-2:2017定义了以下三种机制，用于将位置标识符（PI）（参见ISO 19155）链接到其他编码中存在的特征或对象: -ISO 19136中定义的GML对象的Id属性（GML:Id）； -IETF RFC 4122中定义的通用唯一标识符（UUID）； -IETF RFC 1738中定义的统一资源定位器（URL）。 这些PI链接机制是使用W3C XML链接语言（xlink）中定义的xlink:href启用的。 虽然这些特征或对象的标识符有时可以识别一个地方，但在本文件的范围内，存在于其他编码域中的特征或对象的标识符在概念上被称为其他标识符。 本文件进一步规定，当按照ISO 19155的规定，使用地理标记语言（GML）（ISO 19136）对PI进行编码时，它们将使用GML:id链接到其他GML编码的特征。规范性附录中规定了使用GML:id编码GML实例的详细信息。 其他规范性附录定义了使用UUID和URL将位置标识符链接到其他标识符的编码，并给出了它们的使用示例。 ISO 19155-2:2017适用于基于位置的服务、链接的开放数据、机器人辅助服务和其他需要在真实或虚拟世界中的PI和对象之间建立关系的应用领域。 ISO 19155-2:2017并不是关于创建链接到特定特征或对象的位置标识符注册，以及对gml以外的链接机制的支持: id、UUID和URL不在本文档的范围内。

ISO 19155-2:2017 defines the following three mechanisms for linking Place Identifiers (PIs) (see ISO 19155) to features or objects existing in other encodings: - Id attribute of a GML object (gml:id) as defined in ISO 19136; - Universally Unique Identifier (UUID) as defined in IETF RFC 4122; - Uniform Resource Locator (URL) as defined in IETF RFC 1738. These PI linking mechanisms are enabled using xlink:href as defined in W3C XML Linking Language (XLink). While the identifiers of these features or objects can sometimes identify a place, within the scope of this document, the identifiers of features or objects existing in other encoding domains are referred to conceptually as other identifiers. This document further defines that when PIs are encoded, as specified in ISO 19155, using the Geography Markup Language (GML) (ISO 19136), they are linked using gml:id to other GML encoded features. The details of encoding GML instances using gml:id are specified in a normative annex. Additional normative annexes define encodings for linking Place Identifiers to other identifiers using UUID and URL and present examples for their use. ISO 19155-2:2017 is applicable to location-based services, linked open data, robotic assisted services and other application domains that require a relationship between PIs and objects in either the real or virtual world. ISO 19155-2:2017 is not about creating a registry of Place Identifiers linked to specific features or objects, and support of linking mechanisms other than gml:id, UUID, and URL is out of the scope of this document.