Procurement is a widely adopted collaborative approach for acquiring new systems in the public sector. It exemplifies a situation in which the early stages of digital system design define the boundaries and constraints of a new system that must be specified in the tender document (i.e., a binding offer). Researchers and government officials have long recognized the benefit of end-user participation in system design. Given the central role of the pre-tender phases in procurement processes, however, there is a need to better understand what affects user participation in such early stages. In this paper, we research a procurement process in municipal Child Welfare Services in Norway. We focus on caseworkers' participation in procuring a future case management system. We build on the concept of participatory infrastructuring to characterize how the meaning of participation was shaped through three overarching participatory infrastructuring practices of decision-making within a rigid procurement process: (i) scaling up the project, (ii) negotiating participation in meetings with potential suppliers and in tender documents, and (iii) positioning caseworkers as subject experts. The analysis of these practices reveals that the definition of user needs in the tender documentation and the creation of knotworks define both the boundary conditions and the modalities of participation. We contribute to the conversation on participatory infrastructuring in Computer-Supported Cooperative Work by discussing how participatory infrastructuring provides a conceptual understanding of participation in the context of municipal systems procurement.

采购是公共部门广泛采用的用于获取新系统的协作方法。它举例说明了一种情况，在这种情况下，数字系统设计的早期阶段定义了必须在招标文件（即具有约束力的报价）中指定的新系统的边界和约束。研究人员和政府官员早就认识到最终用户参与系统设计的好处。然而，鉴于招标前阶段在采购过程中的核心作用，有必要更好地了解影响用户参与此类早期阶段的因素。在本文中，我们研究了挪威市政儿童福利服务的采购流程。我们专注于个案工作者参与采购未来的个案管理系统。我们建立在参与式基础设施的概念之上，以描述参与的意义是如何通过严格的采购过程中的三个总体参与式基础设施决策实践来塑造的：（i）扩大项目，（ii）谈判参与与潜在的会议供应商和招标文件，以及 (iii) 将个案工作者定位为主题专家。对这些做法的分析表明，招标文件中用户需求的定义和 knotworks 的创建定义了边界条件和参与方式。