Emerging application scenarios, such as cyber-physical systems (CPSs), the Internet of Things (IoT), and edge computing, call for coordination approaches addressing openness, self-adaptation, heterogeneity, and deployment agnosticism. Field-based coordination is one such approach, promoting the idea of programming system coordination declaratively from a global perspective, in terms of functional manipulation and evolution in "space and time" of distributed data structures called fields. More specifically regarding time, in field-based coordination (as in many other distributed approaches to coordination) it is assumed that local activities in each device are regulated by a fair and unsynchronised fixed clock working at the platform level. In this work, we challenge this assumption, and propose an alternative approach where scheduling is programmed in a natural way (along with usual field-based coordination) in terms of causality fields, each enacting a programmable distributed notion of a computation "cause" (why and when a field computation has to be locally computed) and how it should change across time and space. Starting from low-level platform triggers, such causality fields can be organised into multiple layers, up to high-level, collectively-computed time abstractions, to be used at the application level. This reinterpretation of time in terms of articulated causality relations allows us to express what we call "time-fluid" coordination, where scheduling can be finely tuned so as to select the triggers to react to, generally allowing to adaptively balance performance (system reactivity) and cost (resource usage) of computations. We formalise the proposed scheduling framework for field-based coordination in the context of the field calculus, discuss an implementation in the aggregate computing framework, and finally evaluate the approach via simulation on several case studies.
翻译:新出现的应用情景,如网络物理系统(CPS)、物联网(IoT)和边缘计算等,要求采取协调办法解决开放性、自我适应性、异质性和部署不可知性等问题。实地协调就是这样一种办法,从全球角度促进编程系统协调的理念;从功能操作和在分布式数据结构“空间和时间”字段“应用”的演变角度,从功能操作和“空间和时间”的分布式数据字段。更具体地说,在时间方面,在基于实地的协调(如许多其他分布式的协调方法)中,假设每个装置的当地活动都由公平且不同步的固定时钟在平台一级运作。在这项工作中,我们质疑这一假设,并提出一种替代方法,即从因果关系领域自然地(与通常的外地协调)规划时间安排,从“原因(时间和时间计算需要当地计算)”的分布式计算概念,以及它应该如何在时间和空间之间变化。从低层次的平台触发,这种因果关系的固定时钟在平台上,可以将一个精细的域调整字段组织成多层次的计算,从这个时间框架,然后将我们开始,将一个直观的计算,将时间的计算,然后将这个时间推算的计算到我们的时间推算,然后将一个直判的计算, 将一个直判的计算,将时间轴的计算,将一个直判到一个直判到我们的时间轴的计算到一个直判到一个直判到一个直到一个直到一个时间轴的计算到一个直达到一个过程的计算到我们算到一个直到我们的计算, 直达到最后的计算。