Architecture and specification style in formal descriptions of distributed systems

Objective of this paper is to illustrate relationships that exist between architecture, the abstract subject of distributed system design, and specification style, the way of using a given language to design and implement the architecture. We advocate for a few specification styles thate allow to structure formal specifications and can be used at advantage to pursue explicitly defined design objectives. The establsihment of common and related specification styles is also considered paramount to preserving homogeneity of large specifications developed by teams of specifiers. Such specification styles enable the designer to better control the design trajectory and thus to produce higher quality designs in shorter timescales. The presentation is endowed with simple examples. The specification language LOTOS is used as a vehicle to convey ideas and to present examples, but the reasoning is kept independent of any particular language.