Horizontal communication: a style to compose control software

Abstract

Consumer products become more complex and diverse, integrating functions that were previously available only in separate products. We believe that to build such products efficiently, a compositional approach is required. While this is quite feasible in hardware, we would like to achieve the same in software, especially in the low‐level software that drives the hardware. We found this to be possible, but only if we let software components communicate horizontally, exchanging information along software channels that mirror the hardware signal topology. In this paper a concrete protocol implementing this style of control is described and many examples are given of its use. Copyright © 2003 John Wiley & Sons, Ltd.

Specifying features of an evolving software system

“…However, there is a problem with simply re-tuning the frequency when the user requests the channel to change [4]. The problem is to do with audio and visual 'noises' that TVs produce when the tuner is not tuned to a station, as it is the case while Tuner∼Antenna∼Demodulator is searching for a new frequency.…”

Generating Snapshots of a Component Setting

“…The example is essentially a small version of the one in [14] but contains the necessary detail to help us illustrate our approach towards capturing interactions between components.…”

“…This implies a strong dependency upon the topology of the hardware, which is subject to change in new products but also for the same product during its development. In light of such problems the approach taken in [14] is to allow components to communicate using horizontal communication interfaces in addition to the vertical control interfaces. The idea is that components controlling individual hardware devices have input and output ports that mirror the hardware and communicate through those.…”

“…In [14] the authors describe problems that arise when composing control software in the context of embedded systems used in consumer electronics (CE) products. Many control tasks in a TV, for instance, coordinate devices in the same signal path.…”

“…Especially in the context of embedded software, new products require increasingly complex software to be developed in a timely and affordable fashion. Further, the configuration is likely to change not only for new products but even for a single product during development [14]. Modern software systems often comprise complex combinations of existing functionality.…”