When designing observability and controllability interfaces for systems of services, or any system for that matter, it is essential to consider how it connects the operator to the operational domain in terms of the information content, structure, and (visual) forms. What representation is most effective in the immediate grounding of an operator within a situation? How efficiently and accurately can the information be communicated, playing to perceptual and cognitive strengths? Here is where an abstraction and attention hierarchy can significantly facilitate the monitoring and management of a complex system, chiefly where situational awareness, understanding of dynamics and constraints, and the ability to predict, to some small degree into the future, are of critical importance.
While an abstraction hierarchy consists of multiple levels (or layers), it still relates to the same operational domain, much like situation awareness or service level management. At each level, a new model of terms, concepts, and relations is introduced. An observer of such a hierarchically organized system can decide which particular level of information and interaction is most suitable for the task (or goal) at hand, based on their level of expertise and knowledge of the system. Levels in the abstraction hierarchy regulate lower levels through constraints and conditions, whereas lower levels stimulate state changes in higher levels.
In crossing the layered boundaries, an operator increases their understanding of the system. Moving from bottom to top, the operator obtains a greater awareness of what is significant in terms of the system’s functioning and goals—in contrast, moving from top to bottom, a more detailed explanation and exploration of how a system brings about higher levels’ goals and plans – dynamics surface at the top and data at the bottom. There must be some degree of traceability and relatability in moving in either direction.
Stimlus to Signal
In thinking about an abstraction level, several internal processes and functions occur as information flows upwards from a lower level, passing through before being translated and transformed into something more significant and relevant at a level above. It starts with some stimulus deemed as a happening, an event, originating within either the environment or a lower level if one is present. A recurring stimulus becomes a signal regarding the model and benefits constraint, correction, and conditioning. Then, depending on sensitivities, much of the noise is eliminated to prioritize what is significant or signified by signaling.
Following on from significance, a process of sequence recording, recalling, and recognition results in the synthesis of meaningful patterns. It starts with measurement, passing through to the model, and ending with the memory of such. Finally, the new information produced is propagated upwards to the next level of abstraction in the hierarchy, typically in a far more condensed form that gives utmost attention to changes in patterned or predicated behavior relevant to the means employed in achieving the higher-level goal(s).
With OpenSignals for Services, there is at least a minimum of three levels of abstraction to the hierarchy, leaving out service level management, which can be layered on top. The first level of abstraction pertains to the machine world’s spatial and (meta) state aspects, where a stimulus is sensed – the referent layer. Here services (or endpoints) within a distributed system of executing processes are mapped to a model consisting of Context, Environment, Service, and Name elements.
The next level above, the signaling layer, is where executing instrumented code is transcribed into a series of Signal firings on references within the level below. In this second level, code execution’s complicated nature across service boundaries entailing failure, retry, and fallback mechanisms are translated into a standard set of tokens. The small collection of signals is akin to RISC (reduced instruction set computer) design. Still, instead of a computer execution architecture, it pertains to service-to-service communication across machine and process boundaries.
Depending on the service provider implementation (SPI), the signals will be scored based on sensitivity and sequencing settings. The current state can drive in the level above, and a status inferred for each signaling Service registered within a Context. For recording and diagnostics purposes, the signaling level also allows registering a Subscriber and, in turn, Callback.
Finally, in the last minimum levels, the inference layer, the model is tuned to track registered and signaling services’ Status values. Much like the signaling layer below, this level allows for event Subscription management. As an observer moves up layers in the abstraction and attention hierarchy, the frequency of events emittance is reduced significantly. The meaning and relevance of each element and possibility in the model relate closer to the overall goal. In this top-level, observation, analysis, and (indirect) controllability of the model centers around the switches in the transitions between Status values, the sequencing and scoring of such over periods, and the possibility of predicting near future states of the system.
The scale of analysis also changes, from the signaling and operational status inference of a single service to how changes in the status of a system of (interconnected) services cascade and ripple in unexpected ways through the networked of contexts – both locally and globally. It would be near impossible to do so at the signaling level for a human, at least. At all levels of the hierarchy, the same processes are involved – seeing, sensing, signifying, sequencing, scaling, and synthesizing higher-order information for representation, reduction, recognition, recording, recollection, reasoning, retrospection, reinforcement, regulation, and rectification.