Strider: More information

The concept of a configuration means many different things to many different people. In Strider, a configuration is composed of entities or "items" that are present in a system and the interrelationships between them. In these terms, a configuration can be viewed as a skeletal structure that is not concerned with how work processes are actually performed nor the internal attributes of atomic entities. This makes this form of configuration model an ideal structure for providing access to ethnographic material.

Strider configuration models capture a very thin "skin deep" layer of system configuration whilst at the same time maximising management, support and analysis opportunities. A configuration model captures the static components and relationships within a system at a particular point in time. It models the content, structure and form of all social and technical components. So for example, a configuration model would represent the software, hardware, worker and resource components of a system, as well as the organisational, structural and operational relationships between them. To achieve this, Strider uses a combination of three different concepts: structural models, processes and objectives.

The information present in the structural model is normally relatively easy to determine by observation and discussion with workers and managers within an organisation and investigation of procedural manuals and so on. The structural model indicates some of the fundamental relationships within a configuration, namely those relating to the organisation and physical location of components. The relationships contained within such models indicate the pervasive top-level configurational structure, the physical organisation and spatial positioning of the various elements of a system. An example of a structural mode, showing the structure of the Chaum voting system is shown below.

In addition to the relationships recorded in the structural model, Strider also uses the concept of 'processes' to relate configuration items together. A process is an identifiable low level atomic activity from the socio-technical system under consideration. Examples of such processes could include print document, make phone call and fill out form. By modelling these processes, it is possible to record fragments of interrelationships and collaborations between the various configuration items of a system. This mechanism is particularly flexible and can be used to model a wide variety of operational relationships from both social and technical aspects of a system.

An objective is defined as a goal which can be achieved using the particular socio-technical system configuration under consideration. An objective path is a chain of relationships through a configuration by which a particular objective may be achieved. A single objective may be associated with a number of different paths though a configuration, each of which represents a different way of "getting the job done".

To aid in the construction of configuration models, Strider provides support for the direct recovery or "reclamation" of data from ethnographic reports, manuals, documents and other original source materials. We do not utilise fully automated grammatical analysis techniques due to issues relating to accuracy, scaleability and generalisablity of such approaches. Rather we prefer to keep the human "in the loop" by providing tools to enhance and augment the activities of a human analyst. To support this process the tool provides mechanisms for the selection of fragments of media from original source documents and the population of the configuration models using a specialised "cut and paste" mechanism.

The overall process of modelling should be viewed as a human mediated "harvesting" of pertinent data from verbose system description to be used in the automatic construction of configuration model entities. Support is provided for the importation of electronic texts, hand written notes, photographs, diagrams, scanned artifacts and audio files. With these facilities in place, the generation of the configuration models can be achieved as quickly and as cleanly as possible from the available original source material. The model entities which are created by this process encapsulate and contain references to the fragments of raw data from which their existence was initially determined.

Much can be gained from the modelling of configurations in terms of aiding understanding and communication between the various parties involved in socio-technical systems development and management. In addition to this, significant benefits can be gained from the use of tools to support both the modelling and investigation of configurations. However the most significant benefits of the Strider approach are obtained through automated analysis of the modelled configurations.

Using Strider, it is possible to model the existing configuration of a systems and then perform analysis on that model in order to derive an insight into various dependability attributes of that configuration. The automated analysis performed by Strider is based on the processing of objective paths and configuration item dependencies. By processing these entities it is possible to perform a variety of different analysis tasks. Using these automated analysis features, it is possible to:

o Check availability of paths - Analysis allows us to determine if a specified objective is achievable within a given configuration.

o Ensure multiple paths - The identification of multiple paths within this set for a given objective indicates some resilience to the failure of individual configuration items. If one path is rendered inoperable due to the failure of a configuration item on that path, then alternative paths are available to achieve that objective.

o Check pattern of paths - Strider can reveal the patterns which objective paths follow through a configuration. In doing so it is then possible to identify single points of failure and areas of high utilisation within the system

o Find alternative paths - For an existing system, this may not just be limited to the paths which are used in the day-to-day operation of that system, but may also incorporate possible, yet currently unused mechanisms

o Identify need for additional paths - If only a single path between start and end point is identified, then it may be desirable to perform a reconfiguration of the system in order to produce a more resilient configuration in which it is possible to achieve a particular objective by more than one means. Thus when a single item within a configuration fails, it is less likely to prevent the attainment of the desired objectives.

LINKS

Example: Chaum voting scheme

Scavenger ethnographic harvester