Communities of autonomous units are rule-based and graphtransformational systems with a well-defined formal semantics. The autonomous units of a community act and interact in a common environment while striving for their goals. Ant colony systems consist of a set of autonomously behaving ants and are often employed as a metaheuristics for NP-hard logistic problems. In this paper, we demonstrate how communities of autonomous units can be used as a formal graph-transformational framework for modeling ant colony systems. As a first example we model an ant colony system for the Traveling Salesperson Problem as a community of autonomous units.

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Industry best practices dictate minimum fluid requirements for preservation of subsea equipment. The choice of chemical package to be used in such operations may be guided by a number of criteria, such as: carrier fluid composition and quality, exposure temperatures, pressures, preservation time, metallurgy, risk of microbial induced corrosion, predicted marine growth, expected concentrations of oxygen and or other contaminants (to name a few). Rules of thumb and regulatory/HSSE/regional considerations play an important role in chemical selection. More often than not, there is no off the shelf/one size fits all solution, particularly for deepwater and or remote locations. Thus selection criteria and performance indicators need to be clearly defined, verified and assured under laboratory conditions, before deployment. A well selected formulation is an enabler in ensuring readiness of a fit for purpose package in the operational environment. In this work we present an example of the steps required for a structured approach to chemical selection for preservation. The selection involved looking at various MEG/water ratios proposed as carrier fluids. In addition, specific additives were considered for a defined set of conditions (e.g. temperature, oxygen content, metallurgy). The work focused on traditional chemistries used widely in preservation and novel applications. Some of the chemistries described here have not been reported previously for either water-based and or MEG/water based preservation, to our knowledge. The results from this work show that there are differences in behavior for traditional chemistries employed for water based preservation formulations compared with MEG/water based options. However, it is possible to have an optimum formulation for a MEG/water based preservation fluid to meet KPIs if a structured approach is followed.

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