We describe a behavioural modelling approach based on the concept of a "Protocol Machine", a machine whose behaviour is governed by rules that determine whether it accepts or refuses events that are presented to it. We show how these machines can be composed in the manner of mixins to model object behaviour and show how the approach provides a basis for defining reusable fine-grained behavioural abstractions. We suggest that this approach provides better encapsulation of object behaviour than traditional object modelling techniques when modelling transactional business systems.We relate the approach to work going on in model driven approaches, specifically the Model Driven Architecture initiative sponsored by the Object Management Group.

Mainstream object modelling techniques use Statechart Diagrams as a means of modelling object behaviour. Research into how statecharts can be used in the context of class generalization hierarchies has focused on applying the Liskov Substitution Principle (LSP) to statecharts. This approach is problematic, and we describe three reservations.We propose an alternative approach based on mixin-style composition of state transition diagrams. This avoids the problems we note in the LSP based approach; and is also a basis for separating descriptions of behaviour inherent to the modelled domain from behaviour that is not inherent, but a requirement of the system.

Purpose The purpose of this paper is to investigate the relationship between rates of firearm homicide in New York State (NYS) and indicators of access to and quality of healthcare from 2011 to 2017. Design/methodology/approach Utilizing data from the NYS Division of Criminal Justice Services Uniform Crime Reporting Supplemental Homicide Reports and Robert Wood Johnson Foundation County Health Rankings Program, a county-level ecologic study was conducted, descriptive statistics provided and multivariable analyses conducted to determine the associations between critical indicators of county health and firearm homicide. Findings The majority of firearm homicide victims (n=2,619) were young, Black, men and the highest rates of firearm homicide were situated in urban centers. Subgroup analyses excluding large urban centers and controlling for key demographics illustrated that those counties with lower rates of clinicians were significantly associated with higher rates of firearm homicide. Research limitations/implications Despite challenges integrating two large data sets, the present findings were able to illustrate the critical relationship between access to healthcare and prevalence of firearm homicide. Practical implications The results of this study reinforce the importance of access to primary healthcare services and its relationship to critical health outcomes. Social implications In urban settings, firearm homicides disproportionately impact young Black men, who are among the least likely to have access to healthcare. In more rural areas, access to healthcare is related directly to improved health outcomes, including reduced rates of firearm homicides. Originality/value This is the first study to explore and subsequently establish the relationship between indicators of community health and firearm homicide in NYS.

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State machines can be used to specify the behaviour of objects in a system by describing the relationships between the states of the object and its ability to respond to events presented to it. Suitable choice of semantics for state machines allow multiple machines to be composed in the description of a single object.We describe an extension to this approach whereby different machines in the composition of a single object have different semantic types covering necessary behaviour, encouraged behaviour and discouraged behaviour. This provides expressive power to model the way software interacts with the domain to encourage or discourage events.