Difference between revisions of "Universal object"

Revision as of 21:19, 29 January 2008

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According to the pyrkilo method the assessment products, descriptions of reality, are constructed following a formal universal information structure. It covers both hierarchical and cause-effect relations between objects within the information structure.

The information structure contains the following kinds of objects that have a standardized format:

• Assessment
• Variable
• Class

In addition to the object types listed above we could add contexts as the object type that is above assessments in the hierarchical structure. In practice contexts typically do not need to be explicitly defined as such, rather only their influence in the assessments needs to be explicated, and therefore they are not considered here in any more detail.

Assessments are collections of information for helping decision-making, and the end product of a risk assessment process, that are constructed according to the intended use purpose of the assessment. They can be described as collections of variables, collected with reference to the use purpose that the assessment is intended for, complemented with information about the scope of the assessment and assessment-specific analyses and conclusions. Assessments are discrete objects having defined starting and ending points in time and specific contextually and situationally defined goals.

Variables are descriptions of particular pieces of reality. They can be descriptions of physical phenomena, or descriptions of value judgements. Also decisions included in an assessment are described as variables. Variables are as continuously existing descriptions of reality that develop in time as knowledge about them increases. Variables are therefore not tied into any single assessment, but instead can be included in other assessments. D↷

Variables are objects of event-medium composite -type. They thus describe both the events that occur within the scope of the variable and the medium where these particular events take place. In practice, the events can only be observed through the changes in the state of the medium, and it is therefore reasonable to describe the events and particular media as such composites rather than as separately.

In pyrkilo method all the variables included in an assessment must be causally related , directly or indirectly, to the endpoints of the assessment, and the causal relations must be defined. The event-media structure is the carrier of the cause-effect relations between the variables. An event occuring in a medium causes a change in state of that medium leading to another event to occur changing the state of that medium, causing yet another event to occur and so on. In addition to variables, also classes as generalizations of properties possessed by variables can be causally related to each other.

The full-chain approach used in Intarese project can be taken here as an example of causality on a very general level. The full chain generalizes the environmental health risk issues to follow the source to impact chain as follows: sources cause emissions, causing concentrations, that cause exposures, doses and health effects, that lead to societal impacts.

Classes are sets of objects (variables or classes) that share similar properties. They can be used in describing general information that is shared by more than one variable or class or sharing general information among the classes and variables of similar kind.

All of the above-mentioned object types in the formal universal information structure are described using the same set of attributes:

• Name
• Scope
• Definition
• Result

Name attribute is an identifier for an object that helps to distinguish a particular object from others. Name of an object should be unique and descriptive of what the object is intended to contain, in particular what is the scope of the object.

Scope attribute contains an expression of what is a particular object intended to describe, i.e. the physical and abstract boundaries of the objects. For assessment and variable objects scope description is an expression of what part of reality is the object intended to describe. Scope does not have a true counterpart in reality, it is always referential to the instrumental use purpose of the object it relates to.

Definition attribute contents attempt to describe the internal structure of the part of reality that the object is intended to describe and the relations of the interior with reality outside the scope. For assessment objects definition appears in practice as a list of contents. For variables it is a description of how the result of the variable can be derived or calculated.

Result attribute is an expression of the state of the part of reality that the object describes. It is the outcome of the contents under the definition attribute.

Each attribute may contain three kinds of information:

• Actual content (only this will have an impact on other objects)
• Narrative description (to help understanding the actual content). Includes uncertainty analysis.
• Discussion (argumentation about issues in the actual content)

Despite all the object types mentioned above do have the same unified set of attributes, the sub-attributes can differ (see Assessment and Variable). This derives from the differences in the nature and primary purpose of different object types as well as practical reasons.

In addition to the formally structured objects, there may objects that do not have a standardized format related to risk assessments, such as data and models that are used in defining assessments, classes and variables and their attributes. These freely structured objects are outside the information structure, but can be e.g linked or referred to within the formal defined objects.