Analysis Library \ Glossary of Terms - ARA-Trans/iAM GitHub Wiki
This page contains a glossary of terms used in the iAM analysis engine.
Analysis
The main entry into the scenario. Values associated with the analysis are stored in [SIMULATIONS] table. Inputs include optimization type, budget(s), benefit variable, weighting variable, description, jurisdiction criteria, benefit limit, apply multiple feasible costs (true or false).
Apply Multiple Feasible Costs
If true, multiple costs are filtered by cost criteria, each should be applied. If this variable is false, only the most expensive is applied.
Area
The area to be used by the application. Can also be a count or size of an asset (i.e. number of signs, length of pipe, etc). Currently a single definition of area is allowed.
As Budgets Permit
An analysis type in which the scenario spends money according to priorities and investments by picking projects in order of descending incremental benefit/cost, maximum benefit, remaining life/cost or maximum benefit.
Attribute
An analysis variable in a scenario. May either be a number (double) or a string. Each attribute has a set of values corresponding to time steps in the scenario. Attributes that appear in any field (criteria, equation, combo box) in a scenario are loaded into the analysis at the start of the analysis process. Only attributes used by the scenario are loaded, all others are excluded.
Ascending
This is an attribute property that is true when the attribute gets larger with better performance. An example of an ascending variable is PCI. PCI is 100 when the pavement is new and goes towards 0 as it deteriorates. An example of a false ascending attribute is IRI. IRI is somewhere near 60 for new pavement and increases as the pavement deteriorates. A pavement with an IRI of 1000 is not drive-able.
Benefit Limit
An attribute property which defines the limit below which benefit does not accrue during an analysis. For example a bridge condition index may range from 0-10. Bridge condition indexes below 2 have no value and should not be counted.
Benefit Variable
The attribute that the analysis will optimize on if the incremental benefit/cost or maximum benefit analysis type is selected. The benefit variable can be a calculated attribute. Not used for remaining life analysis types.
Budget
The budget a treatment can spend from. A treatment can spend from multiple budgets. Budget criteria are user defined provisions which determine if money can be spent from a budget based on the evaluation of the criteria statement.
Budget Order
Budgets are spent in a user defined order. For example, if there are three budgets, Maintenance, Rehabilitation, and Reconstruction, then all Maintenance projects will be considered first, then Rehabilitation and so on.
Cash Flow
Cash flow, also known as split treatment, is a criteria filtered splitting algorithm of projects over set budget amounts into multiple year projects. A project is selected using the usual method, and then is split into user determined amounts. Subsequent years of cash flow project are a type of committed project.
Calculated Attributes
Attributes that are calculated from other attributes. The equation to calculate attributes is criteria driven. After every update of consequences, all calculated attributes are recalculated.
Committed Project
A committed project occurs when a treatment is set for a given section for a given time step by user input or by means of scheduled project or cash flow (split treatment). Each committed project’s name, cost and consequence is uniquely defined. Committed projects are often derived from a treatment, but are independent thereof. Committed projects can have their own unique costs (or no costs at all). Committed projects can have unique consequences.
CodeDom Antlr/Linq
Used to compile criteria and equations. Generates a .NET dll for each equation or criteria. Improves performance of iAM during the analysis step.
Criteria
Criteria are a set of user defined expressions evaluated against a set of analysis data. If the criteria expression evaluates to true, the action associated with the criteria occurs (i.e. costs, consequences, deterioration curve selection, feasibility, etc.). Criteria can be blank or null. Blank or null criteria have specific behavior depending on the scenario object using the criteria set. (See below).
Budget criteria
Determines if a treatment can spend from a budget. A blank or null budget criteria allows the treatment to spend from that budget.
Calculated attribute criteria
Determines which calculated attribute equations to use. Blank or null calculated attribute criteria are ignored if another calculated attribute criteria evaluates true.
Consequence criteria
Determines if a consequence should be applied to an attribute. A blank or null consequence criteria are ignored if another consequence criteria has evaluated true.
Cost criteria
Determines if a given cost should be applied to an associated treatment. The total cost will be divided by the area of the asset to determine a cost per unit area. Blank or null cost criteria are evaluated even if other cost criteria evaluate true.
Deficient criteria
Determines whether or not to include sections in deficient calculations. The value for deficient is compared to the value paired with the criteria.
Deterioration criteria
Determine if the deterioration equation should be applied to an attribute. Blank or null deterioration criteria are ignored if another deterioration criteria has evaluated true.
Jurisdiction criteria
Determines which sections are to be included in the scenario. Unlike other criteria, jurisdiction criteria are not evaluated using the CodeDom Antlr/Linq compiler. Instead, a non-null or blank criteria is added to the select statement when filtering sections. The jurisdiction criteria is evaluated against non rolled-forward data.
Priority criteria
Determines if a section is included in a given priority level. Sections can fall into multiple criteria levels. A blank or null criteria level allows all sections to spend from a given priority level.
Remaining life criteria
Determines if the limit for remaining life is to be evaluated. A blank or null criteria applies to all sections means the criteria action applies to all sections.
Target criteria
Determines if a section is included in calculation of a target. Blank and null target criteria always apply to all sections in the scenario as determined by the jurisdiction criteria.
Treatment feasibility
Determines if a given treatment can be selected. Blank and null treatment feasibility are not considered.
Default Value
All attributes have a default value to use if the value is NULL.
Deficient
Determines whether or not to include sections in deficiency calculations. The value representing a deficient section is compared to the value paired with the criteria.
Deterioration
Deterioration is the process that defines how an attribute changes (degrades) over time.
Equations
The calculation of a new value from current values (and/or defaults in the simulation).
Calculated attribute equation
The equation that defines how a calculated attribute changes during each time step in the analysis (this includes consequence application or normal deterioration).
Consequence equation
Calculates a new value of an attribute. Can be applied as follows:
- # By entering a value. This sets the attribute to the value entered.
- +# Adds the number to the current value.
- # Subtracts the number from the current value.
- +%# Increase the current value by the given percentage. Example, current value is 8, with a +10% consequence. New value is 8.8
- -%# - Decreases the current value by that percentage. Example, current value is 8, with a -50% consequence. The new value is 4.
Committed Equations
A special case of a consequence equation. Each committed equation can be unique to a specific committed project.
Cost equation
Determines a cost for a scenario entity. Non-exclusive. Multiple costs can be selected at the same time if the cumulative cost flag is true.
Deterioration curve
Defines how an attribute changes over time. Can be either an equation or piece-wise function. Deterioration curves are applied to sections based on user defined criteria. The scenario warns the user if it detects multiple valid deterioration curves for a section. In the case multiple deterioration curves are valid, the analysis should choose the most conservative (worst performing) curve.
Format
A C# format string to apply to an attribute's output data.
Incremental Benefit/Cost
The area under the deterioration curve after the application of a treatment compared to the area under the deterioration curve if no treatment is applied. (and above the deficiency threshold for the attribute, if it has one?)
Investments
Stores data for start year, length of analysis, budget definitions, budget orders, annual spending for budgets and budget criteria.
Minimum
The minimum value an attribute can have.
Maximum
The maximum value an attribute can have.
Maximum Benefit
A method for selecting a Treatment pick according to the amount of Benefit they give without consideration of the Cost.
Maximum Remaining Life
A method for selecting a treatment to pick according to the amount of remaining life provided by the consequence of the treatment without consideration of the cost of the treatment.
Percent Deficient
The area weighted percentage of sections that are allowed to be deficient during an analysis.
Performance
Synonym for deterioration
Piecewise
A type of deterioration equations where pairs of age/value are given for an attribute. For years in between given pairs, a linear interpolation is performed.
Priority Level
A criteria filtered limit on the percentage of a budget that can be spent on a treatment. If money allocated to a priority is not spent it carries over to the next lower priority. If the use extra funds across budgets flag is set, the extra money is given to the next budget in the budget order.
Project
A treatment for a given section.
Remaining Life
The remaining life of a section is the number of years (fractional) that a section will take for one of its attributes to become reach its remaining life limit. Remaining life cannot be negative. The attribute with the lowest remaining life (multiple remaining life Criteria value pairs for a single Attribute can be valid simultaneously) is the sections remaining life.
Remaining Life/Cost
A method for selecting treatments ordered by remaining life divided by the unit cost.
Roll Forward
The process of applying deterioration curve functions and calculated attribute equations to attribute data, for each time step up, to the start year of the scenario analysis.
Scheduled
A treatment that is scheduled (or committed) in future years as a result of a current project. A scheduled treatment is considered when calculating incremental benefit and remaining life.
Section
The logical unit on which scenario analyses are performed. A section can be a single bridge, a length of road between two mileposts, a group of assets (all lights in a parking lot) or a building. Sections are defined during the segmentation process.
Supersedes
Refers to a criteria filtered list of treatments that the current treatment supersedes. For example, if a section can have both a minor maintenance and a reconstruction treatment, supersedes can require the minor maintenance not be performed if a reconstruction is feasible. If a treatment is listed in the supersedes of a feasible treatment, it will remove that treatment from consideration. Two treatments may mutually remove each other (there is no supersedes precedent).
Targets
A target for an attribute for sections which meet a criteria. For example, the average condition index of all sections in a county must be greater than 8 (on a 0-10 scale). Sections can be included in multiple targets. Targets are always calculated when the analysis runs. In targets/deficient met analysis the analysis picks projects in order to meet targets.
Targets/Deficients Met
A method for picking projects in order to meet criteria filtered targets.
Treatment
A specific set of feasibility, costs, consequences, and supersedes.
Weighting
A number attribute that is multiplied by a benefit attribute value for determining benefit.
Year
The year the Priority, Target or Deficient should apply for.
Years Same
Number of years before the same treatment can be applied again to a section. Committed projects may ignore this rule.
Years Any
Number of years before any treatment can be applied to a section. Committed projects may ignore this rule.