MCE processes sequences of time-variant data. Each time-value pair within this data is a Data Point, and each sequence of them is a Data Point List.

A Data Item owns a single Data Point List, providing properties including name and an equation for applying to each Data Point in the Data Point List if applicable. As well as having implicit Data Item dependences, Data Item equations can also refer to the Data Point Lists of other Data Items.

With these concepts in mind, the work of MCE can be summarised as

• Interpreting Data Item equations and processing their Data Point Lists.
• Monitoring dependencies between Data Items.
• Caching and storing Data Item properties and their Data Point Lists.
An Item is an application-specific collection of Data Items with a higher level of associated properties. It represents the various stages of Item-Type processing from imported raw data to usable data that has undergone pre-processing, unit conversion, data reduction (aggregation) and equation processing . Typical applications of the system usually express this data as a cost or cost relative to target data.

The Data Point and Data Point List

A Data Point has the following properties:
 Property Description Example Value A numeric value 12.345 Time Time the value applies to. 12:57:34 17-03-2008 Interpolated Flag Set if the value has been derived due to insufficient data available True

A Data Point list is a time-ordered collection of these Data Points. All calculations are performed at a Data Point List (i.e. time range) or Data Point (i.e. point-in-time) level. The concepts of Data Items and Meters are responsible for the state, behaviour and properties of the calculations performed.

There are a number of properties and functions available on a Data Point List that are defined here.

The Data Item

A Data Item contains all of the information required to process its Data Point List. There are two fundamental types:

Raw Data Item
This type contains raw real-world data imported into storage. The data is simply retrieved and cached from storage when required. No calculations are performed.
Calculated data Item
This type derives calculated data, typically by performing calculations based on other Data Item Data Point Lists.

Calculations

Calculations are broken up into two stages. The first stage involves determining the times at which Data Points should exist, referred to as Data Item Calculation. The second stage calculates the value (and interpolated flag) of each Data Point, known as Value Calculation.

The logic of the Data Item Calculation stage is defined by a Data Item Calculator Template file. The Value Calculation Stage also has its own Value Calculator Template file, which combined with an equation defines value calculation logic. Both templates are uncompiled, human-readable code files which can be modified or replaced to suit a particular Data Item calculation requirement.

Equations

An equation is a textual description of logic to apply to each Data Point in the owned Data Point List. A multitude of functions are available, including those available from the Value Calculator Template, Data Point List, and Microsoft .Net libraries.

Dependencies

A Calculated Data Item has dependencies on other Data Items if it references their data in either of its calculation stages . Such references are referred to as Child Data Item references. The collection of Child Data Items referenced by a Data Item is referred to as the Consumed List. Conversely, the collection of Data Items that reference a specific Data Item is the Consumer List.

Dirty Storage State

Calculated Data Item calculations are only performed when its Data Point List is requested. Once calculated, the data is cached for performance and stored. Re-calculations are only performed when the Data Point List is requested and it is considered to be in a Dirty state. The data is marked dirty when:

• Data Item properties are changed that could affect calculations
• Child Data Items are dirtied
Data Item Properties
 Property Description Example Name Data Item full name. Company1|Site1|Meter1|CALC IsCalculated Flag indicating whether the Data Item is calculated (Calculated Data Item) or contains raw data (Raw Data Item). True Equation The equation used on each Data Point in the owned Data Point List. This is empty if a Raw Data Item. [CALC1].GetValueAtTime(Time) * 10 Equation Error A description of detected equation errors. This is empty if the equation is valid or not set. At least one child Data Item must be referenced within the equation. DataItemCalculatorTemplate The code file used to create the owned Data Point List. This is empty for Raw Data Items. CalculatedDataItemCalculatorTemplate ValueCalculatorTemplate The code file used to calculate the value of each Data Point within the Data Point List. This is empty for Raw Data Items. StandardValueCalculatorTemplate IsStorageDirty Flag indicating whether storage is dirty. If dirty, the owned Data Point list is re-calculated when required. This only applies to Calculated Data Items. True IsReadOnly Indicates whether the equation can be modified. This only applies to Calculated Data Items. False