RVPF Metadata

Revised: 2010-03-10.


Table of Contents

Behavior
ClassDef
ClassLib
Content
Def
Engine
Input
Origin.
Param
ParamDef
Point
Store
Transform

The Metadata is at the heart of the framework. It holds all the information about the point definitions needed by the components to perform their duties. It can also be used as a reference for definitions held in proprietary systems. Its external format is XML and is specified by a DTD.

Behavior

Each point value entering the system may affect many other point values. It may trigger the computation of a new value, or of previously computed values, combined with other values. We call the specifics of these actions the behavior of input values on result values.

The Behavior entity represents the behavior of an input value on a result computed from that value.

ClassDef

A ClassDef entity holds the informations for the creation of instances of a class or declares an interface. This is used during the setup of a framework component to prepare the Metadata objects needed by this component.

The informations include the class name, its package and a reference to its ClassLib entity.

The interfaces that the class implements should be specified (unless, of course, it is declaring such an interface).

ClassDef Class Hierarchy.

ClassLib

A ClassLib entity holds the informations to add a class library to the classpath. When the entity is identified (with a name, uuid or id attribute), that library will be accessed only if it is referenced by an activated ClassDef. Otherwise, it is immediately put on the classpath. Since a ClassLib may be remote, it may also be cached and have more than one URL from which it may be downloaded (the caching and multiple URL support is not yet implemented).

Content

A Content provides logic for the content of a point's values. Its main responsibility is the normalization before supplying an input value for the computation of a result value and the denormalization of that result value after computation.

This allows the computation to ignore the choice of storage representation of the points.

Def

All selectable entities are classified as definitions (Def). The only fields actually used by the framework are name and uuid; the other fields are present only for documentation purposes.

Def Class Hiearchy.

Engine

An Engine implements the machinery used to produce a result value from its input values.

Input

An Input expresses the relationship between the values of a Point as the result of a transformation and the values of other Points as input to that transformation.

Origin.

An Origin represents the origin of a Point's values. It may be from within the framework, like the Clock Service, or from outside.

Param

Many entities may have additional informations supplied in the form of parameter (Param).

Each Param must reference a ParamDef.

Param Relations.

ParamDef

A ParamDef acts as a reference for the parameters of holding entities.

Point

A Point entity holds the reference information for a set of timestamped values.

It has a UUID as primary key, but may be located according to its Origin, its Store, or from its relationships (Input or result) with other Points.

When its Origin is a RVPF Processor, its values are the result from a Transform applied to the values of its Inputs.

When one of its values is received by a RVPF Processor, it may trigger an update of the values for some or all of the Points using it as an Input on this Processor.

Its Store allows access to its values.

Point Relations.

Store

A Store entity holds the informations for accessing the service holding the values for a Point. This information is held explicitly by its Params and implicitly by its ClassDef.

Transform

A Transform holds the informations required for a specific transformation of input values to a result value. These informations are used by the referenced Engine to perform the computation.