Table of Contents
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.
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.
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.
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).
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.
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.
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.
An Origin represents the origin of a
Point's values. It may be from within the
framework, like the Clock Service, or from
outside.
Many entities may have additional informations supplied in the form
of parameter (Param).
Each Param must reference a
ParamDef.
Param Relations.
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.
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.