In MDF, a 'module' is a processing function which may be plugged
into the framework. An MDF module is responsible for processing one
or more 'metadata sets' received from an application or another
module and producing, as a result of that processing, zero or more
metadata sets to be passed to a third module (or to the
application). During this processing, a module may interact with
other systems, reading from or writing to other datastores as
necessary.
downstream module
The downstream module of a particular MDF module is the module which receives metadata sets from this module
metadata set
A metadata set is a collection of property/value pairs stored in
an implementation specific table which is accessible via the
property. Properties should be strings. Values may be strings or
other object types, although strings are to be preferred for
purposes of simplyfying interfacing with other modules.
processing chain
A collection of MDF modules connected
together such that one module forms the head of the chain, with no
upstream module and connected to a
single downstream module, one
module forms the tail of the chain with no downstream module but a
single upstream module and all other modules are connected to one
upstream and one downstream module in such a way that no two
modules have the same upstream module or the same downstream
module. In otherwords, a simple chain of modules connected
together.
upstream module
The upstream module of a particular MDF module is the module which provides metadata sets to that module for
processing.