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abstract needs of the management interface clients. The CRUDx interface
provides database-like functionality of management instrumentation resources
to client management interfaces.
The Instrumentation API has a similar, but slightly more rigidly defined
CRUDx interface. This interface definition choice satisfied the middleware
layer's management instrumentation needs enabling it to operate on managed
resource instances and on data and services directly.
Across both interfaces, request data is passed and response data is returned
in a data-oriented fashion. Function oriented APIs were not used as they
restrict input/output to the context of the specific function, making them less
portable. Data orientation promotes efficient use of individual
instrumentation APIs and allows a single request to more efficiently use the
services of many different instrumentation components.
The third challenge was to determine how to design the system for optimal
model management. Examination of the problem domain indicated that there
was a large amount of overlap between the instrumentation models and
potential for efficient model reuse streamlining both the design and
development. Model libraries were defined to promote implementation and
extension of common model components. This led to the imposition of model
version constraints that impacted model content and how models, model
libraries and model elements were referenced by the system.
Modeling decisions led to the proposition that the management interfaces
could be models and such models could reference instrumentation data and
services using abstract identifiers. This broached the subject of dynamic and
static model management. Instrumentation models are static, compiled at
build-time and are part of the application image. Dynamic models, such as
those defining a CLI or an SNMP MIB, may be statically defined at build-
time or loaded and compiled at runtime. Faced with the option of utilizing
static or dynamic models, a half way solution was adopted. Management
interface models were pre-compiled at build-time into quasi-object models
moved the compilation and validation step to build time. This optimization
enabled the run-time system to perform only the interpretation of validated
and prepared pre-compiled models for operation.
An API Implementation Example
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