Information Technology Reference
In-Depth Information
Object Format/Common Information Model) for WBEM (Web-Based Enterprise
Management), MIB (Management Information Block) for SNMP (Simple Network
Management Protocol) and PIB (Policy Information Block) for COPS (Common
Open Policy Service) are not considered because they do not use XML, which is a
key requirement in the design of the overall routing policy management framework.
However, although policies are defined and managed initially in XML, they can be
finally implemented and enforced in real devices using any of the other proposed
formats, as the XML specification can be transformed to an equivalent MIB or PIB,
for example, without loosing any semantics. This is because of the use of an
information model that provides the semantics and basic conceptualization regardless
the specific syntax in use.
Meta Model
Level
CIM Meta Model
(class, property , association ,…)
CIM Models
(core, common, extensions )
Models Level
Implementation
Level
MIB
PIB
WBEM
XML
Fig. 2.
CIM modeling levels
There are two main different models for mapping CIM into XML: schema
mapping and metaschema mapping. DMTF defines a metaschema mapping for the
representation of CIM elements and messages in XML [7]. This mapping defines a
XML scheme that is used to describe the CIM metaschema, where both CIM classes
and instances are valid XML documents for that schema. In other words the XML
schema is used to describe in a generic fashion the notion of a CIM class or instance.
In fact, in this approach CIM element names are mapped to XML attribute or element
values, rather than XML element names.
The second approach, schema mapping, defines an XML Schema to describe the CIM
classes; in this approach CIM Instances are mapped to valid XML documents for that
schema. Essentially this means that each CIM class generates its own XSD fragment
whose XML element names are the same that the corresponding CIM element names.
The metaschema mapping was mainly adopted by the DMTF, as it only requires one
standardized DTD for the whole CIM regardless the version of this information model
used in one particular implementation. However, our research identified several
benefits related to the use of the schema mapping rather than the metaschema. The
most important ones were more validation power and a more intuitive representation.
To build automatically such XML schema from any CIM version we designed an
XML transformation using XSL Transformations (XSLT) [18]. XSLT is a language
for transforming XML documents into other XML documents.
For our purpose, the main design principles identified as part of this mapping
process were:
