COSMOS Design 208584

Update CMDBf query and registration service implementations to 1.0 spec level

This is the design document for bugzilla 208584. This documents the approach we are taking to update the query and registration service implementations from the CMDBf 0.95 spec to CMDBf 1.0.

Change History

Name:	Date:	Revised Sections:
David Whiteman	11/21/2007	Initial version
Ali Mehregani	12/05/2007	Added section 'Service Metadata'

Workload Estimation

Rough workload estimate in person weeks

Process	Sizing	Names of people doing the work
Design	1	David
Code	1	David/Ali
Test	0.4	David/Ali
Documentation	0.2
Build and infrastructure	0.2
Code review, etc.*	0.2
TOTAL	3.0

Terminologies/Acronyms

The terminologies/acronyms below can be used throughout this document. Note: These definitions are not meant to be general definitions of these terms, but rather refer to how the terms are used within this design document as applied to COSMOS.

Term	Definition
CMDB	Configuration Management Database as defined by ITIL
CMDBf	CMDB Federation Specification
MDR	Management Data Repository as defined by CMDBf
Federating CMDB	As defined by the CMDBf spec, a CMDB that federates data from multiple MDRs
SML	Service Modeling Language - An XML-based language used for modeling
SML Model	A set of SML compliant resources
SML Repository	The SML Repository describes any SML model together with a set of COSMOS API used to add new SML resources to the SML model and to query the SML model. In COSMOS, the SML repository has been implemented as an MDR.
CMDBf query	MDRs make data available via a query service defined in the CMDBf specification. The input and output of a CMDBf query is a structured XML document described in the specification.
CMDBf modules	The modules provided by COSMOS' CMDBf framework that adopters can directly extend to implement a query and/or registration service for their data source
CMDBf toolkit	The code provided by COSMOS that interacts with the query and registration service framework, and provides the WSDM endpoints needed to communicate with the federating CMDB

Purpose

This enhancement is associated with bugzilla 208584.

As part of a previous enhancement¹, the COSMOS team provided a CMDBf framework that allowed adopters to implement a CMDBf query and registration service. That enhancement was implemented per the CMDBf spec, version 0.95. Since that time, the CMDBf spec has been updated to version 1.0.

The purpose of this design is to describe the approach we are taking to update the query and registration service implementations from the CMDBf 0.95 spec to CMDBf 1.0.

Spec Change Impacts

The following spec changes impact the implementation of the CMDBf framework in COSMOS. The affected modules are noted as follows:

C	Common module
Q	Query module
R	Registration module

1. CMDBf 1.0 introduces the concept of a recordMetadata element to the query response that contains "common information about the record itself". There is also a new recordMetadata attribute on the propertyValue element that "indicates the property to be evaluated is in the <recordMetadata> element of the record". Q
2. recordTypeSelector and propertyValueSelector are renamed and aggregated under a common parent element, recordConstraint. The new names are listed in the spec changes summary table. Q
3. xpath1Selector is renamed xpathExpression, and is now mutually exclusive of all other subelements commonly shared between itemTemplate and relationshipTemplate elements. Further, a dialect attribute has been added so that XPath content is not restricted to the 1.0 version of XPath. The subelement formerly named xpathExpression that contains the raw XPath content is now named expression. Q
4. The semantics of the XPath expression in a CMDBf query have changed. In CMDBf 0.95, the XPath expression was used as a selector that evaluated to either true or false. In 1.0, the content of the record element contained by an item template is determined by the evaluation of the XPath expression. See line #1181 of the CMDBf 1.0 spec for more details. Q
5. depthLimit is a new subelement of relationshipTemplate that defines whether multiple edges or nodes should be traversed when conducting the query Q
6. propertySubsetDirective is now contentSelector and has a matchedRecords attribute that controls whether returned record content must match the selected type. Also, the selectedRecordType element has been introduced to control whether entire records or selected properties (through use of selectedProperty child elements) are returned. Q
7. the mdrId element of the <registerRequest> element has been corrected to be defined as anyURI instead of MdrScopedType in the schema Q
8. The specification now indicates a set of graph query faults and register operation faults that should be issued in certain failure conditions are met when processing a query, registration, or deregistration request. These are enumerated in sections 4.3.3, 5.2.3, and 5.2.6 of the spec. The query and registration services will need to define and throw special exception types containing the code, subcode, reason, and detail data. The MDR code will need to handle these exceptions and envelop them in a SOAP fault as part of the web service failure. Q R
9. Section 6 of the 1.0 spec describes new constructs called queryServiceMetadata and registrationServiceMetadata. These are provided so that a federating CMDB can determine which capabilities and data models are supported by a given MDR. Since this service metadata is considered optional by the spec, and since it can be implemented in parallel, the work has been spun off to a separate enhancement: bugzilla 212185.
10. instanceIdSelector has expanded to allow a collection of instanceIds to be referenced, instead of just one. Now the element is instanceIdConstraint and it contains one or more instanceId elements. Q

Spec changes summary table

Here is a summary in table form of some of the direct high-level changes in the CMDBf spec for version 1.0.

CMDBf 0.95 keyword	CMDBf 1.0 keyword	Module
N/A	recordMetadata	Q
N/A	recordConstraint	Q
recordTypeSelector	recordType	Q
propertyValueSelector	propertyValue	Q
instanceIdSelector	instanceIdConstraint	Q
xpath1Selector	xpathExpression	Q
xpathExpression	expression	Q
propertySubsetDirective	contentSelector	Q
dropDirective	suppressFromResult	Q
source	sourceTemplate	Q
target	targetTemplate	Q
N/A	depthLimit	Q
sourceItem	source	Q
targetItem	target	Q

Service Metadata

Service metadata is a new concept introduced in CMDBf1.0 specification. It's an optional mechanism for an MDR to advertise the query and registration service capabilities and data models. The design for this will be covered in COSMOS Design 212185 and implemented under the associated enhancement.

Task Breakdown

The following section includes the tasks required to complete this enhancement.

1. Copy the new data model schema to the COSMOS code base
2. Update the XML in the JUnit testcases to reflect the changed data model
3. Update the interfaces representing data model artifacts
4. Update the concrete implementations of those interfaces found in the cmdbf.query plug-in to match the new API changes
5. Update SAX parser code that transforms XML to artifacts
6. Update the toXML() methods that convert artifacts to XML representation
7. Update the code snippets in the JUnit testcases that make use of factory classes to instantiate artifacts for testing
8. Update the rest of the common query and registration service code
9. Update the SML repository code that uses the query service
10. Update the example query & registration service code, and the user documentation that accompanies it²
11. Notify early adopters (e.g. the CMDBf toolkit, also found in the data collection subproject) of previous implementation of changed COSMOS code, so they can change their implementations

Open Issues/Questions

All reviewer feedback should go in the Talk page for 208584.

References

1. COSMOS Design 204959
2. Providing a CMDBf Query and Registration Service

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