Pegasus Project Working Paper

{Title}

Authors: {namelist}

Last Update 0/0/0000 0:00 AM

Document: Document4

Revision Status

Introduction

The Definition of NULL starts with the CIM Specification that specificies

Thus we have a clear demand to implement the concept of Null in at least the following

Internally

All CIMValues

Usage of Null values in HTTP Operations and XML specificaitons

The following sections are clipped from the DMTF Specifications with annotations. As a general comment, they indicate that Null is indicated by lack of the <VALUE> or <VALUE.ARRAY> tags. Note that there is no indication what the meaning of the pairs with NO data is (ex. <VALUE></VALUE>.

From the XML Specification Section 2.4

This notation uses the NULL qualifier to indicate parameters whose values may be be specified as NULL in a method call. A NULL (unassigned) value for a parameter is specified by an <IPARAMVALUE> element with no subelement. For parameters which do not possess the NULL qualifier, the CIM Client MUST specify a value for the parameter by including a suitable subelement for the <IPARAMVALUE> element for that parameter.

The XML specification specificies the use of Value as follows:

3.2.5.3. QUALIFIER

The QUALIFIER element defines a single CIM Qualifier. If the Qualifier has a non-array type, it contains a single VALUE element representing the value of the Qualifier. If the Qualifier

has an array type, it contains a single VALUE.ARRAY element to represent the value.

<!ELEMENT QUALIFIER (VALUE|VALUE.ARRAY)>

NOTE: That either a VALUE or VALUE.ARRAY is required. There is no possibility of a Null option here. Thus, it is implied that there is no possibility for a Null value in a qualifier.

3.2.5.4. PROPERTY

The PROPERTY element defines a single (non-array) CIM Property that is not a reference. It contains a single VALUE element representing the value of the Property.

If the Property has no assigned value then the VALUE element MUST be absent.

CIM Reference Properties are described using the PROPERTY.REFERENCE element.

<!ELEMENT PROPERTY (QUALIFIER*,VALUE?)>

3.2.5.5. PROPERTY.ARRAY

The PROPERTY.ARRAY element defines a single CIM Property with an array type. It contains a single VALUE.ARRAY element representing the value of the Property.

If the Property has no assigned value then the VALUE.ARRAY element MUST be absent.

There is no element to model a Property that contains an array of references as this is not a valid Property type according to CIM [1].

<!ELEMENT PROPERTY.ARRAY (QUALIFIER*,VALUE.ARRAY?)>

3.2.5.6. PROPERTY.REFERENCE

The PROPERTY.REFERENCE element models a single CIM Property with reference semantics. In future the features of XML Linking [4] may be used to identify linking elements within

the XML Document; as XML Linking is currently only at Working Draft status no explicit dependencies have been made at this point.

<!ELEMENT PROPERTY.REFERENCE (QUALIFIER*,VALUE.REFERENCE?)>