What +are elements

An element is represented by the CMDBElement class. +The class is a base class for all items that can be stored in the Comms Database. +The class contains the data that is common to all items that can be stored +in the Comms database.

Elements contain three pieces of information:

a unique numeric Id +that defines the location of the element in the database. The Id defines the +meaning of the element in the database schema as a specific Table, Column, +Record or Field. A numeric Id also allows for fast access and retrieval of +an element.
a set of attributes +that controls access to the data.
a value that can be +a single numeric type, a Boolean type, a descriptor, or a composite of one +or more nested elements.

CMDBElement derives from MMetaDatabase. MMetaDatabase provides +the behaviour that allows an element to operate with the Comms Database. [See +accessing the database or words to that effect.]

+ + + +

The Element +Id

The iElementId data member of CMDBElement is +a 32 bit number that contains:

the unique numeric Id +that shows the location of the element in the database. This numeric Id is +known as the Element Id.
the set of attributes +that controls access to the data. The bits define the access levels.

Both pieces of information are encoded in the 32 bit number. The +32 bit number is a TMDBElementId type.

The CMDBElement class provides member functions to +access and to change the information in the Element Id.

The unique +numeric Id

The unique numeric Id has two parts: the Type Id and +the Record Id.

The Type Id defines the type of element; the Record +Id identifies an instance of this type of element.

The class CMDBElement provides the member functions CommsDat::CMDBElement::TypeId() and CommsDat::CMDBElement::RecordId() to +extract this information.

Internally, the Type Id includes a 8 bit +number and a 7 bit number. The 8 bit number is the Table Id and the 7 bit +number is the Column Id. The Type Id and the Record Id are in defined locations +in the 32 bit number iElementId.

+ +

The header file comsdat.h contains the constants +that define the location of these Ids in the 32 bit number:

+ + + +

Table Id

KCDMaskShowRecordType

+ + +

Column Id

KCDMaskShowFieldType

+ + +

Type Id

KCDMaskShowType

+ + +

Record Id

KCDMaskShowRecordId

+ + + +

The set of +attributes that controls access to the data

The access levels of +an element are defined by the bits in the element. The TCDAttributeFlags enum +defines the access levels of an element. These bits are stored in the fourth +byte of the iElementId member of CMDBElement.

+ +

KCDMaskShowAttributes in the header file comsdat.h defines +the location of these access control bits in the 32 bit number.