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    10 <!DOCTYPE concept

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    12 <concept id="GUID-6DAF85AD-E412-5823-81C2-FC1755A90A84" xml:lang="en"><title>What

    13 are elements</title><shortdesc>This topic describes elements. All items that can be stored in

    14 the Comms Database are elements. The topic also discusses the structure of

    15 the unique numeric Id and the attributes that control access to elements. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

    16 <p>An element is represented by the <xref href="GUID-1CDD0B97-8B00-3373-9908-512C9BC1CF51.dita"><apiname>CMDBElement</apiname></xref> class.

    17 The class is a base class for all items that can be stored in the Comms Database.

    18 The class contains the data that is common to all items that can be stored

    19 in the Comms database. </p>

    20 <p>Elements contain three pieces of information: </p>

    21 <ul>

    22 <li id="GUID-42CDC895-ADD7-53E1-86C8-BDCA97874D80"><p>a unique numeric Id

    23 that defines the location of the element in the database. The Id defines the

    24 meaning of the element in the database schema as a specific Table, Column,

    25 Record or Field. A numeric Id also allows for fast access and retrieval of

    26 an element. </p> </li>

    27 <li id="GUID-370BB127-A262-561F-BB53-CFD71D7EF61E"><p>a set of attributes

    28 that controls access to the data. </p> </li>

    29 <li id="GUID-F533113D-25EF-5CAE-8AA4-FF05CA8894B6"><p>a value that can be

    30 a single numeric type, a Boolean type, a descriptor, or a composite of one

    31 or more nested elements. </p> </li>

    32 </ul>

    33 <p> <xref href="GUID-1CDD0B97-8B00-3373-9908-512C9BC1CF51.dita"><apiname>CMDBElement</apiname></xref> derives from <xref href="GUID-1CDD0B97-8B00-3373-9908-512C9BC1CF51.dita"><apiname>MMetaDatabase</apiname></xref>. <codeph>MMetaDatabase</codeph> provides

    34 the behaviour that allows an element to operate with the Comms Database. [See

    35 accessing the database or words to that effect.] </p>

    36 <fig id="GUID-3FE9490C-8766-5F31-9147-7F20A03BBF2D">

    37 <image href="GUID-4B7FA629-BFC9-594B-B253-AC920EAD6E67_d0e85908_href.png" placement="inline"/>

    38 </fig>

    39 <section id="GUID-4DDD4947-D379-5B68-8DC0-B67B074FA852"><title>The Element

    40 Id</title> <p>The <codeph>iElementId</codeph> data member of <xref href="GUID-1CDD0B97-8B00-3373-9908-512C9BC1CF51.dita"><apiname>CMDBElement</apiname></xref> is

    41 a 32 bit number that contains: </p> <ul>

    42 <li id="GUID-4F41A6A2-79FC-5CA7-AC9C-B242D7DC925E"><p>the unique numeric Id

    43 that shows the location of the element in the database. This numeric Id is

    44 known as the Element Id. </p> </li>

    45 <li id="GUID-D8EFDBE9-A897-56F8-939A-E3942FCC34F2"><p>the set of attributes

    46 that controls access to the data. The bits define the access levels. </p> </li>

    47 </ul> <p>Both pieces of information are encoded in the 32 bit number. The

    48 32 bit number is a <xref href="GUID-1CDD0B97-8B00-3373-9908-512C9BC1CF51.dita"><apiname>TMDBElementId</apiname></xref> type. </p> <p>The <xref href="GUID-1CDD0B97-8B00-3373-9908-512C9BC1CF51.dita"><apiname>CMDBElement</apiname></xref> class provides member functions to

    49 access and to change the information in the Element Id. </p></section>

    50 <section> <p id="GUID-32E556BC-55C3-5FBD-9A60-9708139C20D6"><b>The unique

    51 numeric Id</b> </p> <p>The unique numeric Id has two parts: the Type Id and

    52 the Record Id. </p> <p>The Type Id defines the type of element; the Record

    53 Id identifies an instance of this type of element. </p> <p>The class <xref href="GUID-1CDD0B97-8B00-3373-9908-512C9BC1CF51.dita"><apiname>CMDBElement</apiname></xref> provides the member functions <xref href="GUID-1CDD0B97-8B00-3373-9908-512C9BC1CF51.dita"><apiname>CommsDat::CMDBElement::TypeId()</apiname></xref> and <xref href="GUID-1CDD0B97-8B00-3373-9908-512C9BC1CF51.dita"><apiname>CommsDat::CMDBElement::RecordId()</apiname></xref> to

    54 extract this information. </p> <p>Internally, the Type Id includes a 8 bit

    55 number and a 7 bit number. The 8 bit number is the Table Id and the 7 bit

    56 number is the Column Id. The Type Id and the Record Id are in defined locations

    57 in the 32 bit number <codeph>iElementId</codeph>. </p> <fig id="GUID-B3A732DF-8D24-532C-A4AB-D5B42408D832">

    58 <image href="GUID-0B151FE8-21E1-58A1-BEB3-5502EDF052C0_d0e85988_href.png" placement="inline"/>

    59 </fig> <p>The header file <filepath>comsdat.h</filepath> contains the constants

    60 that define the location of these Ids in the 32 bit number: </p> <table id="GUID-1369F999-F42E-5268-AF6F-0D5C9A362878">

    61 <tgroup cols="2"><colspec colname="col0"/><colspec colname="col1"/>

    62 <tbody>

    63 <row>

    64 <entry><p>Table Id </p> </entry>

    65 <entry><p> <xref href="GUID-1CDD0B97-8B00-3373-9908-512C9BC1CF51.dita"><apiname>KCDMaskShowRecordType</apiname></xref>  </p> </entry>

    66 </row>

    67 <row>

    68 <entry><p>Column Id </p> </entry>

    69 <entry><p> <xref href="GUID-1CDD0B97-8B00-3373-9908-512C9BC1CF51.dita"><apiname>KCDMaskShowFieldType</apiname></xref>  </p> </entry>

    70 </row>

    71 <row>

    72 <entry><p>Type Id </p> </entry>

    73 <entry><p> <xref href="GUID-1CDD0B97-8B00-3373-9908-512C9BC1CF51.dita"><apiname>KCDMaskShowType</apiname></xref>  </p> </entry>

    74 </row>

    75 <row>

    76 <entry><p>Record Id </p> </entry>

    77 <entry><p> <xref href="GUID-1CDD0B97-8B00-3373-9908-512C9BC1CF51.dita"><apiname>KCDMaskShowRecordId</apiname></xref>  </p> </entry>

    78 </row>

    79 </tbody>

    80 </tgroup>

    81 </table> </section>

    82 <section><p id="GUID-EE8E5985-4159-5780-8001-E51EB4821D05"><b> The set of

    83 attributes that controls access to the data</b> </p><p>The access levels of

    84 an element are defined by the bits in the element. The <xref href="GUID-2AF9DED8-0AAE-370B-8FA2-B2910939A7B8.dita"><apiname>TCDAttributeFlags</apiname></xref> enum

    85 defines the access levels of an element. These bits are stored in the fourth

    86 byte of the <codeph>iElementId</codeph> member of <xref href="GUID-C36F41FE-1776-3735-89F3-DAAAFA7FDC91.dita"><apiname>CMDBElement</apiname></xref>. </p><fig id="GUID-A1C2FF44-AA19-42B8-8F10-E927170A317A">

    87 <image href="GUID-46673FC4-ADA9-59D1-A743-B4784425D240_d0e86097_href.png" placement="inline"/>

    88 </fig><p> <xref href="GUID-DC185E84-1DC0-36F7-9B3D-19B4B3E641D7.dita"><apiname>KCDMaskShowAttributes</apiname></xref> in the header file <filepath>comsdat.h</filepath> defines

    89 the location of these access control bits in the 32 bit number.</p>  </section>

    90 </conbody></concept>