doc/html/user-guide/cdl-conflicts.html

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  82 ><H1
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  84 ><A
  85 NAME="CDL-CONFLICTS">Conflicts</H1
  86 ><P
  87 >Not all settings of configuration items will lead to a
  88           coherent configuration; for example, the use of a timeout
  89           facility might require the existence of timer support, so if
  90           the one is required the other cannot be removed.  Coherence
  91           is policed by means of consistency rules (in particular, the
  92           goal expressions that appear as CDL items
  93           <SPAN
  94 CLASS="emphasis"
  95 ><I
  96 CLASS="EMPHASIS"
  97 >requires</I
  98 ></SPAN
  99 > and
 100           <SPAN
 101 CLASS="emphasis"
 102 ><I
 103 CLASS="EMPHASIS"
 104 >active_if</I
 105 ></SPAN
 106 > attributes [see
 107           above]).  A violation of consistency rules creates a
 108           <SPAN
 109 CLASS="emphasis"
 110 ><I
 111 CLASS="EMPHASIS"
 112 >conflict</I
 113 ></SPAN
 114 >, which must be resolved in
 115           order to ensure a consistent configuration. Conflict
 116           resolution can be performed manually or with the assistance
 117           of the <SPAN
 118 CLASS="PRODUCTNAME"
 119 >eCos</SPAN
 120 > tools.  Conflicts come in the following
 121           flavors:</P
 122 ><P
 123 ></P
 124 ><UL
 125 ><LI
 126 ><P
 127 >An <SPAN
 128 CLASS="emphasis"
 129 ><I
 130 CLASS="EMPHASIS"
 131 >unresolved</I
 132 ></SPAN
 133 > conflict means that
 134 there is a reference to an entity that is not yet in the current
 135 configuration </P
 136 ></LI
 137 ><LI
 138 ><P
 139 >An <SPAN
 140 CLASS="emphasis"
 141 ><I
 142 CLASS="EMPHASIS"
 143 >illegal value</I
 144 ></SPAN
 145 > conflict is caused
 146 when a configuration item is set to a value that is not permitted
 147 (that is, a <SPAN
 148 CLASS="emphasis"
 149 ><I
 150 CLASS="EMPHASIS"
 151 >legal_values</I
 152 ></SPAN
 153 > goal expression
 154 is failing) </P
 155 ></LI
 156 ><LI
 157 ><P
 158 >An <SPAN
 159 CLASS="emphasis"
 160 ><I
 161 CLASS="EMPHASIS"
 162 >evaluation exception</I
 163 ></SPAN
 164 > conflict
 165 is caused when the evaluation of an expression would fail (for example,
 166 because of a division by zero) </P
 167 ></LI
 168 ><LI
 169 ><P
 170 >An <SPAN
 171 CLASS="emphasis"
 172 ><I
 173 CLASS="EMPHASIS"
 174 >unsatisfied goal</I
 175 ></SPAN
 176 > conflict is caused
 177 by a failing <SPAN
 178 CLASS="emphasis"
 179 ><I
 180 CLASS="EMPHASIS"
 181 >requires</I
 182 ></SPAN
 183 > goal expression </P
 184 ></LI
 185 ><LI
 186 ><P
 187 >A <SPAN
 188 CLASS="emphasis"
 189 ><I
 190 CLASS="EMPHASIS"
 191 >bad data</I
 192 ></SPAN
 193 > conflict arises only rarely,
 194 and corresponds to badly constructed CDL.  Such a conflict can only
 195 be resolved by reference to the CDL writer.</P
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