+ transformations.
+ </para>
+ <para>
+ For example, <literal>scan.chr</literal> contains the following
+ map instructions among others, to make sure that HTML entity
+ encoded Danish special characters are mapped to the
+ equivalent Latin-1 characters:
+ <screen><![CDATA[
+ map (æ) æ
+ map (ø) ø
+ map (å) å
+ ]]></screen>
+ </para>
+ <para>
+ In addition to specifying sort orders, space (blank) handling,
+ and upper/lowercase folding, you can also use the character map
+ files to make &zebra; ignore leading articles in sorting records,
+ or when doing complete field searching.
+ </para>
+ <para>
+ This is done using the <literal>map</literal> directive in the
+ character map file. In a nutshell, what you do is map certain
+ sequences of characters, when they occur <emphasis> in the
+ beginning of a field</emphasis>, to a space. Assuming that the
+ character "@" is defined as a space character in your file, you
+ can do:
+ <screen>
+ map (^The\s) @
+ map (^the\s) @
+ </screen>
+ The effect of these directives is to map either 'the' or 'The',
+ followed by a space character, to a space. The hat ^ character
+ denotes beginning-of-field only when complete-subfield indexing
+ or sort indexing is taking place; otherwise, it is treated just
+ as any other character.
+ </para>
+ <para>
+ Because the <literal>default.idx</literal> file can be used to
+ associate different character maps with different indexing types
+ -- and you can create additional indexing types, should the need
+ arise -- it is possible to specify that leading articles should
+ be ignored either in sorting, in complete-field searching, or
+ both.
+ </para>
+ <para>
+ If you ignore certain prefixes in sorting, then these will be
+ eliminated from the index, and sorting will take place as if
+ they weren't there. However, if you set the system up to ignore
+ certain prefixes in <emphasis>searching</emphasis>, then these
+ are deleted both from the indexes and from query terms, when the
+ client specifies complete-field searching. This has the effect
+ that a search for 'the science journal' and 'science journal'
+ would both produce the same results.
+ </para>
+ </listitem></varlistentry>
+ <varlistentry>
+ <term>equivalent <replaceable>value-set</replaceable></term>
+ <listitem>
+ <para>
+ This directive introduces equivalence classes of characters
+ and/or strings for sorting purposes only. It resembles the map
+ directive, but does not affect search and retrieval indexing,
+ but only sorting order under present requests.
+ </para>
+ <para>
+ For example, <literal>scan.chr</literal> contains the following
+ equivalent sorting instructions, which can be uncommented:
+ <screen><![CDATA[
+ # equivalent æä(ae)
+ # equivalent øö(oe)
+ # equivalent å(aa)
+ # equivalent uü
+ ]]></screen>