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7c6df91dda
pg_relcheck is gone; CHECK, UNIQUE, PRIMARY KEY, and FOREIGN KEY constraints all have real live entries in pg_constraint. pg_depend exists, and RESTRICT/CASCADE options work on most kinds of DROP; however, pg_depend is not yet very well populated with dependencies. (Most of the ones that are present at this point just replace formerly hardwired associations, such as the implicit drop of a relation's pg_type entry when the relation is dropped.) Need to add more logic to create dependency entries, improve pg_dump to dump constraints in place of indexes and triggers, and add some regression tests.
215 lines
6.7 KiB
Plaintext
215 lines
6.7 KiB
Plaintext
<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/comment.sgml,v 1.20 2002/07/12 18:43:12 tgl Exp $
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PostgreSQL documentation
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-->
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<refentry id="SQL-COMMENT">
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<refmeta>
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<refentrytitle id="SQL-COMMENT-TITLE">COMMENT</refentrytitle>
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<refmiscinfo>SQL - Language Statements</refmiscinfo>
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</refmeta>
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<refnamediv>
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<refname>
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COMMENT
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</refname>
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<refpurpose>
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define or change the comment of an object
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</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<refsynopsisdivinfo>
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<date>1999-07-20</date>
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</refsynopsisdivinfo>
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<synopsis>
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COMMENT ON
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[
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TABLE <replaceable class="PARAMETER">object_name</replaceable> |
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COLUMN <replaceable class="PARAMETER">table_name</replaceable>.<replaceable class="PARAMETER">column_name</replaceable> |
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AGGREGATE <replaceable class="PARAMETER">agg_name</replaceable> (<replaceable class="PARAMETER">agg_type</replaceable>) |
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CONSTRAINT <replaceable class="PARAMETER">constraint_name</replaceable> ON <replaceable class="PARAMETER">table_name</replaceable> |
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DATABASE <replaceable class="PARAMETER">object_name</replaceable> |
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DOMAIN <replaceable class="PARAMETER">object_name</replaceable> |
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FUNCTION <replaceable class="PARAMETER">func_name</replaceable> (<replaceable class="PARAMETER">arg1_type</replaceable>, <replaceable class="PARAMETER">arg2_type</replaceable>, ...) |
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INDEX <replaceable class="PARAMETER">object_name</replaceable> |
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OPERATOR <replaceable class="PARAMETER">op</replaceable> (<replaceable class="PARAMETER">leftoperand_type</replaceable>, <replaceable class="PARAMETER">rightoperand_type</replaceable>) |
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RULE <replaceable class="PARAMETER">rule_name</replaceable> ON <replaceable class="PARAMETER">table_name</replaceable> |
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SCHEMA <replaceable class="PARAMETER">object_name</replaceable> |
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SEQUENCE <replaceable class="PARAMETER">object_name</replaceable> |
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TRIGGER <replaceable class="PARAMETER">trigger_name</replaceable> ON <replaceable class="PARAMETER">table_name</replaceable> |
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TYPE <replaceable class="PARAMETER">object_name</replaceable> |
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VIEW <replaceable class="PARAMETER">object_name</replaceable>
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] IS <replaceable class="PARAMETER">'text'</replaceable>
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</synopsis>
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<refsect2 id="R2-SQL-COMMENT-1">
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<refsect2info>
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<date>1999-10-25</date>
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</refsect2info>
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<title>
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Inputs
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</title>
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<para>
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<variablelist>
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<varlistentry>
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<term><replaceable class="PARAMETER">object_name,
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table_name.column_name, agg_name, constraint_name, func_name, op, rule_name, trigger_name</replaceable></term>
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<listitem>
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<para>
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The name of the object to be be commented. Names of tables,
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aggregates, domains, functions, indexes, operators, sequences, types,
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and views
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may be schema-qualified.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><replaceable class="PARAMETER">text</replaceable></term>
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<listitem>
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<para>
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The comment to add.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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</refsect2>
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<refsect2 id="R2-SQL-COMMENT-2">
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<refsect2info>
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<date>1998-09-08</date>
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</refsect2info>
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<title>
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Outputs
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</title>
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<para>
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<variablelist>
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<varlistentry>
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<term><computeroutput>
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COMMENT
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</computeroutput></term>
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<listitem>
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<para>
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Message returned if the table is successfully commented.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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</refsect2>
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</refsynopsisdiv>
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<refsect1 id="R1-SQL-COMMENT-1">
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<refsect1info>
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<date>1998-10-25</date>
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</refsect1info>
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<title>
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Description
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</title>
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<para>
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<command>COMMENT</command> stores a comment about a database object.
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Comments can be
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easily retrieved with <command>psql</command>'s
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<command>\dd</command>, <command>\d+</command>, or <command>\l+</command>
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commands. Other user interfaces to retrieve comments can be built atop
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the same built-in functions that <command>psql</command> uses, namely
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<function>obj_description()</> and <function>col_description()</>.
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</para>
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<para>
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To modify a comment, issue a new <command>COMMENT</> command for the
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same object. Only one comment string is stored for each object.
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To remove a comment, write <literal>NULL</literal> in place of the text
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string.
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Comments are automatically dropped when the object is dropped.
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</para>
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<note>
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<para>
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There is presently no security mechanism
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for comments: any user connected to a database can see all the comments
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for objects in that database (although only superusers can change
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comments for objects that they don't own). Therefore, don't put
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security-critical information in comments.
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</para>
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</note>
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</refsect1>
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<refsect1 id="R1-SQL-COMMENT-2">
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<title>
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Usage
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</title>
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<para>
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Attach a comment to the table <literal>mytable</literal>:
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<programlisting>
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COMMENT ON TABLE mytable IS 'This is my table.';
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</programlisting>
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Remove it again:
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<programlisting>
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COMMENT ON TABLE mytable IS NULL;
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</programlisting>
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</para>
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<para>
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Some more examples:
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<programlisting>
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COMMENT ON AGGREGATE my_aggregate (double precision) IS 'Computes sample variance';
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COMMENT ON COLUMN my_table.my_field IS 'Employee ID number';
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COMMENT ON DATABASE my_database IS 'Development Database';
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COMMENT ON DOMAIN my_domain IS 'Email Address Domain';
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COMMENT ON FUNCTION my_function (timestamp) IS 'Returns Roman Numeral';
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COMMENT ON INDEX my_index IS 'Enforces uniqueness on employee id';
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COMMENT ON OPERATOR ^ (text, text) IS 'Performs intersection of two texts';
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COMMENT ON OPERATOR ^ (NONE, text) IS 'This is a prefix operator on text';
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COMMENT ON RULE my_rule ON my_table IS 'Logs UPDATES of employee records';
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COMMENT ON SCHEMA my_schema IS 'Departmental data';
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COMMENT ON SEQUENCE my_sequence IS 'Used to generate primary keys';
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COMMENT ON TABLE my_schema.my_table IS 'Employee Information';
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COMMENT ON TRIGGER my_trigger ON my_table IS 'Used for R.I.';
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COMMENT ON TYPE complex IS 'Complex Number datatype';
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COMMENT ON VIEW my_view IS 'View of departmental costs';
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</programlisting>
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</para>
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</refsect1>
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<refsect1 id="R1-SQL-COMMENT-3">
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<title>
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Compatibility
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</title>
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<refsect2 id="R2-SQL-COMMENT-4">
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<refsect2info>
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<date>1998-09-08</date>
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</refsect2info>
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<title>
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SQL92
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</title>
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<para>
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There is no <command>COMMENT</command> in <acronym>SQL92</acronym>.
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</para>
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</refsect2>
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</refsect1>
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</refentry>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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sgml-parent-document:nil
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sgml-default-dtd-file:"../reference.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:"/usr/lib/sgml/catalog"
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sgml-local-ecat-files:nil
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End:
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-->
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