mirror of
https://github.com/sigmasternchen/php-doc-en
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af4410a7e1
still using this, after discussion on the phpdoc list. From now on, manual.ced will need to be found at ~/.phpdoc/manual.ced. git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@288721 c90b9560-bf6c-de11-be94-00142212c4b1
82 lines
3 KiB
XML
82 lines
3 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<chapter xml:id="sdo.das.rel.limitations" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
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<title>Limitations</title>
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<para>
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There are the following limitations in the current release of the
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Relational DAS:
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<itemizedlist>
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<listitem>
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<para>
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No support for nulls. There is no support for SQL NULL type.
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It is not legal to assign PHP NULL to a data object property
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and the Relational DAS will not write that back as a NULL to the
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database. If nulls are found in the database on a query,
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the property will remain unset.
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</para>
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</listitem>
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<listitem>
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<para>
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Only two types of SDO relationship. The metadata described below
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allows the Relational DAS to model just two types of SDO relationship:
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multi-valued containment relationships and single-valued
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non-containment references. In SDO, whether a property describes a
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single- or multi-valued relationship, and whether it is containment
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or non-containment, are independent. The full range of possibilities
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that SDO allows cannot all be defined. There may be relationships
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that it would be useful to model but which the current implementation
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cannot manage.
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One example is a single-valued containment relationship.
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</para>
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</listitem>
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<listitem>
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<para>
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No support for the full range of SDO data types. The Relational
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DAS defines all primitive properties in the SDO model as being
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of type string. SDO defines a richer set of types containing various
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integer, float, boolean and data and time types. String is adequate
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for the purposes of the Relational DAS since the combination of PHP,
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PDO and the database will ensure that values passed as strings
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will be converted to the proper type before being put in the database.
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This does affect some scenarios in which the Relational DAS has
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to work with a data graph that has come from or will go to a
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different DAS.
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</para>
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</listitem>
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<listitem>
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<para>
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Only one foreign key per table.
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The metadata only provides the means to specify one foreign key
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per table. This foreign key may be mapped to one of the two types of
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SDO relationship supported. Obviously there are some scenarios
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that cannot be described under this limitation - it is not possible
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to have two non-containment references from one table to another
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for example.
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</para>
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</listitem>
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</itemizedlist>
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</para>
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</chapter>
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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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indent-tabs-mode:nil
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sgml-parent-document:nil
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sgml-default-dtd-file:"~/.phpdoc/manual.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:nil
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sgml-local-ecat-files:nil
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End:
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vim600: syn=xml fen fdm=syntax fdl=2 si
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vim: et tw=78 syn=sgml
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vi: ts=1 sw=1
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-->
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