4_67.php

<?php

return [
    'title' => "The query system loop detector",
    'description' => [
        '1' =>
        "Devise a way to install a loop detector in the query system so as to avoid the kinds of simple loops illustrated in the text and in exercise ",
        '2' =>
        ". The general idea is that the system should maintain some sort of history of its current chain of deductions and should not begin processing a query that it is already working on. " .
        "Describe what kind of information (patterns and frames) is included in this history, and how the check should be made. " .
        "(After you study the details of the query-system implementation in section 4.4.4, you may want to modify the system to include your loop detector.)",
    ],
];