cat and tag

$tax_query = array(
	'relation' => 'OR',
	array(
		'taxonomy'         => 'category',
		'terms'            => array( 'term1', 'term2' ),
		'include_children' => false,
	),
	array(
		'taxonomy'         => 'post_tag',
		'terms'            => array( 'tag1', 'tag2' ),
		'include_children' => false,
	),
);