Filtering is the way the request packets pick out domains to which the requested operation will be applied.
The filter node is presented by the DomainFilterType complex type (domain_input.xsd). This data type is structured as follows:

The filter allows two kinds of filtering:
Individual filtering
The following packet requests hosting settings of three domains specified by their id:
<packet version="1.4.2.0">
<domain>
<get>
<filter>
<id>124</id>
<id>125</id>
<id>127</id>
</filter>
<dataset>
<hosting/>
</dataset>
</get>
</domain>
</packet>
The following packet is identical except it specifies domains by their names:
<packet version="1.4.2.0">
<domain>
<get>
<filter>
<domain_name>advent.co.uk</domain_name>
<domain_name>freescale.co.uk</domain_name>
<domain_name>talkmore.co.uk</domain>
</filter>
<dataset>
<hosting/>
</dataset>
</get>
</domain>
</packet>
The following packet is invalid as both the id node and the domain_name node are used in the same filter:
<packet version="1.4.2.0">
<domain>
<get>
<filter>
<domain_name>advent.co.uk</domain_name>
<id>125</id>
<domain_name>talkmore.co.uk</domain>
</filter>
<dataset>
<hosting/>
</dataset>
</get>
</domain>
</packet>
To fix this problem, use two different <get> sections:
<packet version="1.4.2.0">
<domain>
<get>
<filter>
<domain_name>advent.co.uk</domain_name>
<domain_name>talkmore.co.uk</domain>
</filter>
<dataset>
<hosting/>
</dataset>
</get>
<get>
<filter>
<id>125</id>
</filter>
<dataset>
<hosting/>
</dataset>
</get>
</domain>
</packet>
Bulk filtering
The following packet deletes all domains belonging to two Plesk Clients specified by ID:
<packet version="1.4.2.0">
<domain>
<del>
<filter>
<client_id>1324</client_id>
<client_id>1325</client_id>
</filter>
</del>
</domain>
</packet>
The same packet specifies Plesk Clients by login:
<packet version="1.4.2.0">
<domain>
<del>
<filter>
<client_login>FirstClient</client_login>
<client_login>LastClient</client_login>
</filter>
</del>
</domain>
</packet>
The following packet is invalid as it uses both the client_id node and the client_login node within one filter:
<packet version="1.4.2.0">
<domain>
<del>
<filter>
<client_id>1324</client_id>
<client_login>LastClient</client_login>
</filter>
</del>
</domain>
</packet>
To fix this packet, use two different <del> sections:
<packet version="1.4.2.0">
<domain>
<del>
<filter>
<client_id>1324</client_id>
</filter>
</del>
<del>
<filter>
<client_login>LastClient</client_login>
</filter>
</del>
</domain>
</packet>
The following packet sent by Plesk Administrator deletes all domains available in Plesk. If sent by Plesk Client, it will delete all domains of this Client:
<packet version="1.4.2.0">
<domain>
<del>
<filter/>
</del>
</domain>
</packet>