The validation system can be found on the Portfolio validation group on the navigation bar. Rules will allow you you to add, edit of view the rules for this database. Jobs allows you to create of change jobs, which are a collection of rules. History allows you to view the result of a previous run, including all messages generated.
The system works a follows:
Rules are a collection of values that will validate targets against the actual. The values of there are based on database queries that are executed when the rule is validated. A custom expression will allow you to specify how these values are checked.
Jobs are a collection of rules and are also from where a validation is run. A job has a number of rules that are run based on the order of the rules.