To use the Pack for Salesforce.com to extract updated or deleted data, you need to add a custom object to your Salesforce.com organization that includes the fields required by the Pack.
For example, a Salesforce.com organization might have an AccountManager user who runs an extraction job weekly and a SalesRep user who runs another job daily. Both jobs might extract data from the same Salesforce object. Setting up a unique extractId for each job lets the Pack for Salesforce.com return the data that has changed in the last week to the AccountManager user, and the data that has changed in the last day to the SalesRep.
The extractId can be any text string. The field is limited to 80 characters. You enter the extractId at design time. Optionally, you can save the extractId as a job parameter. This field has the type of Text. This field is Unique Case Insensitive, and it is an External ID field.