Architecting and designing : Structured analysis and design
  
Information Cluster
An Information Cluster is a series of modules that are allowed exclusive access to protected data. Each module is an entry and return point for the protected data. Any combination of modules to be diagrammed as having access to protected data can be included in the cluster. There is no one symbol that is used exclusively for the representation of an information cluster; nor is there the inherent limitation of having a predetermined number of modules that can be included in the definition. Rather, the protected data symbol can have any number of data access paths attaching it to the same number of modules. The group of module symbols connected to the protected data symbol becomes the "cluster."