Project Hemisphere: AT&T Surveillance and Database Systems

Project Hemisphere

Project Hemisphere is a partnership between AT&T and the US Government. The Justice Department has described it as an essential tool.

Hemisphere is a secretive program run by AT&T that searches trillions of call records and analyzes cellular data to determine where a target is located, with whom they speak, and potentially why.

No warrant is required to make use of Hemisphere. AT&T has the ability to extract information because it retains so much of it. The company owns more than three-quarters of U.S. landline switches and the second-largest share of the nation’s wireless infrastructure and cellphone towers.

Database Fundamentals

A database is a collection of related data that can be stored in a central location or in multiple locations, usually as a group of files.

• Field: Individual data element.
• Record: Group of related fields.

Files or "data" are organized and stored in a drawer; on a computer, information is stored in digital files.

Methods for Accessing Files

• Sequential file structure: Records are organized and processed in numerical or sequential order based on a “primary key.” This is usually used for backup and archive files because they need updating only rarely.
• Random access file structure: Records can be accessed in any order. This is fast and very effective when a small number of records need to be processed daily or weekly.
• Indexed sequential access method (ISAM): Records are accessed sequentially or randomly, depending on the number being accessed.

Logical Database Design

• Physical view: How data is stored physically and how data is retrieved from storage media.
• Logical view: How information appears to users and how it can be organized and retrieved. There can be more than one logical view.
• Data model: Determines how data is created, represented, and organized.

The Relational Model

• Relational model: Uses a two-dimensional table of rows and columns of data.
• Data dictionary: Includes field name, field data type, default value, and validation rule.
• Primary key: A unique identifier.
• Foreign key: Establishes relationships between tables.
• Normalization: Improves database efficiency by eliminating redundant data and duplicated fields.

Data Retrieval

These are the different commands run in a DBMS to access data:

• Select
• Join
• Intersection
• Union