M7 Database

This is a summary of what databases do. Read this to help understand my outline below. You are responsible to understand the ACID test and the problem of concurrency.

Reference: http://philip.greenspun.com/sql/introduction.html

 Characteristics of Databases

  • Solve the problem of concurrency
    • “what happens when two people want to update the same record at the same time?”
  • Solves the problems of secure access (security)
    • Some fields or files are readable to everbody – other fields are more sensitive
    • Some fields may only be updated by certain groups
    • Ways of defining groups
      • IP address or IP address range
      • Logon id or groups of logon id’s
      • All other ways of authenticating as shown in security, e.g. key certification.
  • Adds logging
    • All updates and accesses of the database are written to a log
    • The log is capable of restoring the database to an arbitrary time.
    • Log is capable of identifying who performed transactions.
  • Helps with maintaining the integrity of the data (relational)
    • Relations between files may be defined and the the database software will enforce the definition.
    • Fields may be defined a unique and the database will reject non unique data
    • Fields may be constrained by business rules
      • e.g. balance field on a customer file must = the total of the transactions for that customer on the invoice file.
      • A date on an invoice must be after the date the order was placed.
  • Database Interface
    • Usually databases are used as backends
    • Frontend may be Visual Basic, Microsoft Access, or any other Computer language
      • e.g. Frontend may get a new customer name, address, city, state and zip and generate database command such as:
        •  UPDATE CUSTOMER with NAME = "Brian Gulino" CITY = "Encinitas"

    Commonly Used Databases

    SQL – commercial and open source versions available

    MS-SQL – Microsoft product

    Non-SQL based databases usually proprietary

    May have lower overhead (faster)

    May be specialized around a particular application

Social & Political Implications of Databases

We are going to look at the story of Adrian Schoolcraft, from the radio show “This American Life”


A link to an article on the same subject in the Village Voice exists here:


You can read the Village Voice article or listen to the broadcast.

We are studying this because it is about Compstat, the law enforcement database. Compstat helps police deploy in a way which reduces crime. Unfortunately, when Compstat is used to evaluate the performance of police, the police react by enhancing their Compstat statistical profile, often in ways which promote crime.