1.1 The Evolution of Database Systems Database: a collection of data that is managed by a DBMS The DBMS is expected to: 1) Specify the schema using a specialized data-definition language 2) Give users the ability to query and modify the data using data-manipulation language 3) Support the storage of very large amounts of data 4) Enable durability 5) Control access to data from many users at once (isolation and atomicity) Database Systems

1.1.1 Early Database Management Systems The first commercial DBMS appeared in the late 1960’s. File systems : only item (3) supported Applications of DBMS: 1) Banking systems 2) Airline reservation systems 3) Corporate record keeping Hierarchical model and network model Database Systems

1.1.2 Relational Database Systems Since 1970, data systems change significantly. Relations SQL Object-oriented features Database Systems

1.1.3 Smaller and Smaller Systems Database systems available for even very small machines. The use of documents often tagged using XML Database Systems

1.1.4 Bigger and Bigger Systems Some important examples: 1) Google 2) Satellites 3) Flickr or Amazon 4) YouTube 5) Peer-to-peer file-sharing systems Database Systems

1.1.5 Information Integration To build structures on top of existing databases 1) Data ware-houses 2) Middleware: an integrated model Database Systems

1.2 Overview of a Database Management System (See Fig. 1.1) Two distinct sources of commands: 1) Conventional users and application programs 2) A database administrator Database Systems

1.2 Overview of a Database Management System Database Systems

1.2.1 Data-Definition Language Commands Metadata Database Systems

1.2.2 Overview of Query Processing Two separate subsystems: 1) Answering the query a. Buffer manager b. Storage manager 2) Transaction processing a. A concurrency-control manager, or scheduler, responsible for assuring atomicity and isolation of transactions b. A logging and recovery manager, responsible for the durability of transactions Database Systems

1.2.3 Storage and Buffer Managementms The kinds of information: 1) Data 2) Metadata 3) Log records 4) Statistics 5) Indexes Database Systems

1.2.4 Transaction Processing It is normal to group one or more database operations into a transaction, which is a unit of work. The tasks performed by the transaction processor: 1) Logging 2) Concurrency control 3) Deadlock resolution Database Systems

1.2.5 The Query processor Two components: 1) Query compiler ⇒ query plan a. Query parser b. Query preprocessor c. Query optimizer 2) Execution engine Database Systems

1.3 Outline of Database-System Studies Five parts: Relational database modeling a. Functional dependencies and normalization b. E/R model, UML, and ODL 2) Relational database programming a. Relational algebra, Datalog b. SQL 3) Semistructured data modeling and programming a. XML, DTD, and XML schema b. XPATH, XQuery, XSLT Database Systems

1.3 Outline of Database-System Studies 4) Database system implementation a. Storage management b. Query processing c. Transaction processing 5) Modern database system issues a. Search engines b. Information integration c. Data mining d. Data-stream systems e. Peer-to-peer systems Database Systems

The End. Database Systems