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Database Design Where next? John Wordsworth Department of Computer Science The University of Reading [email protected]. Room 129, Ext 6544 April 2002 2/CS/3X WHN 1 Lecture objectives • To summarise what has happened so far. • To review topics for further study. April 2002 2/CS/3X WHN 2 What we have done • History of data management • Modelling data requirements with entityrelationship modelling • Relational model of data, relational algebra, normalisation to BCNF, SQL for data manipulation • Physical files and indexes April 2002 2/CS/3X WHN 3 Security and integrity: risks • Theft and fraud • Loss of confidentiality (secrecy) about corporate data • Loss of privacy in relation to personal data • Loss of integrity (invalid or corrupt data) • Loss of availability (it’s there but we can’t get at it to run the business) April 2002 2/CS/3X WHN 4 Security and integrity: strategies • Access authorization (access privileges) • Access authentication (passwords etc.) • Encryption firewalls (at gateway between networks) • Backups, journals, checkpointing (instantaneous memory dump) • Audit (Quality Assurance applied to all stages of data processing) April 2002 2/CS/3X WHN 5 Transactions: key ideas • The ACID test – – – – • • • • Atomicity Consistency Isolation Durability Serialisability Commitment and rollback Recoverability Locking April 2002 2/CS/3X WHN 6 An e-commerce application Tier 1 Browser April 2002 Tier 2 Web server 2/CS/3X Tier 3 Database WHN 7 Data warehousing • Subject-oriented – decision-support rather than operational applications • Integrated – disparate sources and data types brought together • Time-variant – cumulative, frequently updated, time-stamped • Non-volatile – refreshed at intervals by increment, summarised April 2002 2/CS/3X WHN 8 Data mining • The process of extracting valid, previously unknown, comprehensible and actionable information from large databases and using it to make critical business decisions • e.g. – Identifying buying patterns of customers – Identifying loyal customers – Identifying successful medical therapies for different illnesses April 2002 2/CS/3X WHN 9 Object-oriented databases • Various object-oriented data models • Support the storing and retrieval of objects: – object identifier – attributes – methods • Object Definition Language • Object Query Language April 2002 2/CS/3X WHN 10 Object-relational databases • Extensions to the relational model • User-defined abstract data types (like classes) • Multivalued attributes (set types) • SQL3 April 2002 2/CS/3X WHN 11 Key points • Transactions on databases need to have the ACID properties. • Security controls are important in operational databases. • Data warehousing and data mining are applications based on large databases of historical data. • Data models other than the relational model are emerging. April 2002 2/CS/3X WHN 12