1. April 20022/CS/3XWHN 1 Database Design Where next? John Wordsworth Department of Computer Science The University of Reading J.B.Wordsworth@rdg.ac.uk. Room 129, Ext 6544

2. April 20022/CS/3XWHN 2 Lecture objectives To summarise what has happened so far. To review topics for further study.

3. April 20022/CS/3XWHN 3 What we have done History of data management Modelling data requirements with entity- relationship modelling Relational model of data, relational algebra, normalisation to BCNF, SQL for data manipulation Physical files and indexes

4. April 20022/CS/3XWHN 4 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)

5. April 20022/CS/3XWHN 5 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)

6. April 20022/CS/3XWHN 6 Transactions: key ideas The ACID test –Atomicity –Consistency –Isolation –Durability Serialisability Commitment and rollback Recoverability Locking

7. April 20022/CS/3XWHN 7 An e-commerce application Database Web server Browser Tier 3Tier 2Tier 1

8. April 20022/CS/3XWHN 8 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

9. April 20022/CS/3XWHN 9 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

10. April 20022/CS/3XWHN 10 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

11. April 20022/CS/3XWHN 11 Object-relational databases Extensions to the relational model User-defined abstract data types (like classes) Multivalued attributes (set types) SQL3

12. April 20022/CS/3XWHN 12 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.