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Minimal Sets of FDs (2) Every set of FDs has an equivalent minimal set There can be several equivalent minimal sets There is no simple algorithm for computing a minimal set of FDs that is equivalent to a set F of FDs To synthesize a set of relations, we assume that we start with a set of dependencies that is a minimal set (e.g., see algorithms ...

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Step 9: Mapping of Union Types (Categories). For mapping a category whose defining superclass have different keys, it is customary to specify a new key attribute, called a surrogate key, when creating a relation to correspond to the category. In the example below we can create a relation OWNER to correspond to the OWNER category and include any ...

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Formal Definitions of EER Model (2) Subclass S of C is predicate defined if predicate p on attributes of C is used to specify membership in S; that is, S = C[p], where C[p] is the set of entities in C that satisfy p A subclass not defined by a predicate is called user-defined Attribute-defined specialization: if a predicate A = ci (where A is a...

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The Domain Relational Calculus Another variation of relational calculus called the domain relational calculus, or simply, domain calculus is equivalent to tuple calculus and to relational algebra. The language called QBE (Query-By-Example) that is related to domain calculus was developed almost concurrently to SQL at IBM Research, Yorktown Heigh...

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UPDATE Used to modify attribute values of one or more selected tuples A WHERE-clause selects the tuples to be modified An additional SET-clause specifies the attributes to be modified and their new values Each command modifies tuples in the same relation Referential integrity should be enforced

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Classification of DBMSs Based on the data model used: Traditional: Relational, Network, Hierarchical. Emerging: Object-oriented, Object-relational. Other classifications: Single-user (typically used with micro- computers) vs. multi-user (most DBMSs). Centralized (uses a single computer with one database) vs. distributed (uses multiple compute...

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Cost-estimation-based optimization If the cost of every execution plan can be estimated accurately, then the optimal plan can be eventually found. Two difficulties with cost-estimation based optimization:  There may be too many possible execution plans to enumerate.  It may be difficult to estimate the cost of each execution plan accurately. ...

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Updating tuples in a nested table: update table (select beers from manfs m where m.name = ‘Anheuser’) b set b.color = ‘blue’; First, you have to flatten the object table using the pseudo function table before you can do an update on the object table. Not quite obvious, because update essentially refers only to the object table beers and not ...

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Research Directions (2006-2010) (cont.) Advanced Information Systems: E-/M-Commerce SOA-Based Modern Information Systems Large Database Systems Web Information Systems Modern Information Retrieval Systems Stream Data Management* Bioinformatics*

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Summary Introduction to Database Security Issues Types of Security Threats to databases Database Security and DBA Access Protection, User Accounts, and Database Audits Discretionary Access Control Types of Discretionary Privileges Specifying Privileges Using Views Revoking Privileges Propagation of Privileges Using the GRANT OPTION An ex...

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