Examples of Statement-Level Active Rules
26.1.3 Examples of Statement-Level Active Rules
in STARBURST
We now give some examples to illustrate how rules can be specified in the STAR- BURST experimental DBMS. This will allow us to demonstrate how statement-level rules can be written, since these are the only types of rules allowed in STARBURST.
The three active rules R1S , R2S , and R3S in Figure 26.5 correspond to the first three rules in Figure 26.2, but they use STARBURST notation and statement-level seman- tics. We can explain the rule structure using rule R1S . The CREATE RULE statement specifies a rule name— Total_sal1 for R1S . The ON clause specifies the relation on which the rule is specified— EMPLOYEE for R1S . The WHEN clause is used to spec-
ify the events that trigger the rule. 8 The optional IF clause is used to specify any conditions that need to be checked. Finally, the THEN clause is used to specify the actions to be taken, which are typically one or more SQL statements.
In STARBURST, the basic events that can be specified for triggering the rules are the standard SQL update commands: INSERT , DELETE , and UPDATE . These are speci- fied by the keywords INSERTED , DELETED , and UPDATED in STARBURST nota- tion. Second, the rule designer needs to have a way to refer to the tuples that have been modified. The keywords INSERTED , DELETED , NEW-UPDATED , and OLD- UPDATED are used in STARBURST notation to refer to four transition tables (rela- tions) that include the newly inserted tuples, the deleted tuples, the updated tuples before they were updated, and the updated tuples after they were updated, respec- tively. Obviously, depending on the triggering events, only some of these transition tables may be available. The rule writer can refer to these tables when writing the condition and action parts of the rule. Transition tables contain tuples of the same type as those in the relation specified in the ON clause of the rule—for R1S , R2S , and R3S , this is the EMPLOYEE relation.
In statement-level semantics, the rule designer can only refer to the transition tables as a whole and the rule is triggered only once, so the rules must be written differ- ently than for row-level semantics. Because multiple employee tuples may be
26.1 Active Database Concepts and Triggers 941
R1S: CREATE RULE Total_sal1 ON EMPLOYEE WHEN INSERTED
IF EXISTS ( SELECT * FROM INSERTED WHERE Dno IS NOT NULL ) THEN UPDATE
DEPARTMENT AS D
SET
D.Total_sal = D.Total_sal + ( SELECT SUM (I.Salary) FROM INSERTED AS I WHERE D.Dno = I.Dno )
WHERE
D.Dno IN ( SELECT Dno FROM INSERTED );
R2S: CREATE RULE Total_sal2 ON EMPLOYEE WHEN UPDATED ( Salary )
IF EXISTS ( SELECT * FROM NEW-UPDATED WHERE Dno IS NOT NULL ) OR EXISTS ( SELECT * FROM OLD-UPDATED WHERE Dno IS NOT NULL ) THEN UPDATE
DEPARTMENT AS D
SET
D.Total_sal = D.Total_sal + ( SELECT SUM (N.Salary) FROM NEW-UPDATED AS N
WHERE D.Dno = N.Dno ) – ( SELECT SUM (O.Salary) FROM OLD-UPDATED AS O
WHERE D.Dno = O.Dno )
WHERE D.Dno IN ( SELECT Dno FROM NEW-UPDATED ) OR D.Dno IN ( SELECT Dno FROM OLD-UPDATED );
R3S: CREATE RULE Total_sal3 ON EMPLOYEE WHEN UPDATED ( Dno ) THEN UPDATE
DEPARTMENT AS D
SET
D.Total_sal = D.Total_sal + ( SELECT SUM (N.Salary) FROM NEW-UPDATED AS N
WHERE D.Dno = N.Dno )
WHERE
D.Dno IN ( SELECT Dno FROM NEW-UPDATED );
UPDATE
DEPARTMENT AS D
SET
D.Total_sal = Total_sal – ( SELECT SUM (O.Salary) FROM OLD-UPDATED AS O
WHERE D.Dno = O.Dno )
WHERE
D.Dno IN ( SELECT Dno FROM OLD-UPDATED );
Figure 26.5
Active rules using statement-level semantics in STARBURST notation.
inserted in a single insert statement, we have to check if at least one of the newly inserted employee tuples is related to a department. In R1S, the condition
EXISTS (SELECT * FROM INSERTED WHERE Dno IS NOT NULL ) is checked, and if it evaluates to true, then the action is executed. The action updates
in a single statement the DEPARTMENT tuple(s) related to the newly inserted employee(s) by adding their salaries to the Total_sal attribute of each related depart-
942 Chapter 26 Enhanced Data Models for Advanced Applications
department, we use the SUM aggregate function to ensure that all their salaries are added.
Rule R2S is similar to R1S , but is triggered by an UPDATE operation that updates the salary of one or more employees rather than by an INSERT . Rule R3S is triggered by an update to the Dno attribute of EMPLOYEE , which signifies changing one or more employees’ assignment from one department to another. There is no condition in
R3S , so the action is executed whenever the triggering event occurs. 9 The action updates both the old department(s) and new department(s) of the reassigned employees by adding their salary to Total_sal of each new department and subtract- ing their salary from Total_sal of each old department.
In our example, it is more complex to write the statement-level rules than the row- level rules, as can be illustrated by comparing Figures 26.2 and 26.5. However, this is not a general rule, and other types of active rules may be easier to specify when using statement-level notation than when using row-level notation.
The execution model for active rules in STARBURST uses deferred consideration. That is, all the rules that are triggered within a transaction are placed in a set— called the conflict set—which is not considered for evaluation of conditions and execution until the transaction ends (by issuing its COMMIT WORK command). STARBURST also allows the user to explicitly start rule consideration in the middle of a transaction via an explicit PROCESS RULES command. Because multiple rules must be evaluated, it is necessary to specify an order among the rules. The syntax for rule declaration in STARBURST allows the specification of ordering among the rules to instruct the system about the order in which a set of rules should be consid-
ered. 10 Additionally, the transition tables— INSERTED , DELETED , NEW-UPDATED , and OLD-UPDATED —contain the net effect of all the operations within the transac- tion that affected each table, since multiple operations may have been applied to each table during the transaction.
Parts
» Fundamentals_of_Database_Systems,_6th_Edition
» Characteristics of the Database Approach
» Advantages of Using the DBMS Approach
» A Brief History of Database Applications
» Schemas, Instances, and Database State
» The Three-Schema Architecture
» The Database System Environment
» Centralized and Client/Server Architectures for DBMSs
» Classification of Database Management Systems
» Domains, Attributes, Tuples, and Relations
» Key Constraints and Constraints on NULL Values
» Relational Databases and Relational Database Schemas
» Integrity, Referential Integrity, and Foreign Keys
» Update Operations, Transactions, and Dealing with Constraint Violations
» SQL Data Definition and Data Types
» Specifying Constraints in SQL
» The SELECT-FROM-WHERE Structure of Basic SQL Queries
» Ambiguous Attribute Names, Aliasing, Renaming, and Tuple Variables
» Substring Pattern Matching and Arithmetic Operators
» INSERT, DELETE, and UPDATE Statements in SQL
» Comparisons Involving NULL and Three-Valued Logic
» Nested Queries, Tuples, and Set/Multiset Comparisons
» The EXISTS and UNIQUE Functions in SQL
» Joined Tables in SQL and Outer Joins
» Grouping: The GROUP BY and HAVING Clauses
» Discussion and Summary of SQL Queries
» Specifying General Constraints as Assertions in SQL
» Introduction to Triggers in SQL
» Specification of Views in SQL
» View Implementation, View Update, and Inline Views
» Schema Change Statements in SQL
» Sequences of Operations and the RENAME Operation
» The UNION, INTERSECTION, and MINUS Operations
» The CARTESIAN PRODUCT (CROSS PRODUCT) Operation
» Variations of JOIN: The EQUIJOIN and NATURAL JOIN
» Additional Relational Operations
» Examples of Queries in Relational Algebra
» The Tuple Relational Calculus
» The Domain Relational Calculus
» Using High-Level Conceptual Data Models
» Entity Types, Entity Sets, Keys, and Value Sets
» Relationship Types, Relationship Sets, Roles, and Structural Constraints
» ER Diagrams, Naming Conventions, and Design Issues
» Example of Other Notation: UML Class Diagrams
» Relationship Types of Degree Higher than Two
» Subclasses, Superclasses, and Inheritance
» Constraints on Specialization and Generalization
» Specialization and Generalization Hierarchies
» Modeling of UNION Types Using Categories
» A Sample UNIVERSITY EER Schema, Design Choices, and Formal Definitions
» Data Abstraction, Knowledge Representation, and Ontology Concepts
» ER-to-Relational Mapping Algorithm
» Discussion and Summary of Mapping for ER Model Constructs
» Mapping EER Model Constructs
» The Role of Information Systems
» The Database Design and Implementation Process
» Use of UML Diagrams as an Aid to Database Design Specification 6
» Rational Rose: A UML-Based Design Tool
» Automated Database Design Tools
» Introduction to Object-Oriented Concepts and Features
» Object Identity, and Objects versus Literals
» Complex Type Structures for Objects and Literals
» Encapsulation of Operations and Persistence of Objects
» Type Hierarchies and Inheritance
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» Object-Relational Features: Object Database Extensions to SQL
» Overview of the Object Model of ODMG
» Built-in Interfaces and Classes in the Object Model
» Atomic (User-Defined) Objects
» Extents, Keys, and Factory Objects
» The Object Definition Language ODL
» Differences between Conceptual Design of ODB and RDB
» Mapping an EER Schema to an ODB Schema
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» Overview of the C++ Language Binding in the ODMG Standard
» Structured, Semistructured, and Unstructured Data
» XML Hierarchical (Tree) Data Model
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» XPath: Specifying Path Expressions in XML
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» Extracting XML Documents from
» Database Programming: Techniques
» Retrieving Single Tuples with Embedded SQL
» Retrieving Multiple Tuples with Embedded SQL Using Cursors
» Specifying Queries at Runtime Using Dynamic SQL
» SQLJ: Embedding SQL Commands in Java
» Retrieving Multiple Tuples in SQLJ Using Iterators
» Database Programming with SQL/CLI Using C
» JDBC: SQL Function Calls for Java Programming
» Database Stored Procedures and SQL/PSM
» PHP Variables, Data Types, and Programming Constructs
» Overview of PHP Database Programming
» Imparting Clear Semantics to Attributes in Relations
» Redundant Information in Tuples and Update Anomalies
» Normal Forms Based on Primary Keys
» General Definitions of Second and Third Normal Forms
» Multivalued Dependency and Fourth Normal Form
» Join Dependencies and Fifth Normal Form
» Inference Rules for Functional Dependencies
» Minimal Sets of Functional Dependencies
» Properties of Relational Decompositions
» Dependency-Preserving Decomposition
» Dependency-Preserving and Nonadditive (Lossless) Join Decomposition into 3NF Schemas
» Problems with NULL Values and Dangling Tuples
» Discussion of Normalization Algorithms and Alternative Relational Designs
» Further Discussion of Multivalued Dependencies and 4NF
» Other Dependencies and Normal Forms
» Memory Hierarchies and Storage Devices
» Hardware Description of Disk Devices
» Magnetic Tape Storage Devices
» Placing File Records on Disk
» Files of Unordered Records (Heap Files)
» Files of Ordered Records (Sorted Files)
» External Hashing for Disk Files
» Hashing Techniques That Allow Dynamic File Expansion
» Other Primary File Organizations
» Parallelizing Disk Access Using RAID Technology
» Types of Single-Level Ordered Indexes
» Some General Issues Concerning Indexing
» Algorithms for External Sorting
» Implementing the SELECT Operation
» Implementing the JOIN Operation
» Algorithms for PROJECT and Set
» Notation for Query Trees and Query Graphs
» Heuristic Optimization of Query Trees
» Catalog Information Used in Cost Functions
» Examples of Cost Functions for SELECT
» Examples of Cost Functions for JOIN
» Example to Illustrate Cost-Based Query Optimization
» Factors That Influence Physical Database Design
» Physical Database Design Decisions
» An Overview of Database Tuning in Relational Systems
» Transactions, Database Items, Read and Write Operations, and DBMS Buffers
» Why Concurrency Control Is Needed
» Transaction and System Concepts
» Desirable Properties of Transactions
» Serial, Nonserial, and Conflict-Serializable Schedules
» Testing for Conflict Serializability of a Schedule
» How Serializability Is Used for Concurrency Control
» View Equivalence and View Serializability
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» Guaranteeing Serializability by Two-Phase Locking
» Dealing with Deadlock and Starvation
» Concurrency Control Based on Timestamp Ordering
» Multiversion Concurrency Control Techniques
» Validation (Optimistic) Concurrency
» Granularity of Data Items and Multiple Granularity Locking
» Using Locks for Concurrency Control in Indexes
» Other Concurrency Control Issues
» Recovery Outline and Categorization of Recovery Algorithms
» Caching (Buffering) of Disk Blocks
» Write-Ahead Logging, Steal/No-Steal, and Force/No-Force
» Transaction Rollback and Cascading Rollback
» NO-UNDO/REDO Recovery Based on Deferred Update
» Recovery Techniques Based on Immediate Update
» The ARIES Recovery Algorithm
» Recovery in Multidatabase Systems
» Introduction to Database Security Issues 1
» Discretionary Access Control Based on Granting and Revoking Privileges
» Mandatory Access Control and Role-Based Access Control for Multilevel Security
» Introduction to Statistical Database Security
» Introduction to Flow Control
» Encryption and Public Key Infrastructures
» Challenges of Database Security
» Distributed Database Concepts 1
» Types of Distributed Database Systems
» Distributed Database Architectures
» Data Replication and Allocation
» Example of Fragmentation, Allocation, and Replication
» Query Processing and Optimization in Distributed Databases
» Overview of Transaction Management in Distributed Databases
» Overview of Concurrency Control and Recovery in Distributed Databases
» Current Trends in Distributed Databases
» Distributed Databases in Oracle 13
» Generalized Model for Active Databases and Oracle Triggers
» Design and Implementation Issues for Active Databases
» Examples of Statement-Level Active Rules
» Time Representation, Calendars, and Time Dimensions
» Incorporating Time in Relational Databases Using Tuple Versioning
» Incorporating Time in Object-Oriented Databases Using Attribute Versioning
» Temporal Querying Constructs and the TSQL2 Language
» Spatial Database Concepts 24
» Multimedia Database Concepts
» Clausal Form and Horn Clauses
» Datalog Programs and Their Safety
» Evaluation of Nonrecursive Datalog Queries
» Introduction to Information Retrieval
» Types of Queries in IR Systems
» Evaluation Measures of Search Relevance
» Web Analysis and Its Relationship to Information Retrieval
» Analyzing the Link Structure of Web Pages
» Approaches to Web Content Analysis
» Trends in Information Retrieval
» Data Mining as a Part of the Knowledge
» Goals of Data Mining and Knowledge Discovery
» Types of Knowledge Discovered during Data Mining
» Market-Basket Model, Support, and Confidence
» Frequent-Pattern (FP) Tree and FP-Growth Algorithm
» Other Types of Association Rules
» Approaches to Other Data Mining Problems
» Commercial Data Mining Tools
» Data Modeling for Data Warehouses
» Difficulties of Implementing Data Warehouses
» Grouping, Aggregation, and Database Modification in QBE
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