An Extended Entity-Relationship Model: Fundamentals and by Martin Gogolla PDF

By Martin Gogolla

ISBN-10: 0387576487

ISBN-13: 9780387576480

ISBN-10: 3540576487

ISBN-13: 9783540576488

This textual content provides a complete advent to a longer Entity-Relationship version either on a conceptual and on a proper, mathematicallevel. as well as the primitives given by way of the knowledge version the textual content introduces a language for the formula of constraints with a view to limit database states to constant ones. The textual content explains an implementation of the process selected within the good judgment programing language PROLOG and discusses during this context the computational energy of the proposedcalculus. The prolonged Entity-Relationship calculus is used to outline the which means of the relational question language SQL. a pleasant characteristic of the procedure is that it turns into attainable to turn out language homes on a legitimate mathematical basis.

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Additional resources for An Extended Entity-Relationship Model: Fundamentals and Pragmatics

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Given declaration v3 : r~ ; v2 : r2 ; vl : rl d l . Resulting definitions . . 3: Requirements and resulting definitions for sequences of declarations. 15 Example: Declarations 1. , a assigns to the variable p a single value out of #[ENTTYPE](PERSON). This declaration has no free variables. 2. (a:LTS(addr(p))) is a declaration of variable a with the single free variable p, which binds a to the addresses of the person assigned to the variable p by a given assignment a. 3. (p:LTS(ministers(e))) is a declaration of variable p with the single free variable c, which binds p to the set of ministers of the country assigned to c by assignment a.

2. 1 are both terms of sort T O W N having the single free variable la. Both terms evaluate to the town that participates in the relationship assigned to the variable la by a given a. S E C T I O N 3C. T E R M S A N D F O R M U L A S 43 3. WATERS(r) is a term of sort W A T E R S having the single free variable r. This term evaluates for a given a to the water corresponding to the river assigned to r by a. Indeed, we have assumed every river to be also a water (by an additional constraint). The above is not a correct term in the calculus of [Hohg0] because it does not allow this form of conversion.

V (c:COUNTRY) AVG -[ age(p) I (p:PERSON) A p IN ministers(c) ]- < 65 'p IN ministers(c)' is a simple formula which is used to build the bag-valued term '-[ age(p) I (p:PERSON) p IN ministers(c) ]-' which is part of the more complex formula 'AVG -[ age(p) I (p:PERSON) p IN ministers(c) ]- _< 65'. This is a first example of the cycle 'Formula -+ Term --+ Formula'. The introduction of ranges and declarations is necessary to prevent infinite bags that lead to problems concerning aggregate functions.

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An Extended Entity-Relationship Model: Fundamentals and Pragmatics by Martin Gogolla


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