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

By Martin Gogolla

This textual content offers a entire advent to a longer Entity-Relationship version either on a conceptual and on a proper, mathematicallevel. as well as the primitives given via the information version the textual content introduces a language for the formula of constraints with the intention 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 that means of the relational question language SQL. a pleasant function of the technique is that it turns into attainable to end up language houses on a valid mathematical basis.

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By Martin Gogolla

This textual content offers a entire advent to a longer Entity-Relationship version either on a conceptual and on a proper, mathematicallevel. as well as the primitives given via the information version the textual content introduces a language for the formula of constraints with the intention 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 that means of the relational question language SQL. a pleasant function of the technique is that it turns into attainable to end up language houses on a valid mathematical basis.

Show description

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Extra info for An Extended Entity-Relationship Model: Fundamentals and Pragmatics

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1: Non-hierarchical structure of extended Entity-Relationship calculus. form as ranges. Let us explain the non-hierarchical structure in a simple example. Consider the following constraint demanding that the average age of the ministers in every country is less than or equal to 65. 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'.

26 C H A P T E R 2. 9: Graphical representation of type constructions. 1. 19 where our extended Entity-Relationship approach is specified by means of the extended EntityRelationship model. 17 Remark: Components One can also further restrict the possible interpretations of C O M P O N E N T functions in the following way. , e-ll,e--2' E U e e E N T T Y P E #[ENTTYPE](e). , directcomponent(el',~ ~) holds, iff there is a c E C O M P O N E N T such that e_l~ = #[COMPONENT] (c) (% ~) or e J C # [ C O M P O N E N T ] ( c ) ( e 2 ' ) i n the case that component c is multi-valued.

C. } d .... The semantics could look like this: a. ,c_k} U {_1_}, b. ,c_k}) U {2}, c. ,ck} ~ A* U i-l-} ( = #[DATA](string)), #[ATTRIBUTE](cname) : c_l ~-~ 'France', .... d .... The alphabet A is assumed to be the basic alphabet over which strings are built. Additionally, we have a set C O M P O N E N T of component names to model complex entity types in the sense of [HY84, RNLE85, LN86, SS86, BK86, AB88, ABGvG89]. , an entity may have as a part (component) of itself another entity, a set, list, or bag of entities.

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