M. Gogolla. An Extended Entity-Relationship Model: Fundamentals and Pragmatics, volume 767 of Lecture Notes in Computer Science. Springer-Verlag, Berlin, Germany, 1994.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....these steps have to be embedded into the general database design and implementation process. For instance, the formal specification of integrity constraints has to be coupled with the conceptual modeling of the database schema, which is usually based on an extended entity relationship model [31] or the unified modeling language [11] The decomposition of integrity constraints is a step similar to the normalization of a database schema. For consistency and redundancy checking of integrity constraints, also all model inherent integrity Semantic Integrity Support in SQL 99 and Commercial ....

M. Gogolla. An Extended Entity-Relationship Model --- Fundamentals and Pragmatics, Lecture Notes in Computer Science, Vol. 767. Springer-Verlag, Berlin, 1994.

....of these meta modeling techniques do not have a formal semantics themselves. Naturally, this results in poor modeling support. In particular, it is nearly impossible to support validation of models. The importance of the need of formal semantics for modeling techniques has been stressed by e.g. Gog94, PWM93] A satisfactory CASE shell for all types of modeling techniques seems to be unfeasible, due to the inherent complexity and diversity of such techniques. However, a focus on particular types of modeling techniques may allow for the desired degree of flexibility and expressive power. The ....

M. Gogolla. An Extended Entity-Relationship Model: Fundamentals and Pragmatics, volume 767 of Lecture Notes in Computer Science. Springer-Verlag, Berlin, Germany, 1994.

....an information system. Specification in this layer is usually performed by means of semantic data models Evolution Action Component Component Object Component Data Type Component Figure 1: Layered Approach to Conceptual Modeling [HK87, PM88] enhanced) Entity Relationship models [Che76, EN94, Gog94] or object oriented data models [ABD 89, BM93, KS96] The evolution component describes the behavioral aspects of objects in time. They can be described with temporal logic or finite state machines. The action component describes the implementation independent evaluation of database update ....

....a higher level layer as for example [Saa93, HS97] do to describe long lived application processes and work flows. We see basically two lines of research: On the one hand there is a magnitude of formal models for the description of the single components (e.g. Wir90] data type component, Gog94] object component, Har87] dynamic components) and on the other hand there are many approaches which deal with schema modification and database evolution [BKKK87, FMZ 95, Odb95, PO97, SZ87, Zic92] However, only few approaches (as for example [PO97] apply formal description techniques to ....

Martin Gogolla. An extended entity-relationship model fundamentals and pragmatics. Lecture Notes in Computer Science, 767, 1994.

....variable (t : TOWN) as a kind of parameter. The query follows the well known select from where structure proposed in SQL. In our approach, the result of a query is a bag of values retaining duplicates; sets can also be obtained by applying an operator eliminating the duplicates (for details, see [Gog94] The where part is a formula which returns true if the parameter town t is an element of the set town(c) The select terms are only evaluated and returned for those countries for which the where part yields true. Although we expect the query to return exactly one string value, we must ....

....mathematical basis. Thus, comprehension and implementation is supported without any ambiguities. 1.6 Formal Definition This section gives (in a very condensed way) the formal definitions neccessary for the well definedness of our approach. A more elaborate treatment is given for example in [Gog94,HG94] Readers with no or little mathematical background are invited to inspect those papers first. We start with some preliminary notations. Notation: Let sets S; S 1 ; Sn be given. Then F(S) denotes the restriction of the powerset of S to finite sets, B(S) the set of finite multisets ....

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M. Gogolla. An Extended Entity-Relationship Model -- Fundamentals and Pragmatics. Springer, Berlin, LNCS 767, 1994 (Also http://www.db.informatik. uni-bremen.de).

.... nat counts the elements in a set (also defined for bags) OCC bag(s) bag(s) Theta s nat counts the occurrences of a given item in a bag, IN set(s) set(s) Theta s denotes the membership predicate (also defined for bags) There are many other generic functions (for details see [GH91, Gog94, Her95] All operations induced by sort expressions are summarized in Omega Gamma S Expr (S) Analogously all predicates induced by sort expressions are combined in Pi(S Expr (S) From now on let Sigma D = SD ; Omega D ; Pi D ) denote a data signature according to Definition 1 so that ....

....the from and where clause of select terms. With the aggregate function CNT it is always possible to replace the formula 9ffi( by CNT [ c j ffi; 1 (in which c represents an arbitrary constant term) In this respect quantifiers can be regarded as syntactic sugar in our query formalism [Gog94] Definition 7 (declarations) The syntax of declarations is given by a set Decl and the functions free; decl : Decl F(Var) defined by the following rules. i. If v 2 Var s , 2 Term set(s) and v = 2 free( then (v : 2 Decl , free( v : free( and decl( v : fvg. ii. ....

M. Gogolla, An Extended Entity-Relationship Model --- Fundamentals and Pragmatics, Springer, Berlin, LNCS 767, 1994.

.... method of the Object Modeling Technique (OMT) RBP 91] The way we define the semantics of the models is to translate them into a structurally clear and plain extended Entity Relationship model but which comes along with a precisely defined and expressive calculus [HG88, GH91, Hoh93, Gog94] 2 The Original Entity Relationship Model One of the first semantic data models developed was the Entity Relationship model [Che76] The following diagram is part of a diagram presented in the original article by Chen. It graphically declares a (1:N) relationship between departments and ....

....in the extended Entity Relationship model is a very plain one, because it only depicts plain entity and relationship types. Phi Phi Phi PhiH H H H Phi Phi Phi Phi H H H HDEPT EMP EMPLOYEE DEPENDENT Phi Phi Phi PhiH H H H Phi Phi Phi Phi H H H H DEPARTMENT EMP DEP In [Gog89, Gog94] we have shown how to make the notion of an Entity Relationship schema precise. One can think of it as a signature describing a class of algebras corresponding to the possible database states. In our example this would look as follows. SORTS DEPARTMENT, EMPLOYEE, DEPT EMP, OPERATIONS ....

[Article contains additional citation context not shown here]

M. Gogolla. An Extended Entity-Relationship Model -- Fundamentals and Pragmatics. Springer, Berlin, LNCS 767, 1994.

....variable (t : TOWN ) as a kind of parameter. The query follows the well known select from where structure proposed in SQL. In our approach, the result of a query is a bag of values retaining duplicates; sets can also be obtained by applying an operator eliminating the duplicates (for details, see [Gog94, HG94] The where part is a formula which returns true if the 6 If want we to very precise we have to distinguish syntactically between the type constructor tuple (for example to construct the sort tuple(string; int) and an operation mktuple constructing an appropriate value (for example ....

....Our approach is defined on a formal mathematical basis. Thus, comprehension and implementation is supported without any ambiguities. Due 7 Deep equality again refines to shallow equality and the identity predicate as pointed out in [KC86] to space limitations we have to refer to [Gog94, HG94] for a more elaborate treatment. Retrieving abstract objects by concrete values: Within the observation term approach it is possible to retrieve abstract objects, which are internally identified by surrogates, with the help of concrete data values. After retrieving an object in this way ....

M. Gogolla. An Extended Entity-Relationship Model -- Fundamentals and Pragmatics. Springer, Berlin, LNCS 767, 1994.

....framework for relationships and Use Cases in UML. In the information systems field we are particularly interested in data models and their query languages. We see a strong resemblance between the UML language and notation for class diagrams and traditional Entity Relationship approaches, e.g. [8, 13]. An example comparing a UML class diagram with an EER diagram and integrity constraints in OCL with constraints specified in the EER calculus can be found in [14] The UML might also be appropriate for modeling object oriented database systems according to the ODMG standard [7] In fact, OCL ....

M. Gogolla. An Extended Entity-Relationship Model -- Fundamentals and Pragmatics. LNCS 767. Springer-Verlag, Berlin, 1994.

....bag(s) converts a list to a bag. exploit the distinct properties of certain kinds of sort expressions. For instance, CNT set(s) set(s) nat counts the elements in a set and IN set(s) set(s) Theta s denotes the membership predicate. There are many other generic functions (for details see [25, 23, 27]) All operations induced by sort expressions are summarized in the set Omega (S Expr (S) Analogously all predicates induced by sort expressions are combined in Pi(S Expr (S) From now on let Sigma D = SD ; Omega D ; Pi D ) denote a data signature according to Definition 1 so that Sigma ....

...., and the quantifier 8 might be defined by the given material. With the aggregate functions CNT it is always possible to replace the formula 9ffi( by CNT [ c j ffi; 1 (in which c represents an arbitrary constant term) In this respect quantifiers can be regarded as syntactic sugar [23]. Example (formulas in concrete syntax) x 4 (infix notation of predicate symbols is frequently used) x=y, NOT x=y, x=y AND x=z OR y=z (logical connectives have the usual bindings) and EXISTS p IN PERSON WHERE Name(p) Smith are possible formulas. Definition7 (declarations) The syntax of ....

M. Gogolla, An Extended Entity-Relationship Model --- Fundamentals and Pragmatics, Springer, Berlin, LNCS 767, 1994.

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M. Gogolla. An Extended Entity-Relationship Model: Fundamentals and Pragmatics, volume 767 of Lecture Notes in Computer Science. Springer-Verlag, Berlin, Germany, 1994.

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