Entity Relationship Model

Relationships are an integral part of the design of a database. Comparing and integrating relationships from heterogeneous databases requires that the relationships be mapped to each other or to a common classification. Identifying similarities and resolving differences in relationships across large data sources is a resource-intensive task that could benefit greatly from semi-automated approaches. A prerequisite to developing such approaches is a clear understanding of the semantics of relationships used in database design. This research presents a layered ontology for classifying the semantics of relationships. It consists of a core layer that captures the fundamental types of relationships between entities. A middle layer provides the internal context, obtained from entities surrounding the relationship, to interpret the fundamental types. The outer layer allows further interpretation using the external context, that is, the domain in which a relationship is being used. An initial assessment on relationships from a variety of application domains demonstrates that the ontology can be adequate and useful for comparing relationships across databases.

Performance indicators are key feedback drivers of organisation dynamics. However, the extensive evaluation literature gives no scientific basis for the selection or testing of the opportunities of such indicators. This paper discusses the development of a "dynamic balanced scorecard" for a federal government department. The balanced scorecard suffers from the limitation of all performance indicator systems, namely that the interrelationships, and especially delayed feedback, between indicators are overlooked. Therefore it is essential to take such feedback into account. System dynamics is an appropriate methodology to achieve this. The paper outlines the modelling of causal interactions between organisational responses to work overload, staff morale and productivity, rework and output quality. The component sub-models and management implications of the dynamic BSC are discussed.

Little work has been completed which addresses the logical composition and use of ternary relationships in entity-relationship modeling. Many modeling notations and most CASE tools do not allow for ternary relationships. Alternative methods and substitutes for ternary relationship structures do not necessarily reflect the original logic, semantics or constraints of a given situation. Furthermore, it has been shown that ternary relationships can be constrained by additional implicit binary constraints which do not occur in the logic of binary relationships. This paper develops an analytical perspective of ternary relationships. We investigate the logical relationships implicit to the ternary structure and then identify potential simplification through decomposition into binary equivalents. These alternative binary equivalents allow retention of the implicit logical structure, and consequently also retain the semantics of the original structure. The analysis investigates equivalency of lossless decompositions, preservation of functional dependencies and finally the ability to preserve update constraints (insertions and deletions). We identify which ternary relationships have true, fully equivalent, binary equivalents and those which do not. We provide an exhaustive analysis of cardinality combinations found in ternary relationships which practitioners can use to guide the way in which they deal with ternary relationships in conceptual modeling.

The article examines the fundamental principles of Resource Description and Access (RDA), the new guidelines for the description and the discovery of different kinds of resources aimed to replace the AACR2 since 2013. RDA is included in RDA Toolkit – a web site and a database containing tools and resources useful for the RDA application – which is here described in its contents and structure. The sections (attributes, relationships and appendices) are analysed in some points also through schematic tables translated in Italian. The paper examines the rules' structure and focuses on the use of numbered and unnumbered headings in RDA and in AACR former texts. RDA is analyzed as an entity/relationship data model and as a working tool for librarians too.

A new data model has been developed to handle information relevant to site-specific life cycle Ž. assessments LCA. The model is orientated towards GIS-representations of three generalised subsystems; the technical, the environmental and the social subsystems. The technical and environmental systems are mainly linked through flows of energy and matter, which are the causes of environmental impacts, which subsequently is perceived, evaluated and acted upon by the social subsystem. For all three systems important differences, attributable to geographical locations can be determined. With the new data model a possibility to enhance LCA and reach more relevant results emerge due to a higher site specificity. The high level data model is expressed as Ž. relations between different entities using the entity relationship ER modelling language. An existing LCA-database, SPINE, which is already used by several companies for decision support in product development, can be utilised since the structure of the database supports geographical information. So far, applications with GIS-data are limited, but examples of area specific LCA impact characterisation factors exist.

This article reports the results of research into software project management. the main contribution of this research is a software project management framework that consists of a static structure, shown in an entity-relationship diagram, and a description of each component of the framework. It also describes the procedure to design and validate the framework. This consists of integrating the solutions

Traditional client-server applications relegate query and persistence operations on their data to database systems. The database system operates on data in the form of rows and tables, while the application operates on data in terms of higher-level programming language constructs (classes, structures etc.). The impedance mismatch in the data manipulation services between the application and the database tier was problematic even in traditional systems. With the advent of service-oriented architectures (SOA), application servers and multi-tier applications, the need for data access and manipulation services that are well-integrated with programming environments and can operate in any tier has increased tremendously.

1. What two conditions must be met before an entity can be classified as a weak entity? Give an example of a weak entity. To be classified as a weak entity, two conditions must be met: 1. The entity must be existence-dependent on its parent entity. 2. The entity must inherit at least part of its primary key from its parent entity. entity: 1. CLASS is clearly existence-dependent on COURSE. (You can database course exists.) 2. CRS_CODE. The CRS_CODE attribute is also the PK of COURSE. The conditions that define a weak entity are the same as those for a strong relationship between an entity and its parent. In short, the existence of a weak entity produces a strong relationship. And if the entity is strong, its relationship to the other entity is weak. (Note the solid relationship line in the tex decisions. For instance, if the database designer had decided to use a single-attribute as shown in 8, the CLASS entity wou CLASS_CODE, which is not derived from the COURSE entity.) In this case, the relationship between COURSE and CLASS is weak. However, regardless of how the designer classifies the relationship weak or strong CLASS is always existence-dependent on COURSE. 2. A strong relationship exists when en entity is existence-dependent on another entity and inherits at least part of its primary key from that entity. The Visio Professional software shows the strong relationship as a solid line. In other words, a strong relationship exists when a weak entity is related to its parent entity. (Note the discussion in question 1.)

The concept of multiplicity in UML derives from that of cardinality in entity-relationship modeling techniques. The UML documentation defines this concept but at the same time acknowledges some lack of obviousness in the specification of multiplicities for n-ary associations. This paper shows an ambiguity in the definition given by UML documentation and proposes a clarification to this definition, as well as the use of outer and inner multiplicities as a simple extension to the current notation to represent other multiplicity constraints, such as participation constraints, that are equally valuable in understanding n-ary associations.

Distributed data - data, processed by a system, can be distributed among several computers, but it is accessible from any of them. A distributed database design problem is presented that involves the development of a global model, a fragmentation, and a data allocation. The student is given a conceptual entity-relationship model for the database and a description of the transactions and a generic network environment. A stepwise solution approach to this problem is shown, based on mean value assumptions about workload and service. A management system of a distributed database (SGBDD) is a software system that enables management and distributing BDD transparent to the user. A SGBDD consists of a single database which is decomposed into fragments, poassibly some fragments are multiplied, and each fragment or copy kept on one or more sites under the control of a local DBMS. Each site is capable of processing user queries in the local system, independently of the rest of the network, or ...

This paper develops a modularization scheme based on the functional model of a system. The modularization approach makes use of the function-behavior-state (FBS) model of the system to derive the entity relations. The design structure matrix (DSM) is automatically constructed based on the FBS model. In this way, the tedious work of filling the DSM entries based on expert knowledge is avoided. The approach makes use of k-means clustering algorithm to allow the user to try different number of clusters in a fast way. The k-means clustering is adopted for DSM based modularization by defining a proper entity representation, relation measure and objective function. Two modularization schemes are performed, one based on the immediate relations and one on the deeper behavioral relations between the components. Considering the application on the shifting system of the Delft University of Technology (DUT) Formula Student car, the latter modularization resulted in more mechatronic behavior based modules, while the former resulted in modules based on mere disciplinary and spatial closeness.

Specification is often restricted to the description of syntactical elements. This restricted approach can only be used for simple applications with simple structuring. However, most applications require analysis of data, integration or federation of data, advanced aggregation of data, and advanced basic data types.

Data modeling is a process used to define and analyze data requirements needed to support the business processes within the scope of corresponding information systems in organizations. Entity-Relationship modeling is a technique used for data modeling. It is often the first step in database development lifecycle as the database developers/designers first create a conceptual model of how data items relate to each other. This tutorial teaches how to step-by-step create such models by using ER diagram (Hoffer-Prescott-Mcfadden Notation). Data modeling is a very important topic that every IT professional should know, in order to be prepared in the creation of data conceptual models, and to be able to read and understand such models.

Why a new standard? Opportunity to simplify our rules Encourage use as a content standard for metadata schema Encourage international applicability Need for more consistency and less redundancy, for easier use and interpretation Chance to modernize We've moved from card catalogue to online environment but we still have card-based terminology and rules in our cataloguing code.

A methodology for extracting an extended Entity-Relationship (EER) model from a relational database is presented. Through a combination of data schema and data instance analysis, an EER model is derived which is semantically richer and more comprehensible for maintenance and design purposes than the original database. Classification schemes for relations and attributes necessary for the EER model extraction are derived and justified. These have been demonstrated to be implementable in a knowledge-based system; a working prototype system which does so is briefly discussed. In addition, cases in which human input is required are also clearly identified. This research also illustrates that the database reverse engineering process can be implemented at a high level of automation.

The aim of this study was to develop business process reengineering for a supply chain of fourth range vegetable products and to set up a computerised system for managing product traceability.A framework based on event-driven process chains (EPCs) methodology, the entity-relationship model (ERM) and activity-based costing (ABC) is used to define and analyse the current state of a supply chain

Since its introduction, the Entity-Relationship (ER) model has been the vehicle of choice in communicating the structure of a database schema in an implementation-independent fashion. Part of its popularity has no doubt been due to the clarity and simplicity of the associated pictorial Entity-Relationship Diagrams ("ERD's") and to the dependable mapping it affords to a relational database schema. Although the model has been extended in different ways over the years, its basic properties have been remarkably stable. Even though the ER model has been seen as pretty well "settled," some recent papers, notably [4] and [2 (from whose paper our title is derived)], have enumerated what their authors consider serious shortcomings of the ER model. They illustrate these by some interesting examples. We believe, however, that those examples are themselves flawed. In fact, while not claiming that the ER model is perfect, we do believe that the overhauls hinted at are probably not necessary and possibly counterproductive.

The concept of multiplicity in UML derives from that of cardinality in entity-relationship modeling techniques. The UML documentation defines this concept but at the same time acknowledges some lack of obviousness in the specification of multiplicities for n-ary associations. This paper shows an ambiguity in the definition given by UML documentation and proposes a clarification to this definition, as well as a simple extension to the current notation to represent other multiplicity constraints, such as participation constraints, that are equally valuable in understanding n-ary associations.

This paper discusses the rapidly expanding environment of emerging electronic content and the importance of librarians to partner with new research and teaching communities in meeting users" needs to find, identify, select, and obtain the information and resources they need. The methodology and framework of the International Federation of Library Associations and Institutions" Functional Requirements for Bibliographic Records could serve as a useful tool in building expanded access and content systems. ********** In today's information world, whether planned or not, mature library Web sites are used as fully fledged electronic libraries. Most major academic library Web sites offer a substantial array of library services (such as reference, interlibrary loan, reserve services, instructional tutorials, and circulation), with extensive electronic collections. Increasingly, they provide direct links to numerous external discovery tools and services, which often result in c...

Object-role Modeling (ORM) is a fact-oriented modeling approach for expressing, transforming and querying information at a conceptual level. Unlike Entity-Relationship modeling and Unified Modeling Language class diagramming, fact-oriented modeling is attribute-free, treating all elementary facts as relationships expressed in natural language sentences. For information modeling, ORM graphical notations are typically far more expressive than other notations, and ORM's attributefree nature promotes semantic stability and facilitates natural verbalization. Based on industrial experience that identified ways to improve current ORM languages and associated tools, a project is under way to provide open-source tool support for a second generation ORM (ORM 2), that has significant advances over current ORM technology. This paper provides an overview of, and motivation for, the enhancements introduced by the ORM 2 graphical notation.

Database design methodologies should facilitate database modeling, e ectively support database processing and transform a conceptual schema of the database to a high-performance database schema in the model of the corresponding DBMS. The Entity-Relationship Model is extended to the Higher-order Entity-Relationship Model (HERM) which can be used as a high-level, simple and comprehensive database design model for the complete database information on the structure, operations, static and dynamic semantics. The model has the expressive power of semantic models and possesses the simplicity of the entity-relationship model. The paper shows that the model has a well-founded semantics. Several semantical constraints are considered for this model.

In recent years packet-filtering firewalls have seen some impressive technological advances (e.g., stateful inspection, transparency, performance, etc.) and widespread deployment. In contrast, firewall and security management technology is lacking. In this paper we present Firmato, a firewall management toolkit, with the following distinguishing properties and components: (1) an entity-relationship model containing, in a unified form, global knowledge of the security policy and of the network topology; (2) a model definition language, which we use as an interface to define an instance of the entity-relationship model; (3) a model compiler, translating the global knowledge of the model into firewall-specific configuration files; and (4) a graphical firewall rule illustrator. We demonstrate Firmato's capabilities on a realistic example, thus showing that firewall management can be done successfully at an appropriate level of abstraction. We implemented our toolkit to work with a commercially available firewall product. We believe that our approach is an important step towards streamlining the process of configuring and managing firewalls, especially in complex, multi-firewall installations.

We developed a database compiling in vivo doses of compounds for various activities in certain animal species. The related database covers almost 100 years of experiments. The conceptual scheme of the database was created using concepts of the entity-relationship modeling principles. Using published references, dosages and their effects on laboratory animals were entered as data. As the next stage of our work, we have started to examine the available literature to information about the experimental dosages of various drugs used in other studies. The database provides various interfaces, including graphical-user interfaces and interfaces for Internet access. The database will be useful as a knowledge infrastructure for researchers who have to perform dose-scan experiments for a specific pharmacological activity. The basic benefit of that knowledge infrastructure is that it will enable virtual pharmacological experiments that will be considerably less expensive than conventional labor...

Information system (IS) design concerns di erent activities like conceptual modeling, database design, business process modeling and user modeling. However, despite the presence of an active research community that studies conceptual models for information systems, this term still lacks precise formal underpinnings. Unlike for databases, there is no agreement on what constitutes \principles of information systems." It would hence be desirable to provide formal underpinnings for information system design and to position it with respect to database design.

The need to leverage the information contained in het erogeneous data sources has been widely documented in recent years. In order to accomplish this goal, an or ganization must resolve several types of heterogeneity problems that may exist across different data sources. We investigate one such problem called the entity het erogeneity problem. This problem arises when the same real-world entity type is represented using dif ferent identifiers in different applications. We propose a decision-theoretic model to resolve the problem. Our model uses a distance-based measure to express the similarity between two entity instances. We have im plemented the model, and our experimental results in dicate that this is a viable approach in real-world situ ations. 1001 Relation: CUSTOMERl Name I Phone I Address Robert Tracy 274-3388 123 Broad St,

To develop sophisticated database management systems, there is a need to incorporate more understanding of the real world in the information that is stored in a database. Semantic data models have been developed to try to capture some of the meaning, as well as the structure, of data using abstractions such as inclusion, aggregation, and association. Besides these well-known relationships, a number of additional semantic relationships have been identified by researchers in other disciplines such as linguistics, logic, and cognitive psychology. This article explores some of the lesser-recognized semantic relationships and discusses both how they could be captured, either manually or by using an automated tool, and their impact on database design. To demonstrate the feasibility of this research, a prototype system for analyzing semantic relationships, called the Semantic Relationship Analyzer, is presented.

En la práctica los esquemas Entidad Interrelación generados durante la modelación conceptual no son capaces de especificar  restricciones,  necesarias para garantizar la integridad de un sistema de infomación. Aunque han existido intentos, la comunidad de diseñadores de  bases de datos  no ha adoptado una práctica para el diseño de la integridad de un  sistema de información  dado un esquema  entidad interrelación  del universo de discurso. Por tanto es necesario seleccionar un lenguaje con gran nivel de captación semántica para especificar restricciones. Para ello se  eligió el lenguaje natural controlado RuleSpeak, unido al Semantic of Business Vocabulary and Rules. Finalmente, se muestra la  especificación de aquellas restricciones de integridad definidas por el modelador e impuestas por un agente autorizado del negocio.Palabras clave: lenguaje natural, restricciones de integridad, RuleSpeak, SBVR, sistemas de información.

Database development has mainly be considered as development of database structuring. Functionality and interactivity specification has been neglected in the past. The derivability of functionality has been a reason for this restriction of the database design approach. At the same time, applications and the required functionality became more complex. Functionality specification may be based on workflow engines. Interaction support is often not specified but hidden within the interfaces. It may, however, be specified through the story space and the supporting media type suite. Distributed applications are based on an explicit specification of import/export views, on services provided and on exchange frames. The integration of all these parts has not yet been performed. The co-design approach aims in bridging all these different aspects of applications and provides additionally a sound methodology for development of all these aspects.

A concept for performing threat analysis is developed. The goal is to establish a systematic approach for predicting, detecting and characterizing threat activity; allowing automation of some of these functions. The proposed approach explicitly addresses the fundamental problems of (a) sparse and ambiguous indicators of potential or actualized threat activity buried in massive background data; and (b) uncertainty in threat capabilities, intent and opportunities. Threats are modeled in terms of potential and actualized relationships between perpetrators (threatening entities) and targets (threatened entities). Threats may be intentional or unintentional (e.g. potential natural disasters or human error). Intentional threats can also have unintended consequences. Attack hypotheses are adaptively generated, evaluated and refined as the understanding of the situation evolves. This effort builds upon advances in Situation, Ontology and Estimation theory.

Abstract. The concept of multiplicity in UML derives from that of cardinality in entity-relationship modeling techniques. The UML documentation defines this concept but at the same time acknowledges some lack of obviousness in the specification of multiplicities for n-ary associations. This paper shows an ambiguity in the definition given by UML documentation and proposes a clarification to this definition, as well as a simple extension to the current notation to represent other multiplicity constraints, such as participation constraints, that are equally valuable in understanding n-ary associations.

Database development has mainly be considered as development of database structuring. Functionality and interactivity specification has been neglected in the past. The derivability of functionality has been a reason for this restriction of the database design approach. At the same time, applications and the required functionality became more complex. Functionality specification may be based on workflow engines. Interaction support is often not specified but hidden within the interfaces. It may, however, be specified through the story space and the supporting media type suite. Distributed applications are based on an explicit specification of import/export views, on services provided and on exchange frames. The integration of all these parts has not yet been performed. The co-design approach aims in bridging all these different aspects of applications and provides additionally a sound methodology for development of all these aspects.

This paper concerns the modeling of imprecision, vagueness, and uncertainty in databases through an extension of the relational model of data: the fuzzy rough relational database, an approach which uses both fuzzy set and rough set theories for knowledge representation of imprecise data in a relational database model. The fuzzy rough relational database is formally defined, along with a fuzzy rough relational algebra for querying. Comparisons of theoretical properties of operators in this model with those in the standard relational model are discussed. An example application is used to illustrate other aspects of this model, including a fuzzy entity᎐relationship type diagram for database design, a fuzzy rough data definition language, and an SQL-like query language supportive of the fuzzy rough relational database model. This example also illustrates the ease of use of the fuzzy rough relational database, which often produces results that are better than those of conventional databases since it more accurately models the uncertainty of real-world enterprises than do conventional databases through the use of indiscernibility and fuzzy membership values. ᮊ

Significant effort is expended in developing a high-level conceptual schema for a relational database. However, criticalknowledge is often discarded when the conceptual schema is mapped to aset of relation schemas. As a result, designers and users must employsparser logical-level knowledge to access data. Unfortunately, naiveusers do not possess the detailed logical-level knowledge required toformulate queries corresponding to ad hoc requests.

Reiner@CCA UUCP: decvax!cca!reiner Database Engineering Bulletin is a quarterly publication of the IEEE Computer Society Technical Committee on Database Engineering. Its scope of interest includes: data structures and models, access strategies, access control techniques, database architecture, database machines, intelligent front ends, mass storage for very large databases, distributed database systems and techniques, database software design and implementation, database utilities, database security and related areas. Contribution to the Bulletin is hereby solicited. News items, letters, technical papers, book reviews, meeting previews, summaries, case studies, etc., should be sent to the Editor. All letters to the Editor will be considered for publication unless accompanied by a request to the contrary. Technical papers are unretereed. Opinions expressed in contributions are those of the indi vidual author rather than the oflicial position of the TC on Database Engineering, the IEEE Computer Society, or orga nizations with which the author may be affiliated. Associate Editors, Database Engineering Dr. Haran Boral Microelectronics and Computer Technology Corporation (MCC) 9430 Research Blvd.

Ontology is the fundamental part of Semantic Web. The goal of W3C is to bring the web into (its full potential) a semantic web with reusing previous systems and artifacts. Most legacy systems have been documented in structural analysis and structured design (SASD), especially in simple or Extended ER Diagram (ERD). Such systems need up-gradation to become the part of semantic web. In this paper, we present ERD to OWL-DL ontology transformation rules at concrete level. These rules facilitate an easy and understandable transformation from ERD to OWL. The set of rules for transformation is tested on a structured analysis and design example. The framework provides OWL ontology for semantic web fundamental. This framework helps software engineers in upgrading the structured analysis and design artifact ERD, to components of semantic web. Moreover our transformation tool, ER2OWL, reduces the cost and time for building OWL ontologies with the reuse of existing entity relationship models.

Information modelling is a fundamental tool in the development of information systems. Numerous data modelling languages, such as the Entity Relationship Model, Functional Data Model or Object Oriented Data Model, have been proposed over the years with each purporting to have qualities and advantages not shared by their rivals. The claims are typically qualitative in their nature and it is difficult to provide rigorous support for these claims. The aim of this paper is to provide a methodological framework for the analysis of data modelling tools and for sharpening our understanding of those tools. The framework proposed here is based on ontology, which is the philosophical study of the fundamental categories of "what exists''. The framework uses a given ontology as a "lense'' through which to compare the world views embodied within specific data modelling tools. We propose the Method of Conceptual Comparison and the Method of Conceptual Evaluation for the qualitative analysis of data modelling languages and show how Chisholm's ontology can be used as an underlying theory for these methods. We briefly sketch the application of the method of conceptual comparison and summarise our findings for various data modelling languages.

We explore the criteria that contribute to the structural validity of modeling structures within the entityrelationship (ER) diagram. Our approach examines cardinality constraints in conjunction with the degree of the relationship to address constraint consistency, state compliance, and role uniqueness issues to derive a complete and comprehensive set of decision rules. Unlike typical other analyses that use only maximum cardinality constraints, we have used both maximum and minimum cardinality constraints in defining the properties and their structural validity criteria yielding a complete analysis of the structural validity of recursive, binary, and ternary relationship types. Our study evaluates these relationships as part of the overall diagram and our rules address these relationships as they coexist in a path structure within the model. The contribution of this paper is to provide a comprehensive set of decision rules to determine the structural validity of any ERD containing recursive, binary, and ternary relationships. These decision rules can be readily applied to real world data models regardless of their complexity. The rules can easily be incorporated into the database modeling and designing process, or extended into case tool implementations.

A Machine Readable Dictionary (MRD or Lexicon) can be designed as a large-scale lexical database, having the task of supporting many different applications such as morphological, syntactic and semantic processing, information retrieval, machine translation, educational tools, etc. Regardless of how different these applications may be, they need a comprehensive lexical database to rely on, since it is quite wasteful to develop a different lexicon for each application. This paper deals with a method for designing and organizing a multi-purpose morpheme-based lexical database for Greek. The authors are in favor of morpheme-based lexical databases in order to avoid a repetition of effort from one application to another, and in order to achieve flexibility, reusability and expandability. The proposed method for modeling the lexical database is the Entity/Relationship model, which was originally designed for natural language processing. Even though our system was tested in Greek language, these methods could also be applicable to other languages having similar morphological systems to that of Greek.

This paper addresses DW design problems, with the goal of improving the DW logical design process. Some of the existing work in transformation oriented methodologies for DW design construct the DW starting from an Entity-Relationship model of the source database, and arrive to a conceptual or highlevel-logical dimensional model of the DW. We propose a mechanism for obtaining the DW logical schema through pre-defined transformations applied to the source logical schema, which can be used as a complement to the existing DW design methodologies. The transformations allow a refined logical design of the DW and provide a trace of the design and a mapping between the source and DW logical structures.

OLAP (On-Line Analytical Processing) tools support the decision-making process by giving users the possibility to dynamically analyze high volumes of historical data using operations such as roll-up and drill-down. These operations need well-defined hierarchies in order to prepare automatic calculations. However, many kinds of complex hierarchies arising in real-world situations are not addressed by current OLAP implementations. Based on an analysis of real-world applications and scientific works related to multidimensional modeling, this paper presents a conceptual classification of hierarchies and proposes graphical notations for them based on the ER model. A conceptual representation of hierarchies allows the designer to properly represent users' requirements in multidimensional modeling and offers a common vision of these hierarchies for conceptual modeling and OLAP tools implementers. Time key Day M onth Q uarter Year Event W eekday flag W eekend flag Season O ther attributes Tim e Time fkey Store fkey Product fkey Quantity Sales Cost Num clients Sales facts Store key Store nam e Store num ber Store address City fkey

The Entity-Relationship model is frequently used during conceptual database design phases. However, this model can be enriched and then used for the complete lifecycle of a database as an interface model. For this purpose, the concepts of the ER-model need to be theoretically wellfounded. The aim of this paper is to show how the theoretical basis of one of the most important class of integrity constraints can be constructed and then used for the exploitation in practical database tasks. The concept of cardinality constraints is defined, generalized and used for the simplification of the design, for the improvement of maintenance programs and for the detection of problematic design decisions.

Data modelling reveals the internal structure of an information system, abstracting away from details of the physical representation. We show that entity-relationship modelling, a well-tried example of a data-modelling technique, can be applied to both interactive and non-interactive information artefacts in the domain of HCI. By extending the conventional ER notation slightly (to give ERMIA, Entity-Relationship Modelling for Information Artefacts) it can be used to describe differences between different representations of the same information, differences between user's conceptual models of the same device, and the structure and update requirements of distributed information in a worksystem. It also yields symbolic-level estimates of index of 'cost-of-knowledge' in an information structure, plus a novel index, the 'cost-of-update'; these symbolic estimates offer a useful complement to the highly detailed analyses of time costs obtainable from GOMS-like models. We conclude that, as a cheap, coarse-grained, and easy-to-learn modelling technique, ERMIA usefully fills a gap in the range of available HCI analysis techniques.

We compare EER and OO data models from the point of view of design quality. Quality is measured in terms of (a) correctness of the conceptual schemas being designed, (b) time to complete the design task, and (c) designers' preferences of the models. Result of an experimental comparison of the two models reveal that the EER model surpasses the OO model for designing unary and ternary relationships, it takes less time to design EER schemas, and the EER model is preferred by designers. We conclude that even if the objective is to implement an OO database schema, the recommended procedure is to: (1) create an EER conceptual scheme, (2) map it to an OO schema, and augment the target schema with behavioral constructs that are unique to the OO approach.