A data model, called the entity-relationship model, is proposed. This model incorporates some of the important semantic information about the real world. A special diagrammatic technique is introduced as a tool for database design. An example of database design and description using the model and the diagrammatic technique is given. Some implications for data integrity, infor-mation retrieval, and data manipulation are discussed. The entity-relationship model can be used as a basis for unification of different views of data: t,he network model, the relational model, and the entity set model. Semantic ambiguities in these models are analyzed. Possible ways to derive their views of data from the entity-relationship model are presented. Key Words and Phrases: database design, logical view of data, semantics of data, data models, entity-relationship model, relational model, Data Base Task Group, network model, entity set

Abstract. The correctness of the data managed by database systems is vital to any application that utilizes data for business, research, and decision-making purposes. To guard databases against erroneous data not reflecting real-world data or business rules, semantic integrity constraints can be specified during database design. Current commercial database management systems provide various means to implement mechanisms to enforce semantic integrity constraints at database run-time. In this paper, we give an overview of the semanticintegrity support in the most recent SQL-standard SQL:1999, and we show to what extent the different concepts and language constructs proposed in this standard can be found in major commercial (object-)relational database management systems. In addition, we discuss general design guidelines that point out how the semanticintegrity features provided by these systems should be utilized in order to implement an effective integrity enforcing subsystem for a database. Keywords: Semanticintegrity constraints – SQL:1999 – Object-relational databases – Constraint enforcement

Abstract not found

Abstract. The Resource Space Model (RSM) is a semantic data model based on orthogonal classification semantics for effectively managing various resources in interconnection environment. In parallel with the integrity theories of relational and XML-based data models, this keynote presents the integrity theory for the RSM, including the entity integrity constraints based on the key system of the RSM, the membership integrity constraints, the referential integrity constraints, and the user-defined integrity constraints relevant to applications. This theory guarantees the RSM to correctly and efficiently specify and manage resources. Its implementation approach and application in culture exhibition are demonstrated. 1

Concep..Represented by_System Moles The design of Level 4 includes four modules, each of which repre- sents an abstract concept visible to the system end-user. The RELATION module, for example, defines the operations by which users are able to create, modify, and view the primary data objects (relations) of this level. Likewise, the TUPLE module enables users to create and manipulate n-tuples as seperate entities. The AUTHORIZATION module relates to the concept of security in the data base system. Through the operations of this module it is possible to create authorizations which are assertions defining the allowable user accesses to the abstract data objects of Level 4. Certain operations also make it possible to scan all defined authorizations to determine if a user has access to a specified data object. The INTEGRITY module provides operations for defining and maintaining the semantic integrity of relations. For example, it is possible to create assertions which define allowable of these.

Properties. Given RA, D, and U # as above, a set #={del R 1 (x 1 ), ...,del R n (x n )} of delete requests is called ---founded, if for all del R(x)##, there is a #del R (x # )#U # s.t. (R(x), R # (x # )) # (note that here, we need reflexivity for covering R # (x # ) itself), ---complete,if del R P (y)##and (R C (x), R P (y)) ---feasible, if (i) (R C (x), R P (y)) implies del R P (y) / ##, (ii) del R P (y)##and (R C (x), R P (y)) ---admissible, if it is founded, complete, and feasible.

Abstract. If not all resources accessed by a database transaction are protected from being accessed by other concurrent transactions, then the state “seen ” by the transaction is not necessarily identical to any committed state, nor to any snapshot of the current contents of the stored data. For the theory of concurrent database transactions as well as for all database applications that involve concurrency, it is important to be precise about the states with which theories or applications are dealing. Based on a non-standard notion of data resource, we propose a formalization of committed states, snapshots and I/O states that are ‘seen ’ by concurrent transactions. We intend to apply our concept of states to an application of inconsistency-tolerant integrity checking for concurrent transactions. 1