M. Scholl, C. Laasch, and M. Tresch. Updatable Views in Object-Oriented Databases. In Proc. of DOOD'91, pages 189--207, Munich, Dec. 1991.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....we outline future work. 2 Main characteristics of the Osiris system The Osiris system is an implementation of the p type model defined in [SalesSimonet, 84] This model aims at sharing data through views and statically analysing integrity constraints. In Osiris views are object preserving [Scholl et al. 91] i.e. they are defined as subsets of existing objects. Object generating views (i.e. views that create new objects, as in relational systems) are not permitted. This functionality will be implemented by allowing the creation of new types whose extensions will be defined as general queries. A ....

: Scholl, Laasch, Tresch, Updatable Views in Object-Oriented Databases , Proc. 2nd Intl. Conf. on Deductive and Object-Oriented Databases (DOOD), Lecture Notes in Computer Science, n 566, 1991.

....contexts are: ffl Information bases: An information base describes a set of conceptual entities from the point of view of its designer. Certainly, the designer s viewpoint is influenced by the particular needs of the targeted users. ffl View schemas: A view schema in an object oriented database [23, 1, 18], or in a relational database [7, 2] describes the conceptual entities in the view according to the person that defined that view. ffl Multiversion objects: A multiversion object refers to a set of versions of a generic object [4, 12] Therefore, a multiversion object can be seen as a context ....

Marc H. Scholl, Cristian Laasch, and Markus Tresch. Updatable Views in Object-Oriented Databases. In Proc. of the 2nd Int. Conf. on Deductive and Object-Oriented Database Systems, pages 189--207, Munich, December 1991.

....learning [25, 44, 23] and knowledge representation [28, 42, 40, 46, 8, 38, 6, 4] See also [26] for a general survey on the subject. However, all these notions of context are very diverse and serve different purposes. In software development the notion of context appears in the form of views [3, 11, 14, 33, 1], aspects [31] and roles [12, 34] for dealing with data from different perspectives, or even in the form of workspaces which are used to support cooperative work [19] In machine learning, context is treated as environmental information for concept classification [25, 44, 23] In so called ....

M. Scholl, C. Laasch, and M. Tresch. Updatable Views in Object-Oriented Databases. In Proceedings of the 2nd Int. Conf. on Deductive and Object-Oriented Database Systems, pages 189--207, Munich, Dec. 1991.

....view definition A concept of object oriented views is based on the object oriented paradigm with the notion of objects, classes, and inheritance. There are two basic approaches to view definition. In the first one a view is defined as a virtual class derived from one [3] or more classes [1, 2, 4, 5, 6, 10, 11, 14, 15, 18, 20, 21], called base classes. The second one defines a view as a portion of a database schema containing virtual as well as base classes [17] This concept was implemented in a MultiView system. In this system a view, called view schema, is constructed in the three following steps: first, virtual classes ....

....When virtual classes are created they shotfid also form inheritance hierarchy. Since a virtual class can be der reed using more complex operations that affect not only its type but also extent, it may be difficult to find for such a class a right position in a hierarchy (see for the discussion [17, 20]) To cope with the problem of integration of virtual classes in a database schema two main concepts were developed: 1) generation of intermediate classes, and (2) introduction of additional relationship between a virtual class and its base class. In the first concept [3] MultiView [17] and ....

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M.H. Scholl, C.Laasch, M.Tresch, Updatable Views in Object-Oriented Databases, Int. Conf. Deductive and Object)riented Databases, 1991

....databases [7] are mainly information retrieval oriented, i.e. few possibilities are given to applications running against a view to update the real data s. Views in an ODBMS allow both an efficient retrieval of information and the possibility for applications to update the real data (see [25] [18]) They are therefore much more suitable for simulation purposes which, de facto, implies data to be read but also to be modified. Views as defined for relational databases modify only the perception presentation of the real schema they are based on, but no real modification is performed on the ....

C. Laasch, M.H. Scholl, and M. Tresch. Updatable views in object-oriented databases. In Proc. of the 2nd International Conference on Deductive and Object-Oriented Databases, number 566 in LNCS, Munich, Germany, December 1991. Springer Verlag.

....hierarchy. 1. 3 Related Work Several approaches to object oriented views were proposed in scientific publications (the review can be found in [20] In the majority of approaches a view is defined as a virtual class derived from one or more classes [1] 3] 4] 5] 9] 10] 14] 17] [18], 19] called base classes. The approaches of MultiView [16] and eXor C [6] 7] consider a view as a more complex structure, i.e. a schema. In MultiView a view is deftned as a portion of a database schema containing virtual as well as base classes. In eXoT C a view, called external schema, is ....

....view, called external schema, is composed of derived classes only but the eXoT C views can reference base classes in domains of attributes and method calls. Another aspect to cosider when defining object oriented views is the integration of virtual classes in a database schema. The approaches of [18], MultiView, and [3] integrate virtual classes in a base schema. Because the integration of view classes in a database schema leads to a few serious problems (see [20] for a survey) the approaches of: 19] 02Views [17] 13] eXor C, and Uni SQL [10] use a separated schema for virtual classes. ....

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Scholl, M. H., Laasch, C., Tresch, M.: Updatable Views in Object-Oriented Databases. In proc. Int. Conf. Deductive and Object4)riented Databases, 1991

....For such applications, data should be stored locally, i.e. materialised. The application of object oriented views in this area is very promising. Another aspect to be considered when defining an object oriented view is finding the right place of a victual class in a schema. The approaches of [4], MultiView, and [5] integrate virtual classes in a database schema. Because the integration of view classes in a database schema leads to a few serious problems, the approaches of: 6] 02Views [7] eXoT C, and Uni SQL [8] use a separated schema for virtual classes. When views are used in a ....

Scholl M. H., Laasch C., Tresch M., Updatable Views in Object-Oriented Databases, Proc. of DOOD, 1991, LNCS No. 566, pp. 189-207

.... (by means of a declarative language like SQL) In addition, its functionalities should be extended to take into account the richness of the object oriented model (e.g. adding or redefining methods) In order to include such functionalities in OODBs, in the 90 s, numerous proposals were developed [1, 2, 8, 13, 16, 18] so that the three level ANSI SPARC architecture can be applied for OODBs as in RDBs. In general, these works use particular object models and they differ respect to the schema where the integration of derived classes is In the object oriented context, some authors identify the term view with ....

....for multidatabases, it is also valid to define derived classes in any OODB. The proposed syntax, shown below, is very similar to the ODMG named queries and the one used in RDBs. CreateView DerivedClass as OQLQuery This extension is not a full view mechanism like the object algebras proposed in [9, 13, 18], but it allows the definition of true derived classes which can be also used as input for defining other derived classes. Operations like the ones defined in those object algebras (i.e. projection, selection, join, and so on) may be used to define derived classes in the ODMG framework. However, ....

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M.H. Scholl, C. Laasch, M. Tresch, "Updatable Views in Object-Oriented Databases", Proc. Of the 2nd DOOD. LNCS, Springer, 1991, pp. 189-207.

....the target class name into the roleSet of the object. Through update propagation, this kind of object migration can also be carried out in the same way as the first situation. 7 Related Work In the recent years, a lot of view mechanisms have been developed for OODBs. Most of them [20] 10] 9] 1][17] [15] were realized based on query processing. There are mainly two ways to perform query processing on views. One way is to materialize the derived classes. The other way is to get rid of derived classes by transforming a query into an equivalent set of subqueries which refer to the base ....

Marc H. Scholl, Christian Laasch, Markus Tresch, Updatable Views in Object-Oriented Databases, Proceeding of the 3th DOOD Conference, pp. 189-207 (1991)

....1996) Respect to the derived classes and external schema definition mechanisms, there are two main approaches, depending on the relationship existing between external and conceptual schema. In the first approach, external schemas are subschemas of the conceptual schema (Rundensteiner, 1992a; Scholl et al. 1991) so all the classes in an external schema have to be included in the conceptual schema. Derived classes are integrated in the conceptual schema following the object oriented paradigm (only is a relationships are used) and the definition semantic used is object preserving. Due to the fact that a ....

.... model in which an external schema definition mechanism for OODB is based on, must allow to differentiate between types and classes in order to define is a relationships successfully, offer support to solve the positioning problem of derived classes, and allow the selection of object semantics (Scholl et al. 1991; Motschnig Pitrik, 1996) These issues will define the functionality of the derived class definition mechanism. The proposed mechanism, intends to take advantage of each group of methodologies (to use of repository and to obtain easier schemas) avoiding the problems of each one (complex schemas ....

: Scholl, M.H., Laasch, C. Tresch, M. Updatable Views in ObjectOriented Databases. In Proc. of the 2nd DOOD. pp. 189-207. 1991

....external schemas. The base or conceptual schema is, in the relational model; composed of a set of relations. Views are also relations computed by operators of the relational algebra. Object oriented databases (OODBs) view mechanisms adhere to the same principles as relational views ( 2] 3] [4]) In the object model, views acquire the status of class. Their extension is computed from a query and they are updatable [4] They provide a specialized interface to base classes. However, the semantics of the object model is richer than the relational one and this pose new questions. One of the ....

....relations computed by operators of the relational algebra. Object oriented databases (OODBs) view mechanisms adhere to the same principles as relational views ( 2] 3] 4] In the object model, views acquire the status of class. Their extension is computed from a query and they are updatable [4]. They provide a specialized interface to base classes. However, the semantics of the object model is richer than the relational one and this pose new questions. One of the most complex questions concerns the insertion of a view class in the generalization specialization hierarchy. This insertion ....

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M.H. Scholl, C. Laasch, and M. Tresch. Updatable Views in Object-Oriented Databases. In Proceedings of the Deductive and Object-Oriented Databases, Second International Conference, pages 189-205, December 1991.

.... existing data may be affected and, controlling the impact of changes to persistent objects becomes an important issue [Ber91, FMZ94, FFM 95] The concept of view, dealing with change management issues, has been introduced by a number of authors working on the object model [AB91, Ber91, LST91] Moreover, to promote logical independence, data seen through a view should be manipulated as ordinary data. In particular, updates must be allowed on such data. View updates have been extensively studied in the relational framework and should be revisited in the object context. First steps in ....

....data seen through a view should be manipulated as ordinary data. In particular, updates must be allowed on such data. View updates have been extensively studied in the relational framework and should be revisited in the object context. First steps in that direction have been proposed in [LST91] providing update primitives for views defined through a particular object algebra. Nevertheless, very little has been said about object view updates and, to the best of our knowledge, no commercial object database has implemented a view mechanism to date. The main contribution of this paper is ....

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C. Laasch, M.H. Scholl, and M. Tresch. Updatable views in object-- oriented databases. In Proc. of the 2nd Int. Conference on Deductive and Object--Oriented Databases, number 566 in LNCS, Munich, Germany, December 1991. Springer Verlag.

....schema contains only consistent (valid) relationships between its classes. A complete schema contains all the non redundant relationships existing between any two classes of it. In this paper, a new kind of closure, named reduction closure, is proposed. Unlike the one used in most existing works [Abit91, Scho91, Rund92a, Bert96, Guer97], reduction closure generates closed external schemas without adding classes to the set of classes selected to compose the external schema. Instead, classes with external references are replaced with classes that hide those references. Reduction closure can be used as a method to define external ....

.... external schemas) and the repository schema (metaschema) is still an object oriented schema [Torr01b] In our mechanism, unlike in [Sant95, Guer97] classes of the external schemas are related only using inheritance, aggregation and associations (i.e. ODMG relationships) In addition, unlike in [Scho91, Rund92a], external schemas are defined without generating intermediate and possibly meaningless classes. Nevertheless, some intermediate interfaces may be generated when two classes that are not related by means of inheritance have common behaviour. Figure 1 illustrates the class hierarchy corresponding ....

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Scholl, M.H., Laasch, C. Tresch, M. 'Updatable Views in Object-Oriented Databases'. In Proc. Of the 2nd Deductive and Object-Oriented Databases. pp. 189-207. 1991

....use a virtual class mechanism for instantiating views in object oriented databases. Here, classes for views are explicitly de ned where the attributes of these classes are really methods that retrieve the information from where it is actually stored. Views do not preserve object identity [7] In [8], views are speci ed by a set of query operators which preserve the object identity. Each view class holds a type and an extension. 8] gives details on how to insert viewclasses in the global schema. 9] follows the work of [8] and introduces the notion of external schema or view. In [9] a view ....

....the attributes of these classes are really methods that retrieve the information from where it is actually stored. Views do not preserve object identity [7] In [8] views are speci ed by a set of query operators which preserve the object identity. Each view class holds a type and an extension. [8] gives details on how to insert viewclasses in the global schema. 9] follows the work of [8] and introduces the notion of external schema or view. In [9] a view is a coherent subset of classes and view classes from the global schema. A view is a schema which describes relevant information for a ....

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M.H. Scholl, C. Laasch, and M. Tresch. Updatable Views in Object-Oriented Databases. In Proceedings of the Deductive and Object-Oriented Databases, Second International Conference, pages 189205, December 1991.

....object image of the relational schema. We do not address this issue here but provide a simple language that can be used to implement these approaches and that supports efficient optimization strategies. This language is defined in the same spirit as existing object views languages (e.g. AB91, SLT91, Ber91, Run92, DdST95] Classes USER SYSTEM Optimized Algebraic Representation Preliminary Processing Optimization Code Generation Object DDL Program 1 2 3 5 4 6 Migration Control Environment Transaction Launching 7 P1 P2 . Pn Physical Constraints Specification ....

M. H. Scholl, C. Laasch, and M. Tresch. Updatable Views in Object-Oriented Databases. In Proc. of Intl. Conf. on Deductive and Object-Oriented Databases (DOOD), 1991.

....unfortunately remain very limited in terms of flexibility and recovery. There are two aspects to bulk loading : i) specifying source target transformations and (ii) populating the underlying database. The first aspect has been studied in different database research areas such as views [AB91, SLT91, Ber91, Run92, DdST95] format conversion and data integration [CHS 95, Kos96, DK97, TRV96, Jun, PGMW95, FFK 98, CDSS98, MZ98] The aim of these works were not always to achieve bulk loading and we cite them only to point out that if bulk loading aspects arise, our approach can be used in ....

M. H. Scholl, C. Laasch, and M. Tresch. Updatable Views in Object-Oriented Databases. In Proc. of Intl. Conf. on Deductive and Object-Oriented Databases (DOOD), 1991.

....The CSCW environments of a VE can be shared by more than one user who participates in cooperative work. This is similar to that of defining views in databases for each user. Views are very important in databases where they are used to speed up the query processing on large amounts of data [3, 8, 12, 13, 17, 18, 19]. In this paper, we extend the definition of database view in order to define two types of CSCW environments, namely, local and global environment, for supporting VEs. The local environment defines the available data and operations to each user, and the global environment defines data and ....

M. H. Scholl, C. Laasch, and M. Tresch. Updatable Views in Object-Oriented Databases. In Proceeding of the 3th DOOD Conference, pages 189--207, 1991.

....[76, 130, 71] and knowledge representation [84, 122, 126, 121, 135, 31, 116, 26, 18] See also [80] for a general survey on the subject. However, all these notions of context are very diverse and serve different purposes. In software development the notion of context appears in the form of views [7, 44, 49, 98, 2], aspects [92] and roles [45, 99] for dealing with data from different perspectives, or even in the form of workspaces which are used to support cooperative work [56] In machine learning, context is treated as environmental information for concept classification [76, 130, 71] In the so called ....

....incomplete descriptions which arise because of different responsibilities or roles assigned to the agents. The combination of an agent and its view that the agent holds form a viewpoint [33] where each viewpoint constitutes a context. i) View schemas. Aviewschema in an object oriented database [98, 2, 81], or in a relational database [44, 7] constitutes a context, whereas the view itself constitutes the contents of the context. j) Multiversion objects. A multiversion object refers to a set of versions of a generic object [20, 56] Therefore, a multiversion object can be seen as a context ....

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Marc H. Scholl, Cristian Laasch, and Markus Tresch. Updatable Views in Object-Oriented Databases. In Proceedings of the 2nd Int. Conf. on Deductive and Object-Oriented Database Systems, pages 189--207, Munich, December 1991.

....and knowledge representation [22] 34] 32] 37] 7] 30] 5] 4] See also [20] for a general survey on the subject. However, all these notions of context are very diverse and serve different purposes. In software development the notion of context appears in the form of views [3] 10] [26], 1] aspects [25] and roles [11] 27] for dealing with data from different perspectives, or even in the form of workspaces which are used to support cooperative work [16] In machine learning, context is treated as environmental information for concept classification [19] 17] In so called ....

M. Scholl, C. Laasch, and M. Tresch. Updatable Views in Object-Oriented Databases. In Proc. of DOOD'91, pages 189--207, Munich, Dec. 1991.

....di erent classes of principals but again does not separate policy speci cations from application implementation. The concept of views as an access control concept was rst used for a distributed object system in [Hag94] Views are also used for protection in relational and object oriented databases[SLT91]. Their use for access control purposes resembles the use of type abstraction as a protection concept. Unlike database views that can span multiple types, a view in our model is restricted to objects of a single IDL type. Joining views on di erent IDL types T 1 ; Tn can, however, be modeled ....

Marc H. Scholl, Christian Laasch, and Markus Tresch. Updatable views in object{oriented databases. In Proc. 2. Int. Conf. on Deductive and Object{Oriented Databases, number 566 in LNCS, pages 189-207, Berlin, Germany, 1991. Springer.

....1 Another such system is MultiView [KR96] 1 We finally mention here that our model is independent also of the particular way the class hierarchy in the view is determined. Various approaches to automated inference of the view class hierarchy have been described in the literature (e.g. [AB91, Run94, SLT91]) The further organization of this paper is as follows. Section 2 recalls the basic notions concerning method schemas. Section 3 presents an abstract model of behavioral views. Section 4 defines our extension to method schemas to realize this abstract model. Section 5 deals with consistency ....

M.H. Scholl, C. Laasch, and M. Tresch. Updatable views in objectoriented databases. In Delobel et al. [DKM91], pages 189--207.

....operation specified through a view. Not all views can be updated the problem of how updates on views can be translated into appropriate updates on the underlying relations is discussed in [27, 79] View updates in object oriented models can be simplified if operations are object preserving [125], meaning that the results of queries are pointers to the input objects (rather than new objects or tuples) allowing updates to immediately propagate from views to base objects and vice versa. View maintenance is the inverse problem of how updates on database relations should be reflected in ....

....Definition Language Dye is a database view definition language which we propose for the purpose of defining and maintaining active views of hygraphs. The Dye language is an object oriented algebra that employs schema preserving relational algebra operations 1 with object preserving semantics [125]. Objects (and their data) are created and destroyed by database insertions and deletions, and can be added to or removed from any number of sets. The idea of object oriented algebras is not new; one similar model is employed in the COCOON system [125] One goal of such hybrid languages is to ....

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M.H. Scholl, C. Laasch, and M. Tresch. Updatable Views in Object-Oriented Databases. In DOOD '91, pages 189--207, 1991.

....Student and Employee and want to de ne a new class FemaleMember. We 1 naturally want the class FemaleMember to share Student objects and Employee objects that are considered as female. Such a situation cannot be directly modeled by a simple partial ordering. There are some proposals [TYI88, SLT91, AB91] that attempt to overcome this limitation by dynamically generating appropriate classes and then placing them in a class hierarchy. However, this process generally requires the generation of intermediate classes to conform to the presupposed model of extent inclusion based on a partial ....

M. H. Scholl, C. Laasch, and M. Tresch. Updatable views in object-oriented databases. In Deductive and Object-Oriented Databases, number 566 in LNCS, pp. 189-207. SpringerVerlag, Dec. 1991.

....in the object oriented paradigm, views can be used not only for adapting the structure of data to different kinds of applications, but also for redefining the behavior of objects in different contexts. Despite the number of recent proposals of view mechanisms for object oriented databases [AB91, Ber91, HZ90, RB92, SLT91, SS89, TYI88, SDA94], there is very few account on actual implementations [SLT91, KR93] The implementation of views in relational databases has raised a number of interesting issues concerning querying, data integrity, updates and performance [Ker86, Tem86] With objectoriented views, old problems, such as view ....

....different kinds of applications, but also for redefining the behavior of objects in different contexts. Despite the number of recent proposals of view mechanisms for object oriented databases [AB91, Ber91, HZ90, RB92, SLT91, SS89, TYI88, SDA94] there is very few account on actual implementations [SLT91, KR93]. The implementation of views in relational databases has raised a number of interesting issues concerning querying, data integrity, updates and performance [Ker86, Tem86] With objectoriented views, old problems, such as view materialization and view updates, must be reconsidered, given the ....

M. H. Scholl, Christian Laasch, and Markus Tresch. Updatable Views in ObjectOriented Databases. In Proc. DOOD, Munich, Germany, 1991.

....and updating through views. 1 Introduction It has been agreed that, as for relational databases, views are an important tool for adapting data interface to the needs of different applications in objectoriented databases (OODBs) Despite the number of recent proposals for view mechanisms in OODBs [1, 5, 10, 13, 14, 11], there is very few account on prototype implementations and, to date, no commercial OODB system features views. In this paper, we discuss the design and implementation of an object oriented view mechanism in the light of an experience with the design and implementation of O 2 Views [12] a view ....

M. H. Scholl, Christian Laasch, and Markus Tresch. Updatable Views in ObjectOriented Databases. In DOOD, 1991.

....OODB H. M. Haav 2.2.1 Introduction The theory of lattices provides a natural basis for analysis of class and object hierarchies (or lattices) that occur in OO programming and database world. This has been recognized by several OO Programming and Database researchers during the few last years [17, 1, 7, 13, 32]. The purpose of the research is to clarify the meaning of class and object lattices used as underlying semantic structure for different query languages for 7 OODB. The report provides an analysis of lattice based languages. It also points to problems that arise when dealing with evolution of ....

....lattices are seen as static structures. It does not correspond to reality of OODB applications, where updatable (changeable) classes, objects and these lattices are very important to support. There are some proposals about using views (derived classes) as mechanism for schema evolution in OODB [13, 32]. Languages supporting such facilities are mainly based on algebraic approach [32, 28] They have been developed on the basis of nested relational data model and its query languages. Logic based languages for complex objects use object lattices to give semantics for the formulas [17, 18, 1, 34] ....

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Scholl M. H., Laasch C. and Tresch M. Updatable Views in Object-Oriented Databases, DOOD'91, LNCS 566, 1991.

....classes, and the view instances are of class Person the view class. Both the source collection classes and the view collection class are set. 8.2. 2 Use of views Many suggestions have been made about and reasons given for the possible use of views in object oriented databases [SS89, HZ90, SLT91, Bra92, Ber92, PMSL94, SAD94] The ones suggested most often are, ffl Information Hiding ffl Support of Versions ffl Information Restructuring ffl Content based Access Control ffl Query Shorthand ffl Integrating Heterogeneous Systems ffl Defining Dynamic Collections ffl Data Independence ffl ....

....generation of new objects is not necessary in some circumstances. The elimination of duplicates is a result of forming tuples in the first step of a projection. This approach, however, allows the restructuring that the previous proposal does not. Scholl s Proposal The algebra proposed in [SS90, SLT91] contains two non class generating operations: oe f (select) and Gamma (difference) and the following class generating operations: f (project) ffl f (extend) union) and (intersection) Selection (oe f ) creates a new collection whose elements satisfy the condition f. Projection ( f ....

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M. Scholl, C. Laasch, and M. Tresch. Updatable Views in Object-Oriented Databases. In Proceedings of the International Conference on Deductive and Object-Oriented Databases, volume 566 of Lecture Notes in Computer Science, pages 189--207. Springer-Verlag, 1991.

....derived classes 1 given fewer materialized derived classes. In this paper, we demonstrate our solution of the SVR problem on the MultiView [13] and the TSE systems [18] However, while we base our experiments on given systems, we believe the proposed methods also benefit other similar systems [1, 22, 24]. Removing obsolete view schemas will also shorten the forward backward conversion function search for Lautemann s work [15] on schema versions, and a similar technique could be used for view maintenance purpose for alternate view mechanisms proposed by others [11, 23] For a further discussion ....

....identify derived classes if the base classes they are derived from changes. This approach, while avoiding the integration and therefore possibly the removal consistency problem, has the drawback of duplication of information. In systems where the derived classes are integrated in the global schema [1, 19, 22, 24], code reuse as well as sharing of data is assured. Our work addresses the removal of such integrated derived 2 The graph representation is more suitable for implementation in our SVR tool, as it can closely be mapped to a data structure implementation. 2 classes. In systems using conventional ....

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M. H. Scholl, C. Laasch, and M. Tresch. Updatable Views in Object-oriented Databases. Proc. of the 2th Int'l Conference on Deductive and Object-Oriented Databases (DOOD), pages 189--207, Dec. 1991.

....supports behavioral interactions between the cluster and its constituent member objects (and possibly among the constituents themselves) another feature neither supported by a class nor existing in a frame. Recently, there have been some proposals for view support in object databases (e.g. [AB91, SLT91]) Compared with classes, views are closer to our clusters because views basically are also derived from existing objects. However, since views are just another kind of class, most of the above points on comparing clusters and classes are still applicable to views, except for point (iii) as views ....

....views basically are also derived from existing objects. However, since views are just another kind of class, most of the above points on comparing clusters and classes are still applicable to views, except for point (iii) as views also do not create new objects. The work on updatable views in [SLT91] would also veto point (v) partially but not completely, as views typically do not facilitate behavioural interactions among their objects. 3 Real Life Examples To demonstrate the validity and usefulness of conceptual clusters, we introduce an example here in which clusters are found to be a ....

M.H. Scholl, C. Laasch, and M. Tresch. Updatable views in object-oriented databases. In Proceedings of the 2nd Int'l Conference on Deductive and Object-Oriented Databases. Munich, Germany, Dec. 1991.

....notational ambiguity nondeterminacy remains possible if an object is a member of more than one group with the same channel type. Membership and access control measures enable the selective export of particular group interfaces for usage by particular clients. Such channels represent views [26] of objects, permitting rolebased, subject oriented [11] design and programming methods. Group constructs also help tame extreme forms of object evolution encountered in such designs when objects need to acquire roles that were not even defined at the time they were constructed. Rather than ....

Scholl, M., C. Laasch, & M. Tresch, "Updatable Views in Object Oriented Databases", in C. Delobel, M. Kifer & Y. Masunaga (eds.) Deductive and Object-Oriented Databases, Springer-Verlag, 1991.

....tedious, as does the alternative of routinely extracting Type info information probing for possession of these properties. These human factors considerations are sometimes serious barriers to extensibility. RTTI offers an incomplete solution. Other equally incomplete solutions include views [5] and conformance based typing [4] Example 2 This example was made famous in a set of Usenet postings: class Driver . class ProDriver : public Driver . class Vehicle . virtual void Register(Driver d) vd( class Truck : public Vehicle . void ....

Scholl, M, C. Laasch, & M. Tresch, "Updatable views in object-oriented databases", in C. Delobel, M. Kifer & Y. Masunaga (eds.) Deductive and Object-Oriented Databases, Springer-Verlhag, 1991.

.... interface for descriptions, and just role , or for emphasis, role instance for instantiations. The concept of a role is nearly synonymous with that of a subject in the essential sense of Harrison Ossher[25] A role may also be thought of as an abstract access channel[61, 4] providing a view[59] of one or more components, where each view is described by an interface type that lists a set of related operations. Implementation Objects. Interface specifications deal only with roles, not objects. They describe properties of abstract interaction participants[33] each defined via an ....

....The situation fFALSEg (matched by no realizations) is a subsituation of all others. We say that expression expr holds in situation S if S f expr g. Conversely, we define set like operators A B and A [ B in terms of the corresponding boolean relations on their component expressions (cf. [18, 59]) In PSL IDL A B is expressed as fexprAg fexprB g, and A [ B as fexprA g fexprB g. Subsituation relations are analogs of the subtype relations underlying interface inheritance. The simplest andmostcommonmeans of constructing a subsituation is to strengthen an expression by adding an ....

Scholl, M., C. Laasch, & M. Tresch, "Updatable Views in Object Oriented Databases", in C. Delobel, M. Kifer & Y. Masunaga (eds.) Deductive and Object-Oriented Databases, Springer-Verlag, 1991.

....views, user access is easily restricted to the minimal set of information which has to be made visible to the user. The object oriented (OO) database community is searching for a view mechanism which would achieve the same objectives as the relational one. However, despite several efforts (e.g. [2,8,12,13,14]) the objective has not yet been fulfilled. Indeed, the problem is harder in an OO environment where solutions have to be invented for issues which do not arise in a relational DBMS. First, data structures with complex objects are less prone to flexibility: algebras and SQL like OO languages ....

....for both types and populations are allowed. For instance, 12] does not support composite query expressions, while [2] does not support projection queries or queries with multiple root classes. A different approach is to deal with the two issues (typing, classification) separately. In [11, 14] the authors offer a rigorous analysis of view definition based on an algebraic query language and advocate a solution where the type hierarchy is maintained separately from the class hierarchy. 5] extends the proposal for typing to include methods. The disadvantage of the approach is with the ....

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Scholl M.H., Laasch C., Tresch M., "Updatable Views in Object-Oriented Databases", Proc. of Second International Conference DOOD'91, LNCS 566, Springer-Verlag, 1991.

....be performed on clients. None of these ooDBMSs is capable of managing distributed databases. As long as this is not the case, ooDBMSs cannot be used in arbitrarily large projects. To date, there are no ooDBMSs with view definition capabilities. However, there are proposals for views in ooDBMSs [SLT91, AB91] and prototypes are being built. The view definition mechanism defined in [AB91] exactly fits the requirements we presented on views. 5 Conclusions and Further Work Relational DBMSs are inappropriate for storing project graphs, since (1) the data model can not express syntax graphs ....

M. H. Scholl, C. Laasch, and M. Tresch. Updatable Views in Object-Oriented Databases. In C. Delobel, M. Kifer, and Y. Masunaga, editors, Deductive and 21 Object-Oriented Databases -- Proc. of the 2 nd Int. Conf., DOOD '91, Munich, Germany, volume 566 of Lecture Notes in Computer Science, pages 189--207. Springer, 1991.

....applications using the view. The advantage of such a view is that schema modifications do not alter the result of execution of programs using a non side effect view. 2 1 Introduction A variety of view definitions have been defined for object oriented database systems [1] 2] 4] 7] 11] [12]. In this paper we study the problem of what happens to a view when the underlying schema and database are updated. We introduce the new concept of non side effect view. A non side effect view is a view which is re computed dynamically so that schema modifications are (whenever possible) ....

M.Scholl, C.Laasch, M.Tresch: "Updatable Views in Object Oriented Databases", in Proc. 2nd DOOD Conf. Germany, Dec. 1991

....to other constituent databases. The initial version of the project includes two different database modelling approaches: ERC and COCOON. We give below a brief description of the major characteristics of both approaches. A more detailed presentation of the models can be found in [1] and in [2]. Studying interoperability between these two approaches is of particular interest, as they represent two very important and widely used families of models possible in a federation. ERC is an object based extension of the entityrelationship model. It includes an ER algebra and an equivalent ....

.... cars Figure 2: the integrated schema 4. 2 Integration through augmentation In the second approach, correspondences between existing objects of different databases are established by defining (global) object identity in terms of algebraic views [3] using COCOON s view definition facility [2], extended to span multiple databases. It includes mechanisms for linking objects across systems and to deal with semantic conflicts. The necessary view definition method is to extend the local schema by elements of the schema of another system. Considering the example, the DBA starts the ....

Scholl M.H., Laasch C., Tresh M., "Updatable Views in Object-Oriented Databases", 2nd International Conference on Deductive and Object-Oriented Databases, Munich, December 1991

....machine 1 learning [18, 32] and knowledge representation [20, 31, 28, 33, 6, 4, 3] See also [19] for a general survey on the subject. However, all these notions of context are very diverse and serve different purposes. In software development the notion of context appears in the form of views [2, 8, 11, 24, 1], aspects [23] and roles [9, 25] for dealing with data from different perspectives, or even in the form of workspaces which are used to support cooperative work [15] In machine learning, context is treated as environmental information for concept classification [18, 32] In so called multi ....

M. Scholl, C. Laasch, and M.Tresch. Updatable Views in Object-Oriented Databases. In Proceedings of the 2nd Int. Conf. on Deductive and Object-Oriented Database Systems, pages 189--207, Munich, Dec. 1991.

....preferable to support original class definitions (of C) as a set of views over the vertically class fragmented and internally represented classes (i.e. V 1 ; V 2 ; V k ) In this scenario, the class definitions seen by the user will form a set of updatable views over the fragmented classes. [10] discusses how updatable views can be supported in their COCOON object database system. We are currently evaluating the applicability of this work to provide a uniform framework for supporting methods on vertically fragmented classes. 3.2 Path Partitioning Scheme The class composition hierarchy ....

....consists of grouping the objects of all the domain classes that correspond to all the instance variables in the subtree rooted at the composite object. In order to illustrate the concept of path partitioning let us consider the following example. Class Automobile id: integer color: char[10] drivetrain: V dt manufacturer: Comp Class A dt Engine: A Eng transmission: A tr Class A tr type: char . Class A Eng capacity: integer size: integer cylinders: integer Class Comp name: char[50] location: char[70] president: Employee root Manufacturer ....

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M. H. Scholl, C. Laasch, and M. Tresch. Updatable views in object-oriented databases. In Proc. 2nd DOOD Conf., pages 1--19, 1991.

....into account that they now work with objects with an identity (which led to the notion of object preserving queries) and with a much richer type class system that requires typing (and classification) of query results. Informal presentations of COCOON and the COOL language have been given earlier [19, 21]. A formalization of COCOON and COOL using BCOOL was developed in [20] In this paper, we discuss the functional object language BCOOL in detail. We present the formal semantics of query and update operations using a denotational approach. In contrast to [17] and [10] which also propose ....

M. H. Scholl, C. Laasch, and M. Tresch. Updatable views in object-oriented databases. In C. Delobel, M. Kifer, and Y. Masunaga, editors, Proc. Int. Conf. on Deductive and Object-Oriented Databases (DOOD), pages 189-- 207, Munich, Germany, December 1991. LNCS 566, Springer Verlag, Heidelberg.

.... similar to the relational projection or join, and still have queries deliver base objects What flexibility is needed in the type system, and can we still apply (some) static type checking These issues are addressed in this brief overview of the work performed in the COCOON project at ETH Zurich [8, 9]. We first discuss object preserving query semantics of a generic object oriented query language in the style of a relational algebra. Then we show how views defined by such query expressions can be updated: We elaborate on certain fundamental properties of the object model, such as the separation ....

....basic COOL operators, we describe what the membertype and extent is, and how these are positioned in the type and class hierarchies. For ease of presentation, assume that all views are defined over base classes. In general, views may also be defined over other views, or by composite queries (see [8] for a detailed exposition) In the following, let C be a class with member type T. Selection ( define view V as select [P] C) The view class V is a subclass of the base class C, with the same member type T. We now have two classes, V and C, of type T. The extent is the subset of C members ....

[Article contains additional citation context not shown here]

M. Scholl, C. Laasch, and M. Tresch. Updatable views in object-oriented databases. Technical Report 150, ETH Z urich, Dept. of Computer Science, Dec. 1990. Submitted for publication.

No context found.

M. Scholl, C. Laasch, and M. Tresch. Updatable Views in Object-Oriented Databases. In Proc. of DOOD'91, pages 189--207, Munich, Dec. 1991.

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M. H. Scholl, C. Laasch, and M. Tresch. Updatable Views in Object-Oriented Databases. In C. Delobel, M. Kifer, and Y. Yasunga, editors, Proc. 2nd Intl. Conf. on Deductive and Object-Oriented Databases (DOOD), number 566. Springer, 1991.

No context found.

M. H. Scholl, C. Laasch, and M. Tresch. Updatable Views in Object-Oriented Databases. In C. Delobel, M. Kifer, and Y. Yasunga, editors, Proc. 2nd Intl. Conf. on Deductive and Object-Oriented Databases (DOOD), number 566. Springer, 1991.

No context found.

Marc H. Scholl, Christian Laasch, and Markus Tresch. Updatable Views in Object-Oriented Databases. In Proceedings of the Second International Conference on Deductive and ObjectOriented Databases (DOOD91), Munich, Germany, December 16-18, 1991, pages 189--207, December 1991.

No context found.

Marc H. Scholl, Cristian Laasch, and Markus Tresch. Updatable Views in Object-Oriented Databases. In Proceedings of the 2nd Int. Conf. on Deductive and Object-Oriented Database Systems, pages 189--207, Munich, December 1991.

No context found.

Scholl M., Laasch C., Tresch M. "Updatable views in object-oriented databases." In Proc. 2nd Int. Conf. on Deductive and Object-Oriented Databases, LNCS 566, Springer-Verlag, pp. 189--207.

No context found.

Scholl, M., Laasch, C., and Tresch, M. #1991#. Updatable Views in Object-Oriented Databases. In M. Kifer et al., editors, Proc. Second Int'l Conf. on Deductive and ObjectOriented Databases,number 566 in Lecture Notes in Computer Science, pages 189#207.

No context found.

Scholl M, Laasch C, Tresch M. Updatable views in object-oriented databases. Proceedings of the 2nd Deductive and Object-Oriented Databases Conference (DOOD91), 1991; 189--207.

No context found.

Marc H. Scholl, Christian Laasch, Markus Tresch, "Updatable Views in ObjectOriented Databases", DOOD 1991, pp. 189-207.

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M.H. Scholl, C. Laasch, M. Tresch. "Updatable Views in Object-oriented Databases". In Deductive and Object-oriented Databases --- DOOD'91, pages 189-207, 1991.

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