Querying an Object-Oriented Database Using CPL

The Collection Programming Language is based on a complex value model of data and has successfully been used for querying transforming and integrating data from a wide variety of structured data sources - relational, ACeDB, and ASN.1 among others. However, since there is no notion of objects and classes in CPL, it cannot adequately model recursive types or inheritance, and hence cannot be used to query object-oriented databases (OODBs). By adding a reference type and four operations to CPL - dereference, method invocation, identity test and class type cast - it is possible to express a large class of interesting safe queries against OODBs. As an example of how the extended CPL can be used to query an OODB, we will describe how the extended language has been used as a query interface to Shore databases

HOOD : a Higher-Order Object-Oriented Database model and its implementation

Bibliography: pages 133-140.There is no accepted standard for the object-oriented database paradigm at present, which has led to different definitions of features and conformance requirements. HOOD is a Higher-Order Object-Oriented Database system which defines a meta-data model for specifying the requirements of an Object-Oriented Database, which provides uniformity and extensibility. From this specification and by making use of a comprehensive structure system, an exemplar or implementation model is defined. Among the constructs provided by the model are types, instances, objects, values, methods, base types, generic types and metatypes. The mechanisms of instantiation and subtyping allow for relationships between these constructs. Extensibility is provided in the model for types, base types, structures and methods. Uniformity is achieved by defining all constructs as instances and through the use of messages for all operations. There is only one form of object construct which provides persistence and identities. The complex values and extensibility of the model allow it to adapt in order to model the real world instead of adapting the real world to fit the model. We have implemented a subset of the structures and values defined in the model, provided persistence and identities for object, and included the various constructs mentioned above. The method language allows for the specification of methods, the passing of messages, and the use of complex values. The compiler performs type checking and resolution and generates instructions for an abstract machine which manipulates the database

Modularizing application and database evolution - an aspect-oriented framework for orthogonal persistence

In the maintenance of software applications, database evolution is one common difficulty. In object‐oriented databases, this process comprises schema evolution and instance adaptation. Both tasks usually require significant effort from programmers and database administrators. In this paper, we propose orthogonal persistence and aspect‐oriented programming to support semi‐transparent database evolution. A default mechanism for instance evolution is defined, but the user may provide modularized solutions using the aspect‐oriented paradigm. We present our framework AOF4OOP to test the feasibility of our proposed approach. This prototype allows programmes to transparently access data in other versions of the database schema. We evaluate our framework, comparing it to related approaches using two real applications and measuring the improvement of the productivity of the programmer.info:eu-repo/semantics/publishedVersio

Managing change in persistent object systems

Persistent object systems are highly-valued technology because they o er an e ec- tive foundation for building very long-lived persistent application systems (PAS). The technology becomes more e ective as it o ers a more consistently integrated computational context. For it to be feasible to design and construct a PAS it must be possible to in- crementally add program and data to the existing collection. For a PAS to endure it must o er exibility: a capacity to evolve and change. This paper examines the capacity of persistent object systems to accommodate incremental construction and change. Established store based technologies can support incremental construction but methodologies are needed to deploy them e ectively. Evolving data description is one motivation for inheritance but inheritance alone is not enough to support change management. The case for supporting incremental change is very persuasive. The challenge is to provide technologies that will facilitate it and methodologies that will organise it. This paper identi es change absorbers as a means of describing how changes should propagate. It is argued that if we systematically develop an adequate reper- toire of change absorbers then they will facilitate much better quality change man- agement

Making object-oriented databases more knowledgeable (From ADAM to ABEL)

Tesis leida en la Universidad de Aberdeen. 178 p.The salient points of this thesis are as follows: • Object-Oriented Databases can help in solving the impedance mismatch problem by introducing methods. However, methods have sometimes been overused in the sense th at the code encapsulated refers not only to how the operation is implemented but also to other kinds of knowledge that are implicit in the code. The disadvantages of this approach for modelling integrity constraints, user-defined relationships and active behaviour are pointed out. • The ADAM Object-Oriented Database has been extended to allow the designer to specify integrity constraints declaratively. A constraint equation approach is implemented th at supports the inheritance of constraints. • A need for semantic-rich user-defined relationships has been identified. In this thesis, relationships are represented as objects. An approach to enhance the semantics of relationships in both its structural and behavioural aspects is presented. The most novel idea of the approach presented is the support of the inferred properties and the operational semantics of relationships. • Active Databases have recently become an im portant area of research. This thesis shows how to extend an Object-Oriented Database with active capabilities. The principal contribution lies in representing as ‘first-class’ objects not only the active rules but also the rule manager itself. Hence, besides handling active rules as any other object in the system, future requirements can be supported just by specialising the current rule manager. • Active rules have been proposed for several purposes. Several examples, are given of the direct use of rules. However, higher level tools can be provided of which rule

Reducing cross-domain call overhead using batched futures

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1994.Includes bibliographical references (p. 95-96).by Phillip Lee Bogle.M.S

Modeling and Simulating a Software Architecture Design Space

Frequently, a similar type of software system is used in the implementation of many different software applications. Databases are an example. Two software development approaches are common to Þll the need for instances from a class of similar systems: (1) repeated custom development of similar instances, one for each different application, or (2) development of one or more general purpose off-the-shelf systems that are used many times in the different applications. Each approach has advantages and disadvantages. Custom development can closely match the requirements of an application, but has an associated high development cost. General purpose systems may have a lower cost when amortized across multiple applications, but may not closely match the requirements of all the different applications. It can be difÞcult for application developers to determine which approach is best for their application. Do any of the existing off-the-shelf systems sufÞciently satisfy the application requirements? If so, which ones provide the best match? Would a custom implementation be sufÞciently better to justify the cost difference between an off-the-shelf solution? These difÞcult buy-versus-build decisions are extremely important in todayÕs fastpaced, competitive, unforgiving software application market. In this thesis we propose and study a software engineering approach for evaluating how well off-the-shelf and custom software architectures within the design space of a class of OODB systems satisfy the requirements for different applications. The approach is based on the ability to explicitly enumerate and represent the key dimensions of commonality and variability in the space of OODB designs. We demonstrate that modeling and simulation of OODB software architectures can be used to help software developers rapidly converge on OODB requirements for an application and identify OODB software architectures that satisfy those requirements. The technical focus of this work is on the circular relationships between requirements, software architectures, and system properties such as OODB functionality, size, and performance. We capture these relationships in a parametrized OODB architectural model, together with an OODB simulation and modeling tool that allows software developers to reÞne application requirements on an OODB, identify corresponding custom and offthe- shelf OODB software architectures, evaluate how well the software architecture properties satisfy the application requirements, and identify potential reÞnements to requirements

Query processing in temporal object-oriented databases

This PhD thesis is concerned with historical data management in the context of objectoriented databases. An extensible approach has been explored to processing temporal object queries within a uniform query framework. By the uniform framework, we mean temporal queries can be processed within the existing object-oriented framework that is extended from relational framework, by extending the existing query processing techniques and strategies developed for OODBs and RDBs. The unified model of OODBs and RDBs in UmSQL/X has been adopted as a basis for this purpose. A temporal object data model is thereby defined by incorporating a time dimension into this unified model of OODBs and RDBs to form temporal relational-like cubes but with the addition of aggregation and inheritance hierarchies. A query algebra, that accesses objects through these associations of aggregation, inheritance and timereference, is then defined as a general query model /language. Due to the extensive features of our data model and reducibility of the algebra, a layered structure of query processor is presented that provides a uniforrn framework for processing temporal object queries. Within the uniform framework, query transformation is carried out based on a set of transformation rules identified that includes the known relational and object rules plus those pertaining to the time dimension. To evaluate a temporal query involving a path with timereference, a strategy of decomposition is proposed. That is, evaluation of an enhanced path, which is defined to extend a path with time-reference, is decomposed by initially dividing the path into two sub-paths: one containing the time-stamped class that can be optimized by making use of the ordering information of temporal data and another an ordinary sub-path (without time-stamped classes) which can be further decomposed and evaluated using different algorithms. The intermediate results of traversing the two sub-paths are then joined together to create the query output. Algorithms for processing the decomposed query components, i. e., time-related operation algorithms, four join algorithms (nested-loop forward join, sort-merge forward join, nested-loop reverse join and sort-merge reverse join) and their modifications, have been presented with cost analysis and implemented with stream processing techniques using C++. Simulation results are also provided. Both cost analysis and simulation show the effects of time on the query processing algorithms: the join time cost is linearly increased with the expansion in the number of time-epochs (time-dimension in the case of a regular TS). It is also shown that using heuristics that make use of time information can lead to a significant time cost saving. Query processing with incomplete temporal data has also been discussed