Deux et. al. The O System. Communications of ACM, 34(10):34--48, October 1991.  Home/Search   Document Not in Database   Summary   ACM   TOC   Related Articles   Check

....signature files. 1 Introduction During the last decade, the object oriented database management systems become common and proved their advantages and usefulness in several application areas, especially in relatively new for databases. Early research prototypes were followed by several commercial [8, 16, 4], as well as excellent public domain systems [5] Many commercial relational systems are rapidly evolving to incorporate important features of object oriented systems, e.g. powerful capabilities of data modelling and support for complex data structures and integrity constrains. However, while ....

O. Deux et al. The O2 system. Communications of the ACM, 34(10):34--49, 1991.

....a calculus, respectively, over an extended relational data model containing sequences. I Introduction It is generally accepted that sequences (or lists) are useful in many database applications [4, 14, 15] Because of this, new generation database systems, e.g. EX ODUS [61, Galileo [31, 02 [5, 8] and Vbase [12] usu ally support sequenced data. In order to query the sequenced data, these systems require appropriate sequence operations. However, the sequence operations in the systems are usually chosen in an ad .boc manner. Also, the essential properties of the selected operations, such ....

O. Deux et al. The 02 system. Communications of ACM, 34(10):34-48, October 1991.

....databases. The work done in object oriented databases is more closely related to our work. Such systems start with a general object oriented programming language and add support for fast associative access to collections of objects. Some representative systems are GemStone[12, 47, 48] O 2 [23, 24], Orion[4, 36, 37] and ObjectStore[40, 52] Work specifically dealing with 91 indexing falls into two categories: 1. Indexing schemes based on the structure of an object (that is, the values of instance variables) We will call these path based indexing schemes. 2. Indexing schemes based on ....

....interested in comparing space requirements. Various strategies have been proposed for index maintenance for path based indexes; a survey can be found in [9] Of these the multi index is the most commonly used scheme; it was originally proposed for GemStone[47] and is also used in the O 2 [24, 23] and ObjectStore[40, 52] databases. We will cover the GemStone scheme in some detail, then briefly cover the nested index and path index of Bertino and Kim[11] and the join index of Valduriez[60] emphasizing their differences from the GemStone scheme and each other. 4.1.1 Multi indexes ....

O. Deux et al. The O 2 system. Communications of the ACM, 34(10):34--48, October 1991.

....for developers to choose to access individual files on the standard hard disk through the low level file system 8 interface. 4.2 Interacting with O 2 datasources We will now describe the integration of a well structured datasource: an O 2 database. The O 2 object oriented database system [O2] provides a complete object oriented database solution for object developers. As it is in use in the framework of a system aimed at the support of the protection information system of the electrical transmission network, we chose it as a case study for WG Log based datasource integration. As ....

O. Deux et al., The O2 System, Communications of the ACM, Vol. 34, N. 10, Oct. 1991.

....held on containers which on one hand may enhance response time, but on the other hand hinders concurrency and cooperative access. Transaction commits are based on the two phase commit protocol, which is very expensive and may fail in loosely coupled or disconnected environments. 4.1. 3 O 2 O 2 [3, 8, 27] has a client server architecture, implementing a page server, having a cache at both the client side and the server side. Programmers can chose between two persistence models: persistence by declaration and persistence by reachability. In the former model, persistence is determined at object ....

O. Deux et al. The O 2 system. Communications of the ACM, 34(10):34--48, October 1991.

....[ 8] It provides interoperability between applications on different machines by interconnecting multiple object systems through a remote object invocation mechanism. The work presented in this paper concerns interoperability between Guide [5 ] an object oriented distributed system, and O 2 [ 6] an object oriented database system. The main goal of Guide O 2 interoperability is to provide Guide users with database services in order to build new applications that use both distribution and database services. This interoperability saves us the work of integrating database functionalities ....

....object is loaded in the VOM of the current node. If the object was already loaded in the VOM of a distant node, the application diffuses on that node. 2. 3 The O2 System O 2 is an object oriented database management system with a complete development environment and a set of user interface tools [ 6] . The core of the system is O 2 ENGINE an object database engine. O 2 ENGINE stores structured and multimedia objects, provides disk management, transaction management, concurrency, recovery, security and data administration. Two kinds of interface are supported by O2ENGINE, a language ....

O. Deux et Al.. The O2 system. Communications of ACM, Vol. 34, No. 10, pp. 34-48, October 1991.

....[8] It provides interoperability between applications on different machines by interconnecting multiple object systems through a remote object invocation mechanism. The work presented in this paper concerns interoperability between Guide [5] an object oriented distributed system, and O 2 [6] an object oriented database system. The main goal of Guide O 2 interoperability is to provide Guide users with database services in order to build new applications that use both distribution and database services. This interoperability saves us the work of integrating database functionalities ....

....on an object, this object is loaded in the VOM of the current node. If the object was already loaded in the VOM of a distant node, the job diffuses. 2. 3 The O2 System O 2 is an object oriented database management system with a complete development environment and a set of user interface tools [6]. The core of the system is O 2 ENGINE an object database engine. O 2 ENGINE stores structured and multimedia objects, provides disk management, transaction management, concurrency, recovery, security and data administration. Two kinds of interface are supported by O 2 ENGINE, a language ....

O. Deux et Al., The O2 system, Communications of ACM, 34(10 ), pp. 34-48 , October 1991.

....reachable by a root becomes persistent. In this way, persistence is also conferred to an object if this object is referenced by another persistent object. This policy has two main advantages : 1. An object may be temporary or persistent; 6 2. Persistence is independent of the class definition [Deu91]. A root may be an instance of a class or a type, and some roots may have the same domain. The set of roots is noted as Root. Finally, all persistent objects and all method implementations form an instance of schema. The function instanceOf from Root to T ype returns the type of a root which may ....

0. Deux. The O2 system. Communications of the ACM, 34(10):34--48, 1991. 22

....do not support fine grained client to client transfers as desired for the sharing behavior we are considering (described in Section 3.1) 3.2. 2 Object Oriented Databases One alternative for the distributed sharing of persistent data is the objectoriented database (OODB) technology [132] O 2 [39], Thor [83] and GemStone [24] are only a few examples. In contrast with file systems, OODBs provide excellent support for complex data types. In other words, they preserve the structure of data (no marshaling is needed) However, they are very heavyweight, and often come with their own ....

O. Deux et al. The 0 2 system. Communications of the ACM, 34(10):34--48, October 1991.

....(e.g. the language BCOOL [LS93] and the OSCAR ( HFW90] Kla92] project in various parts. In both projects object algebras have been developed. BCOOL is a functional one and so it is more closely to the CROQUE approach than ABRAXAS from OSCAR. ODMG OQL was mainly influenced by the O 2 project [Deu91] A more detailed description of the CROQUE OQL (and ODL) can be found in the CROQUE formalization paper [SRG95] 2 The logical algebra Similar to ODMG ODL our data model consists of classes, their attributes and methods types and type constructors. First, every CROQUE OQL query is transformed ....

O. Deux. The O 2 system. Communications of the ACM, 34(10):34--48, October 1991.

....and optimization. In Won Kim, Jean Marie Nicolas, and Shojiro Nishio, editors, Proceedings of the First International Conference on Deductive and Object Oriented Databases, pages 264 277, December 1989. Tri91] Phil Trinder. Comprehensions, a query notation for DBPLs. Unpublished manuscript, June 1991. VD90] Scott L. Vandenberg and David J. DeWitt. Algebraic support for complex objects with arrays, identity, and inheritance. Technical Report CS TR 987, University of Wisconsin Madison, December 1990. Wad90] Philip Wadler. Comprehending monads. In Proceedings of the 1990 ACM Conference on ....

....[Wad90] Philip Wadler. Comprehending monads. In Proceedings of the 1990 ACM Conference on LISP and Functional Programming, pages 61 78. ACM Press, June 1990. WT91] David A. Watt and Phil Trinder. Towards a theory of bulk types. Manuscript; to appear in expanded form as a FIDE Technical Report, June 1991. 36 [GM88] Goetz Graefe and David Maier. Query optimization in object oriented database systems: A prospectus. In Klaus R. Dittrich, editor, Advances in Object Oriented Database Systems, volume 334 of LNCS, pages 358 363. 2nd International Workshop on Object Oriented Database Systems, ....

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O. Deux et al. The O 2 system. Communications of the ACM, 34(10), October 1991.

....Systems This section presents a review of some features relevant to the issue of encapsulation and inheritance supported by some existing object oriented systems. The systems reviewed are: GEMSTONE [2] EXODUS [3] ORION [20] ENCORE [34] POSTGRES [35, 36] STARBURST [22] IRIS [10] and O 2 [9]. GEMSTONE is an object based system developed at Servio [2, 23] whose basic architecture distinguishes two main subsystems; the GEM Server process for query evaluation and the Stone Monitor for allocating object identifiers in blocks and coordinating commit activity. Its object oriented database ....

....weak support for encapsulation. Objects are accessed, using functions. It supports both single and mutiple inheritance but provides no support for attribute value inheritance. An object at a higher level is used for managing metadata and there is no direct communication between objects. O 2 [9] is an OODBS with origin traced to ALTAIR, a project funded by 1N2 (a Siemens Subsidiary) INRIA (Institut National de Recherche en Informatique) and LRI (Laboratoire de Recherche en Informatique, University of Paris XI) The O 2 architecture consists of eight functional modules which include the ....

O. Deux et al. The o 2 system. Communications of the ACM, 34(10), Oct 1991.

....of several knowledge bases (KB) using CGs as the representation formalism. It is constructed such that it fulfills the general IR requirements [15] In particular, it allows to deal with the properties of relations and their behavior. The platform is implemented using the object oriented DBMS O 2 [23]. A knowledge base is composed by a set of well formed conceptual graphs, corresponding to the facts of a particular domain, and a canon (see section 2) that insures the coherence of the facts described by the graphs of the KB. Each KB in ROGER is defined by the triplet: KB = name, canon, ....

Deux O. and al. The o2 system. Communications of the ACM, 34(10):34--48, 1991.

....Rock Roll [6] LOL [27] Datalog [18] ROL [26, 28] and DO2 [24] However, most of them are only structurally object oriented. Important behaviorally object oriented features such as methods and encapsulation common in object oriented database systems such as GemStone [10] ONTOS [36] O 2 [14], Orion [22] Iris [16] ObjectStore [36] ObjectStore [23] ODMG 93 [12] ODMG 2.0 [13] are not properly supported. In particular, O logic, revised O logic, IQL, LOGRES, LIVING IN A LATTICE, DLT, Gulog, LOL, and ROL do not support methods, let al..one their encapsulation. In Datalog meth [3] and ....

O. Deux et al. The O2 System. Communications of the ACM, 34(10):35-48, 1991.

....an object or a page. Most commercial relational database systems have adopted the query shipping architecture [KCWW92] The advantages and disadvantages of the query shipping architecture are summarized in [HF86, fADF90] Commercial client server object database systems, Observer [HZ87] O2 [Deu91] ObjectStore [LLOW91] and client server EXODUS [CDG 90] employ the data shipping architecture. They use a page as the unit of transfer between the client and the server. This is called the page server architecture. Performance tradeoffs between page and object shipping architectures are ....

O. Deux. The O2 System. Communications of the ACM, 34(10), Oct 1991.

....IBM DBMS implement these features. Records from different relations can also be clustered in the same page by a common attribute [7] Object oriented database systems offer similar capabilities. Users can specify that they want to cluster certain objects into certain places. For example, in O 2 [16, 15] a userdefined placement tree has been suggested to guide the clustering, but it has never been implemented. A more usual feature is simply to allow a user to specify the segment of the database where an object is to be clustered (e.g. in ObjectStore [22] A good survey of clustering research ....

O. Deux. The O 2 system. Communications of the ACM, pages 34--48, October 1991.

....is not recognised. 2 An Implementation of Persistent C Several implementations of persistent C are described in the literature. These fall into two main groups: those that provide C interfaces to general object oriented database systems, for example GemStone [Butterworth 91] and O 2 [Deux 91] and those that extend C with specialised storage facilities for persistent objects, for example E [Richardson 89] and Avalon C [Detlefs 88] A hybrid approach has become more popular recently with the advent of general purpose persistent object managers designed to be able to support a ....

O. Deux et al. The O 2 system. Communications of the ACM, 34(10):34--48, October 1991.

....data model is independent of a particular type model. This means that the model is general and can support interlanguage working. Proc. of the 12th Int. Conf. on the Entity Relationship Approach, Arlington, Texas, USA, December 1993 1 Many existing object oriented database systems such as O 2 [Deu91] ONTOS [Ont91] and ObjectStore [LLOW91] support collections of objects of differing behaviours, e.g. sets, bags (multisets) and sequences. However, the data models of such systems tend mainly to be type models and offer little in the way of constraints over collections of objects. It is ....

O. Deux. The O 2 System. Communications of the ACM, 34(10):34--48, October 1991.

....system uses transactions and incorporates a security architecture. We also provide persistence by reachability, essential for the long term safety of the store. 8. 2 Object oriented databases, persistent object systems and object based systems Object oriented databases (OODBs) 35] such as O 2 [15], Thor [25] GemStone [9] or ObjectStore [24] share many of the same goals as PerDiS. OODBs support complex data types, persistently preserving the structure and type of data. However, they are very heavyweight, and often come with their own specialized programming language. Moreover, an OODB ....

O. Deux et al. The 02 system. Communications of the ACM, 34(10):34-48, October 1991.

....only allows to generalize method arguments, except for the receiver class, and is type safe with local type checking algorithms, while covariance allows to specialize them, but requires a global type check [Jon92] that inhibits separate compilation of modules. Eiffel [Mey93] and O 2 [Deu91] use covariance, while [CW85] and Tool [GM95] use contravariance. Recent languages like Cecil [CL95] or Dylan [BH93] overcome the problem using multi dispatch: An implementation is selected based on the actual type of all object valued arguments. This solves the original problem but introduces ....

....wants to be persistent. Here, persistence is system maintained, and the programmer is freed from the responsibility to care for it. To cope with the problem, the system uses a garbage collector that deletes objects from the database that do not match the programmer s description. Systems like O 2 [Deu91] and GemStone [Ser91] work this way. From both the programmer s and the user s point of view, the second approach is more comfortable. Therefore, it was chosen for the OSCAR project. The declarative description that both mentioned systems use is commonly called persistence by reachability, and ....

O. Deux. The O 2 system. Communications of the ACM, 34(10):34--48, October 1991.

....the efficiency of existent grid based file access solutions. 1. Introduction The advent of high speed networks coupled with a desire to harness more processing power and access immense data stores has lead to the possibility and necessity of federating such resources into computational grids [6, 7, 5]. The unprecedented scale, heterogeneity, and varied usage patterns of such grids pose significant technical challenges to any underlying file system that will support them. Many well known distributed file system problems, such as security, scalability, performance, and usability, are exacerbated ....

....are sophisticated users and application programmers who will prefer a rich interface to take full advantage of the grid s potential. A grid environment should accommodate both types of users. This paper examines the I O infrastructure and performance of Legion, comparing it with Globus. Legion [7] is an object based grid operating system charged with reconciling a collection of heterogeneous resources, dispersed across a wide area, with a single virtual system image. Legion provides resource management, scheduling, and other system level tasks, as does any operating system; however, it ....

A. S. Grimshaw and et al. Metasystems. Communications of the ACM, pages 46--55, Nov. 1998.

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Deux et. al. The O System. Communications of ACM, 34(10):34--48, October 1991.

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O. Deux et al. The O2 system. Communications of the ACM, 34#10#:51#63, October 1991.

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O. Deux et al. The O 2 system. Communications of the ACM, 34(10):34--48, October 1991.

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O. Deux et al. The O 2 system. Communications of the ACM, 34(10):34--48, October 1991.

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