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Topic: Object-Relational impedance mismatch

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InterSystems Caché - Caché Technology - White Papers - Fighting Impedance Mismatch at the Database Level Impedance mismatch is a term borrowed from electrical engineering, but in the software world it refers to the inherent difference between the relational and object data models. Impedance mismatch – the inherent disconnect between object and relational data models – cannot be avoided, but it can be significantly mitigated by the proper choice of database technology. Here is one manifestation of impedance mismatch – an object class with a collection having to be translated to the disparate tables of a relational database engine. www.intersystems.com /cache/technology/whitepapers/matchwp.html   (2194 words)

The Object-Relational Impedance Mismatch The impedance mismatch becomes apparent when you look at the preferred approach to access: With the object paradigm you traverse objects via their relationships whereas with the relational paradigm you join the data rows of tables. Much of the conversation about the impedance mismatch focus on the technical differences between object and relational technologies, and rightfully so because there are significant differences. The cultural impedance mismatch, something that I call the “object-data divide” (Ambler 2000a; Ambler 2000b), refers to the politics between the object community and the data community. www.agiledata.org /essays/impedanceMismatch.html   (2342 words)

Dare Obasanjo aka Carnage4Life - The Unified Theory of Everything One would then think that given the previously stated impedance mismatch and the fact that XML is mainly just a syntactic device that XML representations of the data being transmitted is sent as serialized versions of objects, relational data or some subset of both. The team I work for deals with data access technologies (relational, object, XML aka ROX) so this impedance mismatch is something that we have to rationalize all the time. Many felt (and still feel) that this impedance mismatch is a significant problem. www.25hoursaday.com /weblog/PermaLink.aspx?guid=755443c2-19a6-4b45-8e18-879565e74759   (1547 words)

Solving the Object -Relational impedance mismatch the other way Ted Neward suggests solving the object-relational impedance mismatch by adding relational features to languages, instead of mapping relational databases to objects. I do objects because the OO paradigm is better than the relational one for developing software. Because objects impose constraints in the way I can use my data that don't exist in the relational model. weblogs.asp.net /aaguiar/archive/2003/11/13/37343.aspx   (333 words)

InterSystems Caché - Caché Technology - White Papers - The Impedance Mismatch Impedance mismatch is a term commonly used to describe the problem of an object-oriented (OO) application housing its data in legacy relational databases (RDBMS). Impedance mismatch arises from the inherent lack of affinity between the object and relational models. Given the increasing prevalence of the OO RDBMS impedance mismatch-and its corollary, the mismatch between SQL-based applications and object databases (OODBMS)-an examination of approaches to resolving the resulting problems is both timely and worthwhile. www.intersystems.com /cache/technology/whitepapers/impedance.html   (2228 words)

The meaning of "Impedance Mismatch". The mismatch I refer to is a result of the differences in structure between a normalized relational database and a typical object oriented class hierarchy. Using "impedance mismatch" for the troubles you get when you try to fit a relational DB with an OO application is merely an analogy (while the two phenomenons presented above are actually the _same_ at a basic level). Impedance is the measure of the amount that some object impedes (or obstructs) the flow of a current. haacked.com /archive/2004/06/15/629.aspx   (685 words)

Java Pro - Mapping Classes to Relational Tables Part 1 provides an overview of the necessity to overcome the challenge of impedance mismatch between object-oriented and relational data and of using the horizontal mapping approach. Meet the challenge of impedance mismatch with object to relational mapping. In particular, we'll discuss the pros and cons for various approaches to mapping object inheritance hierarchies to relational tables. www.ftponline.com /javapro/2004_04/online/rjensen_04_28_04   (455 words)

Eliminating the Impedance Mismatch Between Relational Systems and Object-Oriented Programming Languages - Chen, Huang (ResearchIndex) Chen, J. and Huang, Q.-M., "Eliminating the Impedance Mismatch Between Relational Systems and Object-Oriented Programming Languages", in Proce. @misc{ chen95eliminating, author = "J. Chen and Q. Huang", title = "Eliminating the Impedance Mismatch Between Relational Systems and Object-Oriented Programming Languages", text = "Chen, J. and Huang, Q.-M., Eliminating the Impedance Mismatch Between Relational Systems and Object-Oriented Programming Languages, in Proce. 2 Eliminating the Impedance Mismatch Between Relational System.. citeseer.ist.psu.edu /173139.html   (665 words)

Darien's Dialog.. : "The impedance mismatch between object-oriented constructs and relational databases", A Survey by Darien Nagle If you're a OO developer, and you've got an opinion on the object-oriented impedance mismatch, then I'd love to hear from you. Having said that, lots of other writers have plenty to say about the impedance mismatch in general, including such substantial authors as C.J.Date, but you have to dig. Its just that not a lot of.NET developers that I talk to even see the impedance mismatch as a problem. blogs.msdn.com /darien/archive/2004/11/21/267478.aspx   (974 words)

Lack of impedance mismatch This lack of impedance mismatch in Object DBMSs gives them a performance advantage over Relational DBMSs, especially on complex data. Impedance mismatch slows down performance on complex data because of processing needed map from one data structure (tables) to another (objects). This mapping to different data structures is called "impedance mismatch." The figure below shows direct storage at the left and impedance mismatch at the right. www.service-architecture.com /object-oriented-databases/articles/lack_of_impedance_mismatch.html   (573 words)

Object Relational Impedance Mismatch Second, many of the problems purported to belong to the impedance mismatch are due to a lack of understanding of exactly what the relational model is, and how it is intended to work. This mismatch exists only as a result of bad designs, and because of OO people ignoring most fundamental database principles, and on a higher level because of a psychological impedance mismatch. "We explained the impedance mismatch problem, and claimed that the solution to that problem was not to bring the database language down to the record-at-a-time level, but rather to raise the programming language to the set-at-a-time level. c2.com /cgi/wiki?ObjectRelationalImpedanceMismatch   (4031 words)

Object Relational Impedance Mismatch Does Not Exist What someone just posted as a definition of ObjectRelationalImpedanceMismatch is anecdotical and metaphoric description of the psychological impedance mismatch. The psychological mismatch here is again that databases are not supposed to store objects created in an OO language, at least on two grounds: DatabaseApplicationIndependence, and DatabaseIsRepresenterOfFacts. I believe impedance is used by some here to indicate that an isomorphic mapping cannot exist. c2.com /cgi/wiki?ObjectRelationalImpedanceMismatchDoesNotExist   (4606 words)

Dare Obasanjo aka Carnage4Life - The Impedence Mismatch between W3C XML Schema and the CLR This is important given that it reduces the impedance mismatch which occurs when attempting to map the contents of an XML document into a relational database or convert an XML document into an instance of an OOP class There is a lot of discussion one could have about the impedance mismatch between the CLR type system and the XSD type system but one thing you can't say is that it doesn't exist or that it can be ignored if building schema-centric applications. In conclusion, the brief summary is that if one is mapping objects to XML for the purpose of serializing their state then there is a good match between the CLR and XSD type systems since the XSD type system is more expressive than the CLR type system. www.25hoursaday.com /weblog/PermaLink.aspx?guid=b2e5fe03-2205-402a-be18-7da10a9a66fe   (1010 words)

XML Impedance Mismatch - RSS Don Box: One thing I'm noticing is that the "object/XML impedance mismatch" is on the verge of being eclipsed by the "relational/XML impedance mismatch." Randy: I think too much effort is put into criticizing existing technologies and not enough effort is put into developing real applications. Not that I mind, I seem to be the only person focused on verticals v. www.kbcafe.com /rss?guid=20040907080632   (61 words)

TopLink The problem of bridging these fundamentally different technologies is known as the object-relational impedance mismatch. It must be efficient, scalable, and allow sufficient flexibility in defining the runtime behavior to enhance application performance. www.oracle.com /technology/documentation/1012_solaris/tour/qt/toplink002.htm   (111 words)

Hibernate in Action: Practical Object/Relational Mapping Object/Relational Mapping (ORM) is the name given to automated solutions to this transformation problem - known as the object/relational impedance mismatch. Transformations between the Java object model and the persistent relational model are often complex, tedious and costly to implement. Applications built with an ORM tool can be expected to be cheaper, more performant, more portable and more resilient in the face of changes to the internal object or underlying relational models. www.theserverside.com /books/review/HibernateReview.jsp   (688 words)

Object Persistence with the db4o Object Database However, the interface is complicated by the "impedance mismatch" between the domain object model of the application and the relational model of the database. The object model is based on software engineering principles and models the objects in the problem domain, while the relational model is based on mathematical principles and organizes data for efficient storage and retrieval. Object databases may, at lower levels, use all sorts of storage methods- direct to filesystems, or even a network (or relational!) database. www.theserverside.com /news/thread.tss?thread_id=30353   (6659 words)

XML Exchange: Share Your Data as XML In the early 1990s, object-oriented (OO) programmers decided that the impedance mismatch between an object with its data attributes and a relational table with columns was simply too complex for development teams to deal with. Object views gave DBAs and programmers the ability to create a database view of a UDT, where the result set is a collection of objects instead of a set of relational rows. Objects are still a large part of Oracle's strategy, and they're fully supported in Oracle Database 10g. www.oracle.com /technology/oramag/oracle/05-jan/o15xml.html   (1443 words)

DBMS - July 1997 - Sidebar - The Object Database Management Group Anyone who has built a relational database system using an object-oriented language has probably encountered the "impedance mismatch problem," which is a polite way of referring to the massive difficulties encountered when you try to map complex objects and relationships defined in your runtime system to some sort of tabular representation in your relational database. Transient objects are stored in and managed by the runtime system, be it Smalltalk, Java, or C++ (three languages for which ODMG bindings exist or for which drafts are in progress). Similarly, an object manipulation language (OML) is used to manipulate objects, and it doesn't distinguish between persistent and transient objects. www.dbmsmag.com /9707d131.html   (1443 words)

The Object-Relational Impedance Mismatch Symptoms of the object-data divide include object developers that claim relational technology either shouldn't or can't be used to store objects and data professionals that claim that your object/component models must be driven by their data models. Object techniques proved to work well in practice, not only isn't object technology a fad it has become the dominant development platform, and the status quo has changed to the point that most modern development methodologies devote more than a few pages to data modeling (to their detriment). Yet in reality object developers discover that they need to spend significant portions of their time making their object persistent, perhaps because they’ve run into performance problems after improper mappings or perhaps because they’ve discovered that they didn’t take legacy data constraints into account in their design. www.agiledata.org /essays/impedanceMismatch.html   (2441 words)

Object database - Wikipedia, the free encyclopedia It is most often used in the case of C++ and Java programmers that do not wish to deal with the impedance mismatch of going from an object oriented (OO) programming language to a database query language like SQL programming language that is the current standard. An object database (more correctly referred to as ODBMS or OODBMS or ODBMZ or OODBMZ for Object Database Management System) is a DBMS that stores objects as opposed to rows or tuples in respectively a SQL or a RDBMS (Relational Database Management System). The Object Database Management Group did come up with an industry standard called ODMG 2.0 but it failed to gain acceptance with the ODBMS vendors mostly opting for proprietary features and extensions instead of attempting to grow the ODBMS pie by standards compliance and competing on implementations. en.wikipedia.org /wiki/Object_database   (2441 words)

Computer> Database [encyclopedia] One school of of though considers there is a fundamental impedance mismatch between the object and SQL data models, so misnamed object-relational databases require misnamed object-relational mapping software to map between the SQL model (row-oriented, ad-hoc querying) and the object-oriented model (polymorphic types, navigational traversal of objects). There are several design patterns and research papers on writing object-relational mapping software; additionally, there are many free-software and commercial solutions, with varying degrees of flexibility. Note that writing "object-relational" mapping software is a non-trivial task due to the polymorphic nature of containers in the object paradigm; in other words, it is not as simple as "take all fields in a record, copy them into the object, and voila! kosmoi.com /Computer/Database   (2441 words)

The Third Manifesto - Wikipedia, the free encyclopedia The Third Manifesto (1995) is Christopher J. Date's and Hugh Darwen's proposal for future relational database management systems that would avoid 'Object-Relational Impedance Mismatch' between object-oriented programming languages and RDBMSs by fully supporting all the capabilities of the relational model. The main objective of The Third Manifesto, besides being theoretically sound and avoiding arbitrary restrictions and pragmatic debasement of the relational model, is to make a simple, restricted and precise definition of the role of object orientation in database management systems emphasising the few valid ideas from object modeling that are orthogonal to relational modeling. One of the major tasks has been to illustrate ways in which SQL represents an inadequate reflection of the relational model. en.wikipedia.org /wiki/The_Third_Manifesto   (221 words)

Computer> Database [encyclopedia] One school of of though considers there is a fundamental impedance mismatch between the object and SQL data models, so misnamed object-relational databases require misnamed object-relational mapping software to map between the SQL model (row-oriented, ad-hoc querying) and the object-oriented model (polymorphic types, navigational traversal of objects). Note that writing "object-relational" mapping software is a non-trivial task due to the polymorphic nature of containers in the object paradigm; in other words, it is not as simple as "take all fields in a record, copy them into the object, and voila! This mapping always introduces inefficiency, but may be the only choice for many systems which mandate a SQL database back-end (for legacy reasons). kosmoi.com /Computer/Database   (1255 words)

The Object-Relational Impedance Mismatch The impedance mismatch becomes apparent when you look at the preferred approach to access: With the object paradigm you traverse objects via their relationships whereas with the relational paradigm you join the data rows of tables. Much of the conversation about the impedance mismatch focus on the technical differences between object and relational technologies, and rightfully so because there are significant differences. Unfortunately the two technologies differ, these differences being referred to as “the object-relational impedance mismatch”. www.agiledata.org /essays/impedanceMismatch.html   (1255 words)

Computer> Database [encyclopedia] However, polymorphism complicates OO DBs because clients in general only have access to an abstract pointer to an object to be accessed; in other words, unlike the well-defined relational model, in the object model the application program does not know the concrete type of the objects it is accessing). Note that writing "object-relational" mapping software is a non-trivial task due to the polymorphic nature of containers in the object paradigm; in other words, it is not as simple as "take all fields in a record, copy them into the object, and voila! So not only most, if not all, of the impedance mismatch problem goes away, but also much application logic and integrity constraints can also be implemented in the database, much simplifying both coding and operation. www.kosmoi.com /Computer/Database   (1253 words)

Advanced Systems - February 1995 - Column This feature is a vitally important solution to the "impedance mismatch" problem between relations and objects, which results from the fact that a simple "pointer chase" in the object world normally corresponds to a time-consuming join in the underlying relational database. Once an object is fetched, other objects that have relationships to it are modified so that they point to the new object with a standard Objective-C ID, that is, a simple memory reference. It works by creating two types of auxiliary objects: EOControllers, which are interfaces between objects and their representations in the user interface (for example, an EOController updates an object's state if the user changes a corresponding field on the screen); and EOAssociations, which are links between EOControllers and the actual objects. sunsite.cs.msu.su /sunworldonline/asm-02-1995/asm-02-cs.html   (1343 words)

Advanced Systems - February 1995 - Column This feature is a vitally important solution to the "impedance mismatch" problem between relations and objects, which results from the fact that a simple "pointer chase" in the object world normally corresponds to a time-consuming join in the underlying relational database. Once an object is fetched, other objects that have relationships to it are modified so that they point to the new object with a standard Objective-C ID, that is, a simple memory reference. It works by creating two types of auxiliary objects: EOControllers, which are interfaces between objects and their representations in the user interface (for example, an EOController updates an object's state if the user changes a corresponding field on the screen); and EOAssociations, which are links between EOControllers and the actual objects. sunsite.nstu.nsk.su /sunworldonline/asm-02-1995/asm-02-cs.html   (1385 words)

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