One of the coolest examples of dynamic language untility was provided By Apple's Enterpriise Objects Framework (EOF). Here is a brief quote from http://developer.apple.com/documentation/LegacyTechnologies/WebObjects/WebObjects_4.5/System/Documentation/Developer/EnterpriseObjects/DevGuide/EOFDevGuide.pdf explaining how object relationship fetching from an object<->relational mapping framework was implemented: Resolution of Relationships and Faulting When the Framework fetches an object, it creates objects representing the destinations of the fetched objects relationships. For example, if you fetch an employee object, you can ask for its manager and immediately receive an object; you dont have to get the managers employee ID from the object you just fetched and fetch the manager yourself. The Framework doesnt immediately fetch data for the destination objects of relationships, however. Fetching is fairly expensive, and further, if the Framework fetched objects related to the one explicitly asked for, it would also have to fetch the objects related to those, and so on, until all of the interrelated rows in the database had been retrieved. To avoid this waste of time and resources, the destination objects created are stand-ins, called faults , that fetch their data the first time theyre accessed. Figure 5 illustrates this process. The framework allows you to tune relationship resolution by prefetching relationships and batch faulting . For more information on these features, see the chapter Answers to Common Design Questions on page 221. For more information on the general faulting mechanism, see the chapter Behind the Scenes on page 187.
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