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KNOWLEDGE-BASED SOFTWARE ENGINEERING phần 8

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và nhà cung cấp và người sử dụng cam kết các tiêu chuẩn này (thay vì phát minh ra những cái mới như Microsoft C # hoặc Internet di động của Nokia kỹ thuật Kiến trúc Mita nỗ lực). Dần dần, khi các ứng dụng sẽ bao gồm việc sử dụng trong xây dựng XML, một chặt chẽ hơn | B. Bẹbel and R. Wrembel Method Materialization 227 While materializing an oov one should consider not only materialization of objects structure but also objects methods. The materialization of a method consists in computing the result of the method once storing it persistently in a database and then using the persistent value when the method is invoked rather than computing it every time the method is invoked. When a method result is made persistent it has to be kept up to date when data used to compute this result change. When method m is materialized it may be reasonable to materialize also the intermediate results of methods called from m. We call this technique hierarchical materialization. When an object used to materialize the result of method m is updated then m has to be recomputed. This recomputation can use unaffected intermediate results that have already been materialized thus reducing the time spent on recomputation. There are a few approaches that address method precomputation i.e. materialization in the context of indexing techniques and query optimization 5 1 6 but not in the context of materialized object-oriented views. The work of 5 sets up the analytical framework for estimating costs of caching complex objects. Two data representations are considered i.e. procedural representation and object identity based representation. In the approach of 1 the results of materialized methods are stored in an index structure based on B-tree called method-index. A method-index on a method M stores in its key values the results of the invocation of M on the instances of the indexed class. The application of method materialization proposed in 1 is limited to methods that 1 do not have input arguments 2 use only atomic type attributes to compute their values and 3 do not modify values of objects. The concept of 6 proposes data structures supporting materialization of methods and maintenance of materialized results. However this approach does not take into account