Re: Procedural vs Declarative XML transformation approaches
Inquire into the coupling of declarative persistence (how long is a declaration usable) and operational scope (given known and unknown events). We order declarative and procedural techniques to ensure robustness. SQL is a good example. A simplistic order: 1. Design schema. 2. Populate data. 3. Design query. 4. Operate on query result (view). 5. Feed output into next operation. Mixed model or no, without the pre-created structure, we only have event recognition and must deduce pattern, choose process, and hope for the right results in the face of new events. The operational order of technique is as important as the technique. Even OOP systems have this kind of necessary ordering. We have to declare an object's information items, design methods that can operate on them predictably, then schedule recognizable events to invoke methods. We encapsulate to prevent disorganizing events (mal-performed) and declare public interfaces to promote organizing events (well-performed). As noted elsewhere, declarative technique tames complexity by imposing order and relationship, and handles emergence by applying conditions to creating subsets or views as input to a procedure, or as in the case of object, contracting for a specified response. We *make* the system predictable and control the environment to *maintain* it. A pragmatic system is robust given the reciprocity of environment and internal regulation of change that is adaptation. The concept of emergence follows on robustness: a system that is robust has an orderliness that enables emergence. Adaptation by adding features, (eg new handlers for new classes of events) should not break existing behaviors (system is not overly sensitive to change). Declarative systems are sensitive to schema changes (the main rub of namespace strings - single point failures). Procedural systems are sensitive to changes in events (the endless switch). Without the apriori declarative technique, the procedural technique inherits the burden of ordering the input (Recognition). Without the procedural technique, we can't select an input based on a known event or extend it given a new event (Adaptation). Given maintenance and extensibility in the face of changing events, a mixure of the two techniques produces the pragmatic system: adaptible in the face of environmental changes, therefore, robust. Len Bullard Intergraph Public Safety clbullar@i... http://www.mp3.com/LenBullard Ekam sat.h, Vipraah bahudhaa vadanti. Daamyata. Datta. Dayadhvam.h
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