Friday, July 11, 2014

- In larger data sets using SQL engine often access optimization, which means that the first loads

My architecture posts in March pointed out that the data layer is often simplifies the behavioral model, and completing proven SQL (or OLAP) databases, which can serve up answers (cursors / views) on the complex but regular calls, can shrink many Sequence diagrams in UML. Where a long chain of interactions peek of the long complex searches (often navigation between many tables), a number of tables are encapsulated in one component peek (e.g., as a SQL procedure).
But on the other hands they are far too complex readings / searches ("Q", in CQRS). With the emphasis on encapsulation rather than notation, a minimalist Sequence diagrams in arkitektvyn look like this, expressed in UML, but apart from activations (activation bars) and any security layers:
That is finished and tested functionality shrinks SQL search 1 component (and the Sequence Diagram 1 lifeline), instead of displaying peek a number of tables in the internal loops ("under the hood" of the SQL engine or OLAP package). Simple, declarative (think SQL, OCL, Linq, Hibernate, or Erlang, rather than procedural Horizontal / imperative), regardless of different access devices (SQL indexes, Peter Coad's extra associations for Status Collections such as all fully booked departures versus those with places peek still available, etc.), ignoring for the moment both from NIH syndrome (Not Invented Here) and wish "Better test tools for declarative languages," but still shows things that interest the architect.
Although the example is simplified (a trip is only one flight segment, other companies in the same alliance omitted, etc.) so, so no UML expertise to realize that minimalistalternativet with encapsulation outlined above has its advantages over the detailed "procedural" option below :
In addition to more detail does not automatically entail more understanding and consensus, so true this sort of explicit sökkedjor rarely with the reality of declarative environments, in particular SQL, for two main reasons:
- In larger data sets using SQL engine often access optimization, which means that the first loads the tables that effectively shrinks the remaining access road / search space, even where access chain will seem "illogical" for the requirements analyst.
Even in platform-independent UML diagrams usually pay to begin with "encapsulation level" (subsystems or components peek PriserPåTillgängliga in the top picture), and from there make it down to the level of detail (with UML 2 Lifeline decomposition) because levels usually go home at completely different peek roles.
In all Agile modeling is important to first ask what roles and situations model is for and what they get out of reading it, so before you pull on the detailed notation. For example, viewing peek the architect and application developer rarely through the same glasses. But instead of that thing with value for money modeling so I will conclude with a quiz question on the theme "book versus course" peek and a boot to the publishers who preferred the other in front of practical substance while courses prioritized substance:
Guess which of the following two quotes come from an otherwise very good arkitekturbok, and which, from an architecture course at Informator. Both aims to explain the A. in the CAP within distributed computing (CAP = Consistency, Availability, Partition tolerance).
Milan collaborating with Informator since spring 1996 in modeling, UML, requirements, analysis peek and design. Keeps fn courses in Architecture, in modeling (T2715, T2716), and in February 2013, he also Informator's crammed Seminar on use cases.
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