Architectural models

Such an analysis indicates that the zero-sink assumption must be used with extreme caution if accurate flux calculations are required at the local root level. Potassium, for example, is close to the limiting value of A, for the zero sink assumption to be fulfilled, and simulations with larger roots or larger buffer powers could well lead to inaccurate simulation results. Any zero-sink model involving nitrate should be treated with some suspicion. The zero-sink assumption is also widely used in root architecture models (see later). 

Architectural models explicitly specify the di.stribution of roots in space. An alternative approach, which is also useful for rhizosphere studies, is the continuum approach where only the amount of roots per unit soil volume is specified. Rules are defined that specify how roots propagate in the vertical and horizontal dimensions, and root propagation is u.sually viewed as a diffusive phenomenon (i.e., root proliferation favors unexploited soil). This defines the exploitation intensity per unit volume of soil and, under the assumption of even di.stribution, provides the necessary information for the integration step above. Acock and Pachepsky (68) provide an excellent review of the different assumptions made in the various continuum models formulated and show how such models can explain root distribution data relating to chrysanthemum. 

A design described using connectors doesn t depend on a particular way of implementing each category of connector. What s important is that the designer know what each one achieves. We can distinguish the component architecture model (which connectors can be used) from the component architecture implementation (how they work). 

There can be many different implementations of a given architecture model, and the same architecture model can be applied to many different applications. A given component architecture describes its type, or style, and its implementation. 

An architecture is, first, an abstraction of a system s implementation. There are many different architectural models that help you understand the system process, module, usage dependencies, and so on. These models help you analyze certain qualities of the system runtime qualities, such as performance, security, or reliability and development-time qualities, such as modifiability and portability. These qualities are important to different system stakeholders not only the end user but also the system administrator, developer, customer, maintainer, and so on. Different kinds of usage scenarios, including system modifications and deployment scenarios, can help you to evaluate architectures against such qualities. 

In Catalysis, we can use refinement to model abstract objects that do not necessarily correspond to an instance of an OOP class and abstract actions that may not correspond to a single OOP message send. Based on this, we can use all the modeling techniques— including attributes, types, collaborations, refinement, justifications, interactions, snapshots, and states—to describe architectural models and their rationale. 

The architectural models are the primary vehicle for communication among all these stakeholders and for formal review of the models against the system requirements. They form the basis for an early prototype, against which many qualities can be evaluated even though there is minimal end-user functionality implemented. 

Similarly, an architectural model is built from some number of elements processors, modules, components, objects, class libraries, threads, and so on. A good architecture is based on a small set of design elements and uses them in a regular and consistent manner so that the system substructures are simple and similar. 

Packages and their import structure define a development-time architectural model. In Catalysis, the imports define definitional and usage dependencies. 

Design rules for technical architecture This defines the elements used and patterns followed systemwide for dealing with the computing infrastructure aspects of the design. It includes hardware and software platforms and tools, middleware and databases, and the choice of API standards and component architecture, such as JavaBeans or COM. These rules emerge in parallel with the activities in items 11 and 12 architecture models and implementations. 

Horizontal slices The technical architecture model should not be just a paper exercise. Instead, slices of the architecture model should be prototyped in a horizontal fashion where each slice helps complete the end-to-end communication paths but does not introduce new end-user functionality. Nonfunctional requirements—throughput, scalability,... 

Some of the reindeer lichens, especially Cladina alpestris, are shaped like miniature shrubs and trees. Consequently, these plants are sometimes collected, dried, and dyed, and are used in landscaping the layouts for miniature railroads and architectural models. 

During the last two decades, the number of molecular modeling studies on zeolites published annually has grown enormously. As a result of advances in both the development of computational methodologies and new computer architectures, modeling has become an important tool in zeolite research. It can provide useful insight into the structure and reactivity of zeolites and into the sorption of molecules in zeolites. This section gives a brief introduction to computational approaches, as well as a short overview on applications in zeolite research. 

The individual actors in a system are called entities, as in the OSI architectural model [Lini83]. Each entity behaves according to one of the given programs, but, depending on the structure description, there may be many entities with the same program. Entities may even be generated dynamically. ... 

The primary result of the DWQ project consists of a neutral architectural reference model covering the design, the operation, the maintenance, and the evolution of data warehouses. The architecture model is based on the idea, that any data warehouse component can be seen from three different perspectives The conceptual perspective, the logical perspective, and the physical perspective. In the design, operation, and especially evolution of data warehouses, it is crucial that these three perspectives are maintained consistent with each other. 

Concepts for architecture modeling (Subsect. 5.7.2). Firstly, in order to define a suitable vocabulary for architecture modeling an adequate architecture description language is required. Such a language [331] defines the basic modeling idioms, like modules, subsystems, components, interfaces, and relationships, from which an architecture is built. 

The refinement steps shown in box 2a (or alternatively in box 2b) require user interactions. It is the software engineer s knowledge to decide how the TooI COMOS PT is accessed by the Integrator Tool and, in case of an API, which technique is used to realize the API. After determining this interactively, the transformations shown in box 3 and box 4 can be performed by an appropriate architecture modeling tool automatically. When, for example, the software engineer decides later that no homogenizing wrapper is necessary, he can delete this component manually. 

A MethodInvocation represents a local communication, while an In-terprocessCaII represents a distributed one. Therefore, a "Methodlnvoca-tion relation is only feasible between components that are contained within the same Process , whereas an InterprocessCall relation is only allowed accordingly between components of different processes. An architecture modeling tool can again carry out these transformations automatically. 

These and other approaches for architecture modeling [224] claim to be usable to specify architectures independent from the domain and do not consider the needs for domain-specific architectures [843]. Therefore, PsiGene [934] allows to combine design patterns as presented in [580] and to apply them to class diagrams. A technique to specify patterns in the area of distributed applications and to combine them to a suitable software architecture is shown in [374]. 

Klein, P. Architecture Modeling of Distributed and Concurrent Software Systems. PhD thesis, RWTH Aachen University (2000)... 

Client-Server Architecture refers to a two-tier architecture model where client (user interface, input logic visualization) and server (business logic, database) are separated from each other and are connected via a computer network. 

N-Tier Architecture (multitier architecture) is a software architecture model where multiple software components serve different purposes and are physically separated, such as client-server architectures. 

Figure 8.1 An architectural model (left) and transmission electron micrograph (right) of an aerogel showing the nanostructured network and pore structure. (Left panel reproduced with permission from D. R. Rolison and B. Dunn, J. Mater. Chem. 2001, 11, 963. Copyright 2001 Royal Society of Chemistry. Right panel reproduced with permission from M. L. Anderson et al., Adv. Eng. Mater. 2000, 2, 481. Copyright 2000 Wiley-VCH.)...

Eigure 7 Network Traffic Comparison, a) Two-tier architecture model, b) Three-tier architecture model. 

Figure 33 Ovum Knowledge-Management Tools Architectural Model. (From Woods and Sheina...

The architectures modeled in this appendix are the "generic" architectures. Actual commercial implementations may vary. While the architecture concepts are presented with programmable electronic controllers the concepts apply to sensor subsystems and final element subsystems. 

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