An RMI Soil Server

Let us consider the Soil component presented in the previous section, and implement it as a server using the RMI technology. The Soil component will provide its services to any other component or system residing in the same address space or in other servers located anywhere in the network. Therefore, the behavior of component Soil will be slightly different besides the behavior needed in the simulation process, the Soil component will be provided with additional behavior to function as an RMI...

The Use Case Diagram

The set of all use cases in a problem domain is referred to as the use case model and the diagram representing it is referred to as the use case diagram. A use case model shows the set of functionalities a system should provide. By examining a use case model, we can say whether all the user requirements are satisfied or not. A use case model is important, as it presents a general view of the system without being overwhelmed by implementation details. Let us consider IFAS's extension document...

Operations

An operation is the implementation of a service that can be requested from any object of the class to affect behavior BRJ99 . The set of all operations of a class define its behavior. The behavior of the class is defined during the analysis and design phases, and depends on the role that the class has in the domain. A class may have any number of operations but the number of operations should reflect the behavior of the class. An operation has a name that usually is a verb or a verb phrase that...

Petraq Papajorgji And Panos Pardalos

A book is never the result of the author's work only, and this book does not make exception form this general rule. Several are they who deserve credit for their objective and unselfish help that made this book better. We would like to express our gratitude to all of them for their criticism and suggestions that contributed to improve the quality of our work. Special thanks go to Dr. Tamara Shatar, a young and talented scientist who joined our team at IFAS, University of Florida, just after...

Conceptual Models

Interaction (sequence and collaboration) diagrams help us to understand how modeling elements dialog with each other to achieve functionality. It is a good modeling practice to start the design process by developing a conceptual diagram that represents our knowledge of the application domain expressed through concepts, abstractions, and their relationships. Conceptual diagrams are the result of an activity that is referred to as conceptual modeling. Conceptual modeling can be defined as the...

Sequence diagram for the use case

Figure 8-4 shows the sequence diagram for the Start Simulation use case. As shown in this figure, the sequence diagram presents all the elements of the system that participate in the simulation. Messages are numbered to show the order in which they are sent. The process starts with the user sending the message simulate to Simulator. Messages number 2 through 14 show what the Simulator should do in order to fulfill the received request. Simulator is responsible for the creation of all needed...

Polymorphism

Polymorphism is one of the most important features offered by the object-oriented paradigm. Polymorphism comes from the Greek term polymorphos meaning having many forms. In object-oriented programming, it refers to the ability of the language to process object differently depending on their class (Webopedia at http www.webopedia.com). Szyperski Szy99 defines polymorphism as the ability of something to appear in multiple forms, depending on the context the ability of different things to appear...

The iterator pattern

The purpose of the iterator pattern is to separate the logic of an algorithm manipulating the data from the particular structure of the container containing the data GHJ95 . As an example, let us consider the problem of obtaining weather data for a simulation model. As previously mentioned, different authors have solved this problem using different mechanisms some authors read the weather data from a text file saved locally in the system HWH01 . Others have developed complex systems to obtain...

Analysis Of An Irrigationscheduling Model

Figure 10-6 contains a diagram that represents the Irrigation Scheduling Model (ISM) developed by GSR00 . As in the Ritchie model, the only methods assigned to class Weather are for calculation of reference ET. However, ISM provides several methods for its calculation, such as the Penman-Monteith, Blaney Criddle, or Priestley-Taylor methods. The model also allows for user input of already-calculated reference ET. The ISM Weather class has been provided with a larger number of attributes,...

Packaging The Application

Before starting to write code, it is important to create a flexible and logical structure for storing files. Files could be organized in packages A package for component. The entire application is stored in the package referred to as Kraalingen, as shown in Figure 8-40. Within this package, five other packages are defined named Interfaces, Plant, Simulator, Soil, and Weather. Each of the packages contains a file of type JAR that is the compressed code for the class component. Thus, the package...

Collaboration diagrams

BRJ99 defines a collaboration diagram as an interaction diagram that emphasizes the structural organization of the objects that send and receive messages a diagram that shows interaction organized around instances and their links to each other. An example of a collaboration diagram is shown in Figure 6-9. Figure 6-9. Example of a collaboration diagram. Figure 6-9. Example of a collaboration diagram. In a collaboration diagram, all the messages that start at an object and the ones that end at...

Collaboration diagram for the use case

Collaboration diagrams provide another level of detail of the use case realization. We now know that sequence and collaboration diagrams are semantically the same, as they represent the interaction between the same elements, but the focus of the interaction is different. In the sequence diagram, the focus is on the order in time that messages are sent whereas in a collaboration diagram, the focus is on the object. Figure 8-5 shows the collaboration diagram for the Start Simulation use case....

The Interface Definition Language IDL

Interfaces need to be described in a common language VD98 . This common language is referred to as Interface Definition Language (IDL) and is used to describe the interface of an object. IDL is an object-oriented declarative language for specifying server interfaces. It is not a programming language it cannot be used to write code. As we know, interfaces define the operations that an implementation object should provide. As an example, Figure 11-1 shows the module definition for a hypothetical...

Analysis Of A Waterbalance Model

In order to develop specific class diagrams for individual models, each participating class in the template is populated with attributes and methods representing the model-specific input requirements and processes. This structure clearly shows the model data input requirements and the processes represented and can be used to organize code. Figure 10-5 represents a class diagrams for a water-balance model developed by Ritchie Rit98 . Ritchie's model requires certain weather data, such as...

Info

15 public double getSolarRadiation() Figure 8-34. The implementation of class DailyWeatherData in Java (Part 1 of 2). Lines 3 through 6 define the attributes of the class. Note that these attributes are defined as private they cannot be accessed outside the class definition by using the attribute name. Lines 8 through 13 define the class constructor, the Java mechanism for creating instances of a class. Lines 15 through 26 define methods to access values attributes hold. Lines 27 through 39...

Control classes

Control classes are used to model the behavior that is required for the realization of one or more use cases. Thus, a control class should provide the behavior that expresses the realization logic of a use case therefore, they are use case specific. If the logic of a use case changes, then the behavior of the corresponding control classes should be adjusted accordingly. Figure 8-12 shows the UML symbols for a control class each of them can be used interchangeably. Figure 8-12. UML symbols for a...

Components

There are several definitions of the component-based approach. BRJ99 define a component as a physical and replaceable part of a system that conforms to and provides the realization of a set of interfaces. This definition is broad and considers the component to be an organizational concept representing a set of functionalities that can be reused as a unit. According to this definition documents, executables, files, libraries and tables could be considered as components. The emphasis in this...

History Of Increasing The Level Of Abstraction

When developing software one deals with levels of abstraction, ranging from the real world where the problem represents the highest level of abstraction, to machine language that represents the solution in the lowest level of abstraction. Between the highest and lowest levels of abstraction, one should develop software in as many levels of abstraction as the problem demands. The history of software development is the history of increasing the level of abstraction at each step. In the early days...

The Kraalingen Approach To Crop Simulation

The crop simulation model considered in this study is the one developed by Kraalingen Kra95 . This approach uses the rate-state concept of simulation modeling PL82 , Calculations and statements are divided into four categories Initialization, rate calculations, integration calculations, and the output of results. These calculations are executed sequentially. The simulation starts at the beginning of a time step with a certain value for its state variables therefore, the initialization step must...

Uml

A condition or situation during the life of an object during which it satisfies some condition, performs some activity, or waits for some event BRJ99 , A diagram that shows a state machine statechart diagrams address the dynamic view of a system BRJ99 . A behavior that specifies the sequences of states an object goes through its lifetime in response to events, together with its responses to those events BRJ99 . The Unified Modeling Language, a language for visualizing, specifying, constructing,...

Statechart Diagrams

Statechart diagrams are one of the five kinds of diagrams UML uses to model dynamic aspects of systems. They are used to model different states of an object during its lifetime from the time it is created until it is destroyed. A statechart diagram shows the flow of control from one state to another. Figure 6-12 shows an example of a statechart diagram. Figure 6-12. States of object plant during the simulation. Figure 6-12. States of object plant during the simulation. A statechart diagram...

Stereotypes

A stereotype is rendered as a name enclosed by guillemots and placed above the name of another element BRJ99 . Figure 3-16 shows an example of a stereotype. The stereotype in Figure 3-16 is the word subsystem that gives to the package Accounting a special meaning or classification. Without the stereotype, the package Accounting is a general package. The stereotype allows the designer to create a new modeling element. Therefore, as shown in Figure 3-16, the stereotype converts a general package...

Class Diagram For The Kraalingen Approach

In the previous sections we discussed issues about how to identify the future classes and their particular role in the system. Now is the time to analyze the relationships between classes in order for the system to provide the required functionality. As we have previously mentioned, the main characteristic of the object-oriented approach is to model concepts of the problem domain using objects and provide objects with data and behavior so that they can play a well-defined role. Objects send...

Corba

OMG was created in 1989 to develop, adopt, and promote standards for the development and deployment of applications in distributed heterogeneous environments Vin97 , VD98 . OMG is a large consortium with more than 800 companies trying to reach a consensus on an appropriate component model and services for developing component-based distributed applications (http www.omg.org). OMG is the world's largest computer consortium and is a nonprofit organization that started initially with eight members...

O

Example of a bidirectional use case. additional reviewers in the case that the document deals with issues that none of the reviewers is a specialist in the field. Figure 5-6 shows the use case model for the department chair approval process. In this figure, the use case Add Reviewer extends the base use case Approve Document. According to the problem description, the department chair can add an additional reviewer to a document when he judges that a more specialized reviewer should...

Conceptual model for the Kraalingen approach

In order to develop a conceptual diagram for the Kraalingen approach, let us take a closer look at the equations of this model. Equations 1, 2, and 3 (see Chapter 8, The Kraalingen Approach) represent the relationships between objects plant, soil, and weather. Equation 2 shows that soil water factor data are needed to calculate changes (delta) in the leaf area index of the plant. The same equation shows that the temperature-based limiting factor, calculated by Equation 1, is needed to calculate...

Sequence diagrams

A sequence diagram is an interaction diagram that emphasizes the time ordering of messages BRJ99 . A sequence diagrams represents objects participating in the interaction in a timely manner. The time when messages are sent to objects is important and altering this order may produce unexpected results. Figure 6-5 shows an example of a sequence diagram. Farmer plays the role of an actor as the farmer sends a request to the system to obtain some weather data. 4 Figure 6-5. Example of a sequence...

References

Designing an object-oriented structure for crop models. Ecological Modelling 94, 33-44 (1997) Alex77 Alexander, C. A. Pattern Language Towns, Buildings, Constructions, Oxford University Press, New York (1977) Alex79 Alexander, C. The Timeless Way of Building. Oxford University Press, Oxford, UK (1979) AW85 Addiscott, T.M. Wagenet, R.J. Concepts of solute leaching in soils a review of modeling approaches. Journal of Soil Science 36, 411-424 (1985) BJ98 Beck, H.,...

A Corba Soil Server

Let us consider the Soil component developed in Chapter 8, The Kraalingen Approach, and implement a simplified version of it as a server using CORBA. This means that the soil class component will provide its services to any other class component or system residing in the same address space or in other servers located anywhere in the network. Therefore, the behavior of this class component will be slightly different besides the behavior needed in the simulation process, the component will be...