Minggu, 18 Maret 2012

Resource Sharing (Berbagi Sumber Daya


Definis Resource
Pembuatan sebuah sistem memiliki tujuan untuk memaksimalkan resource yang ada. Sebuah aktifitas dari program aplikasi pasti membutuhkan resource. Resource atau sumber daya merupakan semua perangkat keras atau sebuah virtual sistem yang terhubung ke sebuah sistem. Untuk sistem komputer memiliki beberapa resource seperti printer, memori, hard disk dan sebagainya. Resource yang tadi merupakan resource yang berupa perangkat keras. Untuk vitual sistem bentuk sumber daya(resource) berupa waktu cpu, file atau berupa koneksi jaringan.
Seperti kita ketahui bahwa resource bisa dikategorikan perangkat keras atau virtual sistem. Berikut penjelasan dari contoh resource atau sumber daya baik berupa perangkat keras dan virtual sistem.
  • CPU time adalah sejumlah waktu yang digunakan oleg central processing unit (cpu) dalam memproses sebuah intruksi dalam program komputer. Waktu cpu ini sering diukur dalam satuan detik. Dan biasanya juga waktu cpu menjadi tolak ukur dari presantase kapsitas cpu dalam waktu tertentu di lingkungan multi tasking. 
  • Memori merupakan tempat penyimpanan data. Memori yang digunakan biasa berupa RAM. RAM singkatan dari Random Access Memory. Memori ini berupa stick yang dapat dihapus dan ditulis kembali datanya. Namun, ketika memori ini kehilangan sumber daya, maka data yang ada di dalam memori ini akan hilang. Salah satu RAM yang dipakai pada saat ini, yaitu DDRAM. Selain itu, memori sekarang sudah punya bentuk logis(logical) yang disebut virtual memori. Virtual memori merupakan sebuah teknik manajemen memori yang dibangun untuk sistem yang mempunyai fitur multi tasking. Teori umum virtual memori, hard disk atau flash disk dijadikan sebuah memori yang cara kerja mirip dengan RAM. Jaid, apabila memori RAM penuh dengan data/proses, maka data/proses yang masuk ke memori akan dialokasikan ke memori virtual ini alias di-swap. Untuk lebih jelasnya dapat dilihat pada gambar di bawah ini.
  •  Network throughput merupakan sebuah hubungan koneksi ke suatu jaringan. Sumber daya koneksi ini bisa berupa media kabel atau nirkabel. Sumber daya dilihat dari kecepatan data yang bisa yang dilakukan oleh sebuah komputer untuk mentransfer data ke komputer lainnya atau sebaliknya sebuah komputer yang membutuhkan data dari komputer lainnya.
  • Hard disk space. Hard disk adalah sebuah tempat penyimpan data yang mempunyai kapasitas cukup besar. Hard disk juga bisa digunakan sebagai virtual memori seperti keterangan sebelumnya. 
  • Electrical Power (listrik), sebuah energi listrik untuk mengaktifkan komponen yang ada elektronika di komputer. Listrik akan diatur penggunaannya. Untuk secara perangkat lunak yang berperan disini adalah sistem opersinya.
  • periperal Input/Output. periperal Input adalah sebuah alat untuk memberi masukan ke sebuah komputer, baik berupa suara, gerakan, sentuhan dan sebagainya. Contoh periperal input seperti mouse, keyboard, mikrophone, light pen, dan masih banyak lagi.Sedangkan periperal output adalah sebuah alat sebagai media keluaran dari hasil proses komputer. Contoh output seperti speaker, printer, monitor dan sebagainya.

 Teori Resource Sharing
Dalam sebuah sistem mempunyai fitur mukti tasking seperti real time system terdapat masalah terhadap resource(sumber daya). Seperti kita ketahui bahwa setiap komputer atau jaringan memiliki resource terbatas. Sedangkan sistem real time system menitiberatkan ketepatan waktu dalam memproses setiap respon dari pengguna. Dan setiap proses tersebut pasti memiliki kesamaan sumber daya.
Untuk itulah diperlukan sebuah kegiatan berbagi resource bersama yang lebih kenal dengan istilah resource sharing. Dalam resource sharing memungkin dua buah proses atau lebih dapat menggunakan data atau perangkat keras (hardware) secara simultan. Sedangkan, di jaringan memungkinkan dua buah komputer atau lebih dapat menggunakan data atau perangkat keras (hardware) dalam sebuah jaringan kerja komputer. Namun, sistem operasi yang khususnya sistem waktu nyata untuk dapat melakukan resource sharing terdapat beberapa cara. 

keyword: definisi resource sharing, definisi sumber daya berbagi, contoh resource sharing, teori resource sharing,


Lapisan Kedua OSI (Data Link)


Teknologi komunikasi terus berkembang dari waktu ke waktu. Perkembangan teknologi komunikasi ini lebih mengfokuskan kecepatan transfer data. untuk menaikan kualitas transfer dan menimiliskan kerusakan/kehilangan data, maka dibuat sebuah model teknologi yang disebut Model OSI. Model osi merupakan kumpulan protokol yang mengatur dalam transfer data di sebuah jaringan. Salah satu protokol adalah data link. Data link terletak pada lapisan dua di model OSI.
Data link merupakan sebuah lapisan kedua dari bawah ke dalam yang sebagai media pengontrol data yang membentuk frame dari bit mentah hasil proses lapisan fisik yang akan digunakan pada lapisan atasnya dan begitu sebaliknya mengubah dari frame menjadi bit mentah untuk diproses oleh lapisan fisik.
Frame merupakan sebuah blok dari sekumpulan bit terdiri dari bit start, data bit, parity bit, dan stop bit. proses di dalam data link sebagai berikut
      • konfigurasi jalur
      • flow ontrol
      • error control
      • protokol data link kontrol
  1. Konfigurasi jalur

     konfigurasi jalur ini berfungsi untuk dapat mengidentifikasi awal dan akhir tiap frame . tiga karakteristik pembeda pada konfigurasi jalur dapat dilihat dari topologi fisik, duplexity, dan line discipline (rancangan tata tertib)

   2.  Flow Kontrol
suatu teknik untuk memastikan / meyakinkan bahwa suatu stasiun transmisi tidak menumpuk data pada suatu stasiun penerima. tanpa flow control, buffer dari receiver akan penuh sementara sedang memproses data lama. karena ketika data diterima, harus dilaksanakan sejumlah proses sebelum buffer dapat dikosongkan dan siap menerima banyak data.

3. Error Kontrol
 berfungsi untuk mendeteksi dan memperbaiki error-error yang terjadi dalam transmisi frame-frame. ada dua tipe error yang mungkin :
frame hilang : suatu frame gagal mencapai sisi yang lain
frame rusak : suatu frame tiba tetapi beberapa bit-bit-nya error. 



Sabtu, 17 Maret 2012

Tugas Mencari Jurnal Komputer


Berikut ini contoh jurnal komputer  yang saya ambil di itb journal


Integration and Communication of Process Support Tools in
an online Virtual Learning Environment
L. Raeside
Department of Informatics and Enginneering,
Institute of Technology Blanchardstown,
Blanchardstown Road North, Blanchardstown,
Dublin 15, Ireland
B. Busschots, Shen Fei, J. G. Keating
Department of Computer Science,
National University of Ireland, Maynooth,
Maynooth, Co. Kildare, Ireland
May 7, 2006
Abstract
The Education through Virtual Experience (EVE) research group based at the National University of Ireland Maynooth have successfully developed an online Virtual Learning Environment (VLE) for Astronomy as part of the Virtual Telescopes in Education (VTIE) project. The VTIE VLE has been developed to provide online software support for the engagement of schoolchildren and their teachers in a scientific process. The development of an online VLE to support a scientific process has brought about complex interactions from the user perspective. This has lead to complex integration and communication challenges from the software implementation perspective. This paper contains a high level user-centered summary of the integration and communication challenges that have arisen during the VLE development and summarizes the mechanisms used to meet these challenges.

1. Introduction
The VTIE VLE, the virtual learning environment discussed in this paper, has already been used successfully to engage schoolchildren in a scientific process through Astronomy based experimentation [1]. The VLE has been constructed using a rapid prototyping approach combined with formative evaluations [2]. The VLE provides a software environment through which schoolchildren and their teachers can create project proposals, investigate and analyze data and images associated with that proposal and engage in team based collaborative writing to summarize all of the work carried out during the course of a project [3]. The completion of the VTIE scientific process culminates in the production of a project research paper. Following the completion of the formative evaluations of the VLE, the requirement for a set of fully integrated process support tools was identified. The aim of these tools is to fully support of all the above phases of the VTIE scientific process from project proposal to the generation of the project research paper. These tools are required to work online and be consistent in terms of look-and-feel, interoperability and usability within the VLE. The EVE research team have developed a number of tools to support the scientific process including the Collaborative Writing Environment (the CWE includes the Project Design and Management Interfaces) [4], the Scrapbook Tool, the Imaging Tool [5] and the Graphing Tool. The CWE allows students to produce a collaboratively written document within the VTIE environment that amalgamates all of the experiences of a group of students working on a particular project into a research paper. The Scrapbook Tool provides the basis for sharing of information resources between students within the VLE. The Imaging Tool provides a mechanism for students to analyze images and produce data about the images being analyzed. Finally, the Graphing Tool ensures that student data can be shown graphically via plots and graphs, these graphs are added to the group research paper. This paper summarizes the software design
constraints applied to the VLE in order to ensure consistent interoperability between the process support tools.

2. VTIE VLE Architecture
The VTIE VLE is a Java-based solution that has been constructed to operate within the Firefox web browser. The Firefox browser is part of the Mozilla project, is available online and may be downloaded and installed by participating schools at no cost [6]. There are a number of features that make the Firefox browser a suitable front-end for the VTIE VLE including the provision for rich customizability through software extensions, the provision of separate browser tabs which enhance the usability while navigating the VLE, and a high level of compatibility with the W3C standards [7]. In order to maximize the ease of integration of tools within VTIE, the VLE has been implemented using the Apache Struts framework [8].
The Apache Struts framework is based on the Model View Controller Model 2 (MVC2) design pattern and offers a well structured architecture through which new tools can be seamlessly introduced [9]. Each new software tool introduced into the VLE must follow the Struts framework specification, i.e., JSP is used for the view and the model is implemented using Java classes (namely Action classes). The Struts Controller is implemented as a servlet that maps events to particular classes using an XML based configuration file. The integration of new tools involves the editing of this configuration file and the addition of server classes to implement program logic [10]. Access to the VTIE database is carried out in a unified manner using Java utility classes designed at the architectural level. This ensures that each of the software tools can achieve database access without having to implement the low-level code statements to store and share information. The VTIE utility packages also provide unified access to various session-related information such as direct access to information relating to the current users and user groups. Communication between the various tools within the VLE is achieved using XML. The front-end communicates with the server via AJAX [11] and the server based components use the JDOM package [12] to produce and parse XML schema.
The XML schema are used to represent data passed between tools and between the client andserver. Figure 1 shows a diagram of the VTIE VLE Architecture and the communications mechanisms between the client and server components.
Figure 1: Architectural Diagram of The VITIE VLE
3. Examples of Tool Integration and Communication in VTIE
The requirement to support the VTIE scientific process has been the determining factor with respect to the communications between the various software tools. The communication links between the various tools have been formed directly from the user requirements and the educational goals of the VLE. This section provides examples of some of the communication that takes place between the process support tools within VTIE.
           The Project Design and Management interface (a component within the CWE) is responsible for initializing projects, setting up assignments, assigning students into various groups and the assignment of members of each group to particular aspects of each project. The Project Design and Management interface is used primarily by the students’ mentor, the mentor may be a teacher or any other person acting as the coordinator of student groups. The mentor can use this interface to assign particular sections of a document to particular members of each student group. The students then work in their respective teams while following the VTIE scientific process described above. The UML Use Case diagram in Figure 2 represents the main functions that each student carries out while completing a project. The Write Paper Use Case shown in Figure 2 involves the use of the Scrapbook Tool to gather various resources and include them in the project research paper, it also involves the use of the Collaborative Writing interface within the CWE and may also require the use of the Graphing Tool if the student wishes to produce a graph of project data. The Analyze Images Use Case shown in Figure 2 involves the launching of the Imaging Tool. The student may have stored images relating to the project and may wish to carry out measurements on these images. The Browse Web Use Case involves the use of the Firefox browser to search other online resources for information relating to the project, this phase of the project uses the Scrapbook Tool to store URLs, text, and any other information relating to the project. The Scrapbook Tool is capable of persistently storing any online resource while students browse the Web. This information is stored automatically in the VTIE database and can be shared within the students’ group and may also be viewed by the mentor.
Figure 2: UML Use Case Diagram of Main activities for the student within  The VITIE process
            The Scrapbook Tool is implemented as a Firefox extension. This tool operates within the browser window and can be used within the VTIE environment. However, this tool can also be used as a general purpose tool for the storage and retrieval of online resources within Firefox. The UML Use Case diagram in Figure 3 represents a student-centered view of the main functions performed through the Scrapbook Tool. The Scrapbook Tool integrates and communicates with all of the other tools within the VTIE VLE and provides a universal linking mechanism to the project research paper. The Scrapbook Tool represents an example of a communication intermediary between other tools within the VTIE VLE. The Scrapbook Tool communicates with other tools in the VLE through direct interaction with the students and is constantly available in the left pane of the browser window. Students simply carry out click-and-drag operations on online resources from the main browser window into the Scrapbook Tool as required. The student resources are automatically saved to the database and are associated with either the individual student or the student’s group. The Scrapbook Tool is also used as an intermediate communication link between the Imaging Tool and the Graphing Tool and the research paper created using the CWE. Images that have been modified within the Imaging Tool and graphs that have been generated within the Graphing Tool can be saved directly to the Scrapbook Tool as with all other online resources. The Add Scrap To Paper Use Case shown in Figure 3 allows students to add any of the resources collected into the project research paper including those images and plots generated within the VLE.
Figure 3: UML Use Case diagram of main functionality provided by the VTIE Scrapbook Tool
        The analysis of images using the Imaging Tool and the Graphing Tool represents a direct tool-to-tool communication link within the VTIE VLE using the VTIE database and XML. The UML Use Case diagrams in Figures 4 and 5 represent a student-centered view of the functionality provided by the Imaging and Graphing Tools respectively. As part of the analysis phase of the process the student must be able to gather data about images and then plot that data when required. Students may choose to gather data as one brief activity or they may choose to accumulate data over many days, weeks and perhaps even longer periods of time. In order to cater for the various time lapsed experiments that students may perform using VTIE it is important that data associated with images be stored persistently and that this data be associated with the student, the project and the image being analyzed. The Imaging
Tool provides the functionality to store data associated with the student images in the database using an XML representation.
        Figure 6 shows an example of the type of information stored in the database, the XML instance shown represents an angular measure carried out using the Imaging Tool (an angle measure requires the storage of three points in the image and the angle calculated between those points using the Imaging Tool). It is this XML database representation that forms the communication link between the Imaging Tool and Graphing Tool. When the student collects the necessary data from the image being analyzed this data is stored in XML format into the database, subsequently, the Graphing Tool may be launched by the student via the Imaging Tool or from elsewhere within the VTIE VLE. When the student chooses to launch the Graphing Tool directly from within the Imaging Tool an XML representation of all of the data saved for the current image is retrieved by the Graphing Tool from the database. The Graphing Tool retrieves the XML representation of the image being analyzed and uses JDOM to extract the image data for display within the data interface component of the Graphing Tool. Finally, the options interface of the Graphing Tool allows the student to select and modify the data they wish to display so that the graph is of the desired format to be added to the project research paper. The Graphing Tool provides the functionality to store the current plot as an image representation that can be retrieved, stored, and shared via the VTIE Scrapbook Tool as described above.



Figure 4: UML Use Case diagram of main functionality provided by the VTIE Imaging Tool
Figure 5: UML Use Case diagram of main functionality provided by the VTIE Graphing Tool
Figure 6: XML Representation of and Angle measurement using the VTIE Imaging Tool


4. Conclusions
The formative evaluations of the VTIE VLE have demonstrated that it is possible to successfully engage schoolchildren and their teachers in a scientific process using an online environment. The software required to support this scientific process has been continuously evolving in response to user testing. The complexity of the user interactions during the engagement within the scientific process has necessitated the implementation of complex integration and communication links between the various process support tools in the VLE. This paper has provided a high level user-centered model of the integration and communication necessary to support the various stages of the VTIE process from which more detailed models will emerge. The modeling of the integration and communication links between the tools within the VTIE VLE will provide the EVE research team with a valuable representation from which to base future development. Finally, the integration of the VTIE process support tools has served to illustrate the importance of applying sound software engineering practices to the development of a complex learning environment.

References
[1.]Hoban, S., desJardins, M., Farrell, N., Rathod, P., Sachs, J., Sansare, S., Yesha, Y., Keating, J.
G., Busschots, B., Means, J., Clark, G., Mayo, L., & Smith, W. (2002). Virtual Telescopes in
Education. Journal of Digital Information, 2(4), Article No. 104, 2002-05-23.
[2.] B. Busschots, L. Raeside, J. G. Keating (2005). Formative evaluations of a virtual learning
environment for Astronomy education. Accepted Journal Paper: Computers and Education
[3.] Hoban, S., Keating, J. G., Sachs, J., Laughlin, D., & Yesha, Y. (2003). Science Investigation
System for Telescopes in Education Research. Proceedings of the 36th Annual Hawaii
International Conference on System Sciences, Track 1 - Volume 1, p35.1.
[4.] B. Busschots, L. Raeside, S. Waddington, J. G. Keating (2006). The VTIE collaborative writing
environment. Proceedings of the 2nd International WEBIST Conference on Web Information
Systems and Technologies, Volume 2, P. 221-228
[5.] L. Raeside, B. Busschots, E. O’Cinneide, S. Foy, J. G. Keating (2005). Empowering
schoolchildren to do astronomical science with images. Proceedings SPIE Vol. 5827, P. 669-678
[6.] getfirefox.com (2005). The Firefox web browser, http://www.getfirefox.com. Available online.
Accessed on the 26th of March 2006
[7.] w3.org (2006). World Wide Web Consortium, http://www.w3.org. Available online. Accessed
on the 5th of May 2006
[8.] apache.org (2005). The Struts Framework, http://www.apache.org/struts. Available online.
Accessed on the 26th March 2006
[9.] javasoft.com (2005). The Model View Controller Model 2 Design Pattern,
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[10.] S. Speilman (2003). The Struts Framework. Morgan Kaufmann
[11.] xulplanet.com (2006). Advanced Javascript and XML, http://www.xulplanet.com. Accessed on
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[12.] jdom.org (2006). The JDOM XML solution, http://www.jdom.org. Accessed on the 26th of
March 2006



keyword: jurnal, journal, ilmu komputer