A Standard Framework for Database Development and Modeling of Energy Supply-demand System

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1 A Standard Framework for Database Development and Modeling of Energy Supply-demand System Yukinobu Koyama 1,*, Tatsuzo Kawakami 2 and Tetsuo Tezuka 3 Graduate School of Energy Science, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto , Japan Abstract: We developed a prototype of energy-environmental web-based database system to support the research on energyenvironmental field. We made the mathematical programming (MP) model of bio-energy in Thailand and collected the data nec essary for the model simulation. The database for analyzing the bio-energy in Thailand has been made as one of the application example of this web-based database system. The parameter given to the MP model can be selected from the web-based database. The most notable feature of this web-based database is tracing back from extensible Markup Language (XML)-formatted data file to the original source like. For those who want understand the model behavior, tracing function is important for understanding model, data and simulation results. In this paper we show the basic system framework and demonstrate the efficiency of this web-based database system by using modeling and evaluation of bio-energy in Thailand. This system will contribute to the acceleration of the research on the energy environmental-systems. Keywords: Energy-environmental Systems, Biomass, Web-based Database, Extendable Database, Mathematical Programming 1. INTRODUCTION Recently, energy-environmental issues have been attracting much attention such as global warming issue due to carbon-dioxide emission and the issue of the energy-substitute for fossil fuels. The evaluation about energy environment is important to design the policy about energy-environmental problems. To make and simulate the mathematical programming (MP) model is one of the common quantitative evaluation techniques for energy-policy design. We often face the two problems when the contents of the report of which conclusion is based on the MP model simulation is investigated. One is the lack of model information and the other is the lack of data information. Authors of the reports usually describe very important system-boundary conditions, assumptions and evidence for the setting of the parameters of the MP model in their reports. They, however, do not offer the complete set for reproducing the simulation results. Therefore, there is no way to reexamining the simulation result of the MP model for other researchers. The conclusions obtained by simulating the MP model cannot be successfully understood by other researchers if some important clues are missing. It is also necessary to clarify the source of the values of parameters. Therefore, each researcher makes the model from scratch in spite that the similar models have been developed. From these viewpoints we propose the framework for the extendable modeling including database development. 2. WEB-BASED DATABASE SYSTEM 2.1 System configuration System overview Figure.1 shows the overview of the web-based database system. XM L (MP Model) XM L (MP Model) PC with Windows XP Scr ipt (Perl) Full-Text Search Engine (Namazu) Spread Sheet (MS-Excel) Spread Sheet (OpenOffice Calc) Scr ipt (JavaScript) Internet (HTTP) Web Server (Apache) PostgreSQL Client PSQL Optional Client (GAMS) K yoto-u member can use only. Browser Scr ipt (PHP) RDBM S (PostgreSQL) RDBM S (M S-A ccess) Client Ser ver Client (ODBC) Internet Domain XML (Data) XML (Data) Fig. 1 Overview of the web-based database system General users on the client side can access to the web-based database system by using the browser. Data in extensible Markup Language (XML) format is downloaded after the data are selected. The general users can use the XML-formatted file as a parameter file for using optional software like mathematical programming (MP), for example. If we open the XML-formatted data file on the local PC by browser, we can view the original source. The original source means the report like. Corresponding author: koyama@eecom.energy.kyoto-u.ac.jp 1

2 2.1.2 Settings General users on the client side can access to this web-based database system through the Internet by using the arbitrary browser where JavaScript runs. We checked the operation of this system using Internet Explorer, Firefox, and Netscape. The general users have to turn on the HTTP cookie function of the browser for storing the information which is selected from the web-based database Web server and script language Except for operating system, the server is built by using free software. This system is built on Windows XP in this study, and it can be also built on Unix-like free operating system like Linux though there is some small difference for setting. This web-based database system adopts Apache HTTP SERVER as web server software. Apache HTTP SERVER is de facto standard of web server software in both Windows- and Linux-based system. This system adopts Hypertext Processor (PHP) which is a general-purpose script language which is especially suitable for the web development. PHP makes web contents described with HyperText Markup Language (HTML) dynamically Database software PostgreSQL, MySQL and Oracle are typical Relational DataBase Management System (RDBMS), and SQL is the computer language used to create, modify, retrieve and manipulate data of RDBMS. PostgreSQL uses free license, MySQL uses free license for academic use, and Oracle uses commercial license. The specification of PostgreSQL is close to the specification of Oracle which is standard RDBMS for business. Many database engineers are accustomed to using Oracle. Therefore, the maintenance of PostgreSQL by the administrator is easy. Simply speaking, PostgreSQL is equal to Oracle in the range of the function which we use, and it is dominant on the cost side. On the other hand, MySQL is superior to PostgreSQL on the execution speed but our project doesn t face the performance problem. PostgreSQL supports more SQL commands than MySQL's and it is convenient that convenient SQL commands are supported. For the above-mentioned reasons, this system adopts PostgreSQL as database software. PostgreSQL stores the data picked up from the original source. In addition, PostgreSQL stores the location information as Uniform Resource Locator (URL) of the original source. PostgreSQL have ability to store the large data like using the special data structure which is called large object. In our web-based database system, PostgreSQL does not store the large object. Basically, the original sources are stored in the area where the Apache HTTP server has permitted to access to the server. However, if the original sources can not be put on our server by copyright problems, only the URL information is stored Output file for application (gams, etc.) For tracing-back function which is explained later in 2.2, output file has to include the additional information about the original source. It is one of the choices to include this information into Comma Separated Value (CSV)-formatted file because a lot of MP solvers can use CSV-formatted file as parameter file. However, MP solver doesn't demand the CSV file which includes the additional information. If this web-based database system outputs a CSV file which includes usual data and additional data like comment and reference, general users have to classify the data which MP solver needs when general users simulate with MP solver. What this file s contents show might not be understood because CSV-formatted file does not have information which is necessary for general users to understand the contents. Therefore, it is possible that the value in the CSV-formatted file will walks by oneself. On the other hand, if only usual data which MP solver can handle is preserved in CSV, this system have to output the other file which stores the addition information like comment and reference information. If this system outputs two or more files, management of the files by general users will become a little complex. This system finally adopted the XML-formatted file and put all information like data, comment, and reference into it. If general users want to use the CSV-formatted file, data will be extracted from this XML-formatted file because all data is included in the XML-formatted file. XML format is skillful to express the tree structure because tag style attribute can be nested in the multiple. It is suitable for storing data like the energy balance sheet because it doesn't influence the structure of the parent node even if the child node is subdivided. By the way, you might wonder that the XML-database is not used in our system. XML database which handles data in the form of XML exists but the main stream of the database system is still RDBMS. We just give XML-formatted file which we downloaded as parameter to arbitrary client software. Fig. 2 shows one of the examples of XML-formatted data file. 1:<?xml version="1.0"?> 2:<?xml-stylesheet type="text/xsl" href=" 3:<mtable> 4: <mtr> 5: <mtd> 6: <data>palm-oil</data><comment>see p.12</comment> 7: <reference> 8: 9: </reference> 10: </mtd> 11: <mtd> 12: <data>164250</data><comment>see p.12</comment> 13: <reference> 14: 15: </reference> 16: </mtd> 17: </mtr> 18: <mtr> 19: <mtd> 20: <data>jatropha-oil</data><comment>see p.12</comment> 2

21: <reference> 22: http://localhost/biomass/display.php?

3 21: <reference> 22: 23: </reference> 24: </mtd> 25: <mtd> 26: <data></data><comment> </comment> 27: <reference> 28: 29: </reference> 30: </mtd> 31: Fig. 2 A part of XML-formatted data file. First 2 lines indicate the header information. <mtable>, <mtr>, <mtd> tags indicate matrix, row vector, and element respectively. "<data>" tag shows data obviously. The <comment> tag can put information and etc. when general users extract the data. If you want to put equation into this comment column, you can use MathML which is a low-level specification for describing mathematics is based on XML. If you want to put figure into this column, you can use SVG which a language for describing twodimensional graphics and graphical applications in XML. You may use the expression of LaTeX because it can input anything to this column if it is a text form. <reference> tag stores URL information to reach the original data. In this prototype, this XMLformatted data file stores minimum information for tracing back. In a present specification, only URL where the original source is put is stored, and report name and etc. are not described by referring in XML using text editor. It is very easy to put the report name etc. in XML sentences technically. The specification might have to be reconsidered Interface for database For accessing to PostgreSQL database, it is general to use psql which is the special client software for PostgreSQL. There is another way to access to the database using general-purpose software application like MS-Excel, MS-Access, and OpenOffice-Calc and etc. with Open DabaBase Connectivity (ODBC). The users who belong to the same Internet domain as the server can access to the web-based database server by using those products of software. However, general users can't access to this system through the Internet by those clients because of security problems. Fig. 3 shows the snapshot of the web-based database system. (a) Main screen (b) Selected data Fig. 3 Snapshot of the web-based database This web-based database system needs the following procedures for selecting data. 1. Input the size of MxN matrix for storing the data which are selected in Fig. 3(b). 2. Click the circular button in Fig. 3(b) for opening the database as is shown in Fig. 3(a). 3. Click the data which users want to select in Fig. 3(a). If you click the Click in Fig. 3(a), you can check the information of original source like (b) Fig. 6(a). Data are displayed in an empty column which users selected in Fig. 3(b). 6. You can input some comments into each element about selecting data if you click the white note icon in Fig. 3(b). 7. You can also view the original source in (b) Fig. 6(a) if you click the book icon in Fig. 3(b). 10. Click the Download button in Fig. 3(b) for downloading the data which you selected as XML-formatted file if you finish to collect. See also Fig. 1. 3

Since the purpose of this paper is to show the basic framework of the extendable modeling, the interface shown in figures might have to be reconsidered. Fig. 3(b) corresponds to Fig. 2.

4 Since the purpose of this paper is to show the basic framework of the extendable modeling, the interface shown in figures might have to be reconsidered. Fig. 3(b) corresponds to Fig Tracing back function The one of the salient features of this web-based database system is tracing back function from the XML-formatted data file to the original source. Fig. 4 shows the snapshot when we open the XML-formatted data file on the local PC by browser to trace back. If the users want to view the information as is shown in Figure 4, for example, some additional information to XML file is needed. The second line in Fig. 2 means to refer the style sheet which is written by extensible Stylesheet Language (XSL). XSL is for defining XML document transformation and presentation. It is possible to convert the contents of XML file into an arbitrary format like XML, CSV, HTML, and so on by description of XSL. XSL Transformations (XSLT) is necessary to interpret the description by this XSL. This function is equipped in most of general browsers and OS. Fig. 4 This is snapshot of browser which load the XML-formatted file on the client PC Fig. 5 shows an example of the XSL-formatted file which is defined for Fig. 4. HTML sentences (link, table, etc.) are defined by the XSL-formatted file. 1:<?xml version="1.0" encoding="shift_jis"?> 2:<xsl:stylesheet xmlns:xsl=" version="1.0"> 3: <xsl:output method="html" encoding="shift_jis" /> 4: <xsl:template match="/"> 5: <html> 6: <head> 7: <link rel="stylesheet" type="text/css" 8: href="balance_sheet/balance_sheet.css" /> 9: </head> 10: 11: <body> 12: <table border="1"> 13: <xsl:apply-templates select="model" /> 14: </table> 15: </body> 16: </html> 17: </xsl:template> Fig. 5 An example of XSL-formatted file In Fig. 4, if the element on this screen is clicked, the general users can get the original source. The original source s name and number of page are displayed in (b) Fig. 6(a). 4

5 (a) (b) Fig. 6 Snapshot of original source When the original source in (b) Fig. 6 is clicked, the original source is displayed like (b) Fig. 6(b). If the server stores the original source, general users can see it. For instance, if the original source is a report included in an international journal, we cannot save the original source in our server because we face the copyright problem. If the original source is on the online journal, this web-based database points the URL information of the original source. If institute which general users belong to has the site license of the online journal, general users can see the original source. If it is not, general users can t see it and can get the title of the original source only. However, leaving source information is also important for the users. This database can store the PowerPoint-formatted data file and etc. which were used in an international conference and academic society in each country. The reliability of it might be lower than that of the report on the international journal, but it will become easy to collect data because it can publish only by obtaining the individual researcher s permission when such data is collected. 2.3 MP model (XML) It is important that the authors describe boundary conditions and preconditions a MP model. First of all, we confirmed whether there was already a suitable definition because MP model is not only for energy science field but also for another field. The other institute are making XML standard for representing linear programming problem and solution instances which is called LPFML. The MP model is described in a united language and this is converted into the optional software. We examined the adoption of this standard but we focus on writing the information about system boundary conditions, preconditions, parameters, and etc of the MP model. Fig. 7 shows the our original format of XML for describing the MP model information. We don t treat the MP model data by PostgreSQL because this model information is different with the data. We consider about the introduction such as Concurrent Version System (CVS) for storing this XML-formatted file. This treatment might have to be reconsidered. 2.4 Other feature To use the collected original sources more effectively, this system adopted the full-text search engine for free which is called Namazu. Namazu is reliable free-software, and it has been also introduced in the National Diet Library of Japan, Ministry of the Environment of Japan, for example. Available is Apache Lucene which is also a full-featured text search engine library with free license. Both of them can do full-text search to PDF-, PowerPoint-, Word-formatted file. The important difference of the two is about handling of two-byte characters like Chinese character. Namazu can treat two-byte characters easily because it is developed by Japanese programmer. Namazu was adopted in consideration of the number of data donors. Namazu extracts character string information from file which is not protected. Therefore, the data offer which is not protected is hoped for. 3. APPLICATION EXAMPLE (BIOMASS IN THAILAND) To evaluate the future bio-energy supply from the viewpoints of amount, cost, carbon-dioxide emission and supply stability quantitatively is important for considering energy-environmental problems. Kawakami et al. have been developing the model where the scenarios about bio-energy in Thailand are evaluated by using General Algebraic Modeling System (GAMS) which is a modeling system for MP and optimization. We stored this model as XML-formatted model file on the server. PostgreSQL stores the amount of biomass, the conversion ratio, and so on. The arbitrary application for our case is GAMS as shown in Fig. 1. Details of the model are not described in this paper and please refer to [3] for details. This report focuses on the data stream. Fig. 7 shows a part of XMLformatted MP model file. The procedures for the analysis are as follows: 1. Download the XML-formatted model file in Fig Access the web-based database and select data in Fig Download the XML-formatted data file Fig. 1. See also Fig. 2, Fig Convert XML-formatted model file into GAMS-formatted (TEXT-formatted) file. XSL-formatted file to convert to TEXT-formatted is not shown in this paper. 5. Convert XML-formatted data file into CSV-formatted data file. XSL-formatted file for this translation is also not 5

6 1:<?xml version="1.0" encoding="shift_jis"?> 2: 3:<model> 4: <file_name>biomass_thailand.gms</file_name> 5: <programmer>tatsuzo KAWAKAMI, Graduate School of Kyoto University</programmer> 6: <format>gams</format> 7: <solver>cplex</solver> 8: <energy>true</energy> 9: <economy>false</economy> 10: <environment>true</environment> 11: <boundary> </boundary> 12: <objective_function> 13: In this model,... 14: (1)About the replacement of fuels... 15: (2)About the relation between electricity and heat... 16: </objective_function> 17: 18: <constraint> 19: In this model, constraint is 'resouce constraint'... 20: </constraint> 21: 22: <parameter> 23: p(i) production of biomass i in ton /... 24: </parameter> 25: 26: <source_code> 27: i biomass /... 28: </source_code> 29:</model> 30: Fig. 7 XML-formatted MP model file about biomass in Thailand shown. 6. Execute GAMS. It is assumed that data have already been stored in the database. We applied the data obtained by this web-based database system to GAMS. If general users apply to arbitrary software, the system should be converted into the format which it wants by defining the XSL-formatted file. 4. CONCLUSION We have built the web-based database system about bio-energy and made a framework for including enough information and have proposed to leave information on the MP model as XML-formatted file. The efficiency of this web-based database system is demonstrated by applying the example case about bio-energy in Thailand. A late-started researcher can do confirmation simulation and he will extend the model by the web-based database system. It is important for a lot of researchers to use this web-based database system, and to accelerate their research of the energy-environmental field. 5. REFERENCES [1] Tatsuzo KAWAKAMI, Yukinobu KOYAMA, Surin Ngaemngam and Tetsuo TEZUKA, (2006) Database-development, Modeling and Evaluation of Bio-energy in Thailand, Proceedings of The 3rd International Symposium on Sustainable Energy System, pp [2] Yukinobu KOYAMA, Tetsuo TEZUKA, (2006) Database-development, Modeling and Evaluation of Bio-energy in Thailand, Proceedings of The 3rd International Symposium on Sustainable Energy System, pp [3] Tatsuzo KAWAKAMI, Yukinobu KOYAMA, Surin Ngaemngam, Tetsuo TEZUKA, (2006) Database-development, Modeling and Evaluation of Bio-energy in Thailand, to be presented at The 2nd Joint International Conference on Sustainable Energy and Environment (SEE 2006) 6

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