P2P Network and Incentive Design for Sharing Teaching Material

數位內容的興起以及通訊網路的發達，促成了內容在網路上的分享的現象。教材分享(TMS)即是內容遞送網路(CDN)中的一種重要應用。藉由教材分享，教師們可以互相學習各自的專長並且促成優質教材的產生和創意教學的實現。除此之外，教材分享也能緩和城鄉之間的數位與教育落差。如何讓教師們能夠便利的創造和分享教材以及如何促使教師們積極的分享教材，是目前我們面臨的重大問題。 本論文探討國小教師在台灣學術網路(TANet)上分享教材的兩個問題: 第一個是討論如何去設計一個符合目前國小教育結構的點對點內容遞送網路之教材分享環境；第二個在於如何去設計誘因以鼓勵教師們在點對點內容遞送網路之教材分享環境上分享教材。目前的挑戰包括了：教材製作呈現、教材發布與傳遞、教材品質評鑑、教師信用記帳，教師行為模型以及在非營利環境下的誘因。 在研究了目前國小教育結構以及現存的內容遞送網路後，我們發現有超結點的混合式點對點網路(Hybrid P2P)與目前國小教育結構極為相似。因此我們在台灣學術網路上設計了一個以點對點網路為基礎的教材分享環境，整個環境包含了：以SCORM作為教材製作呈現的標準、以混合式點對點網路作為教材發布與傳遞的平台、一個教材品質評鑑的評分系統及一個交易與教師信用的記帳系統。 在誘因設計(incentive design)部分，首先我們考量以下因素來建立系統模型：一. 教師的利益函數(teacher benefit function)是由從報酬得到的效益減去教材編轉的成本而成，並且在考量了教師在分享環境中可能的行為後，將利益函數中的因素做細微分類；二. 藉由觀察教師上傳行為之特性後，使用巴氏模型(Bass model)去捕捉教師上傳教材意願的動態(dynamics)。接著，我們提出兩部份之誘因機制：第一種是以聲譽為基礎的報酬誘因(reputation-based reward)來鼓勵教師分享優質教材；第二種是以信用為基礎的懲罰限制 (credit-based constraint)來迫使教師回傳評分以達消除搭便車(free-riding)問題。這兩種誘因機制都需要經由政府的資源來促使他們能正常運作。其後，我們做了幾個數值實驗，實驗結果均顯示誘因設計的確有助於教師的利益的上升以及分享意願的增加。 在我們的系統模型之下，數值實驗結果顯示出誘因機制的確有引導更多教材上傳和教材交流的現象發生。我們觀測到誘因造成的影響有：一. 教師信用制迫使教師對分享系統做最低程度的貢獻，二. 以聲譽為基礎的報酬鼓勵教師積極的分享教材，三. 教材評分使教材品質量化，四. 記帳系統使教師的對分享系統的貢獻與使用程度有明顯的紀錄。 最後，本論文在.net framework和 IIS 的web service之上實做了一個具體而微的以混合式點對點為基礎之教材分享環境，並且將與教育架構相對應的實體在教材分享環境中實現。此外，我們設計的兩部分誘因機制也同時加注於此教材分享環境之中，以讓教材分享系統更加完善。Content digitalization and advancement of communication network lead to content sharing on the internet. Teaching material sharing (TMS) is one of the important applications of content delivery networks (CDNs). TMS enables teachers to leverage on each other’s specialty, to produce quality teaching materials and to nurture creative teaching. TMS may also help alleviate digital divide. How to makes teachers create and share TM conveniently and how to incite teachers sharing their TMs positively are important problem in TMS. This thesis focuses on TMS among elementary school teachers over TANet. Our research aims at two issues: (i) How to design a P2P-based CDN for TMS that matches the organizational structure of elementary school system, and (ii) How to design incentives that encourage teachers to use and sharing teaching materials (TM) over the P2P TMS network. Challenges include TM presentation, TM discovery and delivery, TM quality evaluation, credit accounting, teacher behavior modeling, modeling organizational objective, incentive in a non-profit environment. We design a P2P-based TMS environment over TANet by combining the following four items: (i) Sharable Content Object Reference Model (SCORM) for TM presentation, (ii) Hybrid P2P network for TM discovery and delivery, (iii) a review system of TM quality evaluation, (iv) A transaction and credit accounting system. The Hybrid P2P architecture matches the organizational structure of elementary school system. In designing the incentive, firstly we build system model by considering: (i) utility from reward minus cost of creating TM equals to teacher’s benefit function, (ii) using Bass model to capture the dynamics of teacher’s willingness to upload TM. Secondly two kinds of incentive are proposed: (i) Accounting of TM quantity and quality for reputation-based reward incentive, (ii) Credit-based constraint avoids free-riding by enforcing teacher to review. Two parts of incentives are supported by government’s resource. Under our model, the numerical analysis results show that the incentive can induce more upload and more material exchange. Effects of incentive includes: (i) credit enforce teacher give feedback to the TMS system, (ii) Reputation incite teacher to share TM, (iii) TM score quantizes the quality of TM, (iv) Accounting system makes contribution and exploitation visual. A Hybrid P2P-based TMS environment is implemented over .Net framework and IIS web service. The corresponding entities in organizational structure of elementary school system are realized. In additional, two parts of incentive mechanism proposed by us also be applied to our TMS system that make our TMS more complete.Abstract...................................................I Contents...................................................V List of Figures.........................................VIII List of Tables............................................XI Chapter 1 Introduction.....................................1 1.1 Motivation.........................................1 1.2 Literature Survey..................................2 1.2.1 Teaching Material Sharing Presentation......2 1.2.2 Content Delivery Network(CDN)...............2 1.2.3 Incentive Design............................3 1.3 Scope of Research..................................4 1.4 Thesis Organization................................6 Chapter 2 Problems of Sharing Teaching Material via CDN....7 2.1 Needs of Elementary School Teachers................7 2.1.1 Educational Organization....................9 2.1.2 TANet.......................................9 2.1.3 Teaching Material Sharing Practice.........12 2.1.4 Needs and Challenges.......................12 2.2 Peer-to-Peer-Based CDN Design Problem.............13 2.2.1 Categories and Definitions of P2P Networks.14 2.2.2 Applications to CDN.......................17 2.2.3 Design Issues and Challenges..............18 2.3 Incentive Design Problem..........................19 2.3.1 Free-Riding Avoidance.....................21 2.3.2 Content Provision Encouragement...........22 2.3.3 Design Issues and Challenges..............22 Chapter 3 Design of Hybrid P2P for Teaching Material Sharing...................................................25 3.1 Business Model Overview...........................25 3.2 Teaching Material Presentation: SCORM.............27 3.3 Hybrid P2P over TANet : Architecture..............28 3.4 Building Blocks in Hybrid P2P.....................32 3.4.1 Super-peer for County Management...........32 3.4.2 Peer for School............................33 3.4.3 User-Agent as Middleware...................34 3.5 Operation Procedure for Teaching Material Sharing.35 3.6 Summary...........................................41 Chapter 4 Incentive Design................................43 4.1 Teacher’s Behavior Models........................43 4.1.1 Teacher’s Benefit Function...............44 4.1.2 Dynamic Model of Teacher’s Upload Probability...............................................49 4.2 Design of Reward and Constraint...................56 4.2.1 Reputation-Based Reward...................57 4.2.2 Credit-Based Constraint...................59 4.3 Evaluation of Incentive Design by Numerical Experiment................................................59 4.3.1 Summary of Model and Experiment Design....59 4.3.2 Effect on New Material Upload.............62 4.3.3 Effect on Teacher’s Benefit..............65 4.3.4 Summary...................................67 Chapter 5 Reference Implementation........................69 5.1 System Topology...................................69 5.2 Software Stack....................................70 5.2.1 Super-peer Software Stack.................70 5.2.2 Peer Software Stack........................72 5.3 Implementation Results............................73 Chapter 6 Conclusions and Future Works....................81 6.1 Conclusions.......................................81 6.2 Future Research Directions........................82 Bibliography..............................................85 Appendix A Numerical Experiment Detail Settings...........89 Appendix B Effect on Overall TM Variety...................9