Virtual Enterprise Presentations in the World-Wide Web { The Machine Learning Issue Klaus P. Jantke
Oksana Arnold
May 9, 1998
Abstract
The concept of Virtual Enterprise is becoming more and more popular. It is deemed a crucial approach especially suitable for small and mediumsize enterprises to overcome their limitations under the circumstances of an increasingly tough competition. The concept of a virtual enterprise is evolving, and so are the concepts and technologies to manage virtual enterprises. This applies to a virtual enterprise's appearance in the world-wide web, in particular, due to the unequaled interference of the web's and the enterprise's dynamics. Almost all authors who deal with virtual organization promise solutions to modern market challenges and environmental problems. Unfortunately, only a few papers contain suggestions and hints how to achieve the promised solutions under the conditions of changing patterns of organization and management. There is an obvious de ciency in methodologies and tools. Therefore, the aim of this paper is to develop a concept for a particular part of the implementation challenge. We want to discuss an approach which exploites recent information and communication technology to perform an integral and uni ed appearance in the world-wide web. The approach consists in developing fundamental concepts, outlining appropriate system architectures and functionalities, and developing and implementing algorithms for automatically synthesizing and maintaining web presentations to cope with the dynamics of the virtual enterprise presented. The new issues in our approach include the abandonment of centralized page management and dynamic updating based on di erent information sources. Machine learning concepts and techniques are invoked to meet the necessities of the enormous dynamics of both the virtual enterprise and the worl-wide web in which it appears. We present methodological solutions, software technological details, and a collection of open problems useful as a guideline of future work.
Contents Foreword
1
Contents of the Report
1
1 Motivation and Introduction
2
2 Virtual Enterprises
3
3 Main Issues Adressed
4
4 First Analysis of a Virtual Enterprise's Internet Appearance
5
5 Learning Problems and Scenarios
7
5.1 Where Machine Learning can be Applied { A Systematization of Learning Goals : : : : : : : : : : : : : : : : 5.2 What Type of Machine Learning can be Applied { A Systematization of Learning Techniques : : : : : : : : : : : : : 5.3 How Versions of Machine Learning will Work { A Systematization of Learning Scenarios : : : : : : : : : : : : : :
Foreword The present technical report is the manuscript of a paper presented on a workshop focused on Information Services for the Internet, Cottbus, Germany, in June 1998. The form of a technical report is giving the freedom to discuss the authors' intention less constrained than in a contribution to workshop proceedings, e.g. The particular application domain under consideration are virtual enterprises' Internet presentations like the one depicted here.
provide some more rm basis of the workshop presentation.
Figure 2: Remote Database Access through IntelligentPad Very recently, two more publications have been submitted and both are currently under review. In case of acceptance, the interested reader might nd references to this work later in the year. It is suggested to keep in contact with the authors, in this respect. Figure 1: The Internet Presentation of a Virtual Enterprise
Contents of the Report vs. Outline of the Talk
The report is intended to provide a rather There is some particular motivation for comprehensive introduction into the virtual the rst author's involvement in the present enterprise issue and into related approaches endeavour reported: the exploration of Meme towards appropriate information and commuMedia (of IntelligentPad, esp.) as a basis of nication technologies. Based on these prelimnew generation information systems. inaries, machine learning issues are derived Figure 2 in the right hand column is illus- and systematized. Certain aspects are distrating the appearance of IntelligentPad when cussed in slightly more detail. crossed over to combine their respective funcIn contrast, the oral presentation will be tionalities. based on a quite condensed motivation, only. This report has been written as a courtesy Instead, there will be put considerably more to the workshop's audience. It is intended to emphasis on machine learning issues. 1
1 Motivation and Introduction This presentation deals with the development and systematization of machine learning approaches to advance business administration systems tailored towards the needs of virtual enterprises. These are the information services in the Internet focused. Indeed, the focus of our paper is narrow: we aim at a substantial progress within a quite speci c domain by risking some step properly beyond the limits of current research and applications. In the wide area of business administration systems, in general, and virtual enterprise administrations, in particular, our approach seems to be a novelty. Related to the Internet, innovative ideas, concepts and technologies are inevitable. As usual, it is dicult to separate the wheat from the cha . Virtual enterprises are a highly modern and promising trend in recent worldwide economics, although some fundamentals (cf. [DM92], [BBP93], [Sco94], and [Mar96]) remained quite incomplete and uncertain, so far. A key feature of virtual enterprises is their abandonment of centralized administrations. The characteristics of virtual enterprises bear abundant evidence of the need for appropriate information and communication technologies, esp. for business management systems compensating for the lack of missing centralization. Thus, virtual enterprises pose exciting research and development problems to computer science, in general, and to arti cial intelligence, in particular. In [AFHS95], the authors intend to systematize the essentials of virtual enterprises for laying the cornerstone of future information and communication technology support. We will return to this area in the following section of our report. [Arn96b] and [Arn97] have set the stage for enhancing the available system support to virtual enterprise management. The diculty of business administration tasks to be solved and the complexity of even 2
distributed virtual enterprise management systems results in a speci c desire of intelligent system's behaviour. In [FC96], the authors recently request some degree of exibility which is remarkably beyond the limits of current systems: \In today's rapidly changing business environment, adaptability is a critical weapon for survival." (p. 58) Their conclusion is immediate: \It is no longer acceptable if a software system is correct and solves the problem for which it was designed. Ideally, the system will be able to grow and change to solve slightly di erent problems over time." (p. 59) Thus, learnability1 is becoming a crucial property of powerful virtual enterprise management systems. As the development of those systems is still a hot topic of recent research and development, learnability is not yet an issue of in-depth investigations. The focus of the paper is on developing key approaches towards learning virtual enterprise management systems, on systematizing them, and on exemplifying techniques and applications. Our present research is rmly based on three sources of intensive disciplinary work. First, there is our comprehensive approach towards virtual enterprise management systems (cf. [AFHS95], [Hin96], [Arn96b], and [Arn96c]). Second we adopt our former contributions to machine learning for knowledgebased systems (cf. [Jan89], [Jan95], [JL96]). Last but not least, the realizability of our conceptual ideas towards machine learning to advance virtual enterprise management systems is substantially based on software technological work on software tools supporting creative design of evolving systems and interfaces (cf. [Tan89], [Tan91], [TNAN92], [OT95], [Tan96], [Tan97], and, from an external perspective, [Joh95]). 1Within the present publication, we refrain from an in-depth discussion of learnability concepts. This is not a paper on Machine Learning per se. We con ne ourselves to the remark that learning from usually incomplete and uncertain information, i.e. inductive learning, is assumed to be essential.
2 Virtual Enterprises
De nition (Virtual Enterprise)3:
discussion of problems, the reader is directed especially to [AH95]. [Arn97] may also be of interest in this respect.
The present de nition corresponds essentially to the de nitions in [AH95], [AFHS95] and [Arn97].
A virtual enterprise is a kind of horizontal Under the pressure of an intensi ed national and/or vertical enterprise co-operation of inand international competition, enterprises are dependent companies (with the possible parseeking for more e ective production, man- ticipation of institutions and/or persons) to agement and marketing strategies. All tech- achieve a service or product on basis of a comnological and intellectual resources need to mon understanding of business. Each combe activated. This is neither surprising nor pany will contribute primarily its core compenew, but only proper innovations may result tencies, whereas from the viewpoint of an exin a remarkable advantage of a company over ternal observer the virtual corporation appears its competitors. In this context, the concept as a unitary enterprise. A virtual enterprise of Virtual Enterprise is becoming more and dispenses with centralized administration by more popular. exploiting modern information and commuAlmost all publications in the area promise nication technologies to support coordination solutions for modern market challenges and processes. Its life-cycle nishes when the busiproblems (cf. [DM92], [Kle94], and [PRW96]). ness purpose is ful lled or becomes ine ective. Unfortunately, only a few contain suggestions Based on this de nition, we are interested how to achieve the promised solutions. In in exploiting modern information and coma world where patterns of organization and munication technologies to support the immanagement are changing, where borders are plementation process of virtual corporation. non-rigid and permeable, one might also need [Arn96a], [Arn96b], and [Arn97] provide a rst more exible technologies and tools to go the step towards virtual enterprise management way from general insights to working solu- systems which leads from an analysis of detions. New technologies are emerging. cision problems relevant in coordination proFurthermore, a lot of publications are based cesses of virtual enterprises to a comprehenon di erent interpretations of the concept's sive concept of a prototypical management essentials. It turns out that a certain number tool. Here, we want to discuss an approach of fundamental problems are still open. Some which exploites information and communicakey notions and notations remain unspeci ed, tion technology to perform an integral and and some others are even inconsistent.2 A uni ed appearance in the world wide web. The clari cation is inevitable, for separating the new issues in our approach include the abanwheat from the cha . donment of centralized page management and To abandon this quite unsatisfactory state dynamic updating based on di erent inforof a airs, we need concepts which describe mation sources. This innovative functionality how a virtual enterprise could be eciently partially arises from machine learning techestablished and kept competitively. Thus, our niques never invoked before within any IS. paper, although focused on learning issues, The concepts introduced, the methods debasically aims to develop a concept for a par- veloped, and the algorithms designed lead to ticular part of the implementation challenge, components of next generation IS which are thus contributing to the overall endeavour. intended to contribute to a remarkably higher For going into detail, a common understand- performance of virtual enterprises, basically ing of basic notions is inevitable. We assume through the semi-automated synthesis and the the following concept of virtual enterprises. fully automated maintenance of the virtual enterprise's web appearance. 2 For deeper insights in the state of the art and the 3
3
3 Main Issues Adressed
won't restrict information sources to databases or require any commonly used platform like In the present chapter, we aim at a survey of LotusNotes, e.g. In principle, we take into acthe main issues addressed within this report. count di erent document types the informaIn contrast to the wider spectrum shown here, tion may come from, for instance WinWord the oral presentation is focused on the ma- documents, ASCII les, HTML pages, and chine learning aspects. databases. An integral and uni ed appearance in the Towards a semi-automatically generated, Internet is taken as the topical goal. For any automatically operated and maintained web virtual enterprise, it means that there is no appearance of a virtual enterprise, we have to di erence in presentation and customer sup- solve di erent subproblems. First, we need port compared to any conventional company, some prototypical web presentation of a virwhereas all co-operation partners may pro- tual corporation. Based on this presentation, duce their own products in parallel to the we have to nd out the peculiarities of a typcommon one, may promote their own images ical virtual enterprise presentation. This will and may pursue their own interests. One can be adressed in some detail the next section. easily identify some gap due to the dispense We should identify which information came of centralized management. On the one hand, from di erent companies, which information a customer should not know much about the changes frequently over time, and which inreal structure the virtual enterprise relies on. formation could be used for distribution of He should contact and ask the unitary corpo- customer messages. Second, we need some ration. On the other hand, there is nobody in speci cation which allows to express the dethe background of the web information system pendencies between a web presentation and who can distribute the questions, the mes- the information sources the presentation relies sages and the orders. Therefore, one needs on as well as between distribution keywords some tool functionality which does that job. and allocation addresses. Third, we should The experienced reader will know how time develop some tool that is able to construct and resource consuming the maintenance of on the y the web presentation based on the web pages might be. A lot of information given speci cation and to distribute customer changes frequently (sometimes every day or messages. Finally, we need some add-on in even several times a day) and, thus, the web order to create and modify interactively the presentation has to be updated rather often. speci cation for a concrete presentation. The crux is that only topical information gives Within this report we will put primarily rise to customer's return, documents the pres- emphasis on the rst task. We will discuss a ence of an enterprise, and carves out attrac- prototypical web presentation and elaborate tive shares of newly arised markets. Thus, precise requirements appropriate formalisms there is a strong desire for an up to date Inter- and tools should meet in order to solve the net presentation. But, in general, this moti- other mentioned subtasks. Furthermore, we vation applies only to single enterprises. The will sketch solutions to the second and third encouragement is easily lost in loosely cou- task in order to outline emerging technologies pled independent corporations. Therefore, we of synthesizing and maintaining information claim that a tool which supports the inte- systems operating in the world-wide web. The gral and uni ed appearance should use dis- features of those technologies re ect the retributed sources, which are obviously avail- quirements of dynamically changing patterns able and maintained in partner companies, in organization and management. We intend to update the web information system of the to mediate the novelties of our approach. The virtual enterprise. Within this approach, we essence is to invoke machine learning. 4
4 First Analysis of a Virtual Enterprise's Internet Appearance
presentation of a single enterprise. The head presents the enterprise's name and a logo. The central frame contains some welcome greetings and a short description of the enterprise's objectives. On the left hand side, there is a Based on some prototypical web presentation, menu for navigating through the present inwhich is available for some virtual enterprise formation system. All the issues on the initial example, we want to identify the peculiari- web page are more or less static. Especially, ties of a typical virtual enterprise presenta- the enterprise's name and the logo as well as tion. For simplicity, we decided to consider the navigation menu will not change during some research project as our virtual enter- the virtual corporation's life time, in general. prise example. We are aware that with re- The welcome greetings will be updated rarely. spect to our own de nition of a virtual enAt a rst glance, there is nothing supristerprise a project team is not really a virtual ing and nothing typical for virtual enterprises. corporation, but there are a lot of character- Consequently, we have to go into depth of the istics the chosen project has in common with information system. Therefore, we focus on a typical virtual enterprise. For instance, the the page behind the People item.4 It shows project team is distributed, some people work the organisation structure of the virtual corin Nurnberg, others in Bern, and Leipzig. All poration due to the goal to meet a visitor's project members are connected by Internet. expectation, i.e. to bring him (or her) in conThey can use e-mail, ftp, and telnet for com- tact with the respective representative who is munication purposes and they have their own responsible for customer's requests, for public web presentations. Furthermore, scienti c pa- relations, and so on. pers and a common report series are the products of the distributed team. They are produced based on a common understanding of business. Therefore, we are convinced of the adequacy of the chosen example.
Figure 3: The Initial Web Page of an Appropriate Web Presentation For this example, gure 3 is displaying a snapshot of the initial page. It looks like the
Figure 4: The Virtual Enterprise's Presentation of the Organisation Structure Customers are interested in getting o ered closer contacts by getting telephone numbers and e-mail addresses. Thus, an appropriate 4
The whole presentation can be visited under
http://www.uni-leipzig.de/oki/vu.
5
Internet presentation of a virtual enterprise should avoid a confusion of customers by providing to much details about the truly scattered structure of the enterprise. If potential customers would primarily learn here that it is necessary to visit a co-operation partner in Australia, for instance, and to search there for a responsible person in order to arrange a demontration appointment for a product a, but contact a co-operation partner in South A rica in order to discuss the di erence between the product a and the product b, the presentation were missing its mark. Thus, we propose a functionality driven presentation of the organisation structure (cf. gure 4) hiding other details. Additionally, we can identify a second peculiarity of virtual enterprise's presentation on this page. A lot of information presented is already available in the project members' home pages { in our example { and in di erent information sources, from a more general point of view.
Figure 5: A Suggestion for some Con guration Tool This is setting the stage for connecting documents and for reducing the update work. Figure 5 contains a snapshot of a con guration tool which allows to create web pages interactively and to mark information sources for updating. As a side e ect every change in the source document will be propagated to the target documents based on added control information to both source and target documents. The speci cation language necessary to mark the dependencies and a propaga6
tion mechanism works on it will be introduced later on. In this subsection we continue our investigations into a typical virtual enterprise web presentation. Besides some enterprise information issues the objectives of a polished web presentation include the implementation of a common point of sales. Therefore, pages for product ordering, customer support, and services should complement the presentation. The contact page of our example provides several services a customer can order. There are a general information supply, a scienti c co-operation, a preparation of an article, a response to a concrete question, a tranfer of scienti c results into applications and a lecture (cf. bottom of gure 6). To each of these service categories a customer can specify di erent topics or describe the desired content in the description box (cf. top part of gure 6).
Figure 6: The Virtual Enterprise's Contact Page Based on the input it is necessary to decide which activities should be performed, which people should be involved, and which result should be presented to the customer. This task exhibits a new peculiarity of any virtual
enterprise's structure. The abandonment of centralized administration leads to the need for generating and controlling a work ow. This might cross the boundaries of the co-operating single enterprises. The generation und control process depends on the interpretation of the input data which includes, in the worst case, a knowledge-based text analysis. We skip this problem, refer to the research area of Natural Language Processing, and assume that some language processing tool extracts attribute value pairs which re ect the user's input correctly. Based on these attribute value pairs a simple logic is required which is able to map attribute values to actions like, just for illustration, informing responsible people by e-mail or activating work ows of an existing work ow management system. The described distribution task di ers remarkably from the updating task discussed before. While the updating mechanism needs control information in HTML documents and in source documents, the distribution mechanism evaluates HTML forms based on the HTTP protocol. We extracted di erent peculiarities of a virtual enterprise's web presentation. These lead to the necessity of some updating mechanism and some distribution mechanism. Both will be considered in the sections 6 and 7 of the present report. Before going into these details, the following chapter is intended to provide a rst quite rough systematization of machine learning problems and approaches to advance any virtual enterprise's web presentation. Particular ideas and techniques of the next section are systematically exploitet within the subsequently following sections which focus on the announced basic functionalities towards an integral and uniform appearance of virtual enterprises. Within the oral presentation of the present report, we will focus on some essentials of machine learning. The following systematization is assumed, but not discussed in much detail. The contents of section 6 is utilized both for motivation and for illustration.
5 Learning Problems and Scenarios Learnability of a virtual enterprise management system is intended to make such a system more powerful, at the moment of its actual use, and adaptable to changing conditions, in the future. Thus, there is a twofold bene t from learnability. On the one hand, this dichotomy exhibits the potentials of machine learning techniques. On the other hand, it suggests that there might be a remarkable variety of di erent approaches to be invoked at di erent positions and under di erent circumstances. It's our aim to systematize these approaches and to contribute to the development, to the implementation, and to the experimental application of machine learning for virtual enterprise administration.
5.1 Where Machine Learning can be Applied { Towards a First Systematization of Learning Goals
Whenever a user is drawing advantage from any virtual enterprise management system as discussed above, (s)he will deal with certain decision problems. During the user's work, a learnable system may acquire knowledge in di erent ways. From the perspective of virtual enterprise management systems, fundamental learning goals are G1 sequences of actions performed by the user, or { even more ambitious { patterns or plans of the user's behaviour, G2 correlations between decisions and { underlying them { knowledge sources like data bases, e,g., G3 correlations between decisions and communication needs (some user may usually call somebody else when being faced to a particular decision problem, for instance), 7
G4 patterns of user-generated documents, For briefty, we have presented a small selecof techniques, only. More important than G5 rules which determine a user's decision tion completeness is the ability to point to avail-
in dependence on given data like (i) asking for further information, under some circumstances, or (ii) rejecting some request under certain conditions. Beyond these individual goals, one needs to develop techniques to attack those goals as well as to specify scenarios when to do so.
able techniques. It is the authors' intention to exhibit that there are possibilities galore to equip virtual enterprise management systems with learnability.
5.3 How Machine Learning will Work { Towards a First Systematization 5.2 What Machine Learning of Learning Scenarios can be Applied { Towards Basically, when using any virtual enterprise a First Systematization of management system enhanced by some maLearning Techniques chine learning features, the user needs to de-
Here, we are minimizing references to the topical literature which is overwhelming. Just for illustration, we refer to the one or the other paper to exhibit that paramount approaches and results are waiting for exploitation. T1 Within the Phi project, there have been developed and implemented some techniques for plan recognition. Those results seem perfectly adequate to make virtual enterprise management systems learnable, in this respect. ([Koh94] is a suciently comprehensive reference.) Those techniques may be particularly suitable for G1. T2 Pattern inference like in [Ang80], e.g., has found dozens of applications and is investigated in a huge amount of subsequent publications. It comes close to the needs of G4. T3 Classi cation rules (for achieving goals like G5, e.g.) are classically learned by ID3 (cf. [Qui86]). A remarkable number of re nements provide a huge reservoir of techniques. T4 If the rules envisaged in G5 are more complex, inductive logic programming (cf. [Mug90] and numerous subsequent publications) might provide the appropriate technological solutions. 8
cide whether or not these features should be activated. Di erent modi must be available. So far, even the most elementary questions are still open. For instance, what should be the default modus, \learning on" or \learning o "? Our common sense does not provide suciently well-based answers to those questions. Instead, computer science and arti cial intelligence research needs to be complemented by cognitive science investigations and by systematic experimentation. This is far beyond the limits of the present paper. In case the learning modus (or, even ner, some particular learning feature) of some given virtual enterprise management system is activated, it makes a serious di erence whether the system's learning results are autonomously transformed into action or not. This is another basic decision usually left to the user. Just for illustration, the system may have learned that for certain decisions a particular button of the main window in use is never pushed whereas another decision is frequently activated after some long navigation through the system's hierarchical structure. It might be highly convenient to nd a useful button automatically in the place of another completely useless one without any user activity. In contrast, it might be confusing if a system's interface is frequently changing its appearance without any authorization.
Here, a sample learning scenario is brie y presented. Sc1 If some action plan is recognized (cf. G1 and T1 above), the system might o er shortcuts to the user. If the system does this fully autonomously, this means either to implement some button for such a shortcut or to replace the interface window by another already incorporating the result of the action sequence learnt. Sc2 If a pattern structure of user-generated data sets is recognized (cf. G4 and T2), the system may automatically generate masks to be lled by the user to ease the design of standard data sets. [Nix83] is a typical work in the area. Sc3 In case the user is faced to problems of a structure where he made clear decisions before, due to certain given data (cf. G5), a learnable system may be able to suggest these decisions to the user, possibly by refering to formerly solved similar5 problems. Sc4 Learning may also proceed gradually by bookkeeping on the user's activities. A functionality never used for a very long time may be degenerate and, perhaps, even disappear once. According to the user's activities, the interface structure may be rearranged automatically to support utility. (Both the shrinking and the swelling buttons are rather illustrative metaphors, in this respect.) Note that we did not investigate in detail all those approaches which are based on machine learning modules which might be invoked like other knowledge processing procedures. Naturally, users of virtual enterprise management This relates to case-based reasoning, in general, and to case-based learning, in particular. Although we are not going into detail, it is worth to be mentioned that structural similarity concepts (cf. [Jan94], [MJ97], and [Mat97], e.g.) are of a particular relevance to the application area under investigation here. 5
systems may call standard learning procedures like ID3 (cf. [Qui86], e.g.) for generating classi ers, they may activate genetic algorithms for proposing design solutions like in [GL95] and [GK94], e.g., and so on. But all this does not abandon traditional perspectives; hence, we left it out. A closer look exhibits that all these learning scenarios admit numerous substantial re nements. We do not go into details. Furthermore, because the present paper is not a topical one in the area of Machine Learning, we do not go into details of a particular learning mechanism. Similarly, as we do not intend to contribute to Learning Theory, we are not striving to prove any theorem about learnability. Nevertheless, we are aware of the readers curiosity about the question how learning goes on and how corporations, especially virtual enterprises, may draw substantial bene t from machine learning in management information systems. Therefore, we will provide more detail in the following section. The oral presentation of this paper is intended to discuss these details. In technical terms, we deal with inductive learning of text patterns like in [Ang80] or [Nix83], e.g. Even more speci cally, the peculiarities of virtual enterprise presentations in the world-wide web require a more general type of text generation mechanisms by so-called erasing substitutions (cf. [JKS+ 94], [MPS96] and [OU96], e.g.). This is due to the necessity to allow for a mutually independent source management within a virtual enterprise. Any attempt to constrain the individual enterprises' web appearance would drastically contradict the gist of joining a virtual enterprise. We conclude our section about learning problems and scenarios with a somehow important hint: To the authors best knowledge, it is still open whether or not those patterns where erasing substitutions are permitted can be learned from positive examples, only. The result in [Sch90] provides some evidence for the hardness of this learning problem. 9
6 Towards an Updating Concept
6.1 Dependency Speci cation Language
We focus on virtual enterprises' web presentations built upon and re ecting { usually more, but at least { the contents of the individual enterprises' presentations which gathered together temporarily. A rst key issue is the design of those presentations including substantial computer support covering automated presentation synthesis. A second issue is to keep those appearances of virtual corporations alive, i.e. to manage the desired functionality of the synthesized web presentation through the distributed functionalities of the source documents, even under the dynamics of the worldwide web and of the virtual corporation under consideration. Among the fundamental problems to be addressed there are syntactical problems like HTML extensions, e.g., semantical problems like transformations and rewrite rules preserving the meaning of constructs translated from source documents to the virtual enterprise's target document, and computational problems like learning and interpretation. We con ne ourselves to a rather condensed discussion.
First of all, we need to establish a connection between the related information parts in the source and the target documents. We return to the example in gure 5 and present how the marked link can be manifested by including control information in both the source and the target document. The mentioned control information consists of two new tags which will be ignored by conventional web browsers. We enclose the part of the source HTML document, which should appear in the target document, (cf. gure 7) and insert some declaration in the target document (cf. gure 8). Most of the present control information is rather intuitive. The particular new tag in the source document encapsulates the document part which should appear in the target document, too, and assignes this part a unique tag name. The new tag in the target document refers the source address including the unique tag name and speci es the type of the source document, an expiration-time, a time stamp of last updating, and some e-mail address of whom to be informed in update error cases.
Figure 9: Comparison of a Source and a Target Product Presentation The rst example deals only with a oneto-one transformation we could not expect, in general. In most cases, there is semantically equivalent information in rather different structures. This phenomenon is unavoidable if an independent source management and development is allowed. The independence of source management and development is a characteristics of virtual enterprises, because the companies which cooperate temporarily due to a common product or service exist before the co-operation starts, will endure after the co-operation ends, and will take part in new and di erent cooperations. Therefore, it is unimaginable that the independence of source management and development can be avoided or restricted. We need mechanisms for dealing with the heterogeneous structure of both the existing and the intended information presentation. Figure 9 illustrates the problem we are faced to and gure 7 shows the corresponding
HTML source structure. In its right perspective, we have to consider pattern languages, whereas HTML documents are instantiations of certain text patterns (cf. [Ang80], for the roots, and [Nix83], for some applications), in order to express the existing dependencies. Figure 8 presents patterns able to generate the rst reference of the source document displayed in gure 7. Variables are indicated by underlining. The interested reader is invited to ponder about an appropriate pattern describing the source text shown in gure 7 which allows for explicit derivation of the related target structure in the same gure. There might be concurring approaches. For the reference under consideration, the intended transformation can be characterized by the two patterns on the bottom of the next page augmented by the pairing of variables such that u1 relates to v1, u2 relates to v3, u3 relates to v2, and so on, up to the mating of u15 and v13. The values of related variables are syntactically equivalent. Unfortunately, the case we did discuss is very trivial. There are at least three practically relevant generalizations. First, one might wish to have context-sensitive couplings of variables within one pattern. This would allow to relate u13 to u15, because their substitutions refer somehow semantically to the same journal. Second, there might be some need for erasing substitutions in order to work with suitable patterns able to cover peculiarities of serveral text pieces. Third, there might be semantically equivalent rewritings of strings from the source into strings of the target document. The replacement of individual companies' names by the common one is a typical application. Furthermore, a virtual enterprise's wep presentation results from some sophisticated dovetailing of the transformed and rewritten texts from a collection of distributed and mutually independent source presentations. Each of the mentioned generalizations leads to an ambitious research task we cannot discuss here in more detail. 11
(a) source document
[AFHS95]
Arnold, Oksana; A HREF="http://..." Faisst, Wolfgang /A ; Härtling, Martina; A HREF="http://..." Sieber, Pascal /A /I : BR A HREF="VU-Abs.html#VU-HMD" Virtuelle Unternehmen als Unternehmenstyp der Zukunft? /A BR In: HMD 32(1995)185, Hüthig GmbH, Stuttgart 1995, S.8-23. /TD
< < >< >
< >
< >
>
< >< >
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[AFHS95]
(b) target document
Oksana Arnold; Wolfgang Faisst; Martina Härtling; Pascal Sieber /I : BR A HREF="VU-Abs.html#VU-HMD" Virtuelle Unternehmen als Unternehmenstyp der Zukunft? /A BR In: HMD 32(1995)185, Hüthig GmbH, Stuttgart 1995, S.8-23. /TD
< >< >
< >< >
Figure 10: HTML Structures of Some Reference Presentation
x2
x3;x4;x5;x6 : x7
y1
y2, y3; A HREF="y4" y5, y6 /A ; y7, y8; A HREF="y9" y10, y11 /A /I : BR A HREF="y12#y13" y14 /A y15 /TD
> < < >< > < < >
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Figure 11: Generating Extended HTML Patterns of Di erent Expressiveness
12
To sum up, we need patterns of document structures and assignments relating target pattern variables to source pattern variables for deriving target document parts from source document parts. Patterns and assignments can be generated manually or by pattern learning techniques. They should be included as transformation rules in the HTML control information tags for certain updating purposes.
6.2 Automated Synthesis, Maintenance, and Operation The crux is that it is not sucient to synthesize a target presentation from its related sources just once. For virtual enterprises, web site design (cf. [PG98]) is only an initial step. The enterprise's integral and uni ed appearance has necessarily to be kept alive during the corporation's life cycle. We must be aware that, due to independent maintenance of any source document, some transformation rules derived in former steps may fail. Therefore, the updating task must be widely automated.
We con ne ourselves to a very condensed sketch of innovative approaches to synthesize and maintain a virtual enterprise's web presentation based on a set of distributed and dynamically changing source presentations. Although some fundamental algorithmic problems related to text patterns are known to be unsolvable (cf. [Sch90] and [JSSY93]), there is a quite impressive collection of working algorithms for learning text patterns (cf. [Shi82], [Nix83], [LW90], and [ERS+ 97], e.g.). Some of them are rather ecient, i.e. running fast, and for most realistic applications where texts are rich in structure, a very small amount of information (cf. [Nix83]) suces for successful learning. Thus, learning text patterns automatically is feasible. As illustrated, there are pairs of source document texts and target document texts related, like in gure 7, e.g. Pattern inference algorithms use such samples in order to learn the key structure. In the sequel, let us denote source document texts by SDT and target document texts by TDT , for short (cf. Figure 10).
u1
i
i
(a) source pattern
u2, u3; A HREF="u4" u5, u6 /A ; u7, u8; A HREF="u9" u10, u11 /A /I : BR A HREF="u12#u13" u14 /A u15 /TD
Figure 12: An Example of Related Source and Target Patterns 13
Pairs (SDT ,TDT ) are called samples. Substitutions assign texts to variables and are denoted by , possibly decorated with some index. If patt is any pattern, a substitution transforms it into some text denoted by (patt). PI shall denote any pattern learning algorithm. When applied to a collection of texts, PI returns some pattern and a list of substitutions. Automation within our application area restricted to relating pattern variables of syntactically equivalent values can be based on the scheme presented in gure 13. i
i
This allows for an automated synthesis of web presentations based on samples. Experiments with the learning scheme have shown that only 3 to 5 samples, on the average, are sucient to learn HTML document structures and related transformations. Thus, if the learning process is started with 2 samples initially chosen, only 1, 2 or 3 loops are necessary to complete learning. This is really feasible. The synthesis of rewriting procedures is dropped from this paper, because of its remarkably higher complexity (cf. [BB93]).
Start with any initial set S of samples. Copy all source document texts from S into SOURCES. Copy all target document texts from S into TARGETS. loop Request another sample (SDTi,TDTi). Insert (SDTi,TDTi) into S. Insert SDTi into SOURCES. Insert TDTi into TARGETS. Run PI on SOURCES and store the output as patts , 1s , ..., ns
[
]
Run PI on TARGETS and store the output as pattt , 1t , ..., nt
[
]
until (1) For all samples (SDTi,TDTi) in S, it holds is (patts) = SDTi and it(pattt) = TDTi. (2) For every variable yk in pattt there exists some variable xl in patts such that all substitutions meet the corresponding conditions:
s i
return
(xl ) =
(y t i
k
)
the pattern of source document texts patts the pattern of target document texts pattt
relating target pattern variables to source pattern variables
the assignement
Figure 13: Invoking Machine Learning Techniques { A Scheme 14
In order to use the present learning scheme for automated updating it is included in the overall maintenance approach. For illustration, assume a set of HTML documents, which have been created for the virtual enterprise's web presentation, which have been built upon serveral source documents, and which might contain now a more or less outdated state of information. Additionally, these HTML documents contain new control information tags introduced in section 4.1. In the sequel, these tags and the encapsulated text will be referred to as dynamic document parts. Assume a customer visiting the virtual enterprise's web page. He will be connected with a CGI-interface program, which checks, whether the speci c HTML document which the customer requests is older than some given timeout, and tries { if necessary { to create an updated HTML document. It reads the source address of the rst dynamic document part, activates a communication to the source for getting the required document, and converts the document according to the speci ed source type. If no transformation rules are available the program replaces the framed part in the target document by the result of convertion. Otherwise, the learning scheme is applied. PI runs on the source samples and returns a pattern with the list of substitutions. If the new output is consistent with the previous learning result stored as transformation rule(s) in the control information tag of the source document, the target document text is generated based on the assignment . Otherwise, learning is invoked to generate a new assignment (and, perhaps, new patterns) exploiting the already existing sample pairs (SDT ,TDT ). This new assignment is used for generating target document text. The CGIprogram will proceed by setting a new time stamp as last update time. The described procedure will be executed on each of the dynamic document parts. On its end, an updated HTML document is presented to the user. It serves as the new speci cation for further updates, too. i
i
During the updating process a connection to a speci ed source might fail. Then, the CGI-program uses the old information to avoid confusing customers. Furthermore, it sends an e-mail about the connection problem to the responsible referee if the expiration time is exceeded. This event-driven mechanism for error handling allows people to do their daywork without the necessity of continuously watching the correctness of the virtual enterprise's web information.
7 Towards a Distribution Concept In section 3 we pointed out that an important objective of a virtual enterprise's web presentation consists in providing a common point of sales. However, the abandonment of centralized administration makes the implementation quite dicult. For an appropriate reaction to a customer's request, a suitable work ow should be generated and controlled. Such a work ow crosses the boundaries of cooperating enterprises, in general. Therefore, existing work ow mangament systems cannot be used, because they are restricted to control work ows within one corporation. Therefore, we propose an approach which controls the overall work ow process by using simple communication techniques and exploits existing work ow management systems for every suitable subtask. The core of our approach consists in a rule-based system which tries to match data a customer provides by lling in a request form with rules describing the actions to be executed. An open rst order predicate logic is the basis for the proposed system. It allows for the combination of di erent attribute value pairs in order to determine under which circumstances which reaction is required. For illustration, we consider the form in gure 6 and the corresponding HTML encoding. Figure 14 contains a passage of encoding. The interesting text pieces are indicated 15
by bold letters. Di erent attributes are able to bind information about the visitor's identity and objectives. While the attributes concerning the visitor's identity cannot dispose of default settings, other attributes can be used with prede ned value ranges. Hence, a multiple value binding is allowed. Furthermore, we use potential value bindings to determine the distribution process by rules. The rules in gure 15 encode some relevant distribution knowledge of our example. Under certain circumstances, it might be necessary to evaluate a visitor's identity data, too, for determining a suitable referee. Frequently, enterprises have local representatives personally responsible for all business issues in some geographically determined area. We refrain from discussing further details. To sum up, the syntax of rules presented above is so simple that no special knowledge about TCP/IP protocols or CGI is required. It is expressive enough to be applicable to different cases. Therefore, we proceed to explain the implementation of the distribution process by example. For illustration, imagine that somebody interested in web presentation maintenance
("Praesentationspflege", cf. gure 15) and lectures ("Vortrag") posted a completed form sheet. The rule-based system { as the activated CGI-program { determines the corresponding rules by reading a speci c hidden attribute of the form sheet which contains the rule base le name and location. Then, it uses the information inside the form sheet for proving the authority of the customer, evaluating the rules, and executing the actions of a valid rule. In the example discussed, the second rule res. The speci ed actions will be executed by general procedures based on given arguments. The invoked procedures send an e-mail with the customer's data to the address [email protected] and present an HTML answer to the customer (cf. gure 16). The action part presented is quite trivial. This is suitable for applications where activating procedures at one moment in time is enough. The control of work ows, which cross co-operating enterprises' boundaries and uses work ow management systems of individual co-operating companies seems to be a more exciting application (cf. [Arn96a], for a highly
exible approach).
...
Name:
Funktion:
Institution:
Straße:
PLZ + Stadt:
Land:
Telefon/Fax:
E-Mail:
...
Automatisierung der Präsentationspflege
...
allgemeine Informationsgewinnung
Beantwortung einer konkreten Fragestellung
Wissenschaftliche Zusammenarbeit
Übernahme von Erkenntnissen in die Praxis
Lieferung eines Artikel
Präsentation im Vortrag
...
Figure 14: Some Passage from the Form Encoding HTML Document 16
RULE1 IF
( keyword = "Praesentationspflege" AND ( aim = "Information" OR aim = "Fragestellung" ) ) THEN ( Inform[[email protected]] AND HTML-Answer[Herr Andreas Ulrich] ) RULE2 IF ( ( keyword = "Praesentationspflege" OR keyword = "Prototyp zur Koordinationsunterstuetzung" ) AND ( aim = "Wissenschaft" OR aim = "Kooperation" OR aim = "Artikel" OR aim = "Vortrag" ) ) THEN ( Inform[[email protected]] AND HTML-Answer[Frau Dr. Oksana Arnold] )
Figure 15: Distribution Rules These are the two concluding gures of the present technical report. The gure above is containing exempli ed rules which lead to an automatically synthesized answer as displayed below.
Figure 16: An Automatically Generated Answer to some Customer's Request The oral presentation of this technical report is intended to focus on the pattern learning techniques discussed above (see gure 13, in particular) which lead to the intelligent behaviour of a virtual enterprise's Internet presentation as illustrated here. In dependence on the feedback from the audience, several aspects of the report's contents might be discussed in more detail.
8 Conclusions Under the circumstances of an increasingly tough international competition { doubtless { the survival of many small and medium-size enterprises will substantially depend on their ability to invoke modern information and communication technologies to overcome some of their limitations. Utilizing the appearance of a virtual enterprise might be sometimes the only way to face the competition, to have share in some ambitious project and to draw bene t from certain synergetic e ects. Currently, both the methodological basis and the appropriate tools which will support such an appearance in the future are still under development. The concentration of nancial and intellectual power towards a remarkable speed-up of research and development might be truly inevitable to many of these corporations. Even for conventional corporations, most recent investigations come up with the insight that \very little is actually known about how organizations are using this new technology" (cf. [PG98]) and, thus, they focus on \Web Site Design" to improve the performance of those enterprises. We go even further in a twofold sense, rst, focusing on the needs of virtual enterprises and, second, going beyond design towards operation and maintenance. 17
The present paper is intended to contribute to this endeavour. We have outlined an approach towards implementing an integral and uni ed appearance of virtual enterprises. For an in-depth investigation, we have narrowed our considerations to an implementation inside the world wide web, exclusively. The new issues addressed include the abandonment of centralized page management, a dynamic updating based on di erent information sources and, last but not least, some autonomous request distribution mechanism. The key techniques invoked stem from the area of machine learning, in general, and pattern inference, in particular. These are the issues focused on. The proposed concepts and developed techniques are already useful, especially for small and medium-size companies, although we are aware of the overwhelming amount of important question which remained open. Problems left to forthcoming investigations include: the representation of necessary structure transformation as well as learning techniques, which can compute structure rewriting based on presented examples, the analysis of unstructured text with the aim to extract the meaning and encode it by assigning values to prede ned attributes, the integration of document parts of commercial application systems into the updating procedure by exploiting the OLE protocol, and the development of a comfortable editing system, which can be used to design web pages in some interactive mode and to integrate di erent document sources, and which supports the development of forms and the de nition of related distribution rules, e.g. Here, we refrain from a further illustration as there is no hope to cover the richness and the depth of the area with a few words. 18
References
[AFHS95] O. Arnold, W. Faisst, M. Hartling, and P. Sieber. Virtuelle Unternehmen als Unternehmenstyp der Zukunft? HMD, 185:8{23, 1995. [AH95] O. Arnold and M. Hartling. Virtuelle Unternehmen: Begri sbildung und -diskussion. Arbeitspapier der Reihe \Informations- und Kommunikationssysteme als Gestaltungselement Virtueller Unternehmen" 3/1995, Institut fur Wirtschaftsinformatik der Universitat Bern, Institut fur Wirtschaftsinformatik der Universitat Leipzig, Bereich Wirtschaftsinformatik I der Universitat Erlangen-Nurnberg, Bern Leipzig ErlangenNurnberg, 1995. [Ang80] D. Angluin. Finding patterns common to a set of strings. Journal of Computer and System Sciences, 21:46{62, 1980. [Arn96a] O. Arnold. Die Therapiesteuerungskomponente einer wissensbasierten Systemarchitektur fur Aufgaben der Prozefuhrung, volume 130 of DISKI, Dissertationen zur Kunstlichen Intelligenz. in x, 1996. [Arn96b] O. Arnold. Ein Prototyp zur Unterstutzung des Management in virtuellen Unternehmen. In K.P. Jantke and G. Grieser, editors, 4. Leipziger Informatik{Tage, 29./30. August 1996, pages 91{96. Forschungsinstitut fur InformationsTechnologien Leipzig e.V., 1996. [Arn96c] O. Arnold. Spezi kation eines Prototypen zur Koordination in Virtuellen Unternehmen. Arbeitspapier der Reihe \Informations- und Kommunikationssysteme als Gestaltungselement Virtueller Unternehmen" 10/1996, Institut fur Wirtschaftsinformatik der Universitat Bern, Institut fur Wirtschaftsinformatik der Universitat Leipzig, Bereich Wirtschaftsinformatik I der Universitat Erlangen-Nurnberg, Bern Leipzig ErlangenNurnberg, 1996. [Arn97] O. Arnold. Die Konzeption eines Prototypen zur Unterstutzung des Managements in Virtuellen Unternehmen. In K.P. Jantke, G. Grieser, and W.S. Wittig, editors, Impulse
fur Informatik-Innovationen, pages 87{95. in x, 1997. [BB93] W. Bibel and A.W. Biermann. Special issue: Automatic programming - foreword of the guest editors. Journal of Symbolic Computation, 15(5 & 6):463{465, 1993. [BBP93] J.A. Byrne, R. Brandt, and O. Port. The virtual corporation. Business Week, pages 36{40, February 1993. [DM92] W.H. Davidow and M.S. Malone. The Virtual Corporation: Structuring and Revitalizing the Corporation for the 21st Century. Harper Business, 1992. [ERS+ 97] T. Erlebach, P. Rossmanith, H. Stadtherr, A. Steger, and T. Zeugmann. Learning one-variable pattern languages very eciently on average, in parallel, and by asking queries. In M. Li and A. Maruoka, editors, Proc. 8th International Workshop on Algorithmic Learning Theory, (ALT'97), October 6{8, 1997, Sendai, Japan, volume 1316 of LNAI, pages 260{276. Springer{Verlag, 1997. [FC96] M. Fayad and M.P. Cline. Aspects of software adaptability. Communications of the ACM, 39(10):58{59, 1996. [GK94] J.S. Gero and V.A. Kazakov. Evolving building blocks for genetic algorithms using genetic engineering. In John S.G., editor, Advances in Formal Design Methods for CAD, pages 31{50. Chapman and Hall, London, 1994. [GL95] J.S. Gero and S.J. Louis. Improving pareto optimal designs using genetic algorithms. Microcomputers in Civil Engineering, 10(4):241{249, 1995. [Hin96] S. Hintersdorf. Fuhrungsinformationssysteme in virtuellen Unternehmen. Master's thesis, Universitat Leipzig, Institut fur Wirtschaftsinformatik, January 1996. [Jan89] K.P. Jantke. Algorithmic learning from incomplete information: Principles and problems. In J. Dassow and J. Kelemen, editors, Machines, Languages, and Complexity, volume 381 of Lecture Notes in Computer Science, pages 188{207. Springer-Verlag, 1989.
[Jan94] K.P. Jantke. Nonstandard concepts of similarity in case-based reasoning. In H.H. Bock, W. Lenski, and M.M. Richter, editors, Information Systems and Data Analysis: Prospects { Foundations { Applications, Proceedings of the 17th Annual Conference of the GfKl, Univ. of Kaiserslautern, 1993, Studies in Classi cation, Data Analysis, and Knowledge Organization, pages 28{43. Springer{ Verlag, 1994. [Jan95] K.P. Jantke. Aktualitat der Wissensreprasentation aus Sicht des Algorithmischen Lernens. KI, 8(5):6{12, 1995. [JKS+ 94] T. Jiang, E. Kinber, A. Salomaa, K. Salomaa, and S. Yu. Pattern languages with and without erasing. Int. J. Comput. Math., 50(3{4):147{163, 1994. [JL96] K.P. Jantke and S. Lange. GOSLER { Algorithmisches Lernen fur wissensbasierte Systeme. In M. van der Meer, R. Schmidt, and G. Wolf, editors, Statusseminar \Kunstliche Intelligenz und Neuroinformatik" des BMBF, 18.{19.4.1996, Munchen, pages 167{194. Deutsche Forschungsanstalt fur Luft- und Raumfahrt (DLR), 1996. [Joh95] B. Johnstone. DIY software. New Scientist, pages 26{31, Aug 1995. [JSSY93] T. Jiang, A. Salomaa, K. Salomaa, and S. Yu. Inclusion is undecidable for pattern languages. In Intern. Conference Automata, Languages and Programming, ICALP'93, July 5{ 9, 1993, Lund, Sweden, volume 700 of Lecture Notes in Computer, pages 301{312. Springer{ Verlag, 1993. [Kle94] S. Klein. Virtuelle Organisation. WiSt, 23(6):309{311, 1994. [Koh94] J. Kohler. Wiederverwendung von Planen in deduktiven Planungssystemen, volume 65 of DISKI, Dissertationen zur Kunstlichen Intelligenz. in x, 1994. [LW90] S. Lange and R. Wiehagen. Polynomialtime inference of pattern languages. In S. Arikawa, S. Goto, S. Oshuga, and T. Yokomori, editors, Proc. 1st International Workshop on Algorithmic Learning Theory, (ALT'90), October 8{10, 1990, Tokyo, pages 289{301, Tokyo, Japan, 1990. Ohmsha Ltd.
19
[Mar96] J. Martin. Cybercorp: The new business revolution. AMACOM, 1996. [Mat97] D. Matuschek. Strukturelle A hnlichkeit im Fallbasierten Schlieen: Moglichkeiten und Grenzen. In K.P. Jantke, G. Grieser, and W.S. Wittig, editors, Impulse fur InformatikInnovationen, pages 169{178. in x, 1997. [MJ97] D. Matuschek and K.P. Jantke. Axiomatic characterizations of structural similarity for case-based reasoning. In D.D. Dankel II, editor, FLAIRS{97, Proc. Florida AI Research Symposium, Daytona Beach, FL, USA, May 11{14, 1997, pages 432{436. Florida AI Research Society, 1997. [MPS96] V. Mitrana, G. Paun, and A Salomaa. Pattern systems. Theoretical Computer Science, 154(2):183{201, 1996. [Mug90] S. Muggleton. Inductive logic programming. In S. Arikawa, S. Goto, S. Oshuga, and T. Yokomori, editors, Proc. 1st International Workshop on Algorithmic Learning Theory, (ALT'90), October 8{10, 1990, Tokyo, pages 42{62, Tokyo, Japan, 1990. Ohmsha Ltd. [Nix83] R.P. Nix. Editing by examples. Technical Report 280, Yale University, Dept. Comp. Sci., 1983. [OT95] Y. Okada and Y. Tanaka. IntelligentBox: a constructive visual software development system for interactive 3D graphic application. In Computer Animation 1995 Conference, Geneva, Switzerland, April 19{21, 1995, pages 114{125. IEEE Computer Society Press, 1995. [OU96] E. Ohlebusch and E. Ukkonen. On the equivalence problem for E{pattern languages. In W. Penczek and A. Szalas, editors, Mathematical Foundations of Computer Science 1996. 21st International Symposium, MFCS'96, volume 1113 of Lecture Notes in Computer, pages 457{468. Springer{Verlag, 1996. [PG98] J.W. Palmer and D.A. Grith. An emerging model of web site design for marketing. Communications of the ACM, 41(3):45{ 51, 1998.
20
[PRW96] S. Picot, R. Reichwald, and R.T. Wigand. Die grenzenlose Unternehmung. Gabler Verlag, 1996. [Qui86] J.R. Quinlan. Induction of decision trees. Machine Learning, 1:82{106, 1986. [Sch90] R.E. Schapire. Pattern languages are not learnable (extended abstract). In Proc. of the 3rd Workshop on Computational Learning Theory, pages 122{129, 1990. [Sco94] G. Scotton. First virtual reality: Now there's the virtual corporation. Financial Post (Computers Special Report), page 13, September 1994. [Shi82] T. Shinohara. Polynomial time inference of pattern languages and its applications. In 7th IBM Symposium on Mathematical Foundations of Computer Science, pages 191{209, 1982. [Tan89] Y. Tanaka. A toolkit system for the synthesis and the management of active media objects. In 1st Intern. Conference on Deductive and Object-Oriented Databases, Kyoto, pages 269{277, 1989. [Tan91] Y. Tanaka. Synthetic dynamic{media system. In Intern. Conferenrence on Multimedia Information Systems, Singapore, pages 299{310, 1991. [Tan96] Y. Tanaka. Meme media and a worldwide Meme pool. In ACM Multimedia 96, Boston, MA, USA, November 18{22, 1996, pages 175{186. ACM, 1996. [Tan97] Y. Tanaka. Meme media and a Meme pool. In Multimedia Technology and Systems, So a, Bulgaria, June 12{17, 1997, pages 175{ 186, 1997. [TNAN92] Y. Tanaka, A. Nagasaki, M. Akaishi, and T. Noguchi. A synthetic media architecture for an object-oriented open platform. In Information Processing 92, IFIP 12th World Computer Congress, Madrid, Spain, September 7{11, 1992, volume III, pages 104{110. North{Holland, 1992.
