Using and Learning GAI-Decompositions for Representing Ordinal Rankings

International audienceWe study the use of GAI-decomposable utility functions for representing ordinal rankings on combinatorial sets of objects. Considering only the relative order of objects leaves a lot of freedom for choosing a particular utility function, which allows one to get more compact representations. We focus on the problem of learning such representations, and give a polynomial PAC-learner for the case when a constant bound is known on the degree of the target representation. We also propose linear programming approaches for minimizing such representations

Apprentissage de GAI-décompositions

National audienceDans cet article, nous étudions l'acquisition de GAI- décompositions de degré connu d'ordres de préférence dont un ensemble d'exemples est donné en entrée. Nous montrons que l'on peut représenter les GAI- décompositions cohérentes avec un ensemble d'exemples comme les solutions d'un système d'équations linéaires. Nous en déduisons un algorithme d'apprentissage passif (utilisant seulement des exemples observés) pour les GAI-décompositions de degré connu et constant. Nous montrons enfin comment généraliser ce résultat pour calculer des GAI-décompositions de degré ou de taille minimaux

Disease Kinds and Functional Explanations.

The present thesis is concerned with the character of kinds in human somatic pathology and the relation that these kinds and their members have with function-based explanations. More precisely, in the first part of the thesis I investigate whether diseased organisms, grouped together on grounds of their shared pathological features, could form natural kinds, taking into account that the paradigmatic natural kinds are the kinds of the exact sciences. The second part of the thesis has as a backdrop the Humean/anti-Humean debate over causation (and the specific construal of explanations according to which to explain is to pinpoint causes). In this backdrop, I enquire into what sort of function-based explanations we could provide for the symptoms and pathological behaviours exhibited by diseased organisms, if we construe such organisms as members of natural kinds. I argue in the first part of the thesis that from a metaphysical point of view, the organisms dealt with in somatic medicine form natural kinds in the same sense in which we take the kinds dealt with in the exact sciences as natural. By comparing a 'classical', exact science kind with a kind of disease, I show that whatever features are associated with natural kind membership (e. g. involvement in laws or inductions, explanatory relevance, possession of 'essential' properties, instantiation of substantive universals, etc. ) there is no 'ontological gap' between disease kinds and the kinds in the exact sciences. The conclusion that diseases are natural kinds has a certain proviso regarding the question of whether the identity of the individual members of natural kinds is dependent upon their kind membership. Should diseases not be natural kinds, the proviso says, it would be because the properties characteristic of natural kinds must have an identity-influence over the kind members. I present in addition serious problems posed by outlining such identity bearing properties. In the second part of the thesis, I argue that function based explanations concerned with diseased organisms - if we construe such organisms as being members of natural kinds - should illuminate positive causes for the symptoms and pathological behaviours they exhibit. We could obtain such function-based explanations, I suggest, if we interpret the functioning of biological items as the manifesting of causal powers. Against the background of the Humean vs. anti-Humean debate on causation, I show that Nancy Cartwright's capacities are a plausible variant for the powers at work in 'pathological' functioning. I argue that one could track down these capacities if one viewed healthy organisms as nomological machines, in the sense in which Cartwright understands this notion. I also suggest that capacities are necessary in order to vindicate general and, more importantly, singular causal claims involved in medical diagnosis and hence to found satisfactory functional explanations

Représentation et apprentissage de préférences

La modélisation des préférences par le biais de formalismes de représentation compacte fait l'objet de travaux soutenus en intelligence artificielle depuis plus d'une quinzaine d'années. Ces formalismes permettent l'expression de modèles suffisamment flexibles et riches pour décrire des comportements de décision complexes. Pour être intéressants en pratique, ces formalismes doivent de plus permettre l'élicitation des préférences de l'utilisateur, et ce en restant à un niveau admissible d'interaction. La configuration de produits combinatoires dans sa version business to customer et la recherche à base de préférences constituent de bons exemples de ce type de problème de décision où les préférences de l'utilisateur ne sont pas connues a priori. Dans un premier temps, nous nous sommes penchés sur l'apprentissage de GAI-décompositions. Nous verrons qu'il est possible d'apprendre une telle représentation en temps polynomial en passant par un système d'inéquations linéaires. Dans un second temps, nous proposerons une version probabiliste des CP-nets permettant la représentation de préférences multi-utilisateurs afin de réduire le temps nécessaire à l'apprentissage des préférences d'un utilisateur. Nous étudierons les différentes requêtes que l'on peut utiliser avec une telle représentation, puis nous nous pencherons sur la complexité de ces requêtes. Enfin, nous verrons comment apprendre ce nouveau formalisme, soit grâce à un apprentissage hors ligne à partir d'un ensemble d'objets optimaux, soit grâce à un apprentissage en ligne à partir d'un ensemble de questions posées à l'utilisateur

Money, reputation and inventories under credit market imperfections.

This thesis analyses the way in which credit market imperfections affect the behaviour of economic agents, and examines how a variety of tangible or intangible assets such as fiat money, reputation and inventories, facilitate bilateral exchange and influence investment decisions of firms under such circumstances. The first chapter of the thesis deals with the role of fiat money as a medium of exchange in a model in which agents hold consumable goods or nonconsumable cash. The physical environment of pairwise random matching for bilateral trade, however, prevents them from issuing debt certificates. Unlike fiat money, consumables have uncertain quality characteristics, and agents can only detect the quality of a subset of goods. As a consequence, barter is plagued by asymmetric information, whereas monetary exchange involving generally recognisable legal tender is not. This suggests that it is because of, rather than despite, its intrinsic uselessness that, as a medium of exchange, fiat money is superior to goods or assets subject to some form of quality uncertainty. The second chapter examines the effects of reputation and internal finance on a firm's investment incentives. An entrepreneur with unknown productivity finances risky production with a combination of internal finance and funds from external investors who, just like himself, are able to learn about his true productivity over time, a process that influences their willingness to lend. However, investment decisions taken by the entrepreneur, are not observable to outsiders. This information problem leads not only to underinvestment but also to premature liquidation. It is shown that the acquisition of reputation and internal funds may counteract such undesirable outcomes. On the other hand, it becomes clear that when assets are low, incentives to invest are disrupted because of a high probability of liquidation in the near future. Young firms appear to be particularly susceptible to effects of this type. Finally, the third chapter studies inventory investment and internal-finance decisions of a financially constrained firm facing an uncertain demand process. The model gives an explanation for the stylised fact that production is more volatile than sales. Assuming that firms have limited access to capital markets they are forced to rely on internal finance. However, following a series of unfavourable sales realisations such funds possibly are so low that firms find themselves unable to re-establish the old inventory level in subsequent periods. Conversely, after a series of high sales the firm has a substantive amount of money to finance output quantities that may be in excess of sales

Representation Theorems and Radical Interpretation

This paper begins with a puzzle regarding Lewis' theory of radical interpretation. On the one hand, Lewis convincingly argued that the facts about an agent's sensory evidence and choices will always underdetermine the facts about her beliefs and desires. On the other hand, we have several representation theorems—such as those of (Ramsey 1931) and (Savage 1954)—that are widely taken to show that if an agent's choices satisfy certain constraints, then those choices can suffice to determine her beliefs and desires. In this paper, I will argue that Lewis' conclusion is correct: choices radically underdetermine beliefs and desires, and representation theorems provide us with no good reasons to think otherwise. Any tension with those theorems is merely apparent, and relates ultimately to the difference between how 'choices' are understood within Lewis' theory and the problematic way that they're represented in the context of the representation theorems. For the purposes of radical interpretation, representation theorems like Ramsey's and Savage's just aren't very relevant after all

Structuring technology strategy and interfirm collaboration: Empirical study on Korean high-tech small firms in telecommunications industry.

Inter-firm collaboration as a technology-sourcing decision of Korean high-tech small firms receives great attention as its strategic importance to the technological innovation and economic growth of Korean economy is growing immensely. However, there exists no extensive data and in-depth analysis of under what conditions the decision-makers actually choose technology alliance, or vice versa. This question remains unanswered because existing studies fail to specify cases under which technology-sourcing decision is employed as well as the scope of technological collaboration. This study is the first attempt to tackle these problems by providing a comprehensive framework to guide decision-makers in making appropriate technology strategy. As a first step, this study investigated how and whether the existing decision-makers would have a clear set of decision rules between in-house development and technology alliance and equity alliance and non-equity alliance. To achieve this, extensive literature reviews were undertaken and some consultation from industry experts was carried out. Then, this study developed a two-staged contingency model which denotes that the decision-makers are likely to go through two sequential and contiguous steps until they reach their final decision. Drawing on the decision-makers' perception of their firms' internal condition, external environment and technology projects, 11 factors and 5 factors were identified as determinants in stage One and in stage Two respectively. The result shows that, in the first stage of decision-making, in-house development was preferred when the firms perceived that their technological capability was strong; while technology alliance was preferred when they perceived that they were more entrepreneurially-oriented, when the projects required specialised asset investment and the technology project was highly risky. In addition, the pressure for social legitimacy influenced their decision to undertake technology alliance. In the second stage of decision-making, equity alliance was preferred what the firms perceived that the scope of the cooperative project was wider, while non-equity alliance was preferred when they perceived some degree of mutual trust with potential partners. Apart from identifying the determinants, this study found that technology cooperation is not widely adopted as a technology-sourcing method compared to in-house development; only one in five responding firms is adopting it. That is because, unless the responding firms perceive that they are technologically far less capable, inter-firm, collaboration is not an attractive option for them even if their technology development projects are in a condition that is favourable for adopting inter-firm collaboration. This study suggests that studies on small firm's inter-firm collaboration and technology-sourcing decision should be led into a new direction. First, they should be based on the careful selection of sample firms and scope of technological collaboration. Second, theoretical integration is essential to understand the complex nature of their technology-sourcing decision. Third, unlike in other studies, the transaction cost (TC) perspective is still powerful in explaining the antecedents; economising is still the most important consideration in a small firm's technology-sourcing decision. Finally, a normative and rationalised approach to the alliance studies has been the major methodology in alliance studies, however, the qualitative approach is becoming more important as the use of formal collaboration is less frequent and the firms exchange relevant information through informal relationships that may exist within their industrial clusters, whose phenomenon can be hard to grasp through statistical analysis

Social limits to economic theory

This dissertation effects a complete re-orientation of economic theory. It shows how the economic cannot be analysed separately from the political and the social, and lays the foundation for an integrated political economy. The work examines the philosophical difficulties faced by economists, and re-draws the history of economic thought as a response to methodological dilemmas. The traditional History of Economics textbooks re-write the history in terms of the contemporary paradigm. This dissertation, by contrast, shows how the philosophical debates have shaped the trajectory of economics, and how the orientations of the schools undergo major changes so as to attempt to deal with the fundamental dilemmas of a 'policy science’. It brings out the 'hidden history’ of economics, and shows both how laissez-faire can only be defended by dropping any notion of economic 'science', and how economic theory has an implied political theory. It then considers the debate over political economic theory and the consequences for economic organisation and for environmental disruption