Complexity of Grammar Induction for Quantum Types

Most categorical models of meaning use a functor from the syntactic category to the semantic category. When semantic information is available, the problem of grammar induction can therefore be defined as finding preimages of the semantic types under this forgetful functor, lifting the information flow from the semantic level to a valid reduction at the syntactic level. We study the complexity of grammar induction, and show that for a variety of type systems, including pivotal and compact closed categories, the grammar induction problem is NP-complete. Our approach could be extended to linguistic type systems such as autonomous or bi-closed categories.Comment: In Proceedings QPL 2014, arXiv:1412.810

EU and US safeguards against Chinese textile exports: What consequences for West African cotton-producing countries?

In 2005, following the phase-out of the Agreement on Textile and Clothing, the EU and the US have implemented new restrictions on textile and clothing imports from China. Available data suggests that the shortfall thus imposed on China, in terms of textile exports to the EU and to the US, is significant. West African cotton-producing countries are very dependant on cotton earnings for their GDP and over the last years, most of the growth of their cotton exports’ revenues has resulted from increasing exports to China. The results of a model of Chinese and West African cotton exchanges suggests that Chinese imports of West African cotton are strongly dependant on its textile exports to the EU and the US. EU and US safeguards against Chinese textile might have seriously hampered West African cotton exports opportunities over the past two years.West-Africa; cotton; ATC; EU and US safeguards; China; textile

Normalization for planar string diagrams and a quadratic equivalence algorithm

In the graphical calculus of planar string diagrams, equality is generated by exchange moves, which swap the heights of adjacent vertices. We show that left- and right-handed exchanges each give strongly normalizing rewrite strategies for connected string diagrams. We use this result to give a linear-time solution to the equivalence problem in the connected case, and a quadratic solution in the general case. We also give a stronger proof of the Joyal-Street coherence theorem, settling Selinger's conjecture on recumbent isotopy

African cotton markets at crossroads : will the price spike turn into a new kick-start ?

After years of diplomatic efforts and legal procedures to obtain the elimination of rich countries'cotton subsidies, policy prospects for African cotton producers remain bleak. However, the world price for cotton has doubled in a year and has hit an all-time high. This paper examines these developments and investigates their potential consequences for African smallholder farmers. It emphasizes the importance of price transmission to domestic markets; assesses the impact of the reforms undertaken in Sub-Saharan African cotton sectors on producers'supply responsiveness; and outlines what remains to be done to ensure that farmers can benefit from a favorable global environment. The paper concludes that improving the functioning of domestic markets remains the priority in the short run. The current high price season will reveal the costs and benefits of different types of sector regulation systems and the capacity of policy-makers and sector stakeholders to deliver on promises. It also offers a last-minute opportunity to rich countries to keep their word in the context of the Doha Development Round.Markets and Market Access,Economic Theory&Research,Environmental Economics&Policies,Emerging Markets,Access to Markets

Sub-Saharan African Cotton Policies in Retrospect

Using a series of market structure criteria, this paper gives a panorama of policies and reforms in all sub-saharan African cotton producing countries from the early 1960s to the present time. Reporting institutional changes precisely and in a consistent manner for all countries offers new opportunities for empirical comparative work. In addition, we identify trends in policy changes, which, to our knowledge, have not yet been described; in particular, we observe a recent but clear tendency towards re-regulation, which, interestingly, seems to transcend the traditional geographical divide.Crop Production/Industries,

Aid for Trade effectiveness: What do evaluations say?.

This item has no abstract.