Knowledge Acquisition for Content Selection

An important part of building a natural-language generation (NLG) system is knowledge acquisition, that is deciding on the specific schemas, plans, grammar rules, and so forth that should be used in the NLG system. We discuss some experiments we have performed with KA for content-selection rules, in the context of building an NLG system which generates health-related material. These experiments suggest that it is useful to supplement corpus analysis with KA techniques developed for building expert systems, such as structured group discussions and think-aloud protocols. They also raise the point that KA issues may influence architectural design issues, in particular the decision on whether a planning approach is used for content selection. We suspect that in some cases, KA may be easier if other constructive expert-system techniques (such as production rules, or case-based reasoning) are used to determine the content of a generated text.Comment: To appear in the 1997 European NLG workshop. 10 pages, postscrip

A cost of being large: genetically large yellow dung flies lose out in intra-specific food competition

Most life history traits are positively influenced by body size, while disadvantages of large size are poorly documented. To investigate presumed intrinsic costs of large body size in yellow dung flies (Scathophaga stercoraria; Diptera: Scathophagidae), we allowed larvae from replicate lines artificially selected for small and large body size for 21 generations to compete directly with each other at 20°C (benign) and 25°C (stressful) and low and high food (dung) availability. Greater mortality of large line flies was evident at low food independent of temperature, suggesting a cost of fast growth and/or long development for genetically large flies during larval scramble competition under food limitation. Our results are congruent with a previous study assessing mortality when competing within body size lines, so no additional mechanisms affecting scramble or contest behavior of larvae need be invoked to explain the results obtained beyond the costs of longer development and faster growth. Thus, artificial selection producing larger yellow dung flies than occur in nature revealed some, albeit weak mortality costs of large body size that otherwise might have remained cryptic. We conclude, however, that these costs are insufficient to explain the evolutionary limits of large body size in this species given persistently strong fecundity and sexual selection favoring large size in both sexes

No size-dependent reproductive costs in male black scavenger flies (Sepsis cynipsea)

Mating is generally assumed to be costly, but mating costs differ between the sexes. Although mating itself is considered cheaper for males, mate search and mate competition are cheaper for females. Nevertheless, studies increasingly reveal considerable mating costs for males, and these costs should depend on the body size of the individual. We investigated size-dependent predation (ecological) and energetic (physiological) mating costs in male black scavenger flies, Sepsis cynipsea (Diptera: Sepsidae), a model organism for studies of reproductive behavior. We addressed costs of mating by assessing predation risk for differently sized flies in male, female, and mixed-sex groups. Males were not more likely to be predated in mating or mate-search situations. Scathophaga stercoraria (Diptera: Scathophagidae) predators preferred smaller females and males as prey. Male movement in these different social situations does not proximately explain this size-selective predation, as small individuals were not more mobile. We addressed energetic costs of mating by measuring residual longevity (or starvation resistance) of starved males exposed to different mating situations. Copulation, courtship, interaction with reluctant females, or brief interactions with other males, all presumably increasing energy demand, did not significantly reduce longevity of males compared with males not interacting with other individuals. In general, small males died sooner when starved. Overall, we found no direct costs of mating for male S. cynipsea, but both predation and physiological costs were size dependent. Copyright 2009, Oxford University Press.