cognitive science technical reports from ircs the institute for research in cognitive science publishes a series of technical reports , representing papers drawn from the fields of computer and information science , linguistics , mathematics , neuroscience , philosophy , and psychology . bound versions of the technical reports are available from the institute for a small fee , while on-line versions of all current ( 1994 ) technical reports are freely available on-line . attached is a list of abstracts for recently published papers . the entire abstract list will be submitted to the linguist listserv as a file . requests for technical-reports should be sent to : jodi kerper institute for research in cognitive science 3401 walnut street suite 400c philadelphia , pa 19104-6228 requests for copies should include a check or money order made payable to " trustees of the university of pennsylvania . " on - line versions of the reports may be obtained via anonymous ftp from the address ftp . cis . upenn . edu in the directory pub / ircs / technical-reports . the reports are stored as compressed postscript files and are listed by tr number . the reports may also be obtained through electronic mail by sending the message " send guide " to ircsserv @ ftp . cis . upenn . edu . you will receive a reply containing a guide on using the information server program . = = = = = = = = = = = = = = = = = = = = = = = = = = = recent ircs reports = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = ircs-tr - 1991-1994 technical report series abstract listing , 1991-1994 ( this report contains a list of all technical papers and abstracts , including papers from 1991-1993 ) . no charge ircs-94 - 14 $ 3 . 69 a general framework for hybrid substructural categorial logics mark hepple some recent categorial proposals have employed structural modalities , modal operators which allow explicit management of resource sensitivity in linguistic derivation . various theoretical , computational and practical problems arise for the use of such operators . i propose an alternative general model of hybrid substructural systems , in which different substructural logics ( i . e . logics differing in their resource usage characteristics ) are brought together into a single system , and which eliminates the need of structural modalities by exploiting natural relations between different substructural levels in terms of the relative informativeness of their characterizations . under this model , the range of substructural levels form a single unified descriptive system , which should facilitate writing grammars for individual languages , and provide a better basis for cross-linguistic generalization . ircs-94 - 15 $ 1 . 05 binding and control in ccg and its relatives mark steedman the ccg account of the unbounded constructions - in particular , relativisation and coordination - generalizes the notion of surface structure in a way that disrupts traditional notions of dominance and command . this has led researchers in other frameworks to suggest that the theory is fundamentally incompatible with a coherent theory of binding and control - the bounded constructions . the present paper offers a theory of binding in ccg which preserves the original account of the unbounded dependencies , and which renders it immediately compatible with other theories , tag in particular . the theory requires the abandonment of one assumption that has been traditional ( though not essential ) in other categorial approaches . the significance of the move is discussed . ircs-94 - 16 $ 3 . 66 null subjects in early child english and the theory of economy of projection tom roeper bernhard rohrbacher in this paper , we present new evidence showing that some of the empty subjects produced by young children acquiring english cannot be subsumed under the performance limitation analysis of bloom ( 1990 ) or the topic - drop analysis of rizzi ( 1994 ) . we argue contra sano & hyams ( 1994 ) that these missing subjects are instances of pro , not pro , and demonstrate that the economy-based pro-drop theory of speas ( 1994 ) handles our data in an elegant fashion . the analysis we propose links the acquisition of subjects to the acquisition of functional morphology , in accordance with the minimalist program developed since chomsky ( 1989 ) . one desirable consequence of the approach taken here is that no recourse to a pro-drop parameter is necessary . ircs-94 - 17 $ 3 . 41 kolmogorov complexity and the information content of parameters robin clark a key goal of linguistic theory is to account for the logical problem of language acquisition . in particular , linguistic constraints can be taken as constraining the learner 's hypothesis space and , so , reducing its computational burden . in this paper , i will motivate an information theoretic approach to explaining some linguistic constraints . in particular , the theory attempts to relate ease of acquisition with the simplicity of linguistic representations and their frequency in the learner 's input text . to this end , the paper reviews some results in information theory and kolmogorov complexity and relates them to a theory of parameters . ircs-94 - 18 $ . 87 active part - decomposition , shape and motion estimation of articulated objects : a physics - based approach ioannis a . kakadiaris dimitri metaxas ruzena bajcsy we present a novel , robust , integrated approach to segmentation shape and motion estimation of articulated objects . initially , we assume the object consists of a single part , and we fit a deformable model to the given data using our physics-based framework . as the object attains new postures , we decide based on certain criteria if and when to replace the initial model with two new models . these criteria are based on the model 's state and the given data . we then fit the models to the data using a novel algorithm for assigning forces from the data to the two models , which allows partial overlap between them and determination of joint location . this approach is applied iteratively until all the object 's moving parts are identified . furthermore , we define new global deformations and we demonstrate our technique in a series of experiments , where kalman filtering is employed to account for noise and occlusion . ircs-94 - 19 $ . 92 active motion - based segmentation of human body outlines ioannis a . kakadiaris dimitri metaxas ruzena bajcsy we present an integrated approach towards the segmentation and shape estimation of human body outlines . initially , we assume that the human body consists of a single part , and we fit a deformable model to the given data using our physics-based shape and motion estimation framework . as an actor attains different postures , new protrusions emerge in the outline . we model these changes in the shape using a new representation scheme consisting of a parametric composition of deformable models . this representation allows us to identify the underlying human parts that gradually become visible , by monitoring the evolution of shape and motion parameters of the composed models . our algorithm is applied iteratively over subsequent frames until all moving parts are identified . we demonstrate our technique in a series of experiments with very encouraging results .