Agent Technologies for Sensor Networks networks consist of small, battery-powered devices that are physically distributed over a wide area and connected through a wireless communication network. Since these networks often must collect data over extended periods of time and are deployed in inhospitable environments where replacing batteries is inconvenient or impossible, much of the research in this domain addresses the challenge of minimizing each sensor's energy needs. To this end, researchers have developed a wide range of energy-effi cient sensor nodes and wireless communication protocols and demonstrated them in varied applications.In addition to the immediate concerns of energy effi ciency and reliable wireless communication, which are normally the concerns of electronics engineers, the distributed nature of such networks and the autonomous behavior expected of them present several more generic challenges. Specifi cally, the individual sensors in these networks must typically coordinate their sensing actions with nearby sensors to achieve systemwide goals (for example, varying their sense/sleep duty cycles to maximize battery life while reducing the redundant sensing of overlapping areas). Furthermore, the network must autonomously adapt its responses in a dynamically changing environment such that it can achieve the long-term systemwide goals without direct human intervention. Such problems have long been the domain of computer scientists, particularly those researching multiagent systems. As such, the multiagent systems community would seem to have an extensive set of formalisms, algorithms, and methodologies in place to address these challenges.However, the mapping from sensor to agent isn't trivial. Research in the multiagent systems domain typically doesn't address the constrained computational and communication resources of low-powered sensor nodes. Moreover, research often fails to consider that communication might be slow and intermittent, hardware might be unreliable and failure prone, and environments might be highly dynamic. As such, although existing agent technologies are extremely valuable, they cannot be used directly. Rather, to address the specifi c constraints and challenges posed by this application setting, we need a new synthesis that adapts and extends traditional technologies using approaches from other disciplines such as electronic engineering.Against this background, this article describes three examples where this synthesis has succeeded. One showcases the development of communication and computationally effi cient decentralized coordination algorithms to coordinate the behavior of physically distributed sensors. The second addresses the real-world challenges of using sensoragent platforms in the fi eld. Finally, we describe intelligent agents that can autonomously acquire data from these networks and perform informationprocessing tasks such as fusion, inference, and prediction. In each case, researchers have demonstrated the work in the wild, implemented it on real sensor hardware, deployed it in real, hostile environments, and evaluated it on real sensor data.As we mentioned, coordinating the activities of physically distributed devices to achieve good systemwide performance is a fundamental challenge. Such coordination might include routing data through the network, choosing the appropriate sampling rates of sensors that exhibit spatial correlations, or determining W ireless sensor networks are increasingly seen as a solution to the problem of performing continuous wide-area monitoring in many environmental, security, and military scenarios. Such

B I O B I B O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O


A Method of Simple Adaptive Control for Nonlinear Systems Using Neural Networks This paper presents a method of simple adaptive control(SAC) for nonlinear systems using neural networks. The control input is given by the sum of the output of a simple adaptive controller and the output of the neural network. The neural network is used to compensate the nonlinearity of plant dynamics that is not taken into consideration in the usual simple adaptive control. The role of the neural network is to construct a linearized model by minimizing the output error caused by nonlinearities in the control sysytems. .n p .∼(4) .(1), (3) ASPR .. , n m (n m ≤ n p ) .,n m n p .e y (k) = y m (k) − y p (k)

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Testing the forensic soundness of forensic examination environments on bootable media In this work we experimentally examine the forensic soundness of the use of forensic bootable CD/DVDs as forensic examination environments. Several Linux distributions with bootable CD/DVDs which are marketed as forensic examination environments are used to perform a forensic analysis of a captured computer system. Before and after the bootable CD/DVD examination, the computer system's hard disk is removed and a forensic image acquired by a second system using a hardware write blocker. The images acquired before and after the bootable CD/DVD examination are hashed and the hash values compared. Where the hash values are inconsistent, a differential analysis is performed on the image files. The differential analysis allows us to quantify and explain the alterations made to the image files by the bootable CD/DVD examination. Our approach can be used to experimentally validate new bootable CD/DVD distributions as forensically sound. A plethora of forensic bootable CD/DVD/USB Linux distributions are available for use in digital investigations. Both commercial and community-developed distributions are available, and most make the claim that they provide a forensically sound examination environment. The bootable CD/DVDs are used by forensic examiners to boot into a trusted operating system on the suspect's computer system. This has numerous advantages in some scenarios:. 1. Conducting a quick examination of the suspect's machine at the scene in a trusted operating system.. 2. Examining the system without the need to perform a time consuming hard disk acquisition where the suspect's machine needs to be powered off and disconnected, the disk removed, and then acquired. 3. Acquiring an image of the RAM of a live system from a trusted operating system, albeit with some degradation caused by the reboot.. However, despite their utility, forensic bootable CD/ DVDs are known to have several problems which compromise their utility and potentially call the digital evidence they are used to collect into doubt (Forensicswiki.org, 2012) . Chief amongst these problems is that the bootable live CD/DVD examination environments may alter the suspect computer system's hard disks during the examination process. Such an alteration calls into question the forensic soundness of the examination.. In this work we test various forensic bootable CD/DVDs based on Linux, through an experiment to evaluate the changes those CD/DVDs make to the suspect's hard disk. A detailed, repeatable method is detailed for the testing of bootable CD/DVDs and bootable USB devices designed for forensic examinations. We use differential analysis to find the nature and quantify the extent to which those distributions change the suspect's hard disk. From these experiments we draw findings and propose future work. We see four major items of future work coming out of this work. The first is a new set of experiments involving multiple computers with a variety of "common" configurations, in order to evaluate whether the bootable CD/DVD distributions we have tested make predictable alterations, or whether the alterations are different after every examination. The second is the expansion of our testing to a much broader set of bootable forensic examination environments, including non-Linux based environments and more commercial tools. The third is a deeper differential analysis of images generated during our testing process. The primary benefit of the second and third items of future work will be to raise awareness about the alterations (if any) made to hard disks during routines conducted with the tested bootable forensic examination environments, and to assist in the answering of the question about whether those distributions are suitable for use in forensic examinations of the host computer's hard disks. The fourth major item of future work is to investigate the causes of the changes made by tested distributions and of the variables involved which may contribute to, mitigate, or prevent such changes. Using bootable media-based forensic examination environments has become important in digital forensic investigations. The notion of altering the data during a forensic investigation has also become more acceptable, providing that we know what, where and how much of the data is being altered. The results from this study indicate that some data on the disk does change when using several popular bootable CD/DVDs, and we document where these changes take place using differential analysis helping both digital practitioners and scientists understand what happens to a disk when a bootable CD/DVD is used on a machine.. The results, summarized in Table 4 , indicated a variation in the amount of data that is being changed on the disk when Helix 3 Pro, Kali and Knoppix are used. All the bootable CD/DVDs altered the disk, but none added any files to the disk during the course of searching the disk by file types and keywords. Knoppix allowed the disk to be written to even when the user has mounted the disk as read only, permitting us to create files using the graphical shell, meaning that it would be easier for a file to be accidentally created and the suspect's disk altered by an examiner using Knoppix. Most of the changes made by the bootable CD/DVDs we tested were in C:y[root]y$LogFile, C:y[root]y$MFT and occasionally in the file C:y[root]yWINDOWSybootstat.dat. Knoppix also altered some other files as well, which is documented in our Knoppix findings. In all cases the only modifications were the "last accessed" timestamps. These changes are minimal, easily attributed to the examination process (since the timestamp reflects the time of the bootable CD/DVD examination), and unless timestamps are somehow relevant to the investigation, unlikely to have any evidentiary impact. In Table 4 we have listed that the alterations made by Helix3 Pro and Kali were acceptable in respect of this minimal impact, however, given Knoppix permits the user to write to the suspect's disk in addition to the timestamp alterations, we have indicated that we do not regard these alterations as acceptable for forensic use, and we believe Kali's auto-mounting hard disk partitions as read-write at boot time makes Kali unacceptable for forensic use even though the alterations it made were minimal. We stress that this assessment is our own, and encourage others to make their own assessment of the forensic soundness/acceptability of a given bootable forensic examination environment for themselves on the basis of their own testing.. We conclude that even though disk alterations are made, they can be documented through experimentation, which can help during an investigation when a question arises on the integrity of using a bootable CD/DVD during an investigation. With the proper testing to support their choice of examination environment and to document and explain any minor changes that environment may make to the original disk, it may therefore be possible for an examiner to justify the use of a particular bootable CD/ DVD. Whether any changes are justifiable or not, what is certain is that rigorous testing of bootable forensic examination environments is required to support their usage in digital forensics, and that such environments, even community-developed forensics-dedicated distributions, cannot be assumed to be safe without such testing. Conducting forensic investigations is becoming more challenging due to the pervasive nature of internet and the increasing size of computer storage media, including hard drives and tape devices (Adelstein, 2006) . The traditional approach to computer forensics, where an investigator first switched off the suspect's machine, took it to a laboratory, removed the hard disk and then took images of confiscated computer hard disk for further analysis is time consuming. On the principle that "justice delayed is justice denied", it is often preferable to conduct some sort of triage or preliminary investigation in situ e indeed, this may even elicit a confession from a suspect when confronted with evidence of their wrong doing at the scene (Casey et al., 2009) . Forensic examination environment boot media can be used in these cases in three main ways:. To provide "known-good" binaries for live analysis of a system. To conduct a dead analysis of the system at the scene without the need to disassemble the computer, and image its hard disk drive. To use the suspect's hardware to examine the disk in cases where the forensic examiner may not have access to specialist or legacy hardware which may be necessary to image certain types of hard disks.. In all of these types of investigation, the suspect's computer is being used to investigate activities which have taken place on the suspect's computer, and thus it may be asked whether we are conducting a live or dead analysis. We differentiate on the basis of whether the suspect computer's operating system is being used by the investigator. Live analysis uses the suspect system's operating system and its resources to conduct forensics. By contrast, dead analysis takes place when that operating system is no longer running, such as when the computer has been booted into another operating system from removable media (Carrier, 2005) . To differentiate between uses of forensic examination environments on CD, DVD and other removable media, we call CD/DVDs which are used for live analysis "tools CDs" (or DVDs) and those used for dead analysis "boot CDs" (or DVDs), since the suspect computer will be rebooted using the operating system on the optical media in the second case. We should note that the terms "live CDs" and "boot CDs" are often used interchangeably in the literature, among the Linux user community, and among the digital forensics community.. Live forensics gives access to information on running processes, open network connections, and open Dynamically Linked Libraries (DLL) in additional to nondvolatile static information (Carvey, 2007) . The main forensic purpose of live CD/DVDs is in investigations where evidence is likely to be found in memory or in other volatile storage locations, where powering down or restarting the computer for a dead analysis is likely to cause that evidence to become corrupt, overwritten or otherwise irretrievable. Live CD/ DVDs can be used to provided trusted tools and utilities for forensic analysis for an investigator to use rather than depending on tools which are found on the suspect computer's hard drive, which might be infected by malware or be otherwise modified and unreliable. In this respect they address to a limited extent the concern that live forensics may be invalidated by low system integrity, but there are still significant problems in their use (Hay et al., 2009) .. In this work we focus on boot CD/DVDs, not live CD/ DVDs, according to the distinction we have given above. Although boot CD/DVDs are not subject to concerns about system integrity caused by a compromised host operating system, there is a growing awareness in the DF community that forensic bootable CD/DVDs can still be problematic and most particularly that their claims that the suspect's hard disk will not be altered have rarely been tested. For example, in the Forensics Wiki 1 an excellent discussion of the issues with forensic bootable CD/DVDs has been a featured article for some time (Forensicswiki.org, 2012) . However, despite this growing awareness in the researchactive part of the DF community, the identified issues are still commonplace in many bootable CD/DVD distributions, and even where they have been fixed, new versions frequently reverse those fixes. Each bootable forensic examination environment was tested according to the following methodology:. 1. An artificial "suspicious usage" scenario was performed on the suspect computer. 2. The suspect computer's hard disk was removed from the (powered down) suspect computer. 3. The suspect computer's hard disk was connected to a hardware write blocker (see Fig. 2 ). 4. The write blocker was connected to the forensic workstation. 5. An image of the suspect computer's hard disk was acquired using FTK Imager (call this image img). 6. The suspect computer's hard disk was disconnected from the write blocker. 7. The suspect computer's hard disk was reinstalled in the suspect computer. 8. The suspect computer was booted from the bootable media containing the forensic examination environment. 9. A forensic examination of the suspect computer's hard disk was performed using the tools on the bootable media. 10. The suspect computer was shut down gracefully. 11. The suspect computer's hard disk was removed from the suspect computer. 12. The suspect computer's hard disk was connected to the write blocker (and forensic workstation) once again. 13. An image of the suspect computer's hard disk was acquired using FTK Imager (call this image img 0 ). 14. Hash values were calculated for img and img 0 .. If the hash values for the two images matched, then the bootable CD/DVD examination did not alter the suspect computer system's hard disk. If the hash values for the two images did not match, then the bootable CD/DVD examination altered the suspect computer's hard disk. We generated SHA1 hash values for all images in our experiment. In our experiment we examined the following bootable forensic examination environments:. This list is by no means exhaustive. The methodology we have employed is easily repeatable and can be applied to test any bootable digital forensics examination environment.

O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


Face Detection Using Quantized Skin Color Regions Merging and Wavelet Packet Analysis Abstract-Detecting and recognizing human faces automatically in digital images strongly enhance content-based video indexing systems. In this paper, a novel scheme for human faces detection in color images under nonconstrained scene conditions, such as the presence of a complex background and uncontrolled illumination, is presented. Color clustering and filtering using approximations of the YCbCr and HSV skin color subspaces are applied on the original image, providing quantized skin color regions. A merging stage is then iteratively performed on the set of homogeneous skin color regions in the color quantized image, in order to provide a set of potential face areas. Constraints related to shape and size of faces are applied, and face intensity texture is analyzed by performing a wavelet packet decomposition on each face area candidate in order to detect human faces. The wavelet coefficients of the band filtered images characterize the face texture and a set of simple statistical deviations is extracted in order to form compact and meaningful feature vectors. Then, an efficient and reliable probabilistic metric derived from the Bhattacharrya distance is used in order to classify the extracted feature vectors into face or nonface areas, using some prototype face area vectors, acquired in a previous training stage. We have presented a novel scheme for human faces detection in color images under nonconstrained scene conditions, such as the presence of a complex background and uncontrolled illumination. First, a LBG color quantization is performed and the quantized images are filtering using approximations of the HSV or YCbCr skin color subspaces, providing skin color regions. A merging stage is then iteratively performed on the set of homogeneous skin color regions in the color quantized image, in order to provide a set of candidate face areas. Constraints related to shape and face texture analysis are applied, by performing a wavelet packet decomposition on each face area candidate and extracting simple statistical features such as standard deviation. These features provide an excellent basis for face detection, if an appropriate distance is used. The use of the Bhattacharyya distance proved to be very suitable for classifying these feature vectors into faces or nonfaces classes. For a data set of 100 images with 104 faces covering most of the cases of human faces appearance, a 94.23% good detection rate, 20 false alarms and a 5.76% false dismissals rate were obtained. A comparison with the CMU face detector system showed that our system is very efficient especially for large size faces detection and that skin color segmentation helps to improve the speed of face detection process by pre-selecting candidate face areas. Thus, the wavelet packet analysis provide a robust scheme for face detection, even if no constraint is imposed on the faces to be detected (except a minimal size). Moreover, very fast implementations of wavelet decomposition are available in hardware form, to cope with real time face detection needs. As an extension of this work, we believe that a slightly different feature extraction process may be performed, that extracts statistical information only from the wavelet images, which convey most information about faces texture.

B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


The Shrinking Property for NP and coNP We study the shrinking and separation properties (two notions well-known in descriptive set theory) for NP and coNP and show that under reasonable complexity-theoretic assumptions, both properties do not hold for NP and the shrinking property does not hold for coNP. In particular we obtain the following results.1. NP and coNP do not have the shrinking property, unless PH is finite. In general, Σ 4. The shrinking property does not hold for NP, unless there exist complete disjoint NP-pairs.Moreover, we prove that the assumption NP = coNP is too weak to refute the shrinking property for NP in a relativizable way. For this we construct an oracle relative to which P = NP ∩ coNP, NP = coNP, and NP has the shrinking property. This solves an open question by Blass and Gurevich [BG84] who explicitly ask for such an oracle. The shrinking property and the separation property are well-known notions from descriptive set theory. In this paper we study these notions with respect to complexity classes like NP. Definition 1.1 1. A class C has the shrinking property, if for all A, B ∈ C there exist disjoint sets A , B ∈ C such that A ⊆ A, B ⊆ B, and A ∪ B = A ∪ B.. 2. A class C has the separation property, if for all disjoint A, B ∈ C there exists an S ∈ C ∩ coC that separates A and B.. Since there is an analogy between NP and RE, complexity theorists started to study the separation and shrinking properties for NP and coNP. While the separation property was investigated rather comprehensively (see e.g. [GSSZ04, GSS05] ), the shrinking property was not considered systematically so far. In this respect, Blass and Gurevich [BG84] and Selivanov [Sel94a] show some first results and identify open questions. As one might expect, the status of both properties in the context of complexity theory is not as clear as in computability theory or descriptive set theory: they turn out to be closely related to some well-known conjectures.. In this paper we continue the study of the separation and shrinking properties in complexity theory, and we give evidence that NP does have these properties. We show that under reasonable complexity-theoretic assumptions (like an infinite PH and UP ⊆ coNP) both properties do not hold for NP and the shrinking property does not hold for coNP. Moreover, Σ P n and Π P n do not have the shrinking property, unless the PH is finite. This solves an open question from [Sel94a] . We also relate the shrinking and separation properties for NP to other well-known notions. For example, we show that the shrinking property does not hold, unless there exist NP-hard disjoint NP-pairs. The existence of such pairs contradicts a conjecture that is related to security aspects of public-key cryptosystems [ESY84, GS88] . Moreover, the shrinking property does not hold for NP, unless there exist complete disjoint NP-pairs. Such complete pairs are studied because of their relations to the theory of propositional proof systems [Raz94, Pud01] . Finally, we will see that the shrinking property for NP is closely related to selectivity, nondeterministic function classes and inverting polynomial-time computable functions (cf. Corollary 3.2) [HNOS96] .. Along with the above-mentioned oracle-independent results, we establish some oracle separations for the discussed notions. In particular, we prove that the assumption NP = coNP is too weak to refute the shrinking property for NP in a relativizable way. For this we construct an oracle relative to which NP has the shrinking property and (NP ∩ coNP) = P = NP. It follows that relative to this oracle, NP ⊆ NPSV-sel and NP = coNP. Moreover, with our construction we solve an open problem by Blass and Gurevich [BG84] who explicitly ask for the existence of such an oracle.. In Section 2 we give the background on disjoint NP-pairs and function classes that is needed for our investigations. In Section 3 we establish implication relationships between the discussed notions, while in Section 4 we discuss oracle separations for some of these notions. We conclude in Section 5 by mentioning the remaining open questions.

O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


Loopback: exploiting collaborative caches for large-scale streaming In this paper, we propose a novel loopback approach in a two-level streaming architecture to exploit collaborative client/proxy buffers for improving the quality and efficiency of large-scale streaming applications. At the upper level we use an overlay to deliver video from a central server to proxy servers, at the lower level a proxy server delivers video with the help of collaborative caches. In particular,a proxy server and its clients in a local domain cache different portions of a video and form delivery loops. In each loop, a single video stream originates at the proxy, passes through a number of clients, and is passed back to the proxy. As a result, with limited bandwidth and storage space contributed by collaborative clients, we are able to significantly reduce the requirements of network bandwidth, I/O bandwidth, and cache space at a proxy. Furthermore, we develop local repair schemes to address the client failure issues for enhancing server quality and eliminating most repairing load at servers. For popular videos, our local repair schemes are able to handle most of single-client failures without service disruption and retransmissions from a central server. Our analysis and simulations have shown the efficacy of loopback in various settings. Video streaming has become one of the most popular applications over the Internet. Many streaming approaches have been proposed in the past two decades. Generally, we have three basic types of video streaming architectures: simple clientserver models on either unicast or multicast networks (e.g., batching [1] , patching [2] , periodic broadcast [3] ), content distribution networks (CDNs) with the help of caching proxy servers (e.g., Akamai), and peer-to-peer streaming approaches using peer resources to reduce server loads (e.g. P2cast [4] , ZIGZAG [5] ). Unfortunately, due to the lack of multicast capability in current IP networks, client-server approaches are not scalable.In the meantime, a CDN approach usually requires high investment in a broad delivery infrastructure and demands a rather large amount of resources to achieve scalability. As a result, it is often difficult for CDNs to deal with the flash crowd problem [6, 7] due to its fixed resources. On the other hand, recent P2P approaches are very attractive in reducing server load, providing system scalability, and potentially solving the flash crowd issue. However, these P2P approaches often do not assure service quality.. A few hybrid approaches have been proposed with different focuses. CoopNet [8] addressed the flash crowd issue by combining a CDN with cooperative clients. CoopNet uses a central server as a directory service for clients to obtain cached contents from cooperative clients accessing the same content at the same time. Similarly, P2Cast [4] also uses a centralized directory server to assist a new client to join an active session and construct an application-level forwarding tree, consisting of a set of active clients in the session. P2Cast mainly addresses the issue of scalability by spreading server load over a set of active clients in a session. Our loopback mechanism further exploits the idea of passing data along by clients proposed in chaining, in which each client not only receives a video from the server but also forwards the same video to another client [10] . However, in chaining, a client may have to cache a whole video in the worst case, which is a rather high requirement for a common client. In this paper, we assume that each client contributes only a limited small buffer for caching. In addition, the extended chaining scheme [10] reduces resource usage by delaying client to extend the chain length. Thus, the improvement is achieved at the cost of an additional delay. In our scheme each client starts receiving data immediately. The fundamental difference between chaining and loopback is that the proxy server and client collaboration play the key roles in our loopback scheme. A client request always goes to the proxy server so that the proxy server can manage collaborative clients for caching data efficiently. Clients arriving close to each other in a local community collaborate with the proxy in a loop that services these clients and reduces the buffer space and bandwidth requirement of the proxy.. The remainder of this paper is organized as follows. In Section 2, we introduce the two-level streaming architecture and describe the loopback approach. In Section 3, we present a formal performance analysis of the loopback approach for serving a single video. In Section 4, we develop a local-repair mechanism to deal with the failures of collaborative caches for ensuring service quality as well as reducing server I/O bandwidth and network bandwidth. In Section 5, we examine the performance of loopback in the case of limited buffer space at proxy servers. In Section 6, we conclude this paper and discuss our ongoing research. We have introduced a loopback mechanism for exploiting client collaboration in a two-level video streaming architecture. We have analyzed the resource usage of the proposed mechanism, namely, server and network bandwidth, proxy bandwidth and storage space. We have shown that even with limited client resources, loopback can significantly reduce the requirements of network bandwidth, I/O bandwidth and buffer space at proxy servers, for moderately and highly popular videos. We have also analyzed the effect of client failures and developed local repair approaches to minimize playback disruption and the costs of repairs. Finally, we have shown that, even with limited proxy buffer space, the loopback scheme is still able to significantly reduce the resource requirements at proxy servers.. We are investigating the broad enhancement of the basic loopback model to allow varying amount of resources committed by each client. In other words, we will consider the case when each client may specify how much disk space can be utilized, how many clients each client is willing to serve, and for which period of time.

O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


Generation of self-similar processes for simulation studies of telecommunication networks It is generally accepted that self-similar processes may provide better models for teletraffic in modern telecommunication networks than Poisson processes. If stochastic self-similarity of teletraffic is not taken into account, it can lead to inaccurate conclusions about the performance of networks. Thus, an important requirement for conducting simulation studies of networks is the ability to generate long synthetic self-similar sequences of incremental processes, to transform them into interevent time intervals, and to do this accurately and quickly. A fast generator for count processes based on wavelets is described. Then a method for transformation of count processes into interevent processes proposed by Leroux and Hassan [1] and an alternative method, that is, inverting the empirical distribution directly, are studied. A case study is discussed to show how long sequences are needed in the steady-state simulation of queueing models with self-similar input processes. This is compared with simulation run lengths of the same queueing models fed by Poisson processes. The search for accurate mathematical models of data streams in modern telecommunication networks 'has attracted a considerable amount of interest in the last few years. The reason is that several recent teletraffic studies of local and wide area networks, including the world wide internet, have shown that commonly used teletraffic models, based on Poisson The use of traditional models of teletraffic can result in overly optimistic estimates of performance of telecommunication networks, insufficient allocation of communication and data processing resources, and difficulties in ensuring the quality of service expected by network users [4,9,10]. On the other hand, if the strongly correlated character of teletraffic is explicitly taken into account, this can also lead to more efficient traffic control mechanisms [ll] .. Several methods for generating pseudorandom self-similar count processes have been proposed. , and so on. Some of them generate asymptotically self-similar sequences and require large amounts of CPU time. For example, Hosking's method [13] , based on the F-ARIMA (0, d, 0) process, needs many hours to produce a self-similar sequence with 131,072 (217) numbers on a Sun SPARCstation [2] . It requires 0(n2) computations to generate n numbers. Even though exact methods of generation of self-similar sequences exist (for example, [12]), they are only fast enough for short sequences, and are usually inappropriate for generating long sequences because they require multiple passes along generated sequences. To overcome this, approximate methods for the generation of self-similar sequences in simulation studies of telecommunication networks have also been proposed [17, 18] .. An important requirement for conducting simulation studies of telecommunication networks is the ability to generate long synthetic self-similar sequences of incremental processes, long enough to ensure an arbitrary statistical precision of the final simulation results. Very little is known of the appropriateness of specific interarrival processes, and transformation to interevent time intervals from arrival counts generated by an FGN process still remains an open research issue [1, 18] .. In this paper, we study a transformation of count process based on l+actional Gaussian Noise and Daubechies Wavelets (FGN-DW) into interarrival processes. A generator of such count processes, based on FGN-DW, was proposed in [19] . These interarrival processes are then used in a steady-state simulation of queueing models with self-similar input processes.. A summary of the basic properties of self-similar processes is given in the next section. Generation and transformations of the FGN-DW count processes are described in Section 3. In Section 4, a case study is discussed to show: (i) how well the self-similarity of the original arrival counts is preserved when the arrival counts are converted into suitable interarrival times; and (ii) how long sequences are needed in the steady-state simulation of queueing models with self-similar input processes (called SSM/M/l/co).. This is compared with simulation run lengths of the same queueing models fed by SRD processes such as the M/M/l/ 00 q ueueing system. The influence of the Hurst parameter on simulation run-length is also analysed, before the final conclusions are formulated. We have examined two main issues of stochastic simulation of telecommunication networks with self-similar teletraffic. We looked at how well the self-similarity of the original arrival count processes are preserved when the arrival counts are converted into suitable interarrival times. Our results showed that using the inverse transformation preserves the self-similarity of the original sequence generated by FGN-DW much better than the interevent process using the exponential transformation.. Finally, to illustrate the scope of the problem that remains, we looked at how many observations are needed in the sequential steady-state simulation of a queueing system with self-similar input processes. As we have shown, assuming self-similar interarrival processes, one needs many more observations to obtain the final simulation results with a required precision than when assuming Poisson interarrival processes.

O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


Scaffolding Development and the Human Condition Abstract This paper addresses the concept of semiotic scaffolding by considering it in light of questions arising from the contemporary challenge to the humanities. This challenge comes from a mixture of scientistic demands, opportunism on the part of Western governments in thrall to neo-liberalism, along with crass economic utilitarianism. In this paper we attempt to outline what a theory of semiotic scaffolding may offer to an understanding of the humanities' contemporary role, as well as what the humanities might offer to the elucidation of semiotic scaffolding. We argue that traditional humanist positions adopted in defence of the humanities fail to articulate the enhancement of humanity that semiotic scaffolding represents. At the same time, we note that the concept of scaffolding is sometimes in danger of taking on a functionalist perspective which understanding the humanities modus operandi is likely to dispel. Putting forward these arguments, we draw on the work of Peirce, Cassirer and Sebeok in elucidating the structural and 'future-orientated' benefits of the scaffolding process as it suffuses the humanities. effectively thrown down the gauntlet to the humanities and challenged them to prove their worth. In what follows, we will argue that some of the responses to these challenges to the humanities uncritically fall back on traditional humanist positions derived from the very traditions of thought that are ultimately challenging the legitimacy of the humanities in the present. We suggest that an alternative perspective on the humanities -one that is critical of crass utilitarianism but is nonetheless unwilling to dismiss usevalue -is offered by cognitive semiotics. Focusing on the process of 'scaffolding' posited by Clark and extended by Hoffmeyer, but anticipated by Peirce and Cassirer, we argue that the idea of 'scaffolding' currently provides the best approach to the structural and 'future-orientated' benefits of the humanities. At the same time, with reference to Sebeok, we consider how descriptions of 'scaffolding' might be revised as a result of thinking through the concept in relation to the humanities.

O O O O O O O O O O O O O B I O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O B O O O O O O O B O O O O O O B I O O O O O O O O O O O B O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O B B O B O O O O O O O O O O O O O O O B O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O B O B O O O O O O O O O O O O O O O O O O O O B O O O O O O O B O O O O O O O O O O O O O O O O O O O O O B


Formal and graphical annotations for digital objects This paper presents graphical tools that facilitate manual building of formal semantic annotations for digital objects. These tools are intended to be integrated in digital object (DO) management systems requiring semantic metadata (e.g. precise indexation, comment, categorization, certification). We define a multidimensional graphical model of semantic annotations that specifically allows contextualization of annotations, and we propose a methodology for building such annotations. The graph-based formalism used (derived from Conceptual Graphs), provides graphical representations that users can easily understand, and are furthermore logically founded. A graphical generic API implementing elements of the SG family has been developed. CoGUI consists of three specialized tools: a tool for defining a CG ontology, another for creating annotations based on a CG ontology, and finally a tool that uses the CoGITaNT platform, for querying an annotated DO base. An enormous amount of documents are available, especially through the web, so it is now essential to have access to tools for adding semantic metadata (also called annotations) to existing documents.. To annotate a (primary) document involves associating a new (secondary) document to the initial one. This very general definition overlooks the great diversity of annotation processes. For instance: Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. SADPI '07, May 21-22, 2007 , Montpellier, France Copyright 2007 ACM 978- 1-15159-668-4 • an annotation process can be automatic or manual or computer-aided;. • an annotation can be a natural language text or a formal expression in some formal language or a blend of both;. • annotations can be added for various reasons, e.g. comments, information, certification, indexation, etc.. • an annotation can be "objective" (e.g. author, date, etc.) or "subjective" (e.g. a point of view concerning the document).. In the present work, complex formal and graphical annotations having a logical semantics are used. Using complex conceptual structures provides precise representations of different comments about various documents. The query language is also built on the annotation language and formal semantics of the answers can be given (the answers are the formulas that entail the query). The principal drawback of this method is that the construction of rich semantical representations requires a substancial amount of human time (for constructing the conceptual vocabulary as well as the annotations themselves). Thus, our method is useful when detailed comments about documents are essential or when automatic indexation is not precise enough for the targeted goals.. An annotating tool basically has to support: reading in documents, decomposing documents into annotatable parts (DOs), creating annotations, linking them to DOs, and storing annotations (cf. for instance, [1] , [17] , [16] , [14] , [11] , [20] , [15] ). The tools presented in this paper do not consider all the tasks an annotating tool should manage. We focus on methods and tools that enable an effective and rigorous work for a human annotator. In this paper, the term "annotator" refers to specialists of at least one aspect of the document base who want to describe a feature of this aspect. Our aim is to provide to an annotator notions (e.g. modular ontologies, patterns, prototypes), and graphical tools (implementing these notions) to facilitate building complex annotations acording to a formal model.. Our participation in several projects for the promotion and publication of a multimedia corpus led us to propose a methodology based on an annotation model. The core of such a model is a formal domain ontology, with an annotation charter which guides the annotator's work. One goal of this charter is to encourage annotators to elaborate complex annotations (i.e. semantic networks of concepts), whereas the traditional work of annotators is generally restricted to finding a set of keywords representing the document content. In order to reduce the time needed for constructing such a complex annotation, the annotation process is based on the identification of "conceptual patterns" the annotator has to choose, to glue these patterns together, and to modify them. These patterns are contextualized on parts of the domain ontology so that the tool can automatically restrict, at a given stage, the usable vocabulary. In this way, with a few "clicks", an annotator can construct a rich and original annotation. Another goal is to ensure that the annotations built respect a formal model. Thus, they can be searched by a logically founded search engine and, if they are built by several annotators (and/or from several points of view), they can be jointly processable.. The proposed annotation model was developed through a collaboration with multimedia document indexation experts, who tested our tools in different projects (Opales, Saphir, Logos). Most of the examples given in this paper come from the Saphir project. Saphir is a French national project headed by INA 1 , MSH 2 , LIRMM, LERIA 3 and NETIA 4 , which aims to develop a computer-aided system for hypermedia publications described by intentional specification and rhetoric modeling. In this project, our annotation model and the associated tools include : an editor of annotation models, an annotation editor, and a query/answering tool, all built on CoGUI 5 , which is a generic GUI for our graphbased models using the CoGITaNT API [9] as a reasoning server, are included in the annotating tool AudioVisualStudio developed by INA to describe a multimedia corpus.. This paper is organized as follows. Section 2 reviews the formalism we use. In section 3, we introduce the multidimensional annotation model and its formalization. Section 4 presents the annotation process and the way to design an annotation charter. Finally, in section 5, we explain how to make use of the annotation base for information retrieval or for query/answering. This work introduces basis of a methodology for formal annotation based on the definition of a multi-dimensional annotation model providing guidance, assistance and validation of a manual annotation work. This methodology is used on CoGUI, our graphical interface for edition, validation and exploitation of knowledge graphs.. This proposition now has to be validated through comprehensive experimentation involving real exploitation of built annotations. The Saphir Project, which aims to produce multimedia publications based on annotations of a corpus, is a first case of experimentation.. We are currently working on the individual markers management problem which arises when annotations are made by several annotators. Experimentations show that annotators often use individual markers. Thus, it is important to ensure that the same individual entity is well identified by a single individual marker and, conversely, that an individual marker is not used to designate two different entities. We propose to base the validation of an annotation on a confidence notion which expresses the level of knowledge of a user on knowledge associated with an individual marker.. Otherwise, we are working on a mecanism of query/answering allowing the fusion of dimensions in a more general dimension to compute approximate answers.

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A normal form algorithm for the Brieskorn lattice This article describes a normal form algorithm for the Brieskorn lattice of an isolated hypersurface singularity. It is the basis of efficient algorithms to compute the Bernstein-Sato polynomial, the complex monodromy, and Hodge-theoretic invariants of the singularity such as the spectral pairs and good bases of the Brieskorn lattice. The algorithm is a variant of Buchberger's normal form algorithm for power series rings using the idea of partial standard bases and adic convergence replacing termination. Isolated hypersurface singularities form the simplest class of singularities. Their intensive study in the past has led to a variety of invariants. The Milnor number is one of the simplest, and can easily be computed using standard basis methods. A finer invariant is the monodromy of the singularity. E. Brieskorn [1] developed the theoretical background for computing the complex monodromy. He gave an ad hoc definition of an object H ′′ , later called the Brieskorn lattice. Its great importance was a priori not clear. The complex monodromy can be expressed in terms of the differential structure of the Brieskorn lattice.. Email address: mschulze@mathematik.uni-kl.de (Mathias Schulze).. The finest known invariants come from a mixed Hodge structure associated to an isolated hypersurface singularity. The notion of a mixed Hodge structure was introduced by P. Deligne [2] as a generalization of the classical Hodge structure on the cohomology of a compact Kähler manifold. J.H.M. Steenbrink [3] defined this mixed Hodge structure in terms of resolutions of singularities. A.N. Varchenko [4] and later J. Scherk and J.H.M. Steenbrink [5] described this mixed Hodge structure in terms of the differential structure of the Brieskorn lattice. The mixed Hodge numbers correspond to the spectral pairs and determine the complex monodromy. The spectral pairs have a semicontinuity property [6] with respect to unfoldings of the singularity.. Based on properties of the mixed Hodge structure, M. Saito [7] constructed two endomorphisms A 0 and A 1 of the Milnor algebra. These two endomorphisms determine the differential structure of the Brieskorn lattice and, immediately, the above invariants.. The Bernstein-Sato polynomial is associated to a general complex polynomial [8] or convergent power series [9] . T. Oaku [10] presented the first algorithm to compute it in the global case. A new method by M. Noro [11] is impressively faster. In the isolated singularity case, B. Malgrange [12] described the Bernstein-Sato polynomial in terms of the Brieskorn lattice and its close relation to the complex monodromy.. In [13] [14] [15] [16] , we have developed algorithmic methods to compute all of the above invariants of isolated hypersurface singularities. There is an implementation [17, 18] of these algorithms in the computer algebra system Singular [19] . Our algorithm to compute the complex monodromy is much faster and can compute much more difficult examples than Brieskorn's algorithm. Our algorithm to compute the local Bernstein-Sato polynomial is based on B. Malgrange's description in terms of the Brieskorn lattice. It is much faster than M. Noro's algorithm since computations in rings of differential operators are replaced by computing their action on power series rings. However, it is restricted to the isolated singularity case while M. Noro's algorithm works in the general global case. All our algorithms require the computation of a basis representation in the Brieskorn lattice. In [13, Sec. 10.2] this is done by a sequence of divisions by the Jacobian ideal which is, in general, very hard to compute. The subject of this article is a normal form algorithm for the Brieskorn lattice replacing this sequence of full divisions by a sequence of partial divisions. This new method turns out to be much more efficient.. In the first section, we recall the definition and the main properties of the Brieskorn lattice. We introduce the formal Brieskorn lattice and describe it as a cokernel of a formal family of differential operators which is finite over the base.. In the second section, we consider such a formal family of differential operators in general. We describe a normal form algorithm to compute a presentation of the cokernel which is a finitely generated module over the formal power series ring in the parameters of the family. This algorithm is a variant of B. Buchberger's [20, 21] normal form algorithm. There are three major differences compared to the classical algorithm:. (1) The polynomial ring is replaced by a formal power series ring. Termination of the algorithm is replaced by adic convergence. (2) The standard basis is replaced by a partial standard basis, a set of power series which specializes to a standard basis. (3) There is only a module structure with respect to the parameters of the family and the partial standard basis is not finite.. Although the algorithm does not terminate in general, it serves to compute exact results by using appropriate degree bounds. The algorithms in [13, 16] implicitly contain such degree bounds to compute the above invariants of isolated hypersurface singularities. There are also a priori degree bounds in [15] , but they are useless in practice. Essentially the double number of variables plus the double Milnor number is a degree bound that satisfies all requirements.. In the third section, we demonstrate the power of our algorithm. We apply the Singular implementation [18] to examples from [13, 16] and [11] and list the timings.. Families which are finite over the base occur in many situations in algebraic geometry and singularity theory. For example, A. Frühbis-Krüger [22] has developed algorithms to compute moduli spaces and adjacencies of singularities based on the idea of partial standard bases. One can expect more applications of our methods in the future.. We shall denote row vectors by a lower bar, column vectors by an upper bar, row indices by lower indices, and column indices by upper indices.

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Wavelet transforms associated to group representations and functions invariant under symmetry groups We study the wavelet transform of functions invariant under a symmetry group, where the wavelet transform is associated to an irreducible unitary group representation. Among other results a new inversion formula and a new covariance principle are derived. As main examples we discuss the continuous wavelet transform and the short time Fourier transform of radially symmetric functions on R d .2000 AMS subject classification: 42C40, 43A65, 43A62, 44A15 In the recent years a lot of research activities were dedicated to wavelet analysis and timefrequency analysis. The outcome of these theories could be successfully applied in various areas such as signal and image processing, the numerical solution of partial differential equations and wireless communication just to mention a few. This paper is dedicated to the wavelet and time-frequency-analysis of functions which are invariant under certain symmetry groups. This aspect of time-frequency-analysis and wavelet analysis was not treated thoroughly in the literature before, at least according to my knowledge.. Suppose a function on R d possesses some symmetries, i.e. is invariant under some symmetry group. Our main example will be radial symmetry or in other words invariance under SO(d), but also other symmetry groups such as finite reflection groups may be considered. Of course, it is possible to do standard wavelet and time-frequency analysis with such a function. For example we may expand it in terms of certain building blocks which will be translates and dilates of a single function in case of wavelet analysis and which consist of modulations and translations of a single function in case of time-frequency analysis. Hereby the expansion can be discrete but also a continuous superposition such as in the inversion formula for the continuous wavelet transform or for the short time Fourier transform (STFT). However, in both examples the building blocks do not in general obey the same symmetry properties as the analyzed function. For example, even if we start with a radial symmetric wavelet, a translated version of it will no longer be radial. So one might ask the question whether it is possible to make use of the symmetry properties. In other words, is it possible to construct the building blocks in such a way that they all possess certain symmetry properties? And can this be done such that all building blocks are derived from one single function similarly as in standard wavelet and timefrequency analysis? This paper presents a very natural approach to this problem. We will only cover the continuous wavelet transform (CWT) and the (continuous) STFT. Their discrete counterparts, i.e. the construction of invariant wavelet frames and invariant Gabor frames, will be treated in a subsequent paper. A generalization of the FeichtingerGröchenig theory [7, 8, 10] will be developed to solve the discretization problem. In the special case of radial functions on R 3 the concept of multiresolution analysis could already be successfully applied to the construction of radial wavelets [14] .. The CWT and the STFT are closely connected to the representation theory of the similitude group of R d and the Heisenberg group, respectively [1, 11] . It is therefore possible to treat both transforms simultaneously in the general framework of representation theory of locally compact groups. This is the reason why I have chosen to investigate the problem in this abstract setting and then specialize to the examples afterwards.. In order to involve a symmetry group A in this abstract setting we need an action on the group G whose representation coefficients V g f (x) = f, π(x)g H give the corresponding wavelet transform where π acting on the Hilbert space H denotes the representation under consideration. (Here we use the term wavelet transform also in the general context). It is reasonable to assume that A is a compact automorphism group of G. Moreover, we require that A has a representation σ on the same Hilbert space H (usually L 2 (R d ) in our examples). As a basic assumption all representationsπ A := π • A, A ∈ A have to be equivalent to π with intertwining operators σ(A), see formula (3.1). The invariant elements of H are those that satisfy σ(A)f = f for all A ∈ A. It turns out that V g f is invariant under A if f, g are invariant and can hence be viewed as a function on the orbits A(x), x ∈ G. The space K of all orbits has a structure called a hypergroup (a generalization of a group) and in an easy way starting from π we construct a representationπ of K on H A , the Hilbert space of all invariant elements of H. The operatorsπ(x) map H A into H A and thus it seems natural to take the elementsπ(x)g as new building blocks. In fact, it holds V g f = f,π(x)g H A for invariant f, g. In our special cases with radial symmetry the scalar product on H A = L 2 rad (R d ) (the space of radial L 2 -functions) can actually be computed by an integral over the positive half line, so this formula means a reduction in complexity. Moreover, we prove as a main result another inversion formula for the wavelet transform where an invariant element is represented by a continuous superposition of the invariant building blocksπ(x)g. Also a covariance principle, which involves a generalized translation coming from the hypergroup K, is shown for the wavelet transform of invariant elements.. The outline of the paper is the following. We start by discussing briefly the CWT of functions with radial symmetry as a motivating example. Afterwards we present the abstract general approach including the main results. In section 4 we continue the discussion of the continuous wavelet transform of radial function thereby illustrating the general theory. It is worth noting that Rösler [15] and independently Trimeche [16] had already introduced this transform (writing it is a transform on the positive halfline) in the context of hypergroup theory. As a second example we discuss the STFT of radially symmetric functions. Actually this example was the original motivation for the investigations contained in this paper. There have been already other approaches for a radial STFT [3, 4, 16] . Unfortunately the transforms introduced in these papers lack some important properties. For example one can show that the Wigner-Bessel transform introduced in [4] has unbounded inverse (which however is not proven in [4] ) and the transform in [3] makes use of a nonlinear modulation which seems a bit strange. As a last example we discuss briefly the situation when SO(d) in both previous examples is replaced by a finite reflection group.

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Generating representative Web workloads for network and server performance evaluation One role for workload generation is as a means for understanding how servers and networks respond to variation in load. In this paper we have described a tool for generating representative Web requests that is based on analytical models of Web use. We have described the characteristics that we feel are important to capture in Web workloads, and why they are important.. We have shown that satisfying this large set of requirements presents challenges, but that these challenges can be addressed. We first consider the differences between SURGE and SPECweb96 in terms of their impact on the server; then we examine their different impacts on the network.. Server Impacts.. The most immediately noticeable difference between the effects of the SURGE and SPECweb96 workloads is in server CPU utilization. Figure 3 shows plots of mean CPU utilization for the two workloads as a function of average packets transferred per second. Errorbars show one sample standard deviation above and below the mean. Mean and standard deviation were measured over the steady state of each experiment, with the startup transient removed. Figure 3 shows that when the average transfer rate approaches 500 packets per second, the SURGE workload causes a sharp increase in the server's CPU load, while the server's CPU is not very heavily loaded under the SPECweb96 workload. The difference in CPU load over time is shown in Figure 4 . This figure plots instantaneous CPU load over the entire course of each of three experiments for both workloads.. This figure shows how the two workloads are quite different in practice.. The figure shows that SURGE results in a highly varying CPU load with utilization as high as 76% for transfer rates of about 500 pps. In contrast, the CPU load is relatively stable and never goes above 37% for the SPECweb96 workload. One reason for the difference in CPU demands of the two workloads can be seen by examining the number of active TCP connections in each case. [15] . Clearly the difference in the number of active connections is likely to be a contributing factor in the CPU utilization differences seen between the two workloads ( Figure 3 Linear behavior with slope greater than -l/2 is suggestive of nontrivial selfsimilarity.. Variance-time plots for SURGE and SPECweb96 traffic are shown in Figure 6 . As the amount of data transferred increases from left to right in the figures, the traffic generated by SURGE In contrast, the traffic generated by SURGE comes from constant-variability sources; it is the number of such sources that increases as workload intensity increases.. Theoretical work [21] has shown that when transfer durations are heavy-tailed (as they are in Suno~) this condition is sufficient for the generation of selfsimilar traffic.. As a result we expect that SURGE will generally produce self-similar network traffic under conditions of both high and low workload intensity. Note that in this respect, the source behavior of SPECweb96 is similar to other Web workload generators whose general goals are to make requests from servers as quickly as possible [16, 201 . Since these workload generators do not preserve significant burstiness in individual thread demands, it is unlikely that under heavy loads they will produce self-similar traffic in practice. The environment for these experiments consisted of six PCs running on a 100 Mbps network that could be isolated from other networks.. The PCs were configured with 200MHz. Pentium Pro CPUs and 32MB of RAM. SURGE clients (from 1 to 5 hosts) ran under Windows NT 4.0, while the server system (a single host) ran Apache ~1.2.4 under Linux 2.0. To avoid resource limitations we never ran more than 50 UE threads on any SURGE host.. On the Web server, we examined CPU utilization and the number of active TCP connections;. for the network, we measured the total number of both files and packets transferred over the run.. The number of open connections on the server was sampled every 100ms and the CPU utilization was sampled every second. Both values were taken from the Linux /proc filesystem.. Measurements of traffic on the network were taken using tcpdump.. In each of the experiments discussed in this sect,ion, the number of UEs is kept constant throughout the experiment.. Thus we only explore the stationary behavior of the workload at this time. This assumption of stationarity in the workload for real servers probably only applies over short timespans during which the number of users at the Web server remains approximately constant.. For this reason we restrict ourselves to runs no greater than 30 minutes.. Note that even over intervals as short as these, Web servers can show high variability in many system metrics [15] .. The workload generated by SPECweb96 depends on two user-defined parameters: a target number of HTTP operations per second, and the number of threads used to make requests.. The general approach used by SPECweb96 is for each thread to generate HTTP requests a.t a constant rate; the request rate for each thread is determined by dividing the target rate by the number of threads.. In all our experiments we used 16 threads, which was sufficient since the achieved operations per second were always close to the requested values.. Thus the intensity of the SPECweb96 workload is specified in terms of expected number of HTTP operations per second, while (as discussed in Section 2) the int,ensity of the SURGE workload is expressed in terms of user equivalents.. To compare the effects of SURGE and SPECweb96, we empirically determined configurations of each resulting in approximately equal amounts of data transferred during a 30 minute run. We identified three such configuration levels of each workload generator;. for each level, the difference between the two in terms of data transferred is less than about 20%. These configuration levels, which are shown in Table 2 , are used only for general comparisons between the two workloads. Table 3 summarizes the SURGE and SPECweb96 workloads used, showing the number of requests satisfied and the number of TCP packets transferred in each 30 minute run.

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Multispectral Panoramic Mosaicing Abstract In mosaicing, images are captured as a camera moves, registered and then stitched to obtain an image with a larger field of view. We introduce the notion of multispectral mosaicing in which much more information about the scene is extracted, by acquiring multiple images of the same scene by different sensors. The objective of this paper is to detail how mosaicing can be used for enhancement of the spectral information. First, we develop a geometric relationship between any two cameras. Now a days various kind of sensors have been made and widely used in industries. However, due to limited resources of material, all those sensors can be made only sensitive to certain spectral band. For example, CCD cameras are designed for collecting visual signals, infrared sensors for measuring temperature (range ). Optical images from Landsat provide information on chemical composition, vegetation, and biological properties of the surface. In many cases, some ambiguities are caused when we use only one kind of sensor to perceive the real world.. In many applications, it is necessary to combine multiple images of the same scene acquired by different sensors, which often provide complementary information about the scene surveyed. For example, one could consider panoramic images of a house -both in the visual band, as well as in the IR band. The latter would be helpful, for example, to check if there has been any seepage in the walls.. Registered multisensor images can be directly fused at the pixel level and subsequent operations such as target detection and target recognition can be carried out using fused images instead of the individual sensor images. This not only saves the computations but also increases the target detection accuracy and target recognition rate. Schechner [8] describes wide field of view (FOV) multispectral imaging. A limitation of their approach is the use of special types of filters attached to the camera. Multispectral data is obtained in an extended FOV, using pushbroom [6] imaging spectrographs, which are generally rather complex and expensive. In [5] , the authors register images (visible, IR) from Landsat and Spot satellites using a contour-based approach. A disadvantage of the above approach is the high computational complexity associated with their feature extraction, as well as registration processes.. In this paper, we develop a geometric relationship between panoramic mosaics in the visible and IR bands, corresponding to the same scene being imaged. Next, we describe a computationally efficient procedure to speed up panoramic mosaicing. In Section 4, we show results in support of the proposed strategies:inter-band superposition of panoramic mosaics. Here we present Multispectral Image mosaicing, which gives information about different modalities into scene, which is not possible with single camera. The registered multisensor images can be fused at the pixel level and subsequent operations can be carried out. This not only saves computations, it increases accuracy because the subsequent operations benefits from the spectral and geometric differences brought out by the fusion operation.

O O B O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O