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Hermannus Balsters - One of the best experts on this subject based on the ideXlab platform.

  • A UML/OCL framework for design of mediated data federations
    The annual research report, 2003
    Co-Authors: Hermannus Balsters
    Abstract:

    This paper describes a general semantic framework for precise specification of so-called mediating systems; such systems provide for tight coupling on a global level of a collection of heterogeneous component databases to a federated database. A mediating system maps in a uniform and systematic manner the underlying database schemas of the component systems to a separate, newly defined integrated database schema. This integrated database is completely virtual, and will constitute the actual federated database. That is, queries posed against the federated system will be posed against this virtual integrated database; these global queries will then be mapped by the mediator to actual local queries against the existing (legacy) component databases. Our approach is based upon the UML/OCL data model. UML is the de facto standard language for analysis and design in object-oriented frameworks, and is being employed more and more for analysis and design of information systems, in particular information systems based on databases and their applications. Database specifications often involve specifications of constraints, and the Object Constraint Language (OCL) - as part of UML - can aid in the unambiguous modelling of database constraints. One of the central notions in database modelling and in constraint specifications is the notion of a database view; a database view closely corresponds to the notion of Derived Class in UML. We will employ OCL and the notion of Derived Class as a means to treat database constraints and database views in a federated context. The paper will demonstrate that our particular mediating system integrates component schemas without loss of constraint information. Furthermore, we will discuss a UML/OCL representation of relational databases.

  • UML - Modelling database views with Derived Classes in the UML/OCL-framework
    Lecture Notes in Computer Science, 2003
    Co-Authors: Hermannus Balsters
    Abstract:

    One of the central notions in database modelling is the notion of a database view. A database view closely corresponds to the notion of Derived Class in UML. This paper will show how the notion of a relational database view can be correctly expressed as a Derived Class in UML/OCL (version 2.0). A central part of our investigation concerns the generality of our manner of representing relational views in OCL. Since, in general terms, a database view closely corresponds to the notion of a named query, an important problem that we address in our paper is the expressiveness of OCL as a query language. In particular, we will discuss the relational completeness of OCL (w.r.t the relational algebra). We will show that OCL (version 2.0) is relationally complete in a minimal sense, but not in a (desired) maximal sense. As a consequence, we will argue for certain language extensions in OCL in order to achieve that OCL is maximally relationally complete.

  • Derived Classes as a basis for views in UML/OCL data models
    The annual research report, 2002
    Co-Authors: Hermannus Balsters
    Abstract:

    UML is the de facto standard language for analysis and design in object-oriented frameworks. Information systems, and in particular information systems based on databases and their applications, rely heavily on sound principles of analysis and design. Many present-day database applications employ object-oriented principles in the phases of analysis and design due to the advantages of expressiveness and clarity of such languages as UML. Database specifications often involve specifications of constraints, and the Object Constraint Language (OCL) - as part of UML - can aid in the unambiguous modelling of database constraints. One of the central notions in database modelling and in constraint specifications is the notion of a database view. A database view closely corresponds to the notion of Derived Class in UML. This paper will show how the notion of a Derived Class in UML can be given a precise semantics in terms of OCL. We will then demonstrate that the notion of a relational database view can be correctly expressed as a Derived Class in UML/OCL. A central part of our investigation concerns the generality of our manner of representing relational views in OCL. An important problem that we address in this respect is the representation of product spaces and relational joins. Joins are often essential in view definitions, and we shall demonstrate how we can express Cartesian products and joins within the current framework of UML/OCL language by employing the notions of Derived Class. As a consequence, OCL will be shown to be equipped with the full expressive power of the relational algebra, offering support for the claim that OCL can be useful as a general query language within the framework of the UML/OCL data model.

Viviana Gubitosi - One of the best experts on this subject based on the ideXlab platform.

Martin Weinmann - One of the best experts on this subject based on the ideXlab platform.

  • A Hybrid Semantic Point Cloud Classification-Segmentation Framework Based on Geometric Features and Semantic Rules
    PFG – Journal of Photogrammetry Remote Sensing and Geoinformation Science, 2017
    Co-Authors: Martin Weinmann, Stefan Hinz, Michael Weinmann
    Abstract:

    Hybrides Framework zur semantischen Klassifikation und Segmentierung von Punktwolken basierend auf geometrischen Merkmalen und semantischen Regeln. Im Rahmen dieses Beitrags wird die semantische Klassifikation von Punktwolken behandelt, wobei auf typische Fehlklassifikationsszenarien eingegangen wird, welche in diversen Untersuchungen aufgezeigt wurden. Zu diesem Zweck wird ein hybrides Verfahren vorgestellt, bei welchem Klassifikation und Segmentierung sowie semantische Regeln in einer kompletten Prozesskette integriert werden. Dabei deckt die Prozesskette selbst eine Datenverarbeitung von irregulär verteilten Punkten bis hin zu semantisch klassifizierten Punktwolken ab. Der erste Teil des Verfahrens besteht aus einer punktweisen semantischen Klassifikation einer Punktwolke basierend auf intuitiven von einem Anwender definierten einfachen geometrischen Merkmalen, welche aus lokalen Nachbarschaften mit flexibler Größe extrahiert werden. Im zweiten Teil des Verfahrens erfolgt eine Verbesserung der erzielten Klassifikationsergebnisse, indem semantische Regeln auf geometrische Merkmale angewendet werden, welche wiederum anhand einer Übersegmentierung der klassenweisen Punktwolken gewonnen werden. Die Leistungsfähigkeit des vorgestellten Verfahrens wird anhand eines Standard-Datensatzes gezeigt, für welchen Klassifikationsergebnisse mit hoher Genauigkeit und hoher Plausibilität erreicht werden. In this paper, we focus on semantic point cloud Classification taking into account standard failure cases reported in a variety of investigations. We present a hybrid two-step framework integrating Classification, segmentation and semantic rules in a common end-to-end processing pipeline from irregularly distributed points to semantically labelled point clouds. The first step of our framework consists of a point-wise semantic point cloud Classification based on rather intuitive, handcrafted, low-level geometric features extracted from local neighbourhoods of locally adaptive size. The second step of our framework consists of refining the point-wise Classification results by considering semantic rules applied to geometric features extracted on the basis of an over-segmentation of the Derived Class-wise point clouds. We demonstrate the performance of our framework on a standard benchmark dataset for which we obtain a semantic labelling of high accuracy and high plausibility.

  • A Hybrid Semantic Point Cloud Classification-Segmentation Framework Based on Geometric Features and Semantic Rules
    PFG – Journal of Photogrammetry Remote Sensing and Geoinformation Science, 2017
    Co-Authors: Stefan Hinz, Martin Weinmann
    Abstract:

    In this paper, we focus on semantic point cloud Classification taking into account standard failure cases reported in a variety of investigations. We present a hybrid two-step framework integrating Classification, segmentation and semantic rules in a common end-to-end processing pipeline from irregularly distributed points to semantically labelled point clouds. The first step of our framework consists of a point-wise semantic point cloud Classification based on rather intuitive, handcrafted, low-level geometric features extracted from local neighbourhoods of locally adaptive size. The second step of our framework consists of refining the point-wise Classification results by considering semantic rules applied to geometric features extracted on the basis of an over-segmentation of the Derived Class-wise point clouds. We demonstrate the performance of our framework on a standard benchmark dataset for which we obtain a semantic labelling of high accuracy and high plausibility.

John C Wain - One of the best experts on this subject based on the ideXlab platform.

  • repetitive gastric aspiration leads to augmented indirect allorecognition after lung transplantation in miniature swine
    Transplantation, 2008
    Co-Authors: Andrew J Meltzer, Stuart L Houser, M J Weiss, H Sahara, M E Cochrane, Joren C Madsen, David H Sachs, Bruce R Rosengard, Gregory Veillette, John C Wain
    Abstract:

    Introduction—Lung transplant recipients with documented gastroesophageal reflux disease (GERD) are at increased risk for graft dysfunction. Here, we present the first large-animal model of gastric aspiration following allogeneic lung transplantation and some preliminary data demonstrating the effect of chronic aspiration on the direct and indirect pathways of allorecognition. Methods—Left orthotopic lung transplants (n=3) were performed in miniature swine across an MHC Class I disparity, followed by 12 days of high-dose cyclosporine (CyA). At the time of transplantation, a trans-tracheal catheter was placed at the carina, above the bronchial anastomosis. A gastrostomy tube was placed for daily aspiration of gastric contents. Subsequently, graft lungs were instilled with gastric aspirate daily (3cc/hr × 8hr/day) for 50 days. Recipients were followed with daily CBC, scheduled chest radiographs, and biopsies. In vitro studies, including cell-mediated lympholysis (CML), mixed lymphocyte reactions (MLR), and peptide proliferation assays (PPA), were performed. Results from these three recipients were compared to those of historical controls (n=6) who were treated identically, except for the tracheal cannulation and simulated gastric aspiration. Results—Two of the experimental animals were sacrificed with non-viable lungs soon after the POD 50 biopsy. In both cases the native lung was normal. The third animal survived to 180 days without evidence of chronic rejection. After immunosuppressive treatment, all animals demonstrated donor-specific hyporesponsiveness by assays of direct alloresponse (CML, MLR). A significant response to synthetic donor-Derived Class I peptide, however, was seen in all animals. A more pronounced and diffuse response was seen in the animals rejecting their grafts. The historical controls showed medium-term graft survival with evidence of chronic rejection in the majority of animals, as previously reported.

  • 31 gastric aspiration leads to the development of an immune response to collagen v and donor Derived Class i peptides following lung transplantation in miniature swine
    Journal of Heart and Lung Transplantation, 2008
    Co-Authors: Andrew J Meltzer, Stuart L Houser, M J Weiss, H Sahara, M E Cochrane, J K Sayre, Joren C Madsen, David H Sachs, Bruce R Rosengard, John C Wain
    Abstract:

    Purpose: Acute and chronic allograft rejection remain formidable problems contributing to poor outcomes after lung transplantation. Immune mechanisms leading to allograft rejection vary between different organs. While CCR2 has been shown to be important for fibrous obliteration of hetertopic tracheal grafts the role of this chemokine receptor in the rejection of vascularized lung allografts is unknown. Methods and Materials: Orthotopic vascularized lung transplants were performed in the following strain combinations: B63B6, Balb3B6 and Balb3B6 CCR2-/-. Recipient bone marrow, peripheral blood and transplanted lungs were analyzed 7 days after transplantation. In a subset of experiments, B6 wildtype and B6 CCR2-/bone marrow monocytes were adoptively transferred into Balb3 B6 (45.1) lung transplants and evaluated 96 hours later. Results: Monocyte (CD11b Ly6C) production in the bone marrow is increased after both syngeneic and allogeneic lung transplants. CCR2 is critical for the mobilization of monocytes from the bone marrow (BM) into the peripheral blood (PB) (Balb3B6 CD11b Ly6C BM: 14.5% 1.2, PB: 8.5% 1.8; Balb3B6 CCR2-/CD11b Ly6C BM: 20.9% 2.1, PB: 0.9% 0.6) thereby impairing the recruitment of CD11c APCs to lung allografts (Balb3B6 21.8% 4.4 Balb3B6 CCR2-/9.7% 1.5). Adoptive transfer studies showed that CCR2 is not required for the recruitment of monocytes from the peripheral blood into lung allografts. However, the potential of monocytes to differentiate into CD11c CD11b dendritic cells is regulated by CCR2. Recipient CCR2-deficiency does not impair the production of IFNby graft-infiltrating T cells and does not prevent the acute rejection of lung allografts. Conclusions: Our findings show that CCR2 regulates differentiation of monocytes and accumulation of APCs in lung allografts. However, unlike the case for other allografts, CCR2 is not required to promote acute lung allograft rejection. Future studies will have to address the role of CCR2 in the development of chronic rejection in vascularized lung allografts.

  • the role of indirect recognition of mhc Class i and ii allopeptides in a fully mismatched miniature swine model of lung transplantation
    Transplantation proceedings, 2006
    Co-Authors: H Sahara, Tsuyoshi Shoji, John C Wain, Stuart L Houser, Ashok Muniappan, D A Guenther, M J Weiss, J K Sayre, A C Pujara, David H Sachs
    Abstract:

    Abstract Considerable evidence suggests that indirect recognition of MHC allopeptides plays an important role in solid-organ rejection. Here, we examine whether immunization with Class I or Class II allopeptides accelerates rejection in a fully MHC-mismatched lung transplant model in miniature swine. Methods Recipients were immunized with either donor-Derived Class I or Class II peptides. Sensitization to the peptides was confirmed by DTH testing and in vitro proliferation assays. Nonimmunized control (n = 6), Class I peptide-immunized (n = 3), and Class II peptide-immunized (n = 3) swine were transplanted with fully mismatched lungs using only a 12-day course of tacrolimus. Results One control animal rejected its graft on postoperative day 103, while the others maintained their grafts for over 1 year. In the Class I peptide-immunized group, two recipients rejected their grafts (days 14 and 52). The third animal has not rejected the graft (day 120, experiment is ongoing). In contrast, in the Class II-peptide immunized group, only one animal rejected its graft on day 52, while the others maintained their grafts over 1 year. Both anti-donor IgM and IgG antibodies were detectable in all acute rejectors, although no alloantibody was detectable in long-term acceptors. Regardless of the fate of the graft, all animals have maintained their proliferative responses to the peptides. However, only acceptors maintained donor-specific hyporesponsiveness in cell-mediated lymphocytotoxity and mixed lymphocyte reaction assays. Conclusions Pretransplant sensitization of lung allograft recipients to donor allopeptides accelerates graft rejection. This appears particularly true for Class I-Derived allopeptides, suggesting that Class II molecules may be less antigenic when presented indirectly.

  • indirect recognition of mhc Class i allopeptides accelerates lung allograft rejection in miniature swine
    American Journal of Transplantation, 2005
    Co-Authors: Tsuyoshi Shoji, John C Wain, Stuart L Houser, Louis C Benjamin, Douglas R Johnston, R Hoerbelt, R S Hasse, Richard S Lee, Ashok Muniappan, D A Guenther
    Abstract:

    The role of indirect allorecognition in graft rejection is examined in two experiments using a swine lung transplantation model. First, two swine received Class I mismatched grafts without immunosuppression; another two recipients were treated postoperatively with cyclosporine (CsA). These swine exhibited acute and chronic rejection, respectively. All four recipients developed T-cell reactivity to donor-Derived Class I major histocompatibility complex (MHC) peptides. Second, six swine were immunized with synthetic donor-Derived Class I allopeptides prior to transplantation. Control groups consisted of nonimmunized recipients (n = 6) and recipients immunized with an irrelevant peptide (n = 3). These recipients all received a 12-day course of post-operative CsA. Swine immunized with allopeptides exhibited accelerated graft rejection, as compared to both control groups (p < 0.01 and p = 0.03, respectively). Within the experimental group, the dominant histologic finding was acute rejection (AR). Obliterative bronchiolitis (OB) was seen in the graft with the longest survival. Both control groups showed a lesser degree of AR, with four out of six nonimmunized swine ultimately developing OB. These studies suggest that indirect allorecognition is operative during lung allograft rejection, and that pre-transplant sensitization to donor-Derived MHC allopeptides can accelerate graft rejection.

Luc Teyton - One of the best experts on this subject based on the ideXlab platform.

  • rapid clip dissociation from mhc ii promotes an unusual antigen presentation pathway in autoimmunity
    Journal of Experimental Medicine, 2018
    Co-Authors: Yoshinaga Ito, Orr Ashenberg, Jason Pyrdol, Adrienne M Luoma, Orit Rozenblattrosen, Matan Hofree, Elena Christian, Lucas Ferrari De Andrade, Rong En Tay, Luc Teyton
    Abstract:

    A number of autoimmunity-associated MHC Class II proteins interact only weakly with the invariant chain–Derived Class II–associated invariant chain peptide (CLIP). CLIP dissociates rapidly from I-Ag7 even in the absence of DM, and this property is related to the type 1 diabetes–associated β57 polymorphism. We generated knock-in non-obese diabetic (NOD) mice with a single amino acid change in the CLIP segment of the invariant chain in order to moderately slow CLIP dissociation from I-Ag7. These knock-in mice had a significantly reduced incidence of spontaneous type 1 diabetes and diminished islet infiltration by CD4 T cells, in particular T cells specific for fusion peptides generated by covalent linkage of proteolytic fragments within β cell secretory granules. Rapid CLIP dissociation enhanced the presentation of such extracellular peptides, thus bypassing the conventional MHC Class II antigen-processing pathway. Autoimmunity-associated MHC Class II polymorphisms therefore not only modify binding of self-peptides, but also alter the biochemistry of peptide acquisition.