ALBERT

Notes: Users of photogrammetric data have often been puzzled by conflicting advice given by companies regarding achievable height accuracies which could be expected from varying scales of aerial photography. The author chairs the Photogrammetry Group which is convened under the auspices of the Council of the UK Land and Hydrographic Survey Association (TSA). The first aim of this Group was to establish some common ground among TSA member companies with regard to achievable heighting accuracies. A series of tests was carried out on the most commonly used photographic scales and guidelines were published to clients based on these tests. 〈section xml:id="abs1-2"〉〈title type="main"〉Résumé Les utilisateurs des données photogrammétriques ont été souvent déconcertés par les avis contraires émanant des entreprises concernant les précisions altimétriques accessibles à partir de diverses échelles des photographies aériennes. Dans ce contexte, le Conseil de ľ‘Association britannique des levées terrestres et hydrographiques (TSA) a mis sur pied un Groupe “Photogrammétrie” et en a confié la présidence àľauteur. Le premier objectif de ce Groupe a consistéàétablir des bases communes aux entreprises membres de la TSA, en ce qui concerne les précisions altimétriques réalisables. On a effectué un ensemble ď essais sur les échelles des photographies aériennes les plus communément utilisées et ľ on a publicé, à partir de ces essais un opuscule destinéà guider les clients. 〈section xml:id="abs1-3"〉〈title type="main"〉Zusammenfassung Die Nutzer photogrammetrischer Daten werden oft durch widerspriich-liche Ratschläge der Firmen in bezug auf die bei verschiedenen Bildmaβstäben erreichbare Höhengenauigkeit verwirrt. Der Autor leitet den photogrammetrischen Ausschuβ, der unter Aufsicht des Council des UK Land and Hydrographic Survey Association (TSA) einberufen wurde. Erstes Ziel dieses Gremiums war es, eine gemeinsame Grundlage unter den TSA-Mitgliedsgesellschaften im Hinblick auf erreichbare Höhengenauigkeit zu schaffen. Es wurde eine Reihe von Versuchen zu den am meisten verwendeten Bildmaβstäben durchgeführt, undes wurden daraufberuhende Richtlinien für Kunden veröffentlicht.

Notes: Cartography andphotogrammetry have always been strongly linked and this paper emphasises a view of cartography as a process of spatial data representation, rather than as a method of creating a product, a map. Of course, the definition of cartography must change with developments in its practice. An outline of the historical background to the subject is presented, followed by a consideration of the relationship between the cartographer and the user of the product. The basic problems involved in the transfer of information from the complex real world to a generalized cartographic product are analysed and technological aspects of the discipline are described. Contemporary applications of cartography include hazard mapping, links with GIS, tactile products and electronic hydrographic representation, all of which represent customer driven progress. It is concluded that the future of cartography is, overall, dependent on a graphical representation of high quality being supplied to the end user, rather than on the methods used to attain this objective. 〈section xml:id="abs1-2"〉〈title type="main"〉Résumé La cartographie et la photogramétrie ont toujours été liées étroitement ľune àľautre, et ľ‘on souligne dans cet article ľ‘idée que la cartographie est un systéme de représentation des données à trois dimensions, plutôt qu‘un ensemble de procédés de fabrication ďun produit, la carte. II est évident que la définition de la cartographie doit changer au fur et à mesure que des évolutions apparaissent dans sa pratique. Aprés un aperçu du contexte historique de ce thème, on examine les relations qui se développent entre le cartographe et ľutilisateur du produit. On analyse les problèmes fondamentaux du transfert ďinformations du monde réel, complexe, à un produit cartographique géneralisé et ľ‘on décrit la technologie qu'utilise cette discipline. Les applications récentes de la cartographie concernent la cartographie des risques naturels, les relations avec les SIG, les cartes qui se lisent par le toucher, et la représentation electronique de ľ‘hydrographic produits qui tous sont issus de cheminements pilotés en aval, par le client. On en déduit que la cartographie est, àľ'avenir, par dessus tout fonction ďune represséntation graphique de haute qualityé fournie à un utilisateur final, plutôt que de processus utilisé pour parvenir à cet objectif.〈section xml:id="abs1-3"〉〈title type="main"〉Zusammenfassung Kartographie und Photogrammetrie waren immer eng verbunden, und dieser Beitrag betont starker eine Auffassung von der Kartographie als einem Prozeβ der Darstellung von Raumdaten als ein Verfahren zur Herstellung eines Erzeugnisses, der Karte. Natürlich muβ sich die Definition der Kartographie bei Entwicklungen in ihrer Praxis ändern. Es erfolgt eine Skizzierung des historischen Hintergrundes des Gegenstands, gefolgt von Betrachtungen zur Beziehung zwischen Kartographen und dem Nutzer des Erzeugnisses. Die mit der Übertragung von Informationen aus der komplexen realen Welt in ein generalisiertes kartographisches System verbundenen grundlegenden Probleme werden analysiert, und es werden technologische Aspekte der Disziplin beschrieben. Zeitgenössische Anwendungen der Kartographie schlieβen die Kartierung von Katastrophen, Verbindungen zu GPS, gefühlsmäβge Erzeugnisse und elektronische hydrographische Darstellungen ein, die alle den vom Nutzer beeinflufiten Fortschritt darstellen. Es wird geschluffolgert, daft die Zukunft der Kartographie vor allem von der graphischen Darstellung hoher Qualität, die dem Endnutzer geliefert wird, abhängig ist undnicht so sehr von den Methoden, me dieses Ziel erreicht wird.

Notes: Since its foundation in 1982, the Institut Cartogràfic de Catalunya has been dealing with digital images. Though digital images and techniques were initially confined to remote sensing, they have been gradually transferred to and combined with photogrammetry. In addition to the development of remote sensing and digital orthophotography systems, this expertise has facilitated the introduction of commercially available digital photogrammetric systems (scanning and stereocompilation) which are now in full operation. The paper describes the experience in scanning, orthophotography production and stereocompilation, draws some conclusions and gives an insight of the future of digital photogrammetry. 〈section xml:id="abs1-2"〉〈title type="main"〉Résumé L‘Institut Cartographique de Catalogue s‘est intéressé au traitement des images numériques depuis le moment où il a été crée, en 1982. Bien qu'au début les images numériques et leur technologie aient été réservées à la télédétection, elles se sont trouvées peu à peu transférées et intégrées à la photogrammétrie. Ce savoir-faire a permis le développement des systèmes de télédétection et ď orthophotographie numérique et a, de plus, facilité la mise à disposition sur le marché de systèmes de photogrammétrie numérique qui sont maintenant pleinement opérationnels. On présente dans cet article ľ expérience acquise dans le domaine du balayage, de la production des orthophotographies et de la stéréocompilation, on en tire quelques conclusions et ľ on termine par un aperçu sur ľ‘avenir de la photogrammétrie numérique. 〈section xml:id="abs1-3"〉〈title type="main"〉Zusammenfassung Seit seiner Gründung im Jahre 1982 hat sich das Institut Cartogràfic de Catalunya mit digitalen Bildern beschäftigt. Obwohl digitate Bilder und Verfahren ursprünglich auf die Fernerkundung begrenzt waren, wurden sie schrittweise auf die Photogrammetrie übertragen bzw. mit ihr kombiniert. Zusätzlich zur Entwicklung von Fernerkundung und digitaler Orthophoto-Systeme hat diese Erfahrung die Einführung kommerziell verfügbarer digitaler photogrammetrischer Systeme erleichtert, die jetzt überall in der Praxis angewendet werden. Der Beitrag beschreibt die Erfahrung bei der Abtastung, der Herstellung von Orthophotos und bei der Stereoauswertung und gibt einige Schluβfolgerungen und Aussichten in bezug auf die Digitalphotogrammetrie wieder.

Notes: The paper entitled The Photogrammetric Society Analogue Instrument Project was published in The Photogrammetric Record, 14(82): 565–582 (October 1993) and contained, as Appendix A, an extract from the Archive concerned with the history of the Zeiss Stereoplanigraph in Great Britain. In The Photogrammetric Record, 14(83): 769–782 (April 1994), three further Appendices were published which dealt with the Williamson Multiplex equipment and other instruments. In this third extract, the history of five other instruments of the Multiplex type are described. This brings to a close that section of the Archive dealing with instruments using direct optical projection.〈section xml:id="abs1-2"〉〈title type="main"〉Résumé On a publicé dans le numéro 14(82) (pp 565–582) ďoctobre 1993 du“Photogrammetric Record”ľarticle intitulé“le projet de la Société (britannique) de Photogrammétrie sur les instruments analogiques” et inséré dans ľannexe A un extrait des Archives relatif a ľhistorie du Stereoplan-igraphe Zeiss en Grande-Bretagne. On a publicé dans le numéro 14 (83) ďavril 1994 du“Photogrammetric Record”(pp 769–782) trois annexes supplémentaires qui traitaient de ľappareil Multiplex de Williamson et ďautres instruments. Dans ce troisième extrait, on présente ľhistorie de cinq autres appareils du type Multiplex. Cette partie des Archives qui traitait des appareils basés sur ľemploi ďuneprojection optique directe, se trouve ainsi achevee.〈section xml:id="abs1-3"〉〈title type="main"〉Zusammenfassung Der Beitrag mit dem Titel“The Photogrammetric Society Analogue Instrument Project”wurde im Photogrammetric Record, 14(82): 565–582 (Oktober 1993) veröffentlicht und enthielt als Anlage A einen Extrakt vom Archiv, das mit der Geschichte des Zeiss Steroplanigraph in Groβbritannien verbunden war. Im Photogrammetric Record, 14(83); 769–782 (April 1984) wurden 3 weitere Anlagen veröffentlicht, die vom Williamson Multiplex und anderen Geräten handelten. In diesem 3. Auszug wird die Geschichte von 5 anderen Geräten des Multiplex-Typs beschrieben. Das führt zum Abschluβ desjenigen Teils des Archivs, das sich mit Geräten mit direkter optischer Projektion befaβt.

Notes: An analysis is given of the modelling of XY stage errors in an analytical plotter by polynomial functions. This is discussed as an alternative to demanding strict mechanical accuracy in the stage construction. In an era of plentiful computational resources, it is concluded that apportioning more of the responsibility to the mathematical co-ordinate refinement is an effective strategy. A second degree polynomial is used for each of the two stages in an analytical plotter, modelling the systematic stage errors to within the variability of a single observation. A requirement for instrument stability is emphasized. Such techniques have application for other instruments such as image scanners. 〈section xml:id="abs1-2"〉〈title type="main"〉Résumé On étudie la modélisation des erreurs des chariots XY ďun restituteur analytique en utilisant des fonctions polynomials. II s‘agit en fait de trouver une alternative à des exigences de prêcision mêcanique très strictes dans la réalisation de ces chariots. A une époque oùľon dispose ďune abondance de ressources en moyens de calcul, il apparait en effet relever ďune stratégie efficace de s'appuyer davantage sur les traitements mathématiques pour améliorer les valeurs des coordonnées. On utilise, pour chacun des deux chariots, un polynome du second degrè pour modéliser les erreurs systématiques des chariots, et les rendre inférieures aux erreurs propres à une observation unique. On insiste sur la nécessitéďune grande stabilityé instrumental. Ces processus peuvent également s'appliquer àďautres instruments comme les scanneurs ďimages. 〈section xml:id="abs1-3"〉〈title type="main"〉Zusammenfassung Es wird die Modellierung von Fehlern des xy-Wagens bei analytischen Auswertegeräten mit Hilfe von Polynomen analysiert. Des wird als Alternative zur Forderung nach einer strengen mechanischen Genauigkeit bei der Bildwagenkonstruktion diskutiert. Im Zeitalter hervorragender Computer-Ressourcen, so wird geschluβfolgert, ist es eine effektive Strategie, sich mehr der mathematischen Koordinatenverbesserung zuzuwenden. Ein Polynom 2. Grades wird für jeden der 2 Bildträger eines analytischen Auswertegerätes genutzt, um die systematischen Fehler im Bereich der Variation von einzelnen Beobachtungen zu modellieren. Bezüglich der Stabilität des Instruments wird eine Anforderung formuliert. Solche Verfahren kännen auch bei anderen Geräten, wie zum Beispiel Bildscanner angewendet werden.

Notes: Photogrammetry is used extensively in British Coal Opencast to provide surface profiles of both new sites and existing sites. This paper will discuss the development of GPS within Opencast and its deployment as a tool to provide the ground control required for mapping. Comparisons with conventional equipment will also be made and relative cost effectiveness assessed. 〈section xml:id="abs1-2"〉〈title type="main"〉Résumé On utilise largement la photogrammétrie dans British Coal Opencast, pour déterminer des profiles de surface, à la fois dans les sites nouveaux et dans les sites en cours. On examine dans cet article ľ emploi du GPS dans ces mines et son développement comme outil permettant ď obtenir les points ď appui sur le terrain nécessaires à la cartographie. On se propose defaire les comparaisons avec les équipements classiques et ďévaluer les avantages relatifs coût/efficacité. 〈section xml:id="abs1-3"〉〈title type="main"〉Zusammenfassung Die Photogrammetrie wird bei den Britischen Kohlen-Tagebauen extensiv zur Beschaffung von Oberflächenprofilen sowohl bei Neuaufschlüssen als auch bei bestehenden Gruben eingesetzt. Im Artikel wird die Entwicklung von GPS und seine Entwicklung als Hilfsmittel zur Beschaffung der für die Kartenherstellung benötigten Paβpunkte diskutiert. Es erfolgen auch Vergleiche mit der konventionellen Ausrüstung und in bezug auf die relative Kosteneffektivität.

Notes: An investigation has been made into the feasibility of using a low cost GPS receiver fitted to a light fixed wing aircraft as an aid to flying parallel flight lines for block aerial vertical photography. Two cases were examined: (I) the pilot controlled the heading of the aircraft according to the indications on the course deviation indicator of the GPS receiver; (2) the autopilot, being connected to the GPS receiver, controlled the heading of the aircraft. The results obtained for both sidelap and endlap were equal to or superior to those obtained with a CCTV system. 〈section xml:id="abs1-2"〉〈title type="main"〉RésuméOn a mené une recherche sur la faisabilité du GPS comme aide au maintien du parallélisme des axes de prises de vues d'un bloc de photographies aériennes verticales, en utilisant un récepteur GPS bon marché fié a un avion léger. On a examiné deux cas: (i) celui ou le pilote a maintenu le cap de l'avion en suivant les indications de l'index de changement de route du récepteur GPS; (ii) celui ou c'est le pilote automatique qui, par une liaison au récepteur GPS, a maintenu le cap de l'uvion. Les résultats obtenus pour le recouvrement latéral et l'extrgmité des bandes se sont révélés égaux ou supérieurs ii ceux obtenus avec un systPme CCTV.〈section xml:id="abs1-3"〉〈title type="main"〉ZusammenfassungEs wurde eine Untersuchung über die mögliche Nutzung billiger GPS-Empfanger, die in ein Kleinjlugzeug als Hilfsmittel zum Flug paralleler Bildstreifen für die blockweise Luftbildaufnahme eingebaut wurden, durchgefuhrt. Dabei wurden 2 Falle geprüft: (1) Der Pilot steuerte das Flugzeug entsprechend der Anzeige auf dem Kursindikator des GPS-Empfangers. (2) Der mit dem GPS-Empfänger verbundene Autopilot steuerte das Flugzeug. Die Ergebnisse sowohl für Querals auch Längsüberdeckung waren gleich oder besser als die mit einem CCTV-System erhaltenen.

Notes: The authors provide an account of current Directorate of Military Survey approaches to the provision of photocontrol by use of GPS and they pay special attention to the requirements of height control. 〈section xml:id="abs1-2"〉〈title type="main"〉SummaryGPS now provides us with a rapid method for determining plan and height for photogrammetric control directly over the points required by the photogrammetrist. By utilizing the slope of the geoid model, orthometric heights can be obtained to an accuracy of 0.15 m to 0.2 m. Surveys can be carried out quickly in all weather conditions and with none of the traditional terrestrial survey skills. Time, cost and manpower are greatly reduced. The plan accuracies are well within any requirements of the photogrammetrist and heights can be achieved to within 0.15 m to 0.2 m on test areas of UK. As photogrammetric height accuracy requires at best 1 m for plotting a 10 metre contour interval, heighting by GPS and the use of a geoid model solves the heighting problem.〈section xml:id="abs1-3"〉〈title type="main"〉Résumé Les auteurs fournissent un compte-rendu de la façon dont le Directorate of Military Survey aborde actuellement le problème de la fourniture de points ďappui photos avec ľemploi du GPS et prêterit une attention particulière à celui des points ďappui altimétriques.〈section xml:id="abs1-4"〉〈title type="main"〉Zusammenfassung Die Autoren geben einen Bericht über die gegenwärtigen Versuche beim Directorate of Military Survey zur Paβpunktbestimmung mit GPS, wobei sie den Anforderungen an die Höhenbestimmung besondere Aufmerksamkeit zollen.

Notes: The operational situation of precise airborne GPS positioning of camera air stations and its use in combined block adjustment for aerial triangulation is reviewed. The acceptance of systematic GPS errors, which occur especially with biased phase ambiguity solutions after loss of lock of signals in-flight, has motivated the method of additional linear GPS drift parameters which are to be solved in the combined block adjustment. It also implies that no absolute GPS co-ordinates are required and that the datum transformation is provided via a few ground control points. A great number of practical examples demonstrates that the method has been successfully applied within a wide range of photoscales and of block sizes. It has proved to be fully operational under various practical conditions. The high accuracy performance of GPS blocks and the economic benefit have been confirmed. It is particularly noticeable that the stationary receiver can be at a great distance, up to 500 km or more from the mission area. The conclusion is drawn that GPS supported aerial triangulation is ready to become standard. The potential improvement from dual frequency receivers and fast ambiguity solutions only enhances that conclusion. 〈section xml:id="abs1-2"〉〈title type="main"〉Résumé On examine, dans cet article, le degréďopérationnalité atteint par le GPS aéroporté dans le positionnement précis des sommets de prises de vues des caméras aériennes, et son insertion dans la compensation par blocs en aérotriangulation. La possibilityéďerreurs systématiques dans le GPS, en particulier en cas de perte des signaux en vol, qui se manifeste par des ambiguïtés de phase et des biais dans les résultats, à conduit a introduire dans la compensation en bloc des inconnues supplémental s, traduisant une dérive linéaire du GPS. II en résulte qu'il n'est pas nécessaire de disposer de coordonnées GPS absolues et que quelques points ďappui sur le terrain suffisent à assurer les changements de coordonnées. On a utilisé avec succès cette méthode dans de nombreux essaispratiques comportant un large eventail ďéchelles de prises de vues et de tallies des blocs. On a pu ainsi mettre en évidence ľentière opérationnalité de cette méthode, dans des conditions réelles différentes. On a également confirmé la haute précision des résultats des blocs GPS et les avantages économiques de ce système. En particulier, il est tout à fait remarquable que le récepteur fixe puisse se trouver à une grande distance de la zone du lasé, 500 km ou plus. On peut en conclure que ľaérotriangulation appuyée sur le GPS est en train de devenir une méthode standard. Les améliorations possibles que peuvent apporter les récepteurs à deux fréquences et la résolution rapide des ambiguïtés, ne font que renforcer cette conclusion. 〈section xml:id="abs1-3"〉〈title type="main"〉Zusammenfassung Die hochgenaue Kamera Positionierung durch GPS und ihre Anwendung für die Aerotriangulation wird zusammengefaβt dargestellt. Die Existenz systematischer GPS Fehler, wie sie inbesondere durch nur genäherte Phasen-Mehrdeutigkeitslösungen nach Signalabrissen im Flug verursacht werden, haben zu der speziellen Methode zusätzlicher linearer GPS Drift Parameter geführt, die in der kombinierten Blockausgleichung bestimmt werden. Ferner wird dabei die Datumtransformation mit Hilfe einiger weniger Paβpunkte bestimmt, d.h. es werden keine absoluten GPS Koordinaten vorausgesetzt. Mit einer groβen Zahl praktischer Beispiele wird demonstriert, daβ die Methode in einem groβen Bereich von Bildmaβstäben und Blockgröβen bereits erfolgreich angewendet wird. Sie hat sich unter den verschiedensten praktischen Bedingungen als voll operationell erwiesen. Dabei wurde die theoretisch erwartete hohe Genauigkeit der GPS Blöcke und ihre Wirtschaftlichkeit bestätigt. Besonders bedeutsam ist der empirische Nachweis, daβ der stationäre GPS Empfänger sehr weit, bis 500 km oder mehr, von dem Fluggebiet entfernt sein kann. Als Ergebnis wird empfohlen, die GPS gestützte Aerotriangulation als verfügbares photogrammetrisches Standardverfahren allgemein zu verwenden. Diese Schluβfolgerung wird durch die neuesten Entwicklungen von Zwei-Frequenz Empfängern und schnellen Mehrdeutigkeitslösungen, in die hohe Erwartungen gesetzt werden, nur noch bekräftigt.

Notes: A description is given of a heighting accuracy test carried out at Cartographical Services Limited on 1:2000 scale aerial photography. Premarked points, with ground surveyed heights, were established on a dual carriageway road near Worcester and photography was flown using a Leica RC20 aerial camera with EMC. Photogrammetric height measurement was carried out with both a Zeiss P3 analytical plotter and a Cartographic Engineering Limited/Carto Instruments AP190 plotter; respective r.m.s.e. accuracies of ± 25 mm and ± 30 mm were obtained. The new Cartographic Engineering Limited CP2 analytical plotter has subsequently been used for height measurement on similar photography and comparable accuracy has been achieved. 〈section xml:id="abs1-2"〉〈title type="main"〉Résumé On présente un essai de précision altimétrique, effectué par la Société“Cartographical Services” de Southampton, sur des photographies aérienne àľéchelledu 1:2000. On a utilisé des points pré-balisés, repartis sur une route à double voie près de Worcester, et dont ľaltitude a été déterminé sur le terrain. La prise de vue a été fait avec une caméra Leica RC20 munie ďun système de compensation du filé longitudinal. On a effectué les déterminations photogrammétriques des altitudes en utilisant à la fois un restituteur analytique Zeiss P3 et une restituteur AP190 de la Société“Cartographic Engineering/Carto Instruments.” On a obtenu comme erreurs moyennes quadratique les valeurs de ± 25 mm et ± 30 mm respectivement. On a enfin utilisé le noveau restituteur analytique CP2 de la Société“Cartographic Engineering” pour ces déterminations altimétriques et ľon a obtenu une précision comparable. 〈section xml:id="abs1-3"〉〈title type="main"〉Zusammenfassung Es wird ein Versuch zur Bestimmung der Höhengenauigkeit, der beim Cartographical Services Ltd. in Southampton für den Bildmaβstab 1:2000 durchgeführt wurde beschrieben. Signalisierte Punkte, deren Höhen im Gelände bestimmt wurden, wurden aufeiner Doppelfahrbahn in der Nähe von Worcester angeordnet undmit einerLeica RC20 mit EMC aufgenommen. Die photogrammetrische Höhenbestimmung erfolgte mit einem analytischen Auswertegerät P3 von Zeiss und einem AP 190 Plotter von Cartographic Engineering Ltd./Carto Instruments. Dabei wurden mittlere Fehler von ± 25 mm bzw. ± 30 mm erhalten. Das neue analytische Auswertegerät CP 2 von Cartographic Engineering Ltd. wurde danach für Höhenmessungen bei ähnlichen Luftbildern genutzt, wobei vergleichbare Genauigkeiten erreicht wurden.

Notes: This paper describes a method for modelling the SPOT satellite imaging process using a single Ground Control Point (GCP) and for extracting ground planimetric information. Satellite position is derived using the collinearity condition equations. Initial orbit is obtained from the given ephemeris data and refinement is carried out using an iterative least squares solution. Attitude variations are taken into account by fitting a third order polynomial in time to the attitudes derived from the ephemeris by integration. After refining the satellite position, planimetric co-ordinates can be derived using the collinearity equations with an accuracy of up to 38 m in latitude and 52 m in longitude (average of the r.m.s. errors from two tests) when the GCP used for modelling is obtained from the 1:50 000 scale map. These figures include the measurement errors as well as the modelling error. It has been found that the method is not sensitive to the location of the GCP used for modelling. Résumé On présente dans cet article une méthode de modélisation du traitement des images du satellite SPOT ne faisant appel qu'à un seul point ďappui au sol et permettant ďextraire des informations planimétriques. On obtient la position du satellite à partir des équations traduisant la condition de colinéarité. On part ďune orbite initiale issue des données fournies par les éphémerides, et on ľameliore par une résolution itèrative, basée sur les moindres carrés. On tient compte des variations ďattitude par ľintermédiaire ďun polynome du troisième ordre fonction du temps et correspondant aux attitudes dérivées des éphémérides par intégration. Une fois obtenue la position définitive du satellite, on peut tirer les coordonnees planimétriques des équations de colinéarité avec une précision qui atteint 38 m en latitude et 52 m en longitude (valeurs moyennes des erreurs moyennes quadratiques rèsultant de deux essais), lorsque le point ďappui au sol utilisé dans la modélisation provident de la carte au 1:50 000. Ces chiffres incluent les erreurs de mesure ainsi que ľerreur de modélisation. On a trouvé que la méthode nétait pas du tout sensible à la position qu'occupait le point ďappui au sol utilisé dans le modélisation. 〈section xml:id="abs1-2"〉〈title type="main"〉Zusammenfassung Im Artikel wird ein Verfahren zur Geländemodellierung des SPOT-Abbildungsprozesses unter Verwendung eines einzelnen Geländepaβpunktes (GCP) und zur Ableitung planimetrischer Informational beschrieben. Die Satellitenposition wird mit Hilfe der Kollinearitätsgleichungen beschrieben. Die Näherungswerte für die Bahnkurve werden aus gegebenen Ephemeriden bestimmt, die durch einen iterativen Prozeβ nach der Methode der kleinsten Quadrate verbessert werden. Veränderungen der Bahn werden rechtzeitig durch Anpassung mit einem Polynom 3. Grades an die aus den Ephemeriden abgeleitete Bahn durch Integration angepaβt. Nach Verbesserung der Satelliten-position können die Lagekoordinaten mit Hilfe der Kollinearitätsgleichungen mit einer Genauigkeit bis zu 38 m in der Breite und 52 m in der Länge (Mittelwert der mittleren Fehler aus 2 Versuchen) bestimmt werden, wenn der Paβpunkt (GCP) aus einer Karte 1:50 000 entnommen wurde. Dabei ist der Meβfehler ebenso wie der Modellierungsfehler enthalten. Es zeigte sich, daβ das Verfahren nicht empfindlich ist in bezug aufdie Lage des zur Modellierung benutzten Paβpunktes.

Notes: Here the author examines the development and implementation of a computer-based system within a financial services organization. It highlights emerging paradoxes within the developments of systems design which utilise quality management methodologies to support IT intensive business processes.

Notes: The ability to reuse existing plans to solve new planning problems can enable a domain-independent planner to improve its average case efficiency by exploiting the problem distribution and avoiding repetition of planning effort. The pay-off from plan reuse, however, crucially depends on finding effective solutions to two important underlying control problems: (i) controlling the retrieval of an appropriate plan and mapping to be reused in a new situation, and (ii) controlling the modification (refitting) of the retrieved plan so as to minimize perturbation to the applicable parts of the plan. This paper is concerned with the development of efficient domain-independent solutions to these two problems. For the retrieval, it provides a domain independent similarity metric that utilizes the plan causal dependency structure to estimate the utility of reusing a given plan in a new problem situation. For the refitting, it presents a minimum-conflict heuristic, again based on the causal dependency structure of the plan, to conservatively control the modification. The paper also discusses the implementation and evaluation of these strategies within the PRIAR plan modification framework.

Notes: The computing occupations are in a state of transition between a technical service and something more central to organizational power and decision-making. This process has had complex implications for the nature of computing work and for careers. There is no certainty that embryonic changes will carry through. But neither should the chances of these occupations of mounting a ‘collective mobility project’ be written off early.

Notes: The relationship between new information and communication technology and organizations is the subject of considerable debate. So too is the nature of organizational transformation. ‘Business process re-engineering’, with its emphasis upon the strategic deployment of information systems, brings both debates together. But does it resolve any of the issues?

Notes: Abstract: This paper presents the architecture of a neural network expert system shell. The system captures every rule as a rudimentary neural network, which is called a network element (netel). The aim is to preserve the semantic structure of the expert system rules, while incorporating the learning capability of neural networks into the inferencing mechanism. These netel rules are dynamically linked up to form the rule-tree during the inferencing process, just as a conventional expert system does. The system is also able to adjust its inference strategy according to different users and situations. A rule editor is provided to enable easy maintenance of the netel rules. These components are housed under a user-friendly interface. An application

Notes: Abstract: Case-based reasoning (CBR) is a problem-solving paradigm where past experiences are used to guide problem-solving. This paradigm shows a great deal of promise for use in intelligent systems. Recent work in intelligent systems focusing on AIDS prevention reflects a growing interest in the case-based paradigm because AIDS prevention experts rely heavily on memory of previous cases when assessing subjects that exhibit AIDS-risky behaviors. If an AIDS prevention expert has seen a subject with similar AIDS-risky behavior previously, he or she is likely to draw on that experience to propose a solution to the new case at hand. This paper describes a CBR system that functions as an AIDS prevention expert. The inputs are risk behavior descriptions and the subject's test results. The system employs fuzzy mathematical algorithms to retrieve and select previous cases, thereby assessing the subject's risk.

Notes: Abstract: Many decision-aiding technologies require valid probability judgements to be elicited from domain experts. But how valid are experts' probability judgements? We describe two approaches to the assessment of quality of probability judgement—calibration and coherence—and review the research findings following from these two approaches. In many cases, expert probability judgement has been found to lack validity and this sub-optimality has largely been attributed to computational errors on the part of the expert. The preferred solution to poor validity in probability judgement has therefore been to reduce the amount of computation performed by the expert. Complex probabilities can be calculated mechanically from simple probability judgements elicited from the expert. We present evidence which suggests that this recomposition technique doesn't guarantee valid probabilities. Our explanation for this finding is that there are various problems concerned with eliciting even the simple probabilities which are necessary for subsequent recomposition. We conclude by proposing some solutions to these elicitation problems which should help ensure that probability judgements of increased validity are available to those attempting to capture subjective assessments for input into decision support systems.

Notes: Teaching Company Scheme programmes involve employing graduates known as Teaching Company Associates in companies on projects which are jointly supervised by academics and company staff. This article presents findings of a study of the effectiveness of these programmes in transferring university expertise in science, technology and management, to industry.

Notes: This article critically examines the phenomenon of ‘Reengineering’ (or Business Process Reengineering: as it is sometimes called) as a transfer of ‘just-in-time’ techniques developed in manufacturing to the office environment. The article concludes that its most likely diffusion will be for ‘downsizing’ and ‘cost-reduction’, and may result in a modest degree of success in only some of its applications to manufacturing and office environments.

Notes: This article is concerned with the application in a case study of three inter-related theoretical issues: new perspectives on technological change, learning organizations, and the question of market versus hierarchy in the relationships between firms. The case study is of the software manual printing industry in Ireland, and its relationship with the major, international software companies.

Notes: Drawing on empirical material from comparative research on jobbing printing in Iceland and Sweden, the author argues that the typesetting process has been subjected to deskilling, and he stresses that the development has been far more complex than often is realised. He concludes that gender, firm size, and production run and variety, must be considered in order to explain the diversity in the typesetting process.

Notes: Book reviews in this article:Technclogy in Working Order: Studies of Work, Interaction, and Technology Graham Button (Ed.)Communication, Technology and the Development of People Bernard WoodsPhotonic Technology and Industrial Policy: US Responses to Technological Change Ernest StembergBeyond Taylorism: Computerization and the New Industrial Relations Lorraine GiordanoJapanization at Work John BrattonWorking for the Japanese Stephanie JonesTechnology and Work in German Industry Norbert Altmann, Christoph Kohler and Pamela Meil (Eds.)Towards Global Localisation: The Computing and Telecommunications Industries in Britain and France Philip Cooke, Frank Moulaert, Erik Swyngedouw, Olivier Weinstein, Peter Wells, Martine Lemattre and Patrice GrevetNew Technology and Practical Police Work S. Ackroyd, R. Harper, J. A. Hughes, D. Shapiro and K. Soothill

Notes: Abstract: Investor is an investment advising hybrid expert system which incorporates two of the most powerful techniques developed in artificial intelligence, the connectionist and the logic programming paradigms, in a unified model. Investor employs a neural network model to detect the interest rate trends and a rule-based component to classify the user into the appropriate investor model. The investor model and the interest rate information are then used by the knowledge base to infer the appropriate investment strategy. Genetic algorithms and classifier systems were employed to train and configure the architecture of Investor's neural network component.

Notes: Abstract: The applicability of feed-forward neural networks for filtering, smoothing and prediction for processes is illustrated in this paper, exemplified by a simulated biochemical process. Filtering, smoothing and prediction are valuable for noisy processes and most of the standard techniques need some knowledge about the process or a model of the process. Artificial neural networks provide a good alternative to the conventional filters and do not need a model of the process. The inputs to the networks were one or more state variables with delayed measurements; the networks calculate the noise-free estimates of the variables. The Levenberg-Marquardt method was used to train the neural networks by minimising the sum of squares of the residuals. The results of filtering, smoothing and prediction were reasonably accurate. Linear activation functions were found to be adequate for most purposes. This is due to the fact that the non-linearity of the process is not very strong in the region of state space considered.

Notes: Abstract: Empirical research into knowledge acquisition (KA) issues is important in the effort to improve the productivity of expert system developers. From an experimental perspective, the few studies that have been reported suffer from certain control and measurement difficulties. Here we conduct a study to demonstrate the feasibility of a new KA experimental strategy. The results of this study partially confirm and partially question results of earlier KA experiments.

Notes: Book reviewed in this article:Neural Networks: Current Applications, P.G.J. Lisboa (Ed.)

Notes: Abstract: A language for multi-agent system design (MAPS) is presented and discussed in this paper. Any agent in MAPS is thought of as an expert system standing on its own. It can communicate through synchronous and asynchronous message sending. Dedicated behaviours are provided which specify how incoming messages are processed. Inter-agent cooperation is controlled via production rules. Two pre-defined agent classes are provided, which are given specific problem-solving roles: Knowledge Server (KS) agents are meant to maintain and transmit knowledge about problem-solving states, while Knowledge Processor (KP) agents are meant to process these elements in order to progress towards a solution. The duality between agent and resource modelling levels on the one hand and between KS and KP modelling styles on the other is shown to allow the specification of various control strategies. The environment is currently running on HP, SUN and DEC workstations.

Notes: Abstract: This paper provides human resource managers with important guidelines when applying expert systems to human resource domains, by reviewing system characteristics, potential benefits and limitations, and appropriate domains to be selected, based on the literature. Structural and procedural aspects of expert systems development in human resource management (represented by a wheel model) and problem descriptions of each expert system respectively are important research results in this paper. We also show semantic networks or semantic nets used for a knowledge representation methodology on such major human resource management activities as human resource planning, recruiting, compensation and labor-management relations. Knowledge representation is a key component in the development stages of expert systems.

Notes: Abstract: This paper is not about knowledge representation, nor knowledge structures, nor knowledge elicitation, nor even expert systems methodology. It is about the use of expert systems in their working context. Little has been written about the usage of expert systems from a theoretical point of view. What has been written from a practitioner's point of view often lacks structure, and thus can make only minor contributions to understanding and predicting the usage of expert systems.In an attempt to fill this gap, this paper proposes a model of benefits of expert systems. The model has three levels and benefits of various kinds are classified into three types. The paper presents a deductive argument for the model, rather than an inductive one, since full empirical studies have yet to be carried out. However, a case study is outlined that indicates the applicability of the model.

Notes: Annabel Beerel, Ellis Horwood, 1993

Notes: Abstract: Production operations managers frequently have to make decisions based on vague, imprecise knowledge. Any software tool developed to aid their decision making needs to take into account the approximate nature of the information available to them and the inexact knowledge to which individual facts are applied. Much of this knowledge is expressed as vague, linguistic articulations. A convenient framework for dealing with such approximate knowledge is fuzzy logic and fuzzy set theory. As a specific example, a system was developed for providing decision support in the Just-in-Time area of production operations management.

Notes: Abstract: Although the benefits of knowledge-based expert systems (ES) and experiences with the methods, techniques and tools employed in knowledge engineering have been extensively reported, less is known about experiences with development and development methodologies. Although ES development is frequently associated with prototyping, a growing number of specific development methodologies have been proposed and are in use. Using information on four development projects at General Electric Industrial and Power Systems, this paper reports on the use of a variation of a prototyping methodology. It identifies some of the advantages, disadvantages and effects of using this approach to development. It raises a number of issues that future ES development methodologies will have to address.

Notes: Abstract: This paper gives a brief overview of the C Language Integrated Production System (CLIPS) with a focus on the object-oriented features. The advantages of an object data representation over the traditional working memory element (WME), i.e. facts, are discussed and the implementation of the Rete inference algorithm in CLIPS is presented in detail. A few methods for achieving pattern-matching on objects with the current inference engine are given and, finally, the paper examines the modifications necessary to the Rete algorithm to allow direct object pattern-matching.

Notes: Abstract: The ultimate criterion of success for interactive expert systems is that they will be used, and used to effect, by individuals other than the system developers. A key ingredient of success in most systems is involving users in the specification and development of systems as they are being built. However, until recently, system designers have paid little attention to ascertaining user needs and to developing systems with corresponding functionality and appropriate interfaces to match those requirements. Although the situation is beginning to change, many developers do not know how to go about involving users, or else tackle the problem in an inadequate way. This paper discusses the need for user involvement and considers why many developers are still not involving users in an optimal way. It looks at the different ways in which users can be involved in the development process and describes how to select appropriate techniques and methods for studying users. Finally, it discusses some of the problems inherent in involving users in expert system development, and recommends an approach which incorporates both ethnographic analysis and formal user testing.

Notes: Book reviewed in this article:Fuzzy Logic for the Management of Uncertainty, Lotfi Zadeh & Janusz Kacprzyk (Eds.) John Wiley & Sons, Inc., 1992, ISBN 0-471-54799-9

Notes: In many head-final languages such as German, Hindi, Japanese, and Korean, but also in some other languages such as Russian, arguments of a verb can occur in any order. Furthermore, arguments can occur outside of their clause (“long-distance scrambling”). Long-distance scrambling presents a challenge both to linguistic theory and to formal frameworks for linguistic description because it is very unconstrained: in a given sentence, there is no bound on the number of elements that can be scrambled nor on the distance over which each element can scramble. We discuss two formal frameworks related to tree-adjoining grammar. First, we show how scrambling facts from Korean can be handled by nonlocal multicomponent TAG (MC-TAG). Then, we argue that overt vWt-movement in German makes this analysis unattractive, and suggest a new version of MC-TAG, called V-TAG, which can handle both Korean and German word order variation. Interestingly, this new version has more attractive computational properties than nonlocal MC-TAG. We conclude that this formalism is an attractive basis for the development of psycholinguistic processing models and practical parsers alike.

Notes: In this paper, we introduce and define a new class of automata (pushdown automata with n stacks, abbreviated as n-SA). The ultimate aim is to give a new characterization of LCRFL, the class of languages accepted by a linear context-free rewriting system (LCFRS). In particular, we introduce 2-SA as a new automaton model for tree-adjoining grammars (TAG). In the simplest cases (0-SA and 1-SA), the languages that are accepted by the automata are the regular and context-free languages respectively. A more complex case is the case of a 2-SA which accepts TALs. The n-SA creates an infinite hierarchy of languages and it seems that this hierarchy corresponds to others in the class LCFRL. The 2-SA corresponds closely to the EPDA (embedded pushdown automaton, an automaton model equivalent to TAGs). Unlike the EPDA, which allows push operations “below the top stack,” an n-SA allows push and pop operations only on the top of their (multiple) stacks. So n-SA trade simpler operations against an also simpler but expanded storage structure.

Notes: This paper discusses variants of nondeterministic one-way S-automata and context-free S-grammars where S is a storage type. The framework that these systems provide can be used to give alternative formulations of embedded pushdown automata and linear indexed grammars. The embedded pushdown automata is obtained by means of a linear version of a class of storage types called iterated pushdowns. Linear indexed grammar is obtained by using the pushdown storage type and restricting the way in which the grammar uses its storage.

Notes: The work presented here attempts to bring out some fundamental concepts that underlie some known parsing algorithms, usually called chart or dynamic programming parsers, in the hope of guiding the design of similar algorithms for other formalisms that could be considered for describing the “surface” syntax of languages. The key idea is that chart parsing is essentially equivalent to a simple construction of the intersection of the language (represented by its grammar) with a regular set containing only the input sentence to be parsed (represented by a finite state machine). The resulting grammar for that intersection is precisely what is usually called a shared forest: it represents all parses of a syntactically ambiguous sentence. Since most techniques for processing ill-formed input can be modeled by considering a nonsingleton regular set of input sentences, we can expect to generalize these ill-formed input processing techniques to all parsers describable with our approach.

Notes: This paper describes a bidirectional head-corner parser for (unification-based versions of) lexicalized tree-adjoining grammars.

Notes: A main purpose of natural language systems (NL-systems) is the simulation of human speech behavior, which divides into generation and analysis, in all kinds of situations. Humans process natural language in an incremental style, which means that sentences are generated or analyzed in a piecemeal fashion. Observations show that there are bidirectional dependencies between these processes. During parsing, hypotheses for the continuation of an utterance may be generated. During generation, the output may be parsed in order to detect ambiguities. This paper presents a two-level incremental parsing algorithm for LD/TLP-TAGs on the basis of Earley's context-free parser. LD/TLP-TAG is a new extension for TAG that increases the descriptive power of the formalism without changing its generative power. Elementary rules are split into local dominance description (LD) and linear precedence rules (TLP) allowing for generalizations of ordering constraints. The presented algorithm is used within an anticipation feedback loop for the incremental syntactic generator TAG-GEN.

Notes: This paper extends the “parsing as deduction” approach to tree-adjoining grammars by showing how a TAG recognition problem can be reduced to a Datalog deduction problem, and presents an SLD selection rule that makes the proof search correspond to a top-down parse using the original grammar. Just as in the DCG extension of context-free grammars, this approach permits nodes to be labeled with firsl-order terms (rather than only atomic symbols). Finally the paper discusses implementation matters, and describes how the control rule can be efficiently implemented in Prolog.

Notes: It is possible within tree-adjoining grammar to reproduce many of the syntactic analyses originally formulated by linguists in transformational terms. To the extent that these analyses are well motivated empirically, this fact makes TAG interesting for use in developing computational learning and processing models (Joshi 1990; Frank 1992; Rambow 1994), since the use of other nontransformational formalisms sometimes forces choices of linguistic description different from those ordinarily made by descriptive syntacticians. Thus, using TAG, one can take advantage in the construction of parsers and learners of the computational tractability of a mathematically restrictive formalism without having to reinvent empirical syntax in order to do so. At the same time, TAG analyses are not identical in every detail to their transformational counterparts; and it is interesting to compare them where they diverge. The differences arise because of a fundamental difference in the way that syntactic recursion is treated in the two frameworks. In TAG, recursive structures are generated by composing elementary syntactic objects, with the result that recursion is factored apart from the representation of local syntactic dependencies. By contrast, in transformational grammar, as in many other frameworks, recursive structure and local dependencies are represented together in a single, full representation of a complex sentence. Because of this difference in the treatment of recursion, it often turns out, when TAG is used to emulate a transformational analysis, that the TAG version has advantages, of both elegance and empirical coverage, over the original. This paper is a demonstration in a new empirical domain, that of nominal constructions, of the advantages of TAG-based syntax. By presenting a linguistically detailed account of these constructions and showing the advantages of using TAG to analyze them, we strengthen the case for the use of mathematically constrained and computationally tractable representational systems in competence-based as well as in computational linguistics.

Notes: This paper presents an algorithm (a parser) for analyzing sentences according to grammatical constraints expressed in the framework of lexicalized tree-adjoining grammar. For the current grammars of English, the algorithm behaves much better and requires much less time than its worst-case complexity. The main objective of this work is to design a practical parser whose average-case complexity is much superior to its worst case. Most of the previous methods always required the worst-case complexity. The algorithm can be used in two modes. As a recognizer it outputs whether the input sentence is grammatically correct or not. As a parser it outputs a detailed analysis of the grammatically correct sentences. As sentences are read from left to right, information about possible continuations of the sentence is computed. In this sense, the algorithm is called a predictive left to right parser. This feature reduces the average time required to process a given sentence. In the worst case, the parser requires an amount of time proportional to G2n6 for a sentence of n words and for a lexicalized tree-adjoining grammar of size G. The worst-case complexity is only reached with pathological (not naturally occurring) grammars and inputs.

Notes: Coupled-context-free grammars are a natural generalization of context-free grammars obtained by combining nonterminals to corresponding parentheses which can only be substituted simultaneously. Refering to the generative capacity of the grammars we obtain an infinite hierarchy of languages that comprises the context-free languages as the first and all the languages generated by TAGs as the second element. Here, we present a generalization of the context-free LL(k)-notion onto coupled-context-free grammars, which leads to a characterization of subclasses of coupled-context-free grammars–and in this way of TAGs as well–which can be parsed in linear time. The parsing procedure described works incrementally so that it can be used for on-line parsing of natural language. Examples show that important elements of the tree-adjoining languages can be generated by LL(k)-coupled-context-free grammars.

Notes: This paper describes a natural language generation system developed for a spoken language translation system. Our system employs Feature-structure-based Tree Adjoining Grammar (FTAG) for generation knowledge representation. Each elementary tree of our grammar is paired with a semantic feature structure which is consistent with semantics defined in Head-driven Phrase Structure Grammar. Feature structures attached to nodes of elementary trees are unrestricted. Thus our formalism allows HPSG style phrase structure description as well as TAG style description. The advantage of our generation knowledge representation is the ability of incorporating HPSG style “core” grammar and TAG style case-based grammar.The system generates a syntactic tree by combining elementary trees so as to satisfy an input semantic structure. The generation algorithm is an application of a semantic head-driven generation. To carry out an adjoining operation. an elementary tree with an adjunction node is dynamically split at the adjunction node during generation.

Notes: This paper presents a knowledge-based learning method and reports on case studies in different domains. The method integrates abduction and explanation-based learning. Abduction provides an improved method for constructing explanations. The improvement enlarges the set of examples that can be explained so that one can learn from additional examples using traditional explanation-based macro learning. Abduction also provides a form of knowledge level learning. Descriptions of case studies show how to set up abduction engines for tasks in particular domains. The case studies involve over a hundred examples taken from diverse domains requiring logical, physical, and psychological knowledge and reasoning. The case studies are relevant to a wide range of practical tasks including natural language understanding and plan recognition; qualitative physical reasoning and postdiction; diagnosis and signal interpretation; and decision making under uncertainty. The descriptions of the case studies include an example, its explanation, and discussions of what is learned by macro-learning and by abductive inference. The paper discusses how to provide and represent the domain knowledge and meta-knowledge needed for abduction and search control. The main conclusion is that abductive inference is important for learning. Abduction and macro-learning are complementary and synergistic.

Notes: The frequent and conventional use of nonliteral language has been a major stumbling block for natural language processing systems since the early machine translation efforts. Metaphor, metonymy, and indirect speech acts are among the most troublesome phenomena. Recent computational efforts addressing these problems have taken an approach that emphasizes the use of systematic knowledge about nonliteral language conventions. We are currently engaged in an effort to supply this knowledge in the case of conventional metaphor. We are constructing MetaBank: an empirically derived and theoretically motivated knowledge-base of English metaphorical conventions. This article describes our three-part approach to the construction of MetaBank: the collection of on-line textual resources and databases of linguistic generalizations, the development of a methodology for analyzing these resources, and the construction of a knowledge-base based on the preceding analyses.

Notes: This paper explores the application of a rich model of pragmatic context to the problem of identifying and correcting real-word spelling errors. Results suggest that such a model can be useful for generating and ranking a list of possible corrections according to their contextual relevance. In the domain of expert consultation discourse, a mode! of pragmatic context must represent not only the user's domain plans, but also the problem-solving processes that explore alternative plans, refining and instantiating the intended plan, and the connections between those problem-solving moves and their resulting discourse manifestations. In the model presented, metaplans are used to represent these problem-solving and discourse levels, while heuristics that take into account the user's problem-solving strategies and world knowledge serve to rank the relative likelihood of different possible next queries. An implementation of this model has been used to suggest pragmatically coherent interpretations that can be matched against a partial parse of the input in order to generate possible corrections for real-word spelling errors.

Notes: A number of grammatical formalisms have been proposed to describe the syntax of natural languages, and the universal recognition problems for some of those classes of grammars have been studied. A universal recognition problem for a class Q of grammars is the one to decide, taking a grammar G ∈ G and a string ui as an input, whether G can generate w or not. In this paper, the computational complexities of the universal recognition problems for parallel multiple context-free grammars, multiple context-free grammars, and their subclasses are discussed.

Notes: We show how multicomponent TAGs, although in their “local” version equivalent to “simple” TAGs, enable one to associate the derived structures with a richer set of derivations. This is especially useful for representing some nonlocal dependencies such as wh-extraction out of NP or extraposition, as soon as one interprets the derivation structures as representing the predicate-argument dependencies. However, there is a formal alternative in the formalism of synchronous TAGs that achieves a similar result, namely, that associates standard syntactic derivations with nonisomorphic semantic derivations, and relies on the latter to represent the dependency relations. We show that the latter treatment accounts for a different range of extraposition facts in French, where the relationship between the head noun and its extraposed dependent is a semantic one.Nous montrons comment les TAGs ensemblistes “locales” (MCTAGs), qui sont équivalentes aux TAGs simples, permettent ?associer aux structures syntaxiques dérivées un ensemble plus large de structures dérivationnelles. Cela est particulièrement utile pour la représentation des dépendances non locales qu'on observe dans les extractions hors du groupe nominal et les extrapositions, à partirdu moment oùľon interprète les arbres de dérivation comme représentant les relations de dépendance. II existe toutefois une autre possibilityé dans le cadre des TAGs synchrones qui associe aux dérivations syntaxiques standard des dérivations sémantiques non isomorphes et interprète les relations de dépendance en se basant sur ces dernières. Nous montrons que cette deuxième possibilityé est mieux adaptée pour des cas ?extraposition en français où la relation de dépendance entre le nom těte et ľélément extraposé est ?ordre sémantique.

Notes: By means of a factorization of linear precedence (LP) information in tree-adjoining grammar (TAG), the possibility to capture syntactic generalizations can be enhanced, especially with respect to languages which exhibit relative free word-order. In TAG(LD/LP) LP-information is factorized in a way reminiscent of the ID/LP format of CFGs. However, in contrast to its context-free counterpart, in TAG(LD/LP) entanglement of constituents is allowed by admitting not only the permutation of sister nodes, but also of non-sister nodes in a structural description. In this paper a generalization of the predictive left-to-right parser for TAG is presented which is able to handle a restricted variant of TAG(LD/LP), which allows the permutation of sister nodes and non-sister nodes within elementary structures, the basic building blocks of TAG(LD/LP).

Notes: Natural-language generation has gained importance since AI systems have become more sophisticated and canned text can no longer serve the elaborate communicative tasks in such a system. In this paper, suggestions are presented to apply uniformly the formalism of tree-adjoining grammar (TAG) for all tasks of natural-language generation. Up to now plan-based systems have been preferred for most of the processing during generation. Since the individual tasks of natural-language generation are very different and complex; for example, the determination of the propositional structure of a text is described using the TAG formalism–extended by constraints and feature descriptions (UCTAC). Nevertheless, this paper proposes basic ideas for the generalization of applying a grammar formalism to natural-language generation in order to build an overall integrated system for natural-language generation. Finally, advantages of such a uniform model are discussed.

Notes: This paper presents an evaluation of a heuristic for partial-order planning, known as temporal coherence. The temporal coherence heuristic was proposed by Drummond and Currie as a method to improve the efficiency of partial-order planning without losing the ability to find a solution (i.e., completeness). It works by using a set of domain constraints to prune away plans that do not “make sense,” or are temporally incoherent. Our analysis shows that, while intuitively appealing, temporal coherence can only be applied to a very specific implementation of a partial-order planner and still maintain completeness. Furthermore, the heuristic does not always improve planning efficiency; in some cases, its application can actually degrade the efficiency of planning dramatically. To understand when the heuristic will work well, we conducted complexity analysis and empirical tests. Our results show that temporal coherence works well when strong domain constraints exist that significantly reduce the search space, when the number of subgoals is small, when the plan size is not too large, and when it is inexpensive to check each domain constraint.

Notes: Default logic has been introduced for handling reasoning with incomplete knowledge. It has been widely studied, and various definitions have been proposed for it. Most of the variants have been defined by means of fixed points of some operator. We propose here another approach, which is based on a study of the way in which general rules with exceptions, used in a default reasoning process, can contradict one another. We then isolate sets of noncontradicting rules, as large as possible in order to exploit as much information as possible, and construct, for each of these sets of rules, the set of conclusions that can be deduced from it. We show that our framework encompasses most of the existing variants of default logic, allowing those variants to be compared from a knowledge representation point of view. Our approach also enables us to provide an operational definition of extensions in some interesting cases. Proof-theoretical and semantical aspects are investigated.