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- Tobian, Arne, 1992-
(författare)
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Entering the dynamic risk space : Assessing planetary boundary interactions through process-based quantifications
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The planetary boundaries framework is an effort to define a safe operating space for humanity. Its rationale is that sustainable development needs to be achieved in ways that safeguard the stability of the Earth system on which human prosperity relies. However, very few studies explicitly examine the interactions of the Earth system processes that underlie individual boundaries.My overarching research question is: how can continued anthropogenic climate change affect the geospatially resolvable land and water planetary boundaries, and what are the implications for human livelihood? For most of my analysis, I use the LPJmL dynamic global vegetation model because it contains suitable process representations that provide a dynamic and adaptive Earth system perspective for my investigation of key planetary boundary interactions of the climate, land, water and ecosystem nexus.Paper I emphasizes the importance of green water dynamics (that is terrestrial precipitation, evapotranspiration and plant-available soil moisture) for ecosystem resilience and human well-being. The underlying analysis suggests that the current status of the proposed planetary boundary for green water is already transgressed. Paper II reveals long-term spatiotemporal dynamics of planetary boundary interactions as breaching the climate change boundary critically affects the world’s major forest biomes. Notably, the most extreme climate change scenarios led to the emergence of a southern boreal dieback in the simulations. Tropical forests further show a shift from evergreen to deciduous rainforest, an important process which is not captured by the definition of the land-system change boundary. Maintaining climate change at the planetary boundary co-stabilizes the land-system change boundary. Paper III extends the biophysical understanding of planetary boundary interactions by discussing their impact on human livelihood and the attainment of the Sustainable Development Goals. Future climate change causes increases in dry anomalies of green water in ~30% of the global land area by the end of the century. As of today (here referring to 2015), nearly a quarter of the world population and ~28% of global harvest would be affected. The dynamic risk space terminology is established to fill the conceptual gap in the analysis of planetary boundary interactions. Paper IV highlights how planetary stability constitutes the non-negotiable fundament for human development and argues why the Sustainable Development Goals have to be aligned with the planetary boundaries framework and which perils might arise from their interactions. Paper V presents the land-system change reallocation tool algorithm which allows for a scenario-driven rearrangement of human land-use to meet varying transgression levels of the land-system change boundary. My results of Paper I-V advance the understanding of interactions in the planetary boundaries framework. Moreover, my analysis in a process-based and validated modeling environment gives spatiotemporal detail of the processes at play that exceeds the potential of previously used conceptual models. My work fills a crucial gap in the operationalization of the planetary boundary framework by providing insights into how and where different policy options produce positive or negative outcomes across boundaries. The holistic understanding I present is a prerequisite for any application of the planetary boundaries framework that focuses on future conditions.
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| 2. |
- Adesam, Yvonne, 1975-
(författare)
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The Multilingual Forest : Investigating High-quality Parallel Corpus Development
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis explores the development of parallel treebanks, collections of language data consisting of texts and their translations, with syntactic annotation and alignment, linking words, phrases, and sentences to show translation equivalence. We describe the semi-manual annotation of the SMULTRON parallel treebank, consisting of 1,000 sentences in English, German and Swedish. This description is the starting point for answering the first of two questions in this thesis.What issues need to be considered to achieve a high-quality, consistent,parallel treebank?The units of annotation and the choice of annotation schemes are crucial for quality, and some automated processing is necessary to increase the size. Automatic quality checks and evaluation are essential, but manual quality control is still needed to achieve high quality.Additionally, we explore improving the automatically created annotation for one language, using information available from the annotation of the other languages. This leads us to the second of the two questions in this thesis.Can we improve automatic annotation by projecting information available in the other languages?Experiments with automatic alignment, which is projected from two language pairs, L1–L2 and L1–L3, onto the third pair, L2–L3, show an improvement in precision, in particular if the projected alignment is intersected with the system alignment. We also construct a test collection for experiments on annotation projection to resolve prepositional phrase attachment ambiguities. While majority vote projection improves the annotation, compared to the basic automatic annotation, using linguistic clues to correct the annotation before majority vote projection is even better, although more laborious. However, some structural errors cannot be corrected by projection at all, as different languages have different wording, and thus different structures.
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| 3. |
- Hall, Johan, 1973-
(författare)
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MaltParser -- An Architecture for Inductive Labeled Dependency Parsing
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This licentiate thesis presents a software architecture for inductive labeled dependency parsing of unrestricted natural language text, which achieves a strict modularization of parsing algorithm, feature model and learning method such that these parameters can be varied independently. The architecture is based on the theoretical framework of inductive dependency parsing by Nivre \citeyear{nivre06c} and has been realized in MaltParser, a system that supports several parsing algorithms and learning methods, for which complex feature models can be defined in a special description language. Special attention is given in this thesis to learning methods based on support vector machines (SVM).The implementation is validated in three sets of experiments using data from three languages (Chinese, English and Swedish). First, we check if the implementation realizes the underlying architecture. The experiments show that the MaltParser system outperforms the baseline and satisfies the basic constraints of well-formedness. Furthermore, the experiments show that it is possible to vary parsing algorithm, feature model and learning method independently. Secondly, we focus on the special properties of the SVM interface. It is possible to reduce the learning and parsing time without sacrificing accuracy by dividing the training data into smaller sets, according to the part-of-speech of the next token in the current parser configuration. Thirdly, the last set of experiments present a broad empirical study that compares SVM to memory-based learning (MBL) with five different feature models, where all combinations have gone through parameter optimization for both learning methods. The study shows that SVM outperforms MBL for more complex and lexicalized feature models with respect to parsing accuracy. There are also indications that SVM, with a splitting strategy, can achieve faster parsing than MBL. The parsing accuracy achieved is the highest reported for the Swedish data set and very close to the state of the art for Chinese and English.
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| 4. |
- Nilsson, Kristina, 1976-
(författare)
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Hybrid Methods for Coreference Resolution in Swedish
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this thesis is to improve coreference resolution in Swedish by providing a hybrid approach based on combining data-driven methods and linguistic knowledge. Coreference resolution here consists in identifying all expressions in a text that have the same referent, for example, a person or an object. The linguistic knowledge is based on Accessibility Theory (Ariel 1990). This is used for guiding the selection of likely anaphor-antecedent pairs from the set of all possible such pairs in a text. The data-driven method adopted is Memory-Based Learning (MBL), a supervised method based on the idea that learning means storing experiences in memory, and that new problems are solved by reusing solutions from similar experiences (Daelemans and Van den Bosch 2005). The referring expressions covered by the system are names, definite descriptions, and pronouns. In order to maximize performance, we use different classifiers with a specific set of linguistically motivated features for each type of expression. The great majority of features used for classification are domain- and language-independent. We demonstrate two ways of using this method of linguistically motivated selection of anaphor-antecedent pairs. First, the amount of training examples stored in memory is reduced. We find that for coreference resolution of definite descriptions and names, the amount of training data can thereby be reduced with only a minor loss in performance, but for pronoun resolution there is a negative effect. Second, selection can be used for improving on coreference resolution results. This is the first step in our hybrid approach to coreference resolution, where the second step is the application of an MBL classifier for determining coreference between the selected pairs. Results indicate that this hybrid approach is advantageous for coreference resolution of definite descriptions and names. For pronoun resolution, there is a negative effect on recall along with a positive effect on precision.
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| 5. |
- Hjelm, Hans, 1973-
(författare)
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Cross-language Ontology Learning : Incorporating and Exploiting Cross-language Data in the Ontology Learning Process
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- An ontology is a knowledge-representation structure, where words, terms or concepts are defined by their mutual hierarchical relations. Ontologies are becoming ever more prevalent in the world of natural language processing, where we currently see a tendency towards using semantics for solving a variety of tasks, particularly tasks related to information access. Ontologies, taxonomies and thesauri (all related notions) are also used in various variants by humans, to standardize business transactions or for finding conceptual relations between terms in, e.g., the medical domain. The acquisition of machine-readable, domain-specific semantic knowledge is time consuming and prone to inconsistencies. The field of ontology learning therefore provides tools for automating the construction of domain ontologies (ontologies describing the entities and relations within a particular field of interest), by analyzing large quantities of domain-specific texts. This thesis studies three main topics within the field of ontology learning. First, we examine which sources of information are useful within an ontology learning system and how the information sources can be combined effectively. Secondly, we do this with a special focus on cross-language text collections, to see if we can learn more from studying several languages at once, than we can from a single-language text collection. Finally, we investigate new approaches to formal and automatic evaluation of the quality of a learned ontology. We demonstrate how to combine information sources from different languages and use them to train automatic classifiers to recognize lexico-semantic relations. The cross-language data is shown to have a positive effect on the quality of the learned ontologies. We also give theoretical and experimental results, showing that our ontology evaluation method is a good complement to and in some aspects improves on the evaluation measures in use today.
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