ABSTRACT We are interested in the problem of validating the consistency of integrity constraints ... more ABSTRACT We are interested in the problem of validating the consistency of integrity constraints when data is modified. In particular, we consider how constraints can be checked with only "partial information". Partial information may include: (1) the constraint specifications only, (2) the constraint specifications and the modified data, or (3) the constraint specifications, the modified data, and portions of the existing data. Methods for constraint checking with partial information can be much more efficient than traditional constraint checking methods (e.g. because work is done at compile time, or because less data is accessed). Partial information methods also enable constraint checking in scenarios where traditional constraint checking methods fail (e.g. in distributed environments where not all data is accessible). We explain how existing methods and results for query containment and for independence can be applied to problems (1) and (2) above, and we give an overview of our research in...
Natural killer T (NKT) cells have recently been implicated in atherogenesis, primarily for their ... more Natural killer T (NKT) cells have recently been implicated in atherogenesis, primarily for their ability to recognize and respond to lipid antigens. Because the atherosclerotic lesion is characterized by the retention and modification of lipids in the vascular wall, NKT cells may be involved in promoting the local vascular inflammatory response. Here, we investigate the proatherogenic role of NKT cells in an adoptive transfer model of atherosclerosis, using as recipients immune-deficient, atherosclerosis-susceptible RAG1(-/-)LDLR(-/-) mice. The adoptive transfer of an NKT cell-enriched splenocyte population from Valpha14Jalpha18 T-cell receptor transgenic mice resulted in a 73% increase in aortic root lesion area compared with recipients of NKT cell-deficient splenocytes derived from CD1d(-/-) mice after 12 weeks of Western-type diet feeding. The total serum from hypercholesterolemic mice leads to a small but significant activation of Valpha14Jalpha18 T-cell receptor-expressing hybridoma line by dendritic cells that is CD1d-dependent. Therefore, these studies demonstrate that NKT cells are proatherogenic in the absence of exogenous stimulation, and this activity is likely associated with endogenous lipid antigens carried by lipoproteins in the circulation and perhaps also in the atherosclerotic plaque.
ABSTRACT Evaluations of SQL queries with the ORDER BY clause is con- sidered. The naive approach ... more ABSTRACT Evaluations of SQL queries with the ORDER BY clause is con- sidered. The naive approach of first computing the result and then sorting the tuples is not suitable for Web applications, since the result could be very large while users expect to get quickly the top-k tuples. Tractabil- ity, in this case, amounts to enumerating answers in sorted order with polynomial delay, under query-and-data complexity. It is proved that an efficient algorithm for finding the top-ranked tuple of a conjunctive query is a sufficient (and not just necessary) condition for tractability. Several classes of orders are shown to have this property when queries are acyclic.
Proceedings of the 35th SIGMOD international conference on Management of data - SIGMOD '09, 2009
ExQueX is an interactive system for exploring and querying XML documents. The exploration is done... more ExQueX is an interactive system for exploring and querying XML documents. The exploration is done by searching, ranking and filtering, and it enables users to discover relationships that exist in a given document. The results of the exploration can be used either directly as tree queries or as building blocks in the process of formulating more complex queries. The latter
Constraints are important, not only for maintaining data integrity, but also because they capture... more Constraints are important, not only for maintaining data integrity, but also because they capture natural probabilistic dependencies among data items. A probabilistic XML database (PXDB) is the probability subspace comprising the instances of a p-document that satisfy a set of constraints. In contrast to existing models that can express probabilistic dependencies, it is shown that query evaluation is tractable in
ABSTRACT We are interested in the problem of validating the consistency of integrity constraints ... more ABSTRACT We are interested in the problem of validating the consistency of integrity constraints when data is modified. In particular, we consider how constraints can be checked with only "partial information". Partial information may include: (1) the constraint specifications only, (2) the constraint specifications and the modified data, or (3) the constraint specifications, the modified data, and portions of the existing data. Methods for constraint checking with partial information can be much more efficient than traditional constraint checking methods (e.g. because work is done at compile time, or because less data is accessed). Partial information methods also enable constraint checking in scenarios where traditional constraint checking methods fail (e.g. in distributed environments where not all data is accessible). We explain how existing methods and results for query containment and for independence can be applied to problems (1) and (2) above, and we give an overview of our research in...
Natural killer T (NKT) cells have recently been implicated in atherogenesis, primarily for their ... more Natural killer T (NKT) cells have recently been implicated in atherogenesis, primarily for their ability to recognize and respond to lipid antigens. Because the atherosclerotic lesion is characterized by the retention and modification of lipids in the vascular wall, NKT cells may be involved in promoting the local vascular inflammatory response. Here, we investigate the proatherogenic role of NKT cells in an adoptive transfer model of atherosclerosis, using as recipients immune-deficient, atherosclerosis-susceptible RAG1(-/-)LDLR(-/-) mice. The adoptive transfer of an NKT cell-enriched splenocyte population from Valpha14Jalpha18 T-cell receptor transgenic mice resulted in a 73% increase in aortic root lesion area compared with recipients of NKT cell-deficient splenocytes derived from CD1d(-/-) mice after 12 weeks of Western-type diet feeding. The total serum from hypercholesterolemic mice leads to a small but significant activation of Valpha14Jalpha18 T-cell receptor-expressing hybridoma line by dendritic cells that is CD1d-dependent. Therefore, these studies demonstrate that NKT cells are proatherogenic in the absence of exogenous stimulation, and this activity is likely associated with endogenous lipid antigens carried by lipoproteins in the circulation and perhaps also in the atherosclerotic plaque.
ABSTRACT Evaluations of SQL queries with the ORDER BY clause is con- sidered. The naive approach ... more ABSTRACT Evaluations of SQL queries with the ORDER BY clause is con- sidered. The naive approach of first computing the result and then sorting the tuples is not suitable for Web applications, since the result could be very large while users expect to get quickly the top-k tuples. Tractabil- ity, in this case, amounts to enumerating answers in sorted order with polynomial delay, under query-and-data complexity. It is proved that an efficient algorithm for finding the top-ranked tuple of a conjunctive query is a sufficient (and not just necessary) condition for tractability. Several classes of orders are shown to have this property when queries are acyclic.
Proceedings of the 35th SIGMOD international conference on Management of data - SIGMOD '09, 2009
ExQueX is an interactive system for exploring and querying XML documents. The exploration is done... more ExQueX is an interactive system for exploring and querying XML documents. The exploration is done by searching, ranking and filtering, and it enables users to discover relationships that exist in a given document. The results of the exploration can be used either directly as tree queries or as building blocks in the process of formulating more complex queries. The latter
Constraints are important, not only for maintaining data integrity, but also because they capture... more Constraints are important, not only for maintaining data integrity, but also because they capture natural probabilistic dependencies among data items. A probabilistic XML database (PXDB) is the probability subspace comprising the instances of a p-document that satisfy a set of constraints. In contrast to existing models that can express probabilistic dependencies, it is shown that query evaluation is tractable in
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Papers by Yonatan Sagiv