Optimization of Spatial Joins Using Filters

When viewing present-day technical applications that rely on the use of database systems, one notices that new techniques must be integrated in database management systems to be able to support these applications efficiently. This paper discusses one of these techniques in the context of supporting a Geographic Information System. It is known that the use of filters on geometric objects has a significant impact on the processing of 2-way spatial join queries. For this purpose, filters require approximations of objects. Queries can be optimized by filtering data not with just one but with several filters. Existing join methods are based on a combination of filters and a spatial index. The index is used to reduce the cost of the filter step and to minimize the cost of retrieving geometric objects from disk. In this paper we examine n-way spatial joins. Complex n-way spatial join queries require solving several 2-way joins of intermediate results. In this case, not only the profit gained from using both filters and spatial indices but also the additional cost due to using these techniques are examined. For 2-way joins of base relations these costs are considered part of physical database design. We focus on the criteria for mutually comparing filters and not on those for spatial indices. Important aspects of a multi-step filter-based n-way spatial join method are described together with performance experiments. The winning join method uses several filters with approximations that are constructed by rotating two parallel lines around the object

Course of functional status and pain in osteoarthritis of the hip or knee: A systematic review of the literature

Objective. To systematically review studies describing the course of functioning in patients with osteoarthritis (OA) of the hip or knee and identifying potential prognostic factors. Methods. A systematic search was performed. Studies involving patients with hip or knee OA, >6 months of followup, and outcome measures on functional status or pain were included. Methodologic quality was assessed using a standardized set of 11 criteria; a qualitative data analysis was performed. Results. Approximately 6,500 titles and abstracts were screened and 48 publications were considered for inclusion. Eighteen studies, 4 of which met the high methodologic quality criteria, were included. For hip OA, there was limited evidence that functional status and pain do not change during the first 3 years of followup. After 3 years, however, a worsening of functional status and pain was seen. For knee OA, there was conflicting evidence for the first 3 years and limited evidence for worsening of pain and functional status after 3 years. Furthermore, limited evidence was established for negative associations between future functional status and laxity, proprioceptive inaccuracy, age, body mass index, and knee pain intensity. In contrast, greater muscle strength, better mental health, better self-efficacy, social support, and more aerobic exercise were protective factors in the first 3 years. Conclusion. Pain and functional status in hip or knee OA seem to deteriorate slowly, with limited evidence for worsening after 3 years of followup. In specific subgroups, prognosis in the first 3 years of followup was either worse or better, as both risk factors and protective factors were identified. Prognostic factors included biomechanical factors, psychological factors, clinical factors, and treatment modalities. To strengthen the evidence, further high-quality longitudinal research on hip or knee OA functioning is needed

Which patients with osteoarthritis of hip and/or knee benefit most from behavioral graded activity?

Our objective was to investigate whether behavioral graded activity (BGA) has particular benefit in specific subgroups of osteoarthritis (OA) patients. Two hundred participants with OA of hip or knee, or both (clinical American College of Rheumatology, ACR, criteria) participated in a randomized clinical trial on the efficacy of BGA compared to treatment according to the Dutch physiotherapy guideline (usual care; UC). Changes in pain (Visual Analog Scale, VAS), physical functioning (WesterOntario and McMaster Universities Osteoarthritis Index, WOMAC, and McMaster Toronto Arthritis Questionnaire, MACTAR), and patient global assessment were compared for specific subgroups. Subgroups were assigned by the median split method and were analyzed using analysis of covariance. Beneficial effects of BGA were found for patients with a relatively low level of physical functioning (p?0.03). Furthermore, beneficial effects of BGA in patients with a low level of internal locus of control were marginally significant (p = .05). Patients with a relatively low level of physical functioning benefit more from BGA compared to UC. Compared to UC, BGA is the preferred treatment option in patients with a low level of physical functioning