Thomas G. Price

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In a high level query and data manipulation language such as SQL, requests are stated non-procedurally, without reference to access paths. This paper describes how System R chooses access paths for both simple (single relation) and complex queries (such as joins), given a user specification of desired data as a boolean expression of predicates. System R is(More)
The recovery subsystem of an experimental data management system is described and evaluated. The transactmn concept allows application programs to commit, abort, or partially undo their effects. The DO-UNDO-REDO protocol allows new recoverable types and operations to be added to the recovery system Apphcation programs can record data m the transaction log(More)
If other processes request the lock while it is granted then they are placed in a queue of waiters and suspended. When the lock becomes available, requests are granted in first-come first-served order. Setting and clearing a lock costs ten instuctions if no waiting is involved. If waiting is involved,it costs 50 instructions plus two process dispatches(More)
In the independent reference model of program behavior, King’s formulas for the expected FIFO (“first-in-first-out”) and expected LRU (“least-recently-used”) miss ratios each contain an exponential number of terms (very roughly nCAP, where n is the number of pages and CAP is the capacity of main memory). Hence, under the straightforward algorithms, these(More)
System R supports a high-level relational user language called SQL which may be used by ad hoc users at terminals or as an embedded data sublanguage in PL/I or COBOL. Host-language programs with embedded SQL statements are processed by the System R precompiler which replaces the SQL statements by calls to a machine-language access module. The precompilation(More)
0018-8670/99/$5.00 © 1999 IBM IBM SYSTEMS JOURNAL, VOL38, NOS 2&3, 1999 BLASGEN ETAL. System R is an experimental data base management system that was designed to be unusually easy to use. System R supports a high-level relational user language called SQL, which may be used by ad hoc users at terminals or by programmers as an imbedded data sublanguage in(More)
ACCESS (Actively-Corrected Coronagraph for Exoplanet System Studies) develops the science and engineering case for an investigation of exosolar giant planets, super-earths, exo-earths, and dust/debris fields that would be accessible to a medium-scale NASA mission. The study begins with the observation that coronagraph architectures of all types (other than(More)
CIAT and CRS have developed a long term Learning Alliance, based on the concepts of market engagement to meet the needs of rural households living in extreme poverty that is transforming how both institutions work. Through this process CRS has shifted from a supply side approach to disaster recovery, with an emphasis on food security based sustainable(More)