Lock-based concurrency control for XML
Bibliographic record
Abstract
As XML gains popularity as the standard data representation model, there is a need to store, retrieve and update XML data efficiently. McXml is a native XML database system that has been developed at McGill University and represents XML data as trees. McXML supports both read-only queries and six different kinds of update operations. To support concurrent access to documents in the McXML database, we propose a concurrency control protocol called LockX which applies locking to the nodes in the XML tree. LockX maximizes concurrency by considering the semantics of McXML's read and write operations in its design. We evaluate the performance of LockX as we vary factors such as the structure of the XML document and the proportion of read operations in transactions. We also evaluate LockX's performance on the XMark benchmark [16] after extending it with suitable update operations [13]. Finally, we compare LockX's performance with two snapshot-based concurrency control protocols (SnaX, OptiX) that provide a committed snapshot of the data for client operations.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.005 | 0.013 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.004 | 0.005 |
| Open science | 0.003 | 0.004 |
| Research integrity | 0.001 | 0.003 |
| Insufficient payload (model declined to judge) | 0.006 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".