The temporal query language TQuel
ACM Transactions on Database Systems (TODS)
Partitioned storage for temporal databases
Information Systems
Understanding the new SQL: a complete guide
Understanding the new SQL: a complete guide
On the semantics of (bi)temporal variable databases
EDBT '94 Proceedings of the 4th international conference on extending database technology: Advances in database technology
On the semantics of “now” in databases
ACM Transactions on Database Systems (TODS)
Understanding SQL's stored procedures: a complete guide to SQL/PSM
Understanding SQL's stored procedures: a complete guide to SQL/PSM
Developing time-oriented database applications in SQL
Developing time-oriented database applications in SQL
Maintaining knowledge about temporal intervals
Communications of the ACM
ACM Transactions on Database Systems (TODS)
The TSQL2 Temporal Query Language
The TSQL2 Temporal Query Language
Temporal Specialization and Generalization
IEEE Transactions on Knowledge and Data Engineering
SQL Extension for Interval Data
IEEE Transactions on Knowledge and Data Engineering
R-Tree Based Indexing of Now-Relative Bitemporal Data
VLDB '98 Proceedings of the 24rd International Conference on Very Large Data Bases
Managing Intervals Efficiently in Object-Relational Databases
VLDB '00 Proceedings of the 26th International Conference on Very Large Data Bases
Coalescing in Temporal Databases
VLDB '96 Proceedings of the 22th International Conference on Very Large Data Bases
Layered Temporal DBMS: Concepts and Techniques
Proceedings of the Fifth International Conference on Database Systems for Advanced Applications (DASFAA)
Effective timestamping in databases
The VLDB Journal — The International Journal on Very Large Data Bases
Indexing of now-relative spatio-bitemporal data
The VLDB Journal — The International Journal on Very Large Data Bases
Light-Weight Indexing of General Bitemporal Data
SSDBM '00 Proceedings of the 12th International Conference on Scientific and Statistical Database Management
Concurrency Control for Perceivedly Instantaneous Transactions in Valid-Time Databases
TIME '97 Proceedings of the 4th International Workshop on Temporal Representation and Reasoning (TIME '97)
ArchIS: an XML-based approach to transaction-time temporal database systems
The VLDB Journal — The International Journal on Very Large Data Bases
Modeling Spatial and Temporal Set-Based Constraints During Conceptual Database Design
Information Systems Research
Journal of Intelligent Information Systems
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Most real-world databases record time-varying information. In such databases, the notion of "the current time," or NOW, occurs naturally and prominently. For example, when capturing the past states of a relation using begin and end time columns, tuples that are part of the current state have some past time as their begin time and NOW as their end time. While the semantics of such variable databases has been described in detail and is well understood, the modification of variable databases remains unexplored. This paper defines the semantics of modifications involving the variable NOW. More specifically, the problems with modifications in the presence of NOW are explored, illustrating that the main problems are with modifications of tuples that reach into the future. The paper defines the semantics of modifications--including insertions, deletions, and updates--of databases without NOW, with NOW, and with values of the type NOW + Δ, where Δ is a non-variable time duration. To accommodate these semantics, three new timestamp values are introduced. Finally, implementation is explored. We show how to represent the variable NOW with columns of standard SQL data types and give a mapping from SQL on NOW-relative data to standard SQL on these columns. The paper thereby completes the semantics, the querying, and the modification of now-relative databases.