Tài liệu Managing time in relational databases- P5 pptx

... whether a point in time is or is not contained in a period of time. Where P and T are, respectively, a point in time and a period of time, and T 1 and T 2 are dates delimiting T using the closed-open ... [aligns] with the time period, then it either [starts] the time period or [finishes] it. Otherwise, the point in time occurs [during] the time period. If the point in...

Ngày tải lên: 24/12/2013, 02:16

... management losing faith in data warehouse projects. As these large projects fell increasingly behind schedule and rose increasingly over budget— something large projects tend to do—the pressure increased to ... concepts. Managing Time in Relational Databases. Doi: 10.1016/B978-0-12-375041-9.00001-7 Copyright # 2010 Elsevier Inc. All rights of reproduction in any form reserved. 11...

Ngày tải lên: 24/12/2013, 02:16

... lacking a standard for the PERIOD datatype, we will continue the practice of defining periods of time in terms of their begin and end points in time. Chapter 3 THE ORIGINS OF ASSERTED VERSIONING: ... record of when business events happen in the real world. In addition, for most business purposes, we assume that a SQL timestamp plus a defined interval of time will result in a s...

Ngày tải lên: 24/12/2013, 02:16

... point in time 1 All effective time relationships exist within shared assertion time. Because this is so important to keep in mind, we will often add the qualifier “within shared assertion time ... Versioning In this variation on versioning, a logical delete flag is included in the version table. It has two values, one marking the row as not being a delete, and the other marking...

Ngày tải lên: 24/12/2013, 02:16

... assertion time and effective time is that two or more effective -time [ intersecting] versions of the same object, in shared assertion time, would vio- late temporal entity integrity, making conflicting ... repre- sentation of a timeline and a snapshot of effective time periods, grouped by common assertion times along that timeline. With the in- line notation, that context, too, is...

Ngày tải lên: 24/12/2013, 02:16

... asserted, what information does it contain that would justify retaining it in the database? Well, in fact, a row in empty assertion time is informative. The informa- tion it contains is information ... along the inflow pipelines whose termination points are production tables, or along the outflow pipelines whose points of origin are those same tables. The points of ori- gin of inflow...

Ngày tải lên: 21/01/2014, 08:20

... 308–309 Pipelines concept of, 268 data, 269 inflow, 268 lost data and, 295–296 outflow, 268 PK. See Primary key Point in time, queries, 382–383 to Period of time, 333–341 to Point in time, 341–342 Point in ... in time 1 [before] Period 1, 338–339, 339f [before] Period 1, inverse of relationship, 338–339 [before] Point in time 2, 341, 342f [before] Point in time 2, inverse...

Ngày tải lên: 26/01/2014, 08:20

... data in which none of that is necessary, a world in which all pipeline datasets are contained in the single table that is their destination or their point of origin. In this world, maintaining ... systems used in education, finance, health care, insurance, manufacturing, retailing and transportation—all industries in which the authors have had consulting experience. In using the...

Ngày tải lên: 24/12/2013, 02:16

... point in time forward to the point in time we are interested in. But the defining feature of reconstructable methods is not the movement of data from off-line to on-line storage. The defining ... any point in time between the starting balance and the current bal- ance by going back to the starting balance and applying trans- actions, in chronological sequence, up to the desire...

Ngày tải lên: 24/12/2013, 02:16

... truth. Temporal Integrity Constraints The three integrity constraints in relational theory are entity integrity, referential integrity and domain integrity. Entity integ- rity insures that the ... effective time than assertion time, we also present an in- line notation for single asserted Managing Time in Relational Databases. Doi: 10.1016/B978-0-12-375041-9.00006-6 Copyright...

Ngày tải lên: 24/12/2013, 02:16