Tài liệu Managing time in relational databases- P14 ppt

... located, and a timeline along which we hold various beliefs. Data in con- ventional tables is “pinned”, along both timelines, to the moving point in time we call “the present” and which, in this book, ... think is a true statement of what that object is like. Whatever semantic differences there may be between accepting, agreeing, assenting, asserting, believing, claiming, knowing, say...

Ngày tải lên: 21/01/2014, 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 ... useful by integrating them into larger patterns. But he has worked in the world of business IT for his entire career. And in that world, theory is fine, but it must xx PREFACE MANAGING...

Ngày tải lên: 24/12/2013, 02:16

... Versioning Asserted Versioning Framework (AVF) xxii PREFACE row the query author is interested in, two of those components being time periods that may or may not intersect in various ways. Continuing ... 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...

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

... [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 time [ excludes] the time period, ... clock ticks. This point in time may either [ intersect] or [exclude] the time period. If the point in time [ intersects] the time period, it also [fills] and [ oc...

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 ... effective -time contiguous series of rows, starting with a row representing that object in the time period T 10 –T 11 and continuing with rows representing the object in time peri...

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 ... within shared assertion time, even a single effective -time clock tick included in another version of that object already in the table. Most physical transactions against bi-...

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

... type of time within which points in time and/or periods of time are ordered. Components: type, point in time, time period. temporal entity integrity Mechanics: (i) for episodes, the constraint that ... 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 Po...

Ngày tải lên: 26/01/2014, 08:20

... 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 ... waiting for the data, and the decisions delayed until the data becomes available. In an increasingly fast-paced business world, the opportunity cost of delays in accessing data is incre...

Ngày tải lên: 24/12/2013, 02:16