Sito in Italia dove è possibile acquistare la consegna acquisto Viagra a buon mercato e di alta qualità in ogni parte del mondo.
TIP: A Temporal Extension to Informix
Computer Science Department, Stanford University
Our research in temporal data warehouses has led us to
with the following datatypes related to time: (1) Chronon
require a relational database system with full SQL as well as
represents a specific point in time, like SQL’s DATE type.
rich temporal support. Most commercial relational database
(2) Span is a duration of time, which can be positive or
systems today support only a DATE type (or its variants).
negative. (3) Instant is either a Chronon or a NOW-relative
A DATE attribute can be used to timestamp a tuple with a
time. A NOW-relative Instant is represented by an offset
specific point in time (e.g., “this patient was taking Prozac
of type Span from the symbol NOW, whose interpretation
as of September 1”). But for general temporal modeling, a
timestamp should be able to consist of multiple time periods
(e.g., “this patient was prescribed Prozac from January to
Instant’s. The first one marks the start of the period and the
April, and then from July to October”). Furthermore, the
second one marks the end. (5) Element is a set of Period’s.
DATE type does not include NOW, a special symbol interpreted
These datatypes allow complex temporal data to be
as the current (transaction) time with many uses in temporal
Consider a table that records the prescription
modeling. Although it is possible to encode NOW and sets
history for patients. We store a patient’s date of birth as
of time periods using DATE as the only type of timestamp,
a Chronon, dosage frequency as a Span, and prescription
doing so can lead to cumbersome queries and inefficient
periods as an Element. The following SQL creates the table:
implementations. An alternative is to use one of the available
temporal database prototypes, but none of them fully meets
(doc CHAR(20),patient CHAR(20),patientDOB Chronon,
the needs of our temporal data warehousing application, as
drug CHAR(20),dosage INT,freq Span,valid Element)
we discuss in the extended version of this description.1
TIP also defines an extensive collection of support rou-
Recently the major relational database vendors have intro-
tines for its datatypes, including casts, arithmetic opera-
duced technologies that allow their systems to be extended
tors (+, -, *, /) and comparison operators (=, <, >, etc.),
with software plugins developed by users or third-party ven-
TIP-defined routines (union, intersect, difference,
dors. Examples include Informix DataBlades
, DB2 Exten-
overlaps, contains, length, etc.), and aggregate func-
, and Oracle Cartridges
. Some time-related extensions
tions (group union, group intersect, etc.). For more
have been developed, such as time-series, spatiotemporal,
details, please refer to the extended version.1 With these sup-
and temporal index extensions. Unfortunately, they do not
port routines, we are able to express many temporal opera-
provide the general-purpose temporal support we need.
tions without adding new language constructs to SQL.
Hence, we built TIP (Temporal
For example, the following query finds all patients who
an extension to the Informix database system based on its
were prescribed Tylenol when they were less than w weeks
DataBlade technology. The TIP DataBlade implements a
old, for input parameter w. In the query, start is a TIP
rich set of datatypes and routines that support modeling
routine that returns the start time of the first period in an
and querying of temporal data. Once the TIP DataBlade
Element. The “::” is Informix’s notation for explicit cast,
is installed, TIP datatypes and routines become available
needed here to convert the string into a Span.
to users as if they were built into the DBMS. Client
applications connect directly to a TIP-enabled database
through a standard API such as ODBC or JDBC, and they
AND start(valid)-patientDOB < ’7days’::Span * :w
manipulate TIP datatypes using C and Java libraries provided
For another example, suppose we want to know who has
by TIP. We have developed a Java client with a powerful
taken Diabeta and Aspirin simultaneously, and exactly when.
graphical user interface for querying and browsing temporal
This temporal self-join query can be expressed as follows:
data. The architecture and implementation of TIP are further
SELECT p1.*, p2.*, intersect(p1.valid, p2.valid)FROM Prescription p1, Prescription p2
described in the extended version,1 which also includes
WHERE p1.drug=’Diabeta’ AND p2.drug=’Aspirin’
screen shots from our temporal browsing interface.
The TIP DataBlade extends the Informix type system
Finally, we compute how long each patient has been on med-
This work was supported by the National Science Foundation under
grant IIS-9811947 and by an Informix Software Grant.
ication using the aggregate function group union, which re-
turns the union of a collection of Element’s.
SELECT patient, length(group union(valid))FROM Prescription GROUP BY patient
Note that TIP does not introduce a new temporal query
language, such as TSQL2. Instead, TIP enables temporalqueries expressed in SQL by providing an extensive set ofbuilt-in datatypes and routines. See the extended version1for more discussion on related and future work.
Resultate-Übersicht «PferdeWoche» Nr. 44 vom 9. November 2011 Eden, 0/0/35.37; 2. Michel Hendrix (NED), Noble, 0/0/36.95; 3. Ben Schro-eder (NED), Floreen, 0/0/38.00; 10. Andreas Erni (SUI), Chairman, CSI4* Lüttich (BEL) 4.-6. November Grand Prix, A, 1 St.: 1. Patrice Delaveau (FRA), Orient Express, 0/0/38.02; CVI-W München (GER) 5./6. November 2. Eugenie Legrand Angot (FRA), Old
Srinivas Deekonda, Ph. D. Department of Chemistry and Biochemistry Objective: To obtain a position in the area of Synthetic Organic /Medicinal Chemistry Highlights: Over fifteen years of research experience in synthetic organic, peptide and medicinal chemistry Strong background in medicinal chemistry, thorough knowledge of organic reaction mechanisms and contemporary synthetic meth