part i  an introduction to twisted

... beginning to the end (for now)    No backing up to read something again (OK to start over) Just as done from the keyboard Writing to a file  Sending output to a file  Done from beginning to end ... fails, it is generally best to stop the program The function exit, halts a program  exit returns its argument to the operating system  exit causes program execution to stop  exit is NOT a member ... flag is an instruction to one of two options ios::fixed is a flag Will be written in fixed-point notation, the way we normally expect to see numbers Calls to setf apply only to the stream named...

Ngày tải lên: 12/09/2012, 22:49

... that history teaches Historians sometimes seem to forget this principle, when they claim to begin and end their books at precise dates We find histories of Europe from 476 to 918, from 1270 to 1492, ... AT FLORENCE VII GIOTTO'S MADONNA VIII HOLY FAMILY BY ANDREA DEL SARTO IV } 264 266 300 342–343 346–347 [Pg 1] INTRODUCTION TO THE HISTORY OF WESTERN EUROPE CHAPTER I THE HISTORICAL POINT OF VIEW ... worse In the towns, if he tried to earn his living, he was forced to mingle with those slaves who were permitted to work for wages and with the freedmen, and he naturally tended to sink to their...

Ngày tải lên: 16/02/2014, 23:20

... way to get round this: goto http://www.google.com/coop/cse/ click "Create a Custom Search Engine" Sign into your Google account give it a name & description, not give it keywords Tell it to search ... you have to encode the table name into hex format to this you can visit this website below http://lab.lowsec.org/Encoder/ type tbl_accounts or the table name you are using into the top box and ... a list of Google search operators http://www.google.com/help/operators.html Open up your custom Google home page and try the following examples (this can be edited to whatever you like) Inurl:php?id=...

Ngày tải lên: 12/07/2014, 19:20

... Third Manifesto, as well as in the book itself As noted earlier, The Third Manifesto also includes a definition of Tutorial D──although, to be frank, there shouldn't be any need to refer to that definition ... have more to say regarding reference [3.3] in particular later in these introductory notes──see the subsection on The Third Manifesto, pages 6-8.) All of that being said, I want to say too that ... into six parts), together with four appendixes, as follows: Part I : Preliminaries An Overview of Database Management Database System Architecture An Introduction to Relational Databases An Introduction...

Ngày tải lên: 06/08/2014, 01:21

... stored file and stored record) ────────── • A stored file is the collection of all currently existing occurrences of one type of stored record • A stored record is a collection of related stored ... objects,* operators, and so forth, that together constitute the abstract machine with which users interact (the objects allow us to model the structure of data, the operators allow us to model its ... relational algebra all apply to relations (possibly to the relations that happen to be the current values of relvars), not to relvars as such; the only operation that applies to relvars specifically...

Ngày tải lên: 06/08/2014, 01:21

... look in SQL?──leads to a brief introduction to nested subqueries) Do not get into details of SQL view updating • START TRANSACTION, COMMIT WORK, ROLLBACK WORK No need to get into the effect of these ... difficult for the reader to be sympathetic [to] Date's criticisms of commercial products." I'd like to respond to this comment I don't think I keep "raising the bar." I certainly try to keep improving ... inevitably, one or two forward references to Chapter 19, but the point I'm trying to make is that the instructor shouldn't be tempted into falling into either: a The trap of thinking that I'd...

Ngày tải lên: 06/08/2014, 01:21

... operator and function To be specific, SQL uses function to mean an operator that's invoked by means of classical functional notation──or an approximation to that notation, at any rate!──and operator ... "databases meet programming languages." It seems to me that the database community ignored this stuff for far too long, to their cost (to ours too, as users) I could certainly quote some nonsense ... a lot 5.6 Type Generators Type generators and corresponding generated many different names Type generators have generic operators and generic constraints with reference to ARRAY (as in the book)...

Ngày tải lên: 06/08/2014, 01:21

... are unordered, left to right Tuples are unordered, top to bottom There are no duplicate tuples Now justify them: Regarding normalization: You should be aware that the history here is somewhat ... implementation is required to assign names to otherwise anonymous columns, but those names are implementation-dependent (they vary from system to system, possibly even from release to release or even ... worth making a separate topic out of them in a live class Relations with No Attributes A gentle introduction to this concept is DEFINITELY worth including as a separate topic Strong logical justification:...

Ngày tải lên: 06/08/2014, 01:21

... Chapter To be specific: Example Example Example Example Example Example 8.3.2 8.3.3 8.3.4 8.3.6 8.3.7 8.3.8 corresponds corresponds corresponds corresponds corresponds corresponds to to to to to to ... directly to the semijoin formulation than to the join one Analogous remarks apply to semidifference Copyright (c) 2003 C J Date page 7.7 Regarding extend: EXTEND is one of the most useful operators ... aggregate operators COUNT, SUM, etc., are first mentioned Observe the important differences (both syntactic and semantic) in the treatment of such operators between Tutorial D and SQL Note too the aggregate...

Ngày tải lên: 06/08/2014, 01:21

... chapter on the subject too, but closer examination revealed that one was using the term to refer to normalization issues solely, while the other two were using it to refer, not to integrity in its ... choose to overlook the fact that the SQL expression results in a table with a left -to- right ordering to its columns) ────────── Here then are SQL expressions corresponding approximately to the ... these result relations a., b., c., then need to be "unioned" together to construct the PART_BILL result The problem is, of course, that there's no way to write n such expressions if the value of...

Ngày tải lên: 06/08/2014, 01:21

... TEACHER to OFFERING, ENROLLMENT to OFFERING, and OFFERING to COURSE are all properly maintained, the referential constraints from TEACHER to COURSE and ENROLLMENT to COURSE will be maintained automatically ... update operation must ever assign to any relvar a value that causes its relvar predicate to evaluate to FALSE The text doesn't say this explicitly, but the rule applies to all relvars, derived as well ... might be to keep the legal city names in a relvar and to use foreign keys to ensure that no other relvar ever includes a city name that isn't one of the legal ones (this approach is likely to be...

Ngày tải lên: 06/08/2014, 01:21

... then we have to face up to questions such as: Does (e.g.) many -to- one mean a relationship that's inherently, necessarily many -to- one, or does it mean one that just happens to be many -to- one because ... applies to INSERT: a Inserting the tuple (s,sn,st,sc,rt) into the join is equivalent to inserting the tuple (s,sn,st,sc) into S (unless it's already present) and inserting the tuple (s,rt) into SR ... fairly self-explanatory (though project is a little trickier than the operators covered prior to this point) Note: The subsection says: "An attempt to update the SC tuple (S1,London) to (S2,London)...

Ngày tải lên: 06/08/2014, 01:21

... way to database design is to a clean logical design first, and then, as a separate and subsequent step, to map that logical design into whatever physical structures the target DBMS happens to ... probably just be skimmed if the instructor doesn't want to get too deeply into formal proofs and the like Indeed, the chapter is included, in part, just to show that there really is some mathematical ... might have a role to play in logical database Copyright (c) 2003 C J Date page 11.1 design──we'll be wanting to get rid of redundancy and therefore we'll be wanting to find ways to get rid of certain...

Ngày tải lên: 06/08/2014, 01:21

... always possible to "spot" a BCNF decomposition──only that it's often possible to so in practical cases To revert to the company database example: As a subsidiary exercise──not much to with normalization ... respect to projection and join Note: "Projection and join" here refers (of course) to those operators as classically understood In Chapter 23, we'll be defining generalized versions of those operators; ... checks the ship -to address */ ; IF everything is OK THEN process the order ; END IF ; If 99 percent of customers actually have only one ship -to address, it would be rather inefficient to put that...

Ngày tải lên: 06/08/2014, 01:21

... well However, it's wrong to think of DK/NF as another step in the progression from 1NF to 2NF to to 5NF, because 5NF is always achievable, but DK/NF is not It's also wrong to say there are "no normal ... remarked) it would be inconsistent to fix the inconsistencies of SQL References and Bibliography Reference [15.1] is recommended as a tutorial introduction to TP monitors References [15.4], [15.7-15.8], ... is straightforward──all that's necessary is to replace the references to FDs and BCNF by analogous references to MVDs and 4NF, thus: Initialize D to contain just R For each non4NF relvar T in...

Ngày tải lên: 06/08/2014, 01:21

... or less self-explanatory Explain the Ingres request modification scheme (relate to view processing, and possibly to integrity enforcement too) Mention audit trails 17.3 Mandatory Access Control ... Self-explanatory 16.5 Deadlock Mostly self-explanatory Explain the Wait-For Graph (it isn't discussed in detail in the text because it's fairly obvious, not to say trivial; see the answer to Exercise ... mention locks, as such, at all──deliberately The idea is to allow an implementation to use some nonlocking scheme if it wants to. ) Explain phantoms and the basic idea (only) of predicate locking Mention...

Ngày tải lên: 06/08/2014, 01:21

... point of the example is to demonstrate the "need" to support MAYBE In other words, if you really want to support 3VL, then you need to support MAYBE (Of course, I don't want to support 3VL at all, ... better to stay in the relational framework and issue separate queries to obtain the separate relations that are the separate results (Or, possibly, to extend the relational algebra to permit operators ... represented in the stored database by two columns, the data column itself and a hidden indicator column, one byte wide, that is stored as a prefix to the actual data column An indicator column value...

Ngày tải lên: 06/08/2014, 01:21

... representation, together with a corresponding selector operator and a corresponding set of THE_ operators (or logical equivalents of same) ■ "=" and ":=" operators ■ Certain type testing operators, to be ... polymorphic operator to execute in response to a particular invocation • The term signature means, loosely, the combination of the name of some operator and the types of the operands to the operator in ... read-only vs update operator distinctions come into play Other approaches don't make these distinctions; they thus allow operators (update as well as readonly operators) to be inherited indiscriminately──with...

Ngày tải lên: 06/08/2014, 01:21

... two-dimensional data into a multi-dimensional form" [Richard Finkelstein] 22.7 Data Mining Data mining is a huge subject books devoted to the topic) to scratch the surface of the sufficient just to go through ... We need to keep historical records showing which suppliers were able to supply which parts when Regarding the first fully temporal ("from -to" ) version, note: a The further revisions to the predicates, ... into it unless asked (and even then I'd take it offline) • The INTERVAL type generator and interval types: generic possrep, generic operators, generic constraints; selectors and "THE_" operators...

Ngày tải lên: 06/08/2014, 01:21

... increases, and it has the potential to give rise to serious human errors What's more, the difficulties would be compounded if we were to discard some of the FROMs and/or TOs by means of projections Such ... etc., etc., began to appear in the research literature However, it isn't always easy to relate such terms and the ideas they represent to familiar database terms and concepts, nor to understand the ... that they aren't applicable only to "logic-based systems"──they can be used in conventional systems too, as the annotation to reference [18.22] explains) Answers to Exercises 24.1 a Valid b Valid...

Ngày tải lên: 06/08/2014, 01:21