&freetds; User Guide

ISO 8859: What everyone would like to forget +- +-ASCII won, it would seem, but the race goes not to the swift. ASCII has many limitations, the most egregious of which is, it's not much good for anything besides English. It encodes all the letters and punctuation (almost) of the English alphabet, but is useless for German, Russian, and Greek, to say nothing of Chinese. +- +- +-ASCII assigns one byte to every character, but deals with only 7 of the 8 available bits, the range 0-127 (with the high bit always zero). Demand for computers that could display and print languages besides English — even English with em dashes and cent (¢) signs — arrived soon enough, with the Marketing Department way out in front of the propeller heads. The predictable result was an array of 8-bit ASCII encoding standards for a wide variety of alphabets. Eventually, they were standardized (or at least enumerated and documented) by the ISO. These are what our friendly database vendors are referring to when they talk about character sets. More information on this subject can be found at webreference.com. +- +- +- +-The upshot is, there is no uniform standard, no agreement on the meaning of a byte, particularly if that byte's value is greater than 127. Let's say your client machine sends HELLO and your database stores it as 72 69 76 76 79. When another client retrieves that value, it will convert it into human-readable form by applying an encoding standard. If everything's tightly wrapped, it will use the very same encoding that your database used (and the same one you had in mind when you sent it), and that client will also see HELLO. If things are not so tightly wrapped but that client is fortunate enough to be using a similar standard to what you were using, say, ISO 8859-1, he'll still see HELLO. Most languages based on the Roman alphabet can be represented by ISO 8859-1, and are thus interchangeable. Beyond that, things get quickly messy. Greek clients, for one, are not so lucky: there are three ISO 8859 standards for Greek, all mutually incompatible. ++

ISO 8859: What everyone would like to forget + +-For more information, see ISO 8859 Alphabet Soup. Roman Czyborra's site is very informative; take your time there if you don't want your head to spin. +- +- +-Database servers need to know what encoding standard to employ, too. It's not obvious at first, but notions like uppercase and lowercase, trailing blanks, and collation rules all depend on what letter is meant by what number. (Collation even depends on what culture is interpreting the letters.) +- ++ASCII won, it would seem, but the race goes not to the swift. ASCII has many limitations, the most egregious of which is, it's not much good for anything besides English. It encodes all the letters and punctuation (almost) of the English alphabet, but is useless for German, Russian, and Greek, to say nothing of Chinese. ++ ++ASCII assigns one byte to every character, but deals with only 7 of the 8 available bits, the range 0-127 (with the high bit always zero). Demand for computers that could display and print languages besides English — even English with em dashes and cent (¢) signs — arrived soon enough, with the Marketing Department way out in front of the propeller heads. The predictable result was an array of 8-bit ASCII encoding standards for a wide variety of alphabets. Eventually, they were standardized (or at least enumerated and documented) by the ISO. These are what our friendly database vendors are referring to when they talk about character sets. More information on this subject can be found at webreference.com. ++ ++The upshot is, there is no uniform standard, no agreement on the meaning of a byte, particularly if that byte's value is greater than 127. Let's say your client machine sends HELLO and your database stores it as 72 69 76 76 79. When another client retrieves that value, it will convert it into human-readable form by applying an encoding standard. If everything's tightly wrapped, it will use the very same encoding that your database used (and the same one you had in mind when you sent it), and that client will also see HELLO. If things are not so tightly wrapped but that client is fortunate enough to be using a similar standard to what you were using, say, ISO 8859-1, he'll still see HELLO. Most languages based on the Roman alphabet can be represented by ISO 8859-1, and are thus interchangeable. Beyond that, things get quickly messy. Greek clients, for one, are not so lucky: there are three ISO 8859 standards for Greek, all mutually incompatible. ++ ++ For more information, see ISO 8859 Alphabet Soup. Roman Czyborra's site is very informative; take your time there if you don't want your head to spin. ++ ++Database servers need to know what encoding standard to employ, too. It's not obvious at first, but notions like uppercase and lowercase, trailing blanks, and collation rules all depend on what letter is meant by what number. (Collation even depends on what culture is interpreting the letters.) +

Unicode: East meets West +- +-ASCII and its 8-bit cousins are on the way out, and with them the assumption that a character can be represented by a single byte. The new kid on the block is Unicode, similar to but not precisely the same as ISO 10646. Unicode (despite its name) is a set of standards. The most widely implemented is the 16-bit form, called UCS-2. As you might guess, UCS-2 uses two bytes per character, allowing it to encode most characters of most languages. Because most is far from all, there are nascent 32-bit forms, too, but they are neither complete nor in common use. +- +- +-In the same sense that 7-bit ASCII was extended to 8 bits, Unicode extends the most prevalent 8-bit ASCII, ISO 8859-1, to 16 and 32 bits. The first 256 values remain in Unicode as in ISO 8859-1: 65 is still A, except instead of being 8 bits (0x40), it's 16 bits (0x0040). Unlike the 8-bit extensions, Unicode has a unique 1:1 map of numbers to characters, so no language context or character set name is needed to decode a Unicode string. +- +- +-UCS-2 is the system employed by Microsoft NT-based systems. Microsoft database servers store UCS-2 strings in nchar and nvarchar datatypes. Microsoft also designed version 7.0 (and up) of the TDS protocol around UCS-2: all metadata (table names and such) are encoded according to UCS-2 on the wire. +- ++

Unicode: East meets West ++ ++ASCII and its 8-bit cousins are on the way out, and with them the assumption that a character can be represented by a single byte. The new kid on the block is Unicode, similar to but not precisely the same as ISO 10646. Unicode (despite its name) is a set of standards. The most widely implemented is the 16-bit form, called UCS-2. As you might guess, UCS-2 uses two bytes per character, allowing it to encode most characters of most languages. Because most is far from all, there are nascent 32-bit forms, too, but they are neither complete nor in common use. ++ ++In the same sense that 7-bit ASCII was extended to 8 bits, Unicode extends the most prevalent 8-bit ASCII, ISO 8859-1, to 16 and 32 bits. The first 256 values remain in Unicode as in ISO 8859-1: 65 is still A, except instead of being 8 bits (0x40), it's 16 bits (0x0040). Unlike the 8-bit extensions, Unicode has a unique 1:1 map of numbers to characters, so no language context or character set name is needed to decode a Unicode string. ++ ++UCS-2 is the system employed by Microsoft NT-based systems. Microsoft database servers store UCS-2 strings in nchar and nvarchar datatypes. Microsoft also designed version 7.0 (and up) of the TDS protocol around UCS-2: all metadata (table names and such) are encoded according to UCS-2 on the wire. +

Unicode's Pluses and Minuses +- +-You will read from time to time that Unicode is not perfect. Surprise, surprise: it's true. From a linguistic point of view, Unicode is incomplete; in particular, UCS-2 is demonstrably too small (!) to hold all the forms of Chinese ideographs used over the centuries. (It is, however, quite useful and widely employed in representing modern Chinese.) Of more common concern to programmers are Unicode's technical problems, or rather, Unix's technical shortcomings vis-a-vis any encoding more complex than ISO 8859-x. +- +- +-The basic problem, from a programmer's perspective, is the ancient agreement Unix entered into 30 years ago, the ASCII Compact, alluded to earlier. Assumptions about ASCII are littered throughout Unix-like systems, beginning with C's convention of representing strings as arrays of characters ending in a zero. Returning to our HELLO example earlier, C will store HELLO as 72 69 76 76 79 0, in very nice ASCII. Many many parts of the operating system and its associated tools and applications will recognize that as a 5-letter word because it's terminated by a null (zero). In UCS-2 Unicode, though, that same HELLO uses 2 bytes for every character and becomes 72 0 69 0 76 0 76 0 79 0 0 0. Practically the whole OS will think that's a 1-letter word, H. Not a good thing. +- +- +-Even if every OS were magically rid of all ASCII assumptions and C strings, there would still be the problem of Endianism. Technical explanations on the subject are not hard to find. The long and short of it is, given a 16-bit integer (2 bytes), different hardware architectures will store the value differently. Asked to store our friend A, (0x41), for instance, a Sparc processor will put the least significant byte at the higher address (00 41) whereas an Intel processor will put it in the lower address (41 00). Put aside the questions of left, right, and wrong; architectures are a fact of life. Endianism shows up wherever integers are stored and retrieved in heterogeneous environments. +- +- +-The Unicode folks knew about Endianism, of course, and had to address it. A Unicode bytestream is supposed to begin with a byte-order mark. Needless to say, perhaps, many don't. +- ++

Unicode's Pluses and Minuses ++ ++You will read from time to time that Unicode is not perfect. Surprise, surprise: it's true. From a linguistic point of view, Unicode is incomplete; in particular, UCS-2 is demonstrably too small (!) to hold all the forms of Chinese ideographs used over the centuries. (It is, however, quite useful and widely employed in representing modern Chinese.) Of more common concern to programmers are Unicode's technical problems, or rather, Unix's technical shortcomings vis-a-vis any encoding more complex than ISO 8859-x. ++ ++The basic problem, from a programmer's perspective, is the ancient agreement Unix entered into 30 years ago, the ASCII Compact, alluded to earlier. Assumptions about ASCII are littered throughout Unix-like systems, beginning with C's convention of representing strings as arrays of characters ending in a zero. Returning to our HELLO example earlier, C will store HELLO as 72 69 76 76 79 0, in very nice ASCII. Many many parts of the operating system and its associated tools and applications will recognize that as a 5-letter word because it's terminated by a null (zero). In UCS-2 Unicode, though, that same HELLO uses 2 bytes for every character and becomes 72 0 69 0 76 0 76 0 79 0 0 0. Practically the whole OS will think that's a 1-letter word, H. Not a good thing. ++ ++Even if every OS were magically rid of all ASCII assumptions and C strings, there would still be the problem of Endianism. Technical explanations on the subject are not hard to find. The long and short of it is, given a 16-bit integer (2 bytes), different hardware architectures will store the value differently. Asked to store our friend A, (0x41), for instance, a Sparc processor will put the least significant byte at the higher address (00 41) whereas an Intel processor will put it in the lower address (41 00). Put aside the questions of left, right, and wrong; architectures are a fact of life. Endianism shows up wherever integers are stored and retrieved in heterogeneous environments. ++ ++The Unicode folks knew about Endianism, of course, and had to address it. A Unicode bytestream is supposed to begin with a byte-order mark. Needless to say, perhaps, many don't. +

Unicode Transformation Format: UTF-8 +- +-The presence of nulls embedded in character data and of byte order issues make straight Unicode i.e., UCS-2 or UCS-4 hard to work with in a heterogeneous environment. Too many opportunities arise for the data to be truncated or misinterpreted, and too many systems would fail even to transmit such data. In short, when 16-bit data are thrust into a multi-architecture 8-bit world, it frequently bodes ill for the data. +- +- +-To answer that problem, to make Unicode transmissible and unambiguous to most machines, several transformation formats were adopted. Their goals were generally similar: to create a generally recognized format that would unambiguously and safely convey Unicode information between machines and across the Internet. To do that, they sought to remove nulls and endianism from the data stream. The most popular one — practically the only one used — is known as UTF-8. +- +- +-UTF-8 found wide acceptance for many reasons. UTF-8 represents any Unicode character as a combination of 1-4 bytes. The number of bytes required depends on the integer value of the Unicode character, and only one byte is used to represent the old ASCII range (0-127). UTF-8 does not use zero to represent any part of any character (except for the ASCII NUL). In consequence, UTF-8 is efficient with respect to space, has no endianism issues, and embeds no nulls. UTF-8 strings can be treated as plain old ASCII strings. These properties make UTF-8 data relatively easy for systems accustomed to processing ASCII data. +- +- +-Here's a small example showing the difference between UCS-2 and UTF-8. ++

Unicode Transformation Format: UTF-8 ++ ++The presence of nulls embedded in character data and of byte order issues make straight Unicode i.e., UCS-2 or UCS-4 hard to work with in a heterogeneous environment. Too many opportunities arise for the data to be truncated or misinterpreted, and too many systems would fail even to transmit such data. In short, when 16-bit data are thrust into a multi-architecture 8-bit world, it frequently bodes ill for the data. ++ ++To answer that problem, to make Unicode transmissible and unambiguous to most machines, several transformation formats were adopted. Their goals were generally similar: to create a generally recognized format that would unambiguously and safely convey Unicode information between machines and across the Internet. To do that, they sought to remove nulls and endianism from the data stream. The most popular one — practically the only one used — is known as UTF-8. ++ ++UTF-8 found wide acceptance for many reasons. UTF-8 represents any Unicode character as a combination of 1-4 bytes. The number of bytes required depends on the integer value of the Unicode character, and only one byte is used to represent the old ASCII range (0-127). UTF-8 does not use zero to represent any part of any character (except for the ASCII NUL). In consequence, UTF-8 is efficient with respect to space, has no endianism issues, and embeds no nulls. UTF-8 strings can be treated as plain old ASCII strings. These properties make UTF-8 data relatively easy for systems accustomed to processing ASCII data. ++ ++Here's a small example showing the difference between UCS-2 and UTF-8. + +-<quote>HELLO</quote> in UCS-2 and UTF-8 ++ <quote>HELLO</quote> in UCS-2 and UTF-8 + +-$ echo HELLO | iconv -f ascii -t UCS-2 | hexdump -C +-00000000 00 48 00 45 00 4c 00 4c 00 4f 00 0a |.H.E.L.L.O..| +-0000000c +-$ echo HELLO | iconv -f ascii -t utf-8 | hexdump -C +-00000000 48 45 4c 4c 4f 0a |HELLO.| +-00000006 +-$ echo HELLO | hexdump -C +-00000000 48 45 4c 4c 4f 0a |HELLO.| +-00000006 +- +- +-It is the similarity of the last two outputs that makes UTF-8 so attractive. It behaves like ASCII when ASCII's all that's needed. But it lacks ASCII's limitations. +- +-While UTF-8 solves many technical problems, it doesn't magically transform every ASCII-assuming system into a Unicode system. For example, to display Unicode data correctly — even Unicode data in UTF-8 format — the system still needs a suitable font. And it must distinguish the buffer size (and byte count) from the character count. +- ++ $ echo HELLO | iconv -f ascii -t UCS-2 | hexdump -C ++ 00000000 00 48 00 45 00 4c 00 4c 00 4f 00 0a |.H.E.L.L.O..| ++ 0000000c ++ $ echo HELLO | iconv -f ascii -t utf-8 | hexdump -C ++ 00000000 48 45 4c 4c 4f 0a |HELLO.| ++ 00000006 ++ $ echo HELLO | hexdump -C ++ 00000000 48 45 4c 4c 4f 0a |HELLO.| ++ 00000006 ++ ++ It is the similarity of the last two outputs that makes UTF-8 so attractive. It behaves like ASCII when ASCII's all that's needed. But it lacks ASCII's limitations. ++ ++While UTF-8 solves many technical problems, it doesn't magically transform every ASCII-assuming system into a Unicode system. For example, to display Unicode data correctly — even Unicode data in UTF-8 format — the system still needs a suitable font. And it must distinguish the buffer size (and byte count) from the character count. +

Unicode and FreeTDS +- +-Microsoft servers using TDS 7.0 and above (anything since SQL Server 6.5) transmit their data in UCS-2 format (16-bit integers). Because most applications linked to &freetds; are not prepared to deal with UCS-2 data, &freetds; can convert the data to something more acceptable, including ASCII. To do so, it employs an iconv library. &freetds; determines the server's encoding from the TDS protocol and information reported by the server (generally per connection, but in the case of TDS 7.1, per result set column). It discovers the client's encoding in &freetdsconf;. &freetds; will happily convert and convey your data in any single-byte format that iconv can provide. In practice, this normally means some form of ISO 8859-x or UTF-8. +- +- +-At some future time, &freetds; aims to support Unicode and other multi-byte character sets. It does not do so at the current time. +- +- +-Sybase servers, by the way, adhere to a server makes right policy: they transmit their data in whatever character set the client requested at login time. The list of available character sets is fairly short, but includes UTF-8. While FreeTDS could convert Sybase data streams as easily as it does Microsoft data streams, to our knowledge no one is doing so. The Sybase server can perform the conversion itself, making FreeTDS's capability in this regard largely redundant and irrelevant. +- +-

For further information +- +- UTF-8 and Unicode FAQ for Unix/Linux, by Markus Kuhn. As the man says, very comprehensive. +- ASCII: American Standard Code for Information Infiltration, by Tom Jennings. Everything you ever wanted know about ASCII, but didn't know whom to ask. +- A Brief History of Character Codes, by Steven J. Searle. Includes useful references. +- Unicode Home Page. +- +- +- +- ++

Unicode and FreeTDS ++ ++Microsoft servers using TDS 7.0 and above (anything since SQL Server 6.5) transmit their data in UCS-2 format (16-bit integers). Because most applications linked to &freetds; are not prepared to deal with UCS-2 data, &freetds; can convert the data to something more acceptable, including ASCII. To do so, it employs an iconv library. &freetds; determines the server's encoding from the TDS protocol and information reported by the server (generally per connection, but in the case of TDS 7.1, per result set column). It discovers the client's encoding in &freetdsconf;. &freetds; will happily convert and convey your data in any single-byte format that iconv can provide. In practice, this normally means some form of ISO 8859-x or UTF-8. ++ ++At some future time, &freetds; aims to support Unicode and other multi-byte character sets. It does not do so at the current time. ++ ++Sybase servers, by the way, adhere to a server makes right policy: they transmit their data in whatever character set the client requested at login time. The list of available character sets is fairly short, but includes UTF-8. While FreeTDS could convert Sybase data streams as easily as it does Microsoft data streams, to our knowledge no one is doing so. The Sybase server can perform the conversion itself, making FreeTDS's capability in this regard largely redundant and irrelevant. ++

For further information ++ ++ UTF-8 and Unicode FAQ for Unix/Linux, by Markus Kuhn. As the man says, very comprehensive. ++ ASCII: American Standard Code for Information Infiltration, by Tom Jennings. Everything you ever wanted know about ASCII, but didn't know whom to ask. ++ A Brief History of Character Codes, by Steven J. Searle. Includes useful references. ++ Unicode Home Page. ++ ++ ++ +

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If there are multiple Invariant Sections with +- the same name but different contents, make the title of each such +- section unique by adding at the end of it, in parentheses, the +- name of the original author or publisher of that section if known, +- or else a unique number. Make the same adjustment to the section +- titles in the list of Invariant Sections in the license notice of +- the combined work. +- +- In the combination, you must combine any sections entitled +- "History" in the various original documents, forming one section +- entitled "History"; likewise combine any sections entitled +- "Acknowledgements", and any sections entitled "Dedications". You +- must delete all sections entitled "Endorsements." +- +- +- +- COLLECTIONS OF DOCUMENTS +- +- You may make a collection consisting of the Document and +- other documents released under this License, and replace the +- individual copies of this License in the various documents with a +- single copy that is included in the collection, provided that you +- follow the rules of this License for verbatim copying of each of +- the documents in all other respects. +- +- You may extract a single document from such a collection, +- and distribute it individually under this License, provided you +- insert a copy of this License into the extracted document, and +- follow this License in all other respects regarding verbatim +- copying of that document. +- +- +- +- AGGREGATION WITH INDEPENDENT WORKS +- +- A compilation of the Document or its derivatives with other +- separate and independent documents or works, in or on a volume of +- a storage or distribution medium, does not as a whole count as a +- Modified Version of the Document, provided no compilation +- copyright is claimed for the compilation. Such a compilation is +- called an "aggregate", and this License does not apply to the +- other self-contained works thus compiled with the Document, on +- account of their being thus compiled, if they are not themselves +- derivative works of the Document. +- +- If the Cover Text requirement of section 3 is applicable to +- these copies of the Document, then if the Document is less than +- one quarter of the entire aggregate, the Document's Cover Texts +- may be placed on covers that surround only the Document within the +- aggregate. Otherwise they must appear on covers around the whole +- aggregate. +- +- +- +- TRANSLATION +- +- Translation is considered a kind of modification, so you may +- distribute translations of the Document under the terms of section +- 4. Replacing Invariant Sections with translations requires +- special permission from their copyright holders, but you may +- include translations of some or all Invariant Sections in addition +- to the original versions of these Invariant Sections. You may +- include a translation of this License provided that you also +- include the original English version of this License. In case of +- a disagreement between the translation and the original English +- version of this License, the original English version will +- prevail. +- +- +- +- TERMINATION +- +- You may not copy, modify, sublicense, or distribute the +- Document except as expressly provided for under this License. Any +- other attempt to copy, modify, sublicense or distribute the +- Document is void, and will automatically terminate your rights +- under this License. However, parties who have received copies, or +- rights, from you under this License will not have their licenses +- terminated so long as such parties remain in full +- compliance. +- +- +- +- FUTURE REVISIONS OF THIS LICENSE +- +- The Free Software Foundation may publish new, revised +- versions of the GNU Free Documentation License from time to time. +- Such new versions will be similar in spirit to the present +- version, but may differ in detail to address new problems or +- concerns. See http://www.gnu.org/copyleft/. +- +- Each version of the License is given a distinguishing +- version number. If the Document specifies that a particular +- numbered version of this License "or any later version" applies to +- it, you have the option of following the terms and conditions +- either of that specified version or of any later version that has +- been published (not as a draft) by the Free Software Foundation. +- If the Document does not specify a version number of this License, +- you may choose any version ever published (not as a draft) by the +- Free Software Foundation. +- +- +- +- How to use this License for your documents +- +- To use this License in a document you have written, include +- a copy of the License in the document and put the following +- copyright and license notices just after the title page: +- +-
+- Copyright (c) YEAR YOUR NAME. +- Permission is granted to copy, distribute and/or modify this document +- under the terms of the GNU Free Documentation License, Version 1.1 +- or any later version published by the Free Software Foundation; +- with the Invariant Sections being LIST THEIR TITLES, with the +- Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST. +- A copy of the license is included in the section entitled "GNU +- Free Documentation License". +-
++Copyright (C) 2000 Free Software Foundation, Inc. ++ 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA ++ Everyone is permitted to copy and distribute verbatim copies ++ of this license document, but changing it is not allowed. ++

++ ++ ++ PREAMBLE ++ + +- If you have no Invariant Sections, write "with no Invariant +- Sections" instead of saying which ones are invariant. If you have +- no Front-Cover Texts, write "no Front-Cover Texts" instead of +- "Front-Cover Texts being LIST"; likewise for Back-Cover +- Texts. ++The purpose of this License is to make a manual, textbook, ++ or other written document "free" in the sense of freedom: to ++ assure everyone the effective freedom to copy and redistribute it, ++ with or without modifying it, either commercially or ++ noncommercially. Secondarily, this License preserves for the ++ author and publisher a way to get credit for their work, while not ++ being considered responsible for modifications made by ++ others. ++ + +- If your document contains nontrivial examples of program +- code, we recommend releasing these examples in parallel under your +- choice of free software license, such as the GNU General Public +- License, to permit their use in free software. +- ++This License is a kind of "copyleft", which means that ++ derivative works of the document must themselves be free in the ++ same sense. It complements the GNU General Public License, which ++ is a copyleft license designed for free software. ++ + +- ++We have designed this License in order to use it for manuals ++ for free software, because free software needs free documentation: ++ a free program should come with manuals providing the same ++ freedoms that the software does. But this License is not limited ++ to software manuals; it can be used for any textual work, ++ regardless of subject matter or whether it is published as a ++ printed book. We recommend this License principally for works ++ whose purpose is instruction or reference. ++ ++ ++ ++ APPLICABILITY AND DEFINITIONS ++ ++ ++This License applies to any manual or other work that ++ contains a notice placed by the copyright holder saying it can be ++ distributed under the terms of this License. The "Document", ++ below, refers to any such manual or work. Any member of the ++ public is a licensee, and is addressed as "you". ++ ++ ++A "Modified Version" of the Document means any work ++ containing the Document or a portion of it, either copied ++ verbatim, or with modifications and/or translated into another ++ language. ++ ++ ++A "Secondary Section" is a named appendix or a front-matter ++ section of the Document that deals exclusively with the ++ relationship of the publishers or authors of the Document to the ++ Document's overall subject (or to related matters) and contains ++ nothing that could fall directly within that overall subject. ++ (For example, if the Document is in part a textbook of ++ mathematics, a Secondary Section may not explain any mathematics.) ++ The relationship could be a matter of historical connection with ++ the subject or with related matters, or of legal, commercial, ++ philosophical, ethical or political position regarding ++ them. ++ ++ ++The "Invariant Sections" are certain Secondary Sections ++ whose titles are designated, as being those of Invariant Sections, ++ in the notice that says that the Document is released under this ++ License. ++ ++ ++The "Cover Texts" are certain short passages of text that ++ are listed, as Front-Cover Texts or Back-Cover Texts, in the ++ notice that says that the Document is released under this ++ License. ++ ++ ++A "Transparent" copy of the Document means a ++ machine-readable copy, represented in a format whose specification ++ is available to the general public, whose contents can be viewed ++ and edited directly and straightforwardly with generic text ++ editors or (for images composed of pixels) generic paint programs ++ or (for drawings) some widely available drawing editor, and that ++ is suitable for input to text formatters or for automatic ++ translation to a variety of formats suitable for input to text ++ formatters. A copy made in an otherwise Transparent file format ++ whose markup has been designed to thwart or discourage subsequent ++ modification by readers is not Transparent. A copy that is not ++ "Transparent" is called "Opaque". ++ ++ ++Examples of suitable formats for Transparent copies include ++ plain ASCII without markup, Texinfo input format, LaTeX input ++ format, SGML or XML using a publicly available DTD, and ++ standard-conforming simple HTML designed for human modification. ++ Opaque formats include PostScript, PDF, proprietary formats that ++ can be read and edited only by proprietary word processors, SGML ++ or XML for which the DTD and/or processing tools are not generally ++ available, and the machine-generated HTML produced by some word ++ processors for output purposes only. ++ ++ ++The "Title Page" means, for a printed book, the title page ++ itself, plus such following pages as are needed to hold, legibly, ++ the material this License requires to appear in the title page. ++ For works in formats which do not have any title page as such, ++ "Title Page" means the text near the most prominent appearance of ++ the work's title, preceding the beginning of the body of the ++ text. ++ ++ ++ ++ VERBATIM COPYING ++ ++ ++You may copy and distribute the Document in any medium, ++ either commercially or noncommercially, provided that this ++ License, the copyright notices, and the license notice saying this ++ License applies to the Document are reproduced in all copies, and ++ that you add no other conditions whatsoever to those of this ++ License. You may not use technical measures to obstruct or ++ control the reading or further copying of the copies you make or ++ distribute. However, you may accept compensation in exchange for ++ copies. If you distribute a large enough number of copies you ++ must also follow the conditions in section 3. ++ ++ ++You may also lend copies, under the same conditions stated ++ above, and you may publicly display copies. ++ ++ ++ ++ COPYING IN QUANTITY ++ ++ ++If you publish printed copies of the Document numbering more ++ than 100, and the Document's license notice requires Cover Texts, ++ you must enclose the copies in covers that carry, clearly and ++ legibly, all these Cover Texts: Front-Cover Texts on the front ++ cover, and Back-Cover Texts on the back cover. Both covers must ++ also clearly and legibly identify you as the publisher of these ++ copies. The front cover must present the full title with all ++ words of the title equally prominent and visible. You may add ++ other material on the covers in addition. Copying with changes ++ limited to the covers, as long as they preserve the title of the ++ Document and satisfy these conditions, can be treated as verbatim ++ copying in other respects. ++ ++ ++If the required texts for either cover are too voluminous to ++ fit legibly, you should put the first ones listed (as many as fit ++ reasonably) on the actual cover, and continue the rest onto ++ adjacent pages. ++ ++ ++If you publish or distribute Opaque copies of the Document ++ numbering more than 100, you must either include a ++ machine-readable Transparent copy along with each Opaque copy, or ++ state in or with each Opaque copy a publicly-accessible ++ computer-network location containing a complete Transparent copy ++ of the Document, free of added material, which the general ++ network-using public has access to download anonymously at no ++ charge using public-standard network protocols. If you use the ++ latter option, you must take reasonably prudent steps, when you ++ begin distribution of Opaque copies in quantity, to ensure that ++ this Transparent copy will remain thus accessible at the stated ++ location until at least one year after the last time you ++ distribute an Opaque copy (directly or through your agents or ++ retailers) of that edition to the public. ++ ++ ++It is requested, but not required, that you contact the ++ authors of the Document well before redistributing any large ++ number of copies, to give them a chance to provide you with an ++ updated version of the Document. ++ ++ ++ ++ MODIFICATIONS ++ ++ ++You may copy and distribute a Modified Version of the ++ Document under the conditions of sections 2 and 3 above, provided ++ that you release the Modified Version under precisely this ++ License, with the Modified Version filling the role of the ++ Document, thus licensing distribution and modification of the ++ Modified Version to whoever possesses a copy of it. In addition, ++ you must do these things in the Modified Version: ++ ++ ++ Use in the Title Page ++ (and on the covers, if any) a title distinct from that of the ++ Document, and from those of previous versions (which should, if ++ there were any, be listed in the History section of the ++ Document). You may use the same title as a previous version if ++ the original publisher of that version gives permission. ++ ++ ++ List on the Title Page, ++ as authors, one or more persons or entities responsible for ++ authorship of the modifications in the Modified Version, ++ together with at least five of the principal authors of the ++ Document (all of its principal authors, if it has less than ++ five). ++ ++ ++ State on the Title page ++ the name of the publisher of the Modified Version, as the ++ publisher. ++ ++ ++ Preserve all the ++ copyright notices of the Document. ++ ++ ++ Add an appropriate ++ copyright notice for your modifications adjacent to the other ++ copyright notices. ++ ++ ++ Include, immediately ++ after the copyright notices, a license notice giving the public ++ permission to use the Modified Version under the terms of this ++ License, in the form shown in the Addendum below. ++ ++ ++ Preserve in that license ++ notice the full lists of Invariant Sections and required Cover ++ Texts given in the Document's license notice. ++ ++ ++ Include an unaltered ++ copy of this License. ++ ++ ++ Preserve the section ++ entitled "History", and its title, and add to it an item stating ++ at least the title, year, new authors, and publisher of the ++ Modified Version as given on the Title Page. If there is no ++ section entitled "History" in the Document, create one stating ++ the title, year, authors, and publisher of the Document as given ++ on its Title Page, then add an item describing the Modified ++ Version as stated in the previous sentence. ++ ++ ++ Preserve the network ++ location, if any, given in the Document for public access to a ++ Transparent copy of the Document, and likewise the network ++ locations given in the Document for previous versions it was ++ based on. These may be placed in the "History" section. You ++ may omit a network location for a work that was published at ++ least four years before the Document itself, or if the original ++ publisher of the version it refers to gives permission. ++ ++ ++ In any section entitled ++ "Acknowledgements" or "Dedications", preserve the section's ++ title, and preserve in the section all the substance and tone of ++ each of the contributor acknowledgements and/or dedications ++ given therein. ++ ++ ++ Preserve all the ++ Invariant Sections of the Document, unaltered in their text and ++ in their titles. Section numbers or the equivalent are not ++ considered part of the section titles. ++ ++ ++ Delete any section ++ entitled "Endorsements". Such a section may not be included in ++ the Modified Version. ++ ++ ++ Do not retitle any ++ existing section as "Endorsements" or to conflict in title with ++ any Invariant Section. ++ ++ ++ ++ ++If the Modified Version includes new front-matter sections ++ or appendices that qualify as Secondary Sections and contain no ++ material copied from the Document, you may at your option ++ designate some or all of these sections as invariant. To do this, ++ add their titles to the list of Invariant Sections in the Modified ++ Version's license notice. These titles must be distinct from any ++ other section titles. ++ ++ ++You may add a section entitled "Endorsements", provided it ++ contains nothing but endorsements of your Modified Version by ++ various parties--for example, statements of peer review or that ++ the text has been approved by an organization as the authoritative ++ definition of a standard. ++ ++ ++You may add a passage of up to five words as a Front-Cover ++ Text, and a passage of up to 25 words as a Back-Cover Text, to the ++ end of the list of Cover Texts in the Modified Version. Only one ++ passage of Front-Cover Text and one of Back-Cover Text may be ++ added by (or through arrangements made by) any one entity. If the ++ Document already includes a cover text for the same cover, ++ previously added by you or by arrangement made by the same entity ++ you are acting on behalf of, you may not add another; but you may ++ replace the old one, on explicit permission from the previous ++ publisher that added the old one. ++ ++ ++The author(s) and publisher(s) of the Document do not by ++ this License give permission to use their names for publicity for ++ or to assert or imply endorsement of any Modified Version. ++ ++ ++ ++ COMBINING DOCUMENTS ++ ++ ++You may combine the Document with other documents released ++ under this License, under the terms defined in section 4 above for ++ modified versions, provided that you include in the combination ++ all of the Invariant Sections of all of the original documents, ++ unmodified, and list them all as Invariant Sections of your ++ combined work in its license notice. ++ ++ ++The combined work need only contain one copy of this ++ License, and multiple identical Invariant Sections may be replaced ++ with a single copy. If there are multiple Invariant Sections with ++ the same name but different contents, make the title of each such ++ section unique by adding at the end of it, in parentheses, the ++ name of the original author or publisher of that section if known, ++ or else a unique number. Make the same adjustment to the section ++ titles in the list of Invariant Sections in the license notice of ++ the combined work. ++ ++ ++In the combination, you must combine any sections entitled ++ "History" in the various original documents, forming one section ++ entitled "History"; likewise combine any sections entitled ++ "Acknowledgements", and any sections entitled "Dedications". You ++ must delete all sections entitled "Endorsements." ++ ++ ++ ++ COLLECTIONS OF DOCUMENTS ++ ++ ++You may make a collection consisting of the Document and ++ other documents released under this License, and replace the ++ individual copies of this License in the various documents with a ++ single copy that is included in the collection, provided that you ++ follow the rules of this License for verbatim copying of each of ++ the documents in all other respects. ++ ++ ++You may extract a single document from such a collection, ++ and distribute it individually under this License, provided you ++ insert a copy of this License into the extracted document, and ++ follow this License in all other respects regarding verbatim ++ copying of that document. ++ ++ ++ ++ AGGREGATION WITH INDEPENDENT WORKS ++ ++ ++A compilation of the Document or its derivatives with other ++ separate and independent documents or works, in or on a volume of ++ a storage or distribution medium, does not as a whole count as a ++ Modified Version of the Document, provided no compilation ++ copyright is claimed for the compilation. Such a compilation is ++ called an "aggregate", and this License does not apply to the ++ other self-contained works thus compiled with the Document, on ++ account of their being thus compiled, if they are not themselves ++ derivative works of the Document. ++ ++ ++If the Cover Text requirement of section 3 is applicable to ++ these copies of the Document, then if the Document is less than ++ one quarter of the entire aggregate, the Document's Cover Texts ++ may be placed on covers that surround only the Document within the ++ aggregate. Otherwise they must appear on covers around the whole ++ aggregate. ++ ++ ++ ++ TRANSLATION ++ ++ ++Translation is considered a kind of modification, so you may ++ distribute translations of the Document under the terms of section ++ 4. Replacing Invariant Sections with translations requires ++ special permission from their copyright holders, but you may ++ include translations of some or all Invariant Sections in addition ++ to the original versions of these Invariant Sections. You may ++ include a translation of this License provided that you also ++ include the original English version of this License. In case of ++ a disagreement between the translation and the original English ++ version of this License, the original English version will ++ prevail. ++ ++ ++ ++ TERMINATION ++ ++ ++You may not copy, modify, sublicense, or distribute the ++ Document except as expressly provided for under this License. Any ++ other attempt to copy, modify, sublicense or distribute the ++ Document is void, and will automatically terminate your rights ++ under this License. However, parties who have received copies, or ++ rights, from you under this License will not have their licenses ++ terminated so long as such parties remain in full ++ compliance. ++ ++ ++ ++ FUTURE REVISIONS OF THIS LICENSE ++ ++ ++The Free Software Foundation may publish new, revised ++ versions of the GNU Free Documentation License from time to time. ++ Such new versions will be similar in spirit to the present ++ version, but may differ in detail to address new problems or ++ concerns. See http://www.gnu.org/copyleft/. ++ ++ ++Each version of the License is given a distinguishing ++ version number. If the Document specifies that a particular ++ numbered version of this License "or any later version" applies to ++ it, you have the option of following the terms and conditions ++ either of that specified version or of any later version that has ++ been published (not as a draft) by the Free Software Foundation. ++ If the Document does not specify a version number of this License, ++ you may choose any version ever published (not as a draft) by the ++ Free Software Foundation. ++ ++ ++ ++ How to use this License for your documents ++ ++ ++To use this License in a document you have written, include ++ a copy of the License in the document and put the following ++ copyright and license notices just after the title page: ++ ++

Copyright (c) YEAR YOUR NAME. ++ Permission is granted to copy, distribute and/or modify this document ++ under the terms of the GNU Free Documentation License, Version 1.1 ++ or any later version published by the Free Software Foundation; ++ with the Invariant Sections being LIST THEIR TITLES, with the ++ Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST. ++ A copy of the license is included in the section entitled "GNU ++ Free Documentation License". ++

++ ++ ++If you have no Invariant Sections, write "with no Invariant ++ Sections" instead of saying which ones are invariant. If you have ++ no Front-Cover Texts, write "no Front-Cover Texts" instead of ++ "Front-Cover Texts being LIST"; likewise for Back-Cover ++ Texts. ++ ++ ++If your document contains nontrivial examples of program ++ code, we recommend releasing these examples in parallel under your ++ choice of free software license, such as the GNU General Public ++ License, to permit their use in free software. ++ ++ ++ +