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1 | \input texinfo @c -*- texinfo -*- |
2 | @c %**start of header | |
ac97a16b | 3 | @setfilename ../../info/nxml-mode |
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4 | @settitle nXML Mode |
5 | @c %**end of header | |
6 | ||
20234d96 | 7 | @copying |
20234d96 | 8 | This manual documents nxml-mode, an Emacs major mode for editing |
867d4bb3 | 9 | XML with RELAX NG support. |
20234d96 | 10 | |
114f9c96 | 11 | Copyright @copyright{} 2007, 2008, 2009, 2010 Free Software Foundation, Inc. |
20234d96 GM |
12 | |
13 | @quotation | |
14 | Permission is granted to copy, distribute and/or modify this document | |
6a2c4aec | 15 | under the terms of the GNU Free Documentation License, Version 1.3 or |
20234d96 GM |
16 | any later version published by the Free Software Foundation; with no |
17 | Invariant Sections, with the Front-Cover texts being ``A GNU | |
18 | Manual,'' and with the Back-Cover Texts as in (a) below. A copy of the | |
19 | license is included in the section entitled ``GNU Free Documentation | |
20 | License'' in the Emacs manual. | |
21 | ||
6f093307 GM |
22 | (a) The FSF's Back-Cover Text is: ``You have the freedom to copy and |
23 | modify this GNU manual. Buying copies from the FSF supports it in | |
24 | developing GNU and promoting software freedom.'' | |
20234d96 GM |
25 | |
26 | This document is part of a collection distributed under the GNU Free | |
27 | Documentation License. If you want to distribute this document | |
28 | separately from the collection, you can do so by adding a copy of the | |
29 | license to the document, as described in section 6 of the license. | |
30 | @end quotation | |
31 | @end copying | |
32 | ||
8cd39fb3 MH |
33 | @dircategory Emacs |
34 | @direntry | |
7aa579d9 | 35 | * nXML Mode: (nxml-mode). XML editing mode with RELAX NG support. |
8cd39fb3 MH |
36 | @end direntry |
37 | ||
38 | @node Top | |
39 | @top nXML Mode | |
40 | ||
5dc584b5 KB |
41 | @insertcopying |
42 | ||
43 | This manual is not yet complete. | |
8cd39fb3 MH |
44 | |
45 | @menu | |
867d4bb3 JB |
46 | * Completion:: |
47 | * Inserting end-tags:: | |
48 | * Paragraphs:: | |
49 | * Outlining:: | |
50 | * Locating a schema:: | |
51 | * DTDs:: | |
52 | * Limitations:: | |
8cd39fb3 MH |
53 | @end menu |
54 | ||
55 | @node Completion | |
56 | @chapter Completion | |
57 | ||
58 | Apart from real-time validation, the most important feature that | |
59 | nxml-mode provides for assisting in document creation is "completion". | |
60 | Completion assists the user in inserting characters at point, based on | |
61 | knowledge of the schema and on the contents of the buffer before | |
62 | point. | |
63 | ||
64 | The traditional GNU Emacs key combination for completion in a | |
65 | buffer is @kbd{M-@key{TAB}}. However, many window systems | |
66 | and window managers use this key combination themselves (typically for | |
67 | switching between windows) and do not pass it to applications. It's | |
68 | hard to find key combinations in GNU Emacs that are both easy to type | |
69 | and not taken by something else. @kbd{C-@key{RET}} (i.e. | |
70 | pressing the Enter or Return key, while the Ctrl key is held down) is | |
71 | available. It won't be available on a traditional terminal (because | |
72 | it is indistinguishable from Return), but it will work with a window | |
73 | system. Therefore we adopt the following solution by default: use | |
74 | @kbd{C-@key{RET}} when there's a window system and | |
75 | @kbd{M-@key{TAB}} when there's not. In the following, I | |
76 | will assume that a window system is being used and will therefore | |
77 | refer to @kbd{C-@key{RET}}. | |
78 | ||
79 | Completion works by examining the symbol preceding point. This | |
80 | is the symbol to be completed. The symbol to be completed may be the | |
81 | empty. Completion considers what symbols starting with the symbol to | |
82 | be completed would be valid replacements for the symbol to be | |
83 | completed, given the schema and the contents of the buffer before | |
84 | point. These symbols are the possible completions. An example may | |
85 | make this clearer. Suppose the buffer looks like this (where @point{} | |
86 | indicates point): | |
87 | ||
88 | @example | |
89 | <html xmlns="http://www.w3.org/1999/xhtml"> | |
90 | <h@point{} | |
91 | @end example | |
92 | ||
93 | @noindent | |
94 | and the schema is XHTML. In this context, the symbol to be completed | |
95 | is @samp{h}. The possible completions consist of just | |
96 | @samp{head}. Another example, is | |
97 | ||
98 | @example | |
99 | <html xmlns="http://www.w3.org/1999/xhtml"> | |
100 | <head> | |
101 | <@point{} | |
102 | @end example | |
103 | ||
104 | @noindent | |
105 | In this case, the symbol to be completed is empty, and the possible | |
106 | completions are @samp{base}, @samp{isindex}, | |
107 | @samp{link}, @samp{meta}, @samp{script}, | |
108 | @samp{style}, @samp{title}. Another example is: | |
109 | ||
110 | @example | |
111 | <html xmlns="@point{} | |
112 | @end example | |
113 | ||
114 | @noindent | |
115 | In this case, the symbol to be completed is empty, and the possible | |
116 | completions are just @samp{http://www.w3.org/1999/xhtml}. | |
117 | ||
118 | When you type @kbd{C-@key{RET}}, what happens depends | |
119 | on what the set of possible completions are. | |
120 | ||
121 | @itemize @bullet | |
122 | @item | |
123 | If the set of completions is empty, nothing | |
124 | happens. | |
125 | @item | |
126 | If there is one possible completion, then that completion is | |
127 | inserted, together with any following characters that are | |
128 | required. For example, in this case: | |
129 | ||
130 | @example | |
131 | <html xmlns="http://www.w3.org/1999/xhtml"> | |
132 | <@point{} | |
133 | @end example | |
134 | ||
135 | @noindent | |
136 | @kbd{C-@key{RET}} will yield | |
137 | ||
138 | @example | |
139 | <html xmlns="http://www.w3.org/1999/xhtml"> | |
140 | <head@point{} | |
141 | @end example | |
142 | @item | |
143 | If there is more than one possible completion, but all | |
144 | possible completions share a common non-empty prefix, then that prefix | |
145 | is inserted. For example, suppose the buffer is: | |
146 | ||
147 | @example | |
148 | <html x@point{} | |
149 | @end example | |
150 | ||
151 | @noindent | |
152 | The symbol to be completed is @samp{x}. The possible completions | |
153 | are @samp{xmlns} and @samp{xml:lang}. These share a | |
154 | common prefix of @samp{xml}. Thus, @kbd{C-@key{RET}} | |
155 | will yield: | |
156 | ||
157 | @example | |
158 | <html xml@point{} | |
159 | @end example | |
160 | ||
161 | @noindent | |
162 | Typically, you would do @kbd{C-@key{RET}} again, which would | |
163 | have the result described in the next item. | |
164 | @item | |
165 | If there is more than one possible completion, but the | |
166 | possible completions do not share a non-empty prefix, then Emacs will | |
167 | prompt you to input the symbol in the minibuffer, initializing the | |
168 | minibuffer with the symbol to be completed, and popping up a buffer | |
169 | showing the possible completions. You can now input the symbol to be | |
170 | inserted. The symbol you input will be inserted in the buffer instead | |
171 | of the symbol to be completed. Emacs will then insert any required | |
172 | characters after the symbol. For example, if it contains: | |
173 | ||
174 | @example | |
175 | <html xml@point{} | |
176 | @end example | |
177 | ||
178 | @noindent | |
179 | Emacs will prompt you in the minibuffer with | |
180 | ||
181 | @example | |
182 | Attribute: xml@point{} | |
183 | @end example | |
184 | ||
185 | @noindent | |
186 | and the buffer showing possible completions will contain | |
187 | ||
188 | @example | |
189 | Possible completions are: | |
b1fbbb32 | 190 | xml:lang xmlns |
8cd39fb3 MH |
191 | @end example |
192 | ||
193 | @noindent | |
194 | If you input @kbd{xmlns}, the result will be: | |
195 | ||
196 | @example | |
197 | <html xmlns="@point{} | |
198 | @end example | |
199 | ||
200 | @noindent | |
201 | (If you do @kbd{C-@key{RET}} again, the namespace URI will | |
202 | be inserted. Should that happen automatically?) | |
203 | @end itemize | |
204 | ||
205 | @node Inserting end-tags | |
206 | @chapter Inserting end-tags | |
207 | ||
208 | The main redundancy in XML syntax is end-tags. nxml-mode provides | |
209 | several ways to make it easier to enter end-tags. You can use all of | |
210 | these without a schema. | |
211 | ||
212 | You can use @kbd{C-@key{RET}} after @samp{</} | |
213 | to complete the rest of the end-tag. | |
214 | ||
215 | @kbd{C-c C-f} inserts an end-tag for the element containing | |
216 | point. This command is useful when you want to input the start-tag, | |
217 | then input the content and finally input the end-tag. The @samp{f} | |
218 | is mnemonic for finish. | |
219 | ||
220 | If you want to keep tags balanced and input the end-tag at the | |
221 | same time as the start-tag, before inputting the content, then you can | |
222 | use @kbd{C-c C-i}. This inserts a @samp{>}, then inserts | |
223 | the end-tag and leaves point before the end-tag. @kbd{C-c C-b} | |
224 | is similar but more convenient for block-level elements: it puts the | |
225 | start-tag, point and the end-tag on successive lines, appropriately | |
226 | indented. The @samp{i} is mnemonic for inline and the | |
227 | @samp{b} is mnemonic for block. | |
228 | ||
229 | Finally, you can customize nxml-mode so that @kbd{/} | |
230 | automatically inserts the rest of the end-tag when it occurs after | |
231 | @samp{<}, by doing | |
232 | ||
233 | @display | |
234 | @kbd{M-x customize-variable @key{RET} nxml-slash-auto-complete-flag @key{RET}} | |
235 | @end display | |
236 | ||
237 | @noindent | |
238 | and then following the instructions in the displayed buffer. | |
239 | ||
240 | @node Paragraphs | |
241 | @chapter Paragraphs | |
242 | ||
243 | Emacs has several commands that operate on paragraphs, most | |
244 | notably @kbd{M-q}. nXML mode redefines these to work in a way | |
245 | that is useful for XML. The exact rules that are used to find the | |
246 | beginning and end of a paragraph are complicated; they are designed | |
247 | mainly to ensure that @kbd{M-q} does the right thing. | |
248 | ||
249 | A paragraph consists of one or more complete, consecutive lines. | |
250 | A group of lines is not considered a paragraph unless it contains some | |
251 | non-whitespace characters between tags or inside comments. A blank | |
252 | line separates paragraphs. A single tag on a line by itself also | |
253 | separates paragraphs. More precisely, if one tag together with any | |
254 | leading and trailing whitespace completely occupy one or more lines, | |
255 | then those lines will not be included in any paragraph. | |
256 | ||
257 | A start-tag at the beginning of the line (possibly indented) may | |
258 | be treated as starting a paragraph. Similarly, an end-tag at the end | |
259 | of the line may be treated as ending a paragraph. The following rules | |
260 | are used to determine whether such a tag is in fact treated as a | |
261 | paragraph boundary: | |
262 | ||
263 | @itemize @bullet | |
264 | @item | |
265 | If the schema does not allow text at that point, then it | |
266 | is a paragraph boundary. | |
267 | @item | |
268 | If the end-tag corresponding to the start-tag is not at | |
269 | the end of its line, or the start-tag corresponding to the end-tag is | |
270 | not at the beginning of its line, then it is not a paragraph | |
271 | boundary. For example, in | |
272 | ||
273 | @example | |
274 | <p>This is a paragraph with an | |
275 | <emph>emphasized</emph> phrase. | |
276 | @end example | |
277 | ||
278 | @noindent | |
279 | the @samp{<emph>} start-tag would not be considered as | |
280 | starting a paragraph, because its corresponding end-tag is not at the | |
281 | end of the line. | |
282 | @item | |
283 | If there is text that is a sibling in element tree, then | |
284 | it is not a paragraph boundary. For example, in | |
285 | ||
286 | @example | |
287 | <p>This is a paragraph with an | |
288 | <emph>emphasized phrase that takes one source line</emph> | |
289 | @end example | |
290 | ||
291 | @noindent | |
292 | the @samp{<emph>} start-tag would not be considered as | |
293 | starting a paragraph, even though its end-tag is at the end of its | |
294 | line, because there the text @samp{This is a paragraph with an} | |
295 | is a sibling of the @samp{emph} element. | |
296 | @item | |
297 | Otherwise, it is a paragraph boundary. | |
298 | @end itemize | |
299 | ||
300 | @node Outlining | |
301 | @chapter Outlining | |
302 | ||
303 | nXML mode allows you to display all or part of a buffer as an | |
304 | outline, in a similar way to Emacs' outline mode. An outline in nXML | |
305 | mode is based on recognizing two kinds of element: sections and | |
306 | headings. There is one heading for every section and one section for | |
307 | every heading. A section contains its heading as or within its first | |
308 | child element. A section also contains its subordinate sections (its | |
309 | subsections). The text content of a section consists of anything in a | |
310 | section that is neither a subsection nor a heading. | |
311 | ||
312 | Note that this is a different model from that used by XHTML. | |
313 | nXML mode's outline support will not be useful for XHTML unless you | |
314 | adopt a convention of adding a @code{div} to enclose each | |
315 | section, rather than having sections implicitly delimited by different | |
316 | @code{h@var{n}} elements. This limitation may be removed | |
317 | in a future version. | |
318 | ||
319 | The variable @code{nxml-section-element-name-regexp} gives | |
320 | a regexp for the local names (i.e. the part of the name following any | |
321 | prefix) of section elements. The variable | |
322 | @code{nxml-heading-element-name-regexp} gives a regexp for the | |
323 | local names of heading elements. For an element to be recognized | |
324 | as a section | |
325 | ||
326 | @itemize @bullet | |
327 | @item | |
328 | its start-tag must occur at the beginning of a line | |
329 | (possibly indented); | |
330 | @item | |
331 | its local name must match | |
332 | @code{nxml-section-element-name-regexp}; | |
333 | @item | |
334 | either its first child element or a descendant of that | |
335 | first child element must have a local name that matches | |
336 | @code{nxml-heading-element-name-regexp}; the first such element | |
337 | is treated as the section's heading. | |
338 | @end itemize | |
339 | ||
340 | @noindent | |
341 | You can customize these variables using @kbd{M-x | |
342 | customize-variable}. | |
343 | ||
344 | There are three possible outline states for a section: | |
345 | ||
346 | @itemize @bullet | |
347 | @item | |
348 | normal, showing everything, including its heading, text | |
349 | content and subsections; each subsection is displayed according to the | |
350 | state of that subsection; | |
351 | @item | |
352 | showing just its heading, with both its text content and | |
353 | its subsections hidden; all subsections are hidden regardless of their | |
354 | state; | |
355 | @item | |
356 | showing its heading and its subsections, with its text | |
357 | content hidden; each subsection is displayed according to the state of | |
358 | that subsection. | |
359 | @end itemize | |
360 | ||
361 | In the last two states, where the text content is hidden, the | |
362 | heading is displayed specially, in an abbreviated form. An element | |
363 | like this: | |
364 | ||
365 | @example | |
366 | <section> | |
367 | <title>Food</title> | |
368 | <para>There are many kinds of food.</para> | |
369 | </section> | |
370 | @end example | |
371 | ||
372 | @noindent | |
373 | would be displayed on a single line like this: | |
374 | ||
375 | @example | |
376 | <-section>Food...</> | |
377 | @end example | |
378 | ||
379 | @noindent | |
380 | If there are hidden subsections, then a @code{+} will be used | |
381 | instead of a @code{-} like this: | |
382 | ||
383 | @example | |
384 | <+section>Food...</> | |
385 | @end example | |
386 | ||
387 | @noindent | |
388 | If there are non-hidden subsections, then the section will instead be | |
389 | displayed like this: | |
390 | ||
391 | @example | |
392 | <-section>Food... | |
393 | <-section>Delicious Food...</> | |
394 | <-section>Distasteful Food...</> | |
395 | </-section> | |
396 | @end example | |
397 | ||
398 | @noindent | |
399 | The heading is always displayed with an indent that corresponds to its | |
400 | depth in the outline, even it is not actually indented in the buffer. | |
401 | The variable @code{nxml-outline-child-indent} controls how much | |
402 | a subheading is indented with respect to its parent heading when the | |
403 | heading is being displayed specially. | |
404 | ||
405 | Commands to change the outline state of sections are bound to | |
406 | key sequences that start with @kbd{C-c C-o} (@kbd{o} is | |
407 | mnemonic for outline). The third and final key has been chosen to be | |
408 | consistent with outline mode. In the following descriptions | |
409 | current section means the section containing point, or, more precisely, | |
410 | the innermost section containing the character immediately following | |
411 | point. | |
412 | ||
413 | @itemize @bullet | |
414 | @item | |
415 | @kbd{C-c C-o C-a} shows all sections in the buffer | |
416 | normally. | |
417 | @item | |
418 | @kbd{C-c C-o C-t} hides the text content | |
419 | of all sections in the buffer. | |
420 | @item | |
421 | @kbd{C-c C-o C-c} hides the text content | |
422 | of the current section. | |
423 | @item | |
424 | @kbd{C-c C-o C-e} shows the text content | |
425 | of the current section. | |
426 | @item | |
427 | @kbd{C-c C-o C-d} hides the text content | |
428 | and subsections of the current section. | |
429 | @item | |
867d4bb3 | 430 | @kbd{C-c C-o C-s} shows the current section |
8cd39fb3 MH |
431 | and all its direct and indirect subsections normally. |
432 | @item | |
433 | @kbd{C-c C-o C-k} shows the headings of the | |
434 | direct and indirect subsections of the current section. | |
435 | @item | |
436 | @kbd{C-c C-o C-l} hides the text content of the | |
437 | current section and of its direct and indirect | |
438 | subsections. | |
439 | @item | |
440 | @kbd{C-c C-o C-i} shows the headings of the | |
441 | direct subsections of the current section. | |
442 | @item | |
443 | @kbd{C-c C-o C-o} hides as much as possible without | |
444 | hiding the current section's text content; the headings of ancestor | |
445 | sections of the current section and their child section sections will | |
446 | not be hidden. | |
447 | @end itemize | |
448 | ||
449 | When a heading is displayed specially, you can use | |
450 | @key{RET} in that heading to show the text content of the section | |
451 | in the same way as @kbd{C-c C-o C-e}. | |
452 | ||
453 | You can also use the mouse to change the outline state: | |
454 | @kbd{S-mouse-2} hides the text content of a section in the same | |
455 | way as@kbd{C-c C-o C-c}; @kbd{mouse-2} on a specially | |
456 | displayed heading shows the text content of the section in the same | |
457 | way as @kbd{C-c C-o C-e}; @kbd{mouse-1} on a specially | |
458 | displayed start-tag toggles the display of subheadings on and | |
459 | off. | |
460 | ||
461 | The outline state for each section is stored with the first | |
462 | character of the section (as a text property). Every command that | |
463 | changes the outline state of any section updates the display of the | |
464 | buffer so that each section is displayed correctly according to its | |
465 | outline state. If the section structure is subsequently changed, then | |
466 | it is possible for the display to no longer correctly reflect the | |
467 | stored outline state. @kbd{C-c C-o C-r} can be used to refresh | |
468 | the display so it is correct again. | |
469 | ||
470 | @node Locating a schema | |
471 | @chapter Locating a schema | |
472 | ||
473 | nXML mode has a configurable set of rules to locate a schema for | |
474 | the file being edited. The rules are contained in one or more schema | |
475 | locating files, which are XML documents. | |
476 | ||
477 | The variable @samp{rng-schema-locating-files} specifies | |
478 | the list of the file-names of schema locating files that nXML mode | |
479 | should use. The order of the list is significant: when file | |
480 | @var{x} occurs in the list before file @var{y} then rules | |
481 | from file @var{x} have precedence over rules from file | |
482 | @var{y}. A filename specified in | |
483 | @samp{rng-schema-locating-files} may be relative. If so, it will | |
484 | be resolved relative to the document for which a schema is being | |
485 | located. It is not an error if relative file-names in | |
867d4bb3 | 486 | @samp{rng-schema-locating-files} do not exist. You can use |
8cd39fb3 MH |
487 | @kbd{M-x customize-variable @key{RET} rng-schema-locating-files |
488 | @key{RET}} to customize the list of schema locating | |
489 | files. | |
490 | ||
491 | By default, @samp{rng-schema-locating-files} list has two | |
492 | members: @samp{schemas.xml}, and | |
493 | @samp{@var{dist-dir}/schema/schemas.xml} where | |
494 | @samp{@var{dist-dir}} is the directory containing the nXML | |
495 | distribution. The first member will cause nXML mode to use a file | |
496 | @samp{schemas.xml} in the same directory as the document being | |
497 | edited if such a file exist. The second member contains rules for the | |
498 | schemas that are included with the nXML distribution. | |
499 | ||
500 | @menu | |
867d4bb3 JB |
501 | * Commands for locating a schema:: |
502 | * Schema locating files:: | |
8cd39fb3 MH |
503 | @end menu |
504 | ||
505 | @node Commands for locating a schema | |
506 | @section Commands for locating a schema | |
507 | ||
508 | The command @kbd{C-c C-s C-w} will tell you what schema | |
509 | is currently being used. | |
510 | ||
511 | The rules for locating a schema are applied automatically when | |
512 | you visit a file in nXML mode. However, if you have just created a new | |
513 | file and the schema cannot be inferred from the file-name, then this | |
514 | will not locate the right schema. In this case, you should insert the | |
40572be6 | 515 | start-tag of the root element and then use the command @kbd{C-c C-s |
8cd39fb3 MH |
516 | C-a}, which reapplies the rules based on the current content of |
517 | the document. It is usually not necessary to insert the complete | |
518 | start-tag; often just @samp{<@var{name}} is | |
519 | enough. | |
520 | ||
521 | If you want to use a schema that has not yet been added to the | |
522 | schema locating files, you can use the command @kbd{C-c C-s C-f} | |
b6f9df0f | 523 | to manually select the file containing the schema for the document in |
8cd39fb3 MH |
524 | current buffer. Emacs will read the file-name of the schema from the |
525 | minibuffer. After reading the file-name, Emacs will ask whether you | |
526 | wish to add a rule to a schema locating file that persistently | |
527 | associates the document with the selected schema. The rule will be | |
528 | added to the first file in the list specified | |
529 | @samp{rng-schema-locating-files}; it will create the file if | |
530 | necessary, but will not create a directory. If the variable | |
531 | @samp{rng-schema-locating-files} has not been customized, this | |
532 | means that the rule will be added to the file @samp{schemas.xml} | |
533 | in the same directory as the document being edited. | |
534 | ||
535 | The command @kbd{C-c C-s C-t} allows you to select a schema by | |
536 | specifying an identifier for the type of the document. The schema | |
537 | locating files determine the available type identifiers and what | |
538 | schema is used for each type identifier. This is useful when it is | |
539 | impossible to infer the right schema from either the file-name or the | |
540 | content of the document, even though the schema is already in the | |
541 | schema locating file. A situation in which this can occur is when | |
542 | there are multiple variants of a schema where all valid documents have | |
543 | the same document element. For example, XHTML has Strict and | |
544 | Transitional variants. In a situation like this, a schema locating file | |
545 | can define a type identifier for each variant. As with @kbd{C-c | |
546 | C-s C-f}, Emacs will ask whether you wish to add a rule to a schema | |
547 | locating file that persistently associates the document with the | |
548 | specified type identifier. | |
549 | ||
550 | The command @kbd{C-c C-s C-l} adds a rule to a schema | |
551 | locating file that persistently associates the document with | |
552 | the schema that is currently being used. | |
553 | ||
554 | @node Schema locating files | |
555 | @section Schema locating files | |
556 | ||
557 | Each schema locating file specifies a list of rules. The rules | |
558 | from each file are appended in order. To locate a schema each rule is | |
559 | applied in turn until a rule matches. The first matching rule is then | |
560 | used to determine the schema. | |
561 | ||
562 | Schema locating files are designed to be useful for other | |
563 | applications that need to locate a schema for a document. In fact, | |
564 | there is nothing specific to locating schemas in the design; it could | |
565 | equally well be used for locating a stylesheet. | |
566 | ||
567 | @menu | |
867d4bb3 JB |
568 | * Schema locating file syntax basics:: |
569 | * Using the document's URI to locate a schema:: | |
570 | * Using the document element to locate a schema:: | |
571 | * Using type identifiers in schema locating files:: | |
572 | * Using multiple schema locating files:: | |
8cd39fb3 MH |
573 | @end menu |
574 | ||
575 | @node Schema locating file syntax basics | |
576 | @subsection Schema locating file syntax basics | |
577 | ||
578 | There is a schema for schema locating files in the file | |
579 | @samp{locate.rnc} in the schema directory. Schema locating | |
580 | files must be valid with respect to this schema. | |
581 | ||
582 | The document element of a schema locating file must be | |
583 | @samp{locatingRules} and the namespace URI must be | |
584 | @samp{http://thaiopensource.com/ns/locating-rules/1.0}. The | |
585 | children of the document element specify rules. The order of the | |
586 | children is the same as the order of the rules. Here's a complete | |
587 | example of a schema locating file: | |
588 | ||
589 | @example | |
590 | <?xml version="1.0"?> | |
591 | <locatingRules xmlns="http://thaiopensource.com/ns/locating-rules/1.0"> | |
592 | <namespace ns="http://www.w3.org/1999/xhtml" uri="xhtml.rnc"/> | |
593 | <documentElement localName="book" uri="docbook.rnc"/> | |
594 | </locatingRules> | |
595 | @end example | |
596 | ||
597 | @noindent | |
598 | This says to use the schema @samp{xhtml.rnc} for a document with | |
599 | namespace @samp{http://www.w3.org/1999/xhtml}, and to use the | |
600 | schema @samp{docbook.rnc} for a document whose local name is | |
601 | @samp{book}. If the document element had both a namespace URI | |
602 | of @samp{http://www.w3.org/1999/xhtml} and a local name of | |
603 | @samp{book}, then the matching rule that comes first will be | |
604 | used and so the schema @samp{xhtml.rnc} would be used. There is | |
605 | no precedence between different types of rule; the first matching rule | |
606 | of any type is used. | |
607 | ||
608 | As usual with XML-related technologies, resources are identified | |
609 | by URIs. The @samp{uri} attribute identifies the schema by | |
610 | specifying the URI. The URI may be relative. If so, it is resolved | |
611 | relative to the URI of the schema locating file that contains | |
612 | attribute. This means that if the value of @samp{uri} attribute | |
613 | does not contain a @samp{/}, then it will refer to a filename in | |
614 | the same directory as the schema locating file. | |
615 | ||
616 | @node Using the document's URI to locate a schema | |
617 | @subsection Using the document's URI to locate a schema | |
618 | ||
619 | A @samp{uri} rule locates a schema based on the URI of the | |
620 | document. The @samp{uri} attribute specifies the URI of the | |
621 | schema. The @samp{resource} attribute can be used to specify | |
622 | the schema for a particular document. For example, | |
623 | ||
624 | @example | |
625 | <uri resource="spec.xml" uri="docbook.rnc"/> | |
626 | @end example | |
627 | ||
628 | @noindent | |
867d4bb3 | 629 | specifies that the schema for @samp{spec.xml} is |
8cd39fb3 MH |
630 | @samp{docbook.rnc}. |
631 | ||
632 | The @samp{pattern} attribute can be used instead of the | |
633 | @samp{resource} attribute to specify the schema for any document | |
634 | whose URI matches a pattern. The pattern has the same syntax as an | |
635 | absolute or relative URI except that the path component of the URI can | |
636 | use a @samp{*} character to stand for zero or more characters | |
637 | within a path segment (i.e. any character other @samp{/}). | |
638 | Typically, the URI pattern looks like a relative URI, but, whereas a | |
639 | relative URI in the @samp{resource} attribute is resolved into a | |
640 | particular absolute URI using the base URI of the schema locating | |
641 | file, a relative URI pattern matches if it matches some number of | |
642 | complete path segments of the document's URI ending with the last path | |
643 | segment of the document's URI. For example, | |
644 | ||
645 | @example | |
646 | <uri pattern="*.xsl" uri="xslt.rnc"/> | |
647 | @end example | |
648 | ||
649 | @noindent | |
650 | specifies that the schema for documents with a URI whose path ends | |
651 | with @samp{.xsl} is @samp{xslt.rnc}. | |
652 | ||
653 | A @samp{transformURI} rule locates a schema by | |
654 | transforming the URI of the document. The @samp{fromPattern} | |
655 | attribute specifies a URI pattern with the same meaning as the | |
656 | @samp{pattern} attribute of the @samp{uri} element. The | |
657 | @samp{toPattern} attribute is a URI pattern that is used to | |
658 | generate the URI of the schema. Each @samp{*} in the | |
659 | @samp{toPattern} is replaced by the string that matched the | |
660 | corresponding @samp{*} in the @samp{fromPattern}. The | |
661 | resulting string is appended to the initial part of the document's URI | |
662 | that was not explicitly matched by the @samp{fromPattern}. The | |
663 | rule matches only if the transformed URI identifies an existing | |
664 | resource. For example, the rule | |
665 | ||
666 | @example | |
667 | <transformURI fromPattern="*.xml" toPattern="*.rnc"/> | |
668 | @end example | |
669 | ||
670 | @noindent | |
671 | would transform the URI @samp{file:///home/jjc/docs/spec.xml} | |
672 | into the URI @samp{file:///home/jjc/docs/spec.rnc}. Thus, this | |
673 | rule specifies that to locate a schema for a document | |
674 | @samp{@var{foo}.xml}, Emacs should test whether a file | |
675 | @samp{@var{foo}.rnc} exists in the same directory as | |
676 | @samp{@var{foo}.xml}, and, if so, should use it as the | |
677 | schema. | |
678 | ||
679 | @node Using the document element to locate a schema | |
680 | @subsection Using the document element to locate a schema | |
681 | ||
682 | A @samp{documentElement} rule locates a schema based on | |
683 | the local name and prefix of the document element. For example, a rule | |
684 | ||
685 | @example | |
686 | <documentElement prefix="xsl" localName="stylesheet" uri="xslt.rnc"/> | |
687 | @end example | |
688 | ||
689 | @noindent | |
690 | specifies that when the name of the document element is | |
691 | @samp{xsl:stylesheet}, then @samp{xslt.rnc} should be used | |
692 | as the schema. Either the @samp{prefix} or | |
693 | @samp{localName} attribute may be omitted to allow any prefix or | |
694 | local name. | |
695 | ||
696 | A @samp{namespace} rule locates a schema based on the | |
697 | namespace URI of the document element. For example, a rule | |
698 | ||
699 | @example | |
700 | <namespace ns="http://www.w3.org/1999/XSL/Transform" uri="xslt.rnc"/> | |
701 | @end example | |
702 | ||
703 | @noindent | |
704 | specifies that when the namespace URI of the document is | |
705 | @samp{http://www.w3.org/1999/XSL/Transform}, then | |
706 | @samp{xslt.rnc} should be used as the schema. | |
707 | ||
708 | @node Using type identifiers in schema locating files | |
709 | @subsection Using type identifiers in schema locating files | |
710 | ||
711 | Type identifiers allow a level of indirection in locating the | |
712 | schema for a document. Instead of associating the document directly | |
713 | with a schema URI, the document is associated with a type identifier, | |
714 | which is in turn associated with a schema URI. nXML mode does not | |
715 | constrain the format of type identifiers. They can be simply strings | |
716 | without any formal structure or they can be public identifiers or | |
717 | URIs. Note that these type identifiers have nothing to do with the | |
718 | DOCTYPE declaration. When comparing type identifiers, whitespace is | |
719 | normalized in the same way as with the @samp{xsd:token} | |
720 | datatype: leading and trailing whitespace is stripped; other sequences | |
721 | of whitespace are normalized to a single space character. | |
722 | ||
723 | Each of the rules described in previous sections that uses a | |
724 | @samp{uri} attribute to specify a schema, can instead use a | |
725 | @samp{typeId} attribute to specify a type identifier. The type | |
726 | identifier can be associated with a URI using a @samp{typeId} | |
727 | element. For example, | |
728 | ||
729 | @example | |
730 | <locatingRules xmlns="http://thaiopensource.com/ns/locating-rules/1.0"> | |
731 | <namespace ns="http://www.w3.org/1999/xhtml" typeId="XHTML"/> | |
732 | <typeId id="XHTML" typeId="XHTML Strict"/> | |
733 | <typeId id="XHTML Strict" uri="xhtml-strict.rnc"/> | |
734 | <typeId id="XHTML Transitional" uri="xhtml-transitional.rnc"/> | |
735 | </locatingRules> | |
736 | @end example | |
737 | ||
738 | @noindent | |
739 | declares three type identifiers @samp{XHTML} (representing the | |
740 | default variant of XHTML to be used), @samp{XHTML Strict} and | |
741 | @samp{XHTML Transitional}. Such a schema locating file would | |
742 | use @samp{xhtml-strict.rnc} for a document whose namespace is | |
743 | @samp{http://www.w3.org/1999/xhtml}. But it is considerably | |
744 | more flexible than a schema locating file that simply specified | |
745 | ||
746 | @example | |
747 | <namespace ns="http://www.w3.org/1999/xhtml" uri="xhtml-strict.rnc"/> | |
748 | @end example | |
749 | ||
750 | @noindent | |
751 | A user can easily use @kbd{C-c C-s C-t} to select between XHTML | |
752 | Strict and XHTML Transitional. Also, a user can easily add a catalog | |
753 | ||
754 | @example | |
755 | <locatingRules xmlns="http://thaiopensource.com/ns/locating-rules/1.0"> | |
756 | <typeId id="XHTML" typeId="XHTML Transitional"/> | |
757 | </locatingRules> | |
758 | @end example | |
759 | ||
760 | @noindent | |
761 | that makes the default variant of XHTML be XHTML Transitional. | |
762 | ||
763 | @node Using multiple schema locating files | |
764 | @subsection Using multiple schema locating files | |
765 | ||
766 | The @samp{include} element includes rules from another | |
767 | schema locating file. The behavior is exactly as if the rules from | |
768 | that file were included in place of the @samp{include} element. | |
769 | Relative URIs are resolved into absolute URIs before the inclusion is | |
770 | performed. For example, | |
771 | ||
772 | @example | |
773 | <include rules="../rules.xml"/> | |
774 | @end example | |
775 | ||
776 | @noindent | |
777 | includes the rules from @samp{rules.xml}. | |
778 | ||
779 | The process of locating a schema takes as input a list of schema | |
780 | locating files. The rules in all these files and in the files they | |
781 | include are resolved into a single list of rules, which are applied | |
782 | strictly in order. Sometimes this order is not what is needed. | |
783 | For example, suppose you have two schema locating files, a private | |
784 | file | |
785 | ||
786 | @example | |
787 | <locatingRules xmlns="http://thaiopensource.com/ns/locating-rules/1.0"> | |
788 | <namespace ns="http://www.w3.org/1999/xhtml" uri="xhtml.rnc"/> | |
789 | </locatingRules> | |
790 | @end example | |
791 | ||
792 | @noindent | |
793 | followed by a public file | |
794 | ||
795 | @example | |
796 | <locatingRules xmlns="http://thaiopensource.com/ns/locating-rules/1.0"> | |
797 | <transformURI pathSuffix=".xml" replacePathSuffix=".rnc"/> | |
798 | <namespace ns="http://www.w3.org/1999/XSL/Transform" typeId="XSLT"/> | |
799 | </locatingRules> | |
800 | @end example | |
801 | ||
802 | @noindent | |
803 | The effect of these two files is that the XHTML @samp{namespace} | |
804 | rule takes precedence over the @samp{transformURI} rule, which | |
805 | is almost certainly not what is needed. This can be solved by adding | |
806 | an @samp{applyFollowingRules} to the private file. | |
807 | ||
808 | @example | |
809 | <locatingRules xmlns="http://thaiopensource.com/ns/locating-rules/1.0"> | |
810 | <applyFollowingRules ruleType="transformURI"/> | |
811 | <namespace ns="http://www.w3.org/1999/xhtml" uri="xhtml.rnc"/> | |
812 | </locatingRules> | |
813 | @end example | |
814 | ||
815 | @node DTDs | |
816 | @chapter DTDs | |
817 | ||
818 | nxml-mode is designed to support the creation of standalone XML | |
819 | documents that do not depend on a DTD. Although it is common practice | |
820 | to insert a DOCTYPE declaration referencing an external DTD, this has | |
821 | undesirable side-effects. It means that the document is no longer | |
822 | self-contained. It also means that different XML parsers may interpret | |
823 | the document in different ways, since the XML Recommendation does not | |
824 | require XML parsers to read the DTD. With DTDs, it was impractical to | |
825 | get validation without using an external DTD or reference to an | |
826 | parameter entity. With RELAX NG and other schema languages, you can | |
827 | simulataneously get the benefits of validation and standalone XML | |
828 | documents. Therefore, I recommend that you do not reference an | |
829 | external DOCTYPE in your XML documents. | |
830 | ||
831 | One problem is entities for characters. Typically, as well as | |
832 | providing validation, DTDs also provide a set of character entities | |
833 | for documents to use. Schemas cannot provide this functionality, | |
834 | because schema validation happens after XML parsing. The recommended | |
835 | solution is to either use the Unicode characters directly, or, if this | |
836 | is impractical, use character references. nXML mode supports this by | |
837 | providing commands for entering characters and character references | |
838 | using the Unicode names, and can display the glyph corresponding to a | |
839 | character reference. | |
840 | ||
841 | @node Limitations | |
842 | @chapter Limitations | |
843 | ||
844 | nXML mode has some limitations: | |
845 | ||
846 | @itemize @bullet | |
847 | @item | |
848 | DTD support is limited. Internal parsed general entities declared | |
849 | in the internal subset are supported provided they do not contain | |
850 | elements. Other usage of DTDs is ignored. | |
851 | @item | |
852 | The restrictions on RELAX NG schemas in section 7 of the RELAX NG | |
853 | specification are not enforced. | |
8cd39fb3 MH |
854 | @end itemize |
855 | ||
856 | @bye | |
ab4c34c6 MB |
857 | |
858 | @ignore | |
859 | arch-tag: 3b6e8ac2-ae8d-4f38-bd43-ce9f80be04d6 | |
860 | @end ignore |