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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 | |
acaf905b | 11 | Copyright @copyright{} 2007-2012 |
d3dfb185 | 12 | Free Software Foundation, Inc. |
20234d96 GM |
13 | |
14 | @quotation | |
15 | Permission is granted to copy, distribute and/or modify this document | |
6a2c4aec | 16 | under the terms of the GNU Free Documentation License, Version 1.3 or |
20234d96 GM |
17 | any later version published by the Free Software Foundation; with no |
18 | Invariant Sections, with the Front-Cover texts being ``A GNU | |
19 | Manual,'' and with the Back-Cover Texts as in (a) below. A copy of the | |
20 | license is included in the section entitled ``GNU Free Documentation | |
21 | License'' in the Emacs manual. | |
22 | ||
6f093307 GM |
23 | (a) The FSF's Back-Cover Text is: ``You have the freedom to copy and |
24 | modify this GNU manual. Buying copies from the FSF supports it in | |
25 | developing GNU and promoting software freedom.'' | |
20234d96 GM |
26 | |
27 | This document is part of a collection distributed under the GNU Free | |
28 | Documentation License. If you want to distribute this document | |
29 | separately from the collection, you can do so by adding a copy of the | |
30 | license to the document, as described in section 6 of the license. | |
31 | @end quotation | |
32 | @end copying | |
33 | ||
0c973505 | 34 | @dircategory Emacs editing modes |
8cd39fb3 | 35 | @direntry |
7aa579d9 | 36 | * nXML Mode: (nxml-mode). XML editing mode with RELAX NG support. |
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37 | @end direntry |
38 | ||
39 | @node Top | |
40 | @top nXML Mode | |
41 | ||
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42 | @insertcopying |
43 | ||
44 | This manual is not yet complete. | |
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45 | |
46 | @menu | |
d3dfb185 | 47 | * Introduction:: |
867d4bb3 JB |
48 | * Completion:: |
49 | * Inserting end-tags:: | |
50 | * Paragraphs:: | |
51 | * Outlining:: | |
52 | * Locating a schema:: | |
53 | * DTDs:: | |
54 | * Limitations:: | |
8cd39fb3 MH |
55 | @end menu |
56 | ||
d3dfb185 GM |
57 | @node Introduction |
58 | @chapter Introduction | |
59 | ||
60 | nXML mode is an Emacs major-mode for editing XML documents. It supports | |
61 | editing well-formed XML documents, and provides schema-sensitive editing | |
62 | using RELAX NG Compact Syntax. To get started, visit a file containing an | |
63 | XML document, and, if necessary, use @kbd{M-x nxml-mode} to switch to nXML | |
64 | mode. By default, @code{auto-mode-alist} and @code{magic-fallback-alist} | |
65 | put buffers in nXML mode if they have recognizable XML content or file | |
66 | extensions. You may wish to customize the settings, for example to | |
67 | recognize different file extensions. | |
68 | ||
69 | Once in nXML mode, you can type @kbd{C-h m} for basic information on the | |
70 | mode. | |
71 | ||
72 | The @file{etc/nxml} directory in the Emacs distribution contains some data | |
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73 | files used by nXML mode, and includes two files (@file{test-valid.xml} and |
74 | @file{test-invalid.xml}) that provide examples of valid and invalid XML | |
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75 | documents. |
76 | ||
77 | To get validation and schema-sensitive editing, you need a RELAX NG Compact | |
78 | Syntax (RNC) schema for your document (@pxref{Locating a schema}). The | |
79 | @file{etc/schema} directory includes some schemas for popular document | |
80 | types. See @url{http://relaxng.org/} for more information on RELAX NG. | |
81 | You can use the @samp{Trang} program from | |
82 | @url{http://www.thaiopensource.com/relaxng/trang.html} to | |
83 | automatically create RNC schemas. This program can: | |
84 | ||
85 | @itemize @bullet | |
86 | @item | |
87 | infer an RNC schema from an instance document; | |
88 | @item | |
89 | convert a DTD to an RNC schema; | |
90 | @item | |
91 | convert a RELAX NG XML syntax schema to an RNC schema. | |
92 | @end itemize | |
93 | ||
94 | @noindent To convert a RELAX NG XML syntax (@samp{.rng}) schema to a RNC | |
95 | one, you can also use the XSLT stylesheet from | |
96 | @url{http://www.pantor.com/download.html}. | |
97 | ||
98 | To convert a W3C XML Schema to an RNC schema, you need first to convert it | |
4d47208a | 99 | to RELAX NG XML syntax using the RELAX NG converter tool @code{rngconv} |
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100 | (built on top of MSV). See @url{https://github.com/kohsuke/msv} |
101 | and @url{https://msv.dev.java.net/}. | |
102 | ||
103 | For historical discussions only, see the mailing list archives at | |
104 | @url{http://groups.yahoo.com/group/emacs-nxml-mode/}. Please make all new | |
105 | discussions on the @samp{help-gnu-emacs} and @samp{emacs-devel} mailing | |
106 | lists. Report any bugs with @kbd{M-x report-emacs-bug}. | |
107 | ||
108 | ||
8cd39fb3 MH |
109 | @node Completion |
110 | @chapter Completion | |
111 | ||
112 | Apart from real-time validation, the most important feature that | |
113 | nxml-mode provides for assisting in document creation is "completion". | |
114 | Completion assists the user in inserting characters at point, based on | |
115 | knowledge of the schema and on the contents of the buffer before | |
116 | point. | |
117 | ||
118 | The traditional GNU Emacs key combination for completion in a | |
119 | buffer is @kbd{M-@key{TAB}}. However, many window systems | |
120 | and window managers use this key combination themselves (typically for | |
121 | switching between windows) and do not pass it to applications. It's | |
122 | hard to find key combinations in GNU Emacs that are both easy to type | |
123 | and not taken by something else. @kbd{C-@key{RET}} (i.e. | |
124 | pressing the Enter or Return key, while the Ctrl key is held down) is | |
125 | available. It won't be available on a traditional terminal (because | |
126 | it is indistinguishable from Return), but it will work with a window | |
127 | system. Therefore we adopt the following solution by default: use | |
128 | @kbd{C-@key{RET}} when there's a window system and | |
129 | @kbd{M-@key{TAB}} when there's not. In the following, I | |
130 | will assume that a window system is being used and will therefore | |
131 | refer to @kbd{C-@key{RET}}. | |
132 | ||
133 | Completion works by examining the symbol preceding point. This | |
134 | is the symbol to be completed. The symbol to be completed may be the | |
135 | empty. Completion considers what symbols starting with the symbol to | |
136 | be completed would be valid replacements for the symbol to be | |
137 | completed, given the schema and the contents of the buffer before | |
138 | point. These symbols are the possible completions. An example may | |
139 | make this clearer. Suppose the buffer looks like this (where @point{} | |
140 | indicates point): | |
141 | ||
142 | @example | |
143 | <html xmlns="http://www.w3.org/1999/xhtml"> | |
144 | <h@point{} | |
145 | @end example | |
146 | ||
147 | @noindent | |
148 | and the schema is XHTML. In this context, the symbol to be completed | |
149 | is @samp{h}. The possible completions consist of just | |
150 | @samp{head}. Another example, is | |
151 | ||
152 | @example | |
153 | <html xmlns="http://www.w3.org/1999/xhtml"> | |
154 | <head> | |
155 | <@point{} | |
156 | @end example | |
157 | ||
158 | @noindent | |
159 | In this case, the symbol to be completed is empty, and the possible | |
160 | completions are @samp{base}, @samp{isindex}, | |
161 | @samp{link}, @samp{meta}, @samp{script}, | |
162 | @samp{style}, @samp{title}. Another example is: | |
163 | ||
164 | @example | |
165 | <html xmlns="@point{} | |
166 | @end example | |
167 | ||
168 | @noindent | |
169 | In this case, the symbol to be completed is empty, and the possible | |
170 | completions are just @samp{http://www.w3.org/1999/xhtml}. | |
171 | ||
172 | When you type @kbd{C-@key{RET}}, what happens depends | |
173 | on what the set of possible completions are. | |
174 | ||
175 | @itemize @bullet | |
176 | @item | |
177 | If the set of completions is empty, nothing | |
178 | happens. | |
179 | @item | |
180 | If there is one possible completion, then that completion is | |
181 | inserted, together with any following characters that are | |
182 | required. For example, in this case: | |
183 | ||
184 | @example | |
185 | <html xmlns="http://www.w3.org/1999/xhtml"> | |
186 | <@point{} | |
187 | @end example | |
188 | ||
189 | @noindent | |
190 | @kbd{C-@key{RET}} will yield | |
191 | ||
192 | @example | |
193 | <html xmlns="http://www.w3.org/1999/xhtml"> | |
194 | <head@point{} | |
195 | @end example | |
196 | @item | |
197 | If there is more than one possible completion, but all | |
198 | possible completions share a common non-empty prefix, then that prefix | |
199 | is inserted. For example, suppose the buffer is: | |
200 | ||
201 | @example | |
202 | <html x@point{} | |
203 | @end example | |
204 | ||
205 | @noindent | |
206 | The symbol to be completed is @samp{x}. The possible completions | |
207 | are @samp{xmlns} and @samp{xml:lang}. These share a | |
208 | common prefix of @samp{xml}. Thus, @kbd{C-@key{RET}} | |
209 | will yield: | |
210 | ||
211 | @example | |
212 | <html xml@point{} | |
213 | @end example | |
214 | ||
215 | @noindent | |
216 | Typically, you would do @kbd{C-@key{RET}} again, which would | |
217 | have the result described in the next item. | |
218 | @item | |
219 | If there is more than one possible completion, but the | |
220 | possible completions do not share a non-empty prefix, then Emacs will | |
221 | prompt you to input the symbol in the minibuffer, initializing the | |
222 | minibuffer with the symbol to be completed, and popping up a buffer | |
223 | showing the possible completions. You can now input the symbol to be | |
224 | inserted. The symbol you input will be inserted in the buffer instead | |
225 | of the symbol to be completed. Emacs will then insert any required | |
226 | characters after the symbol. For example, if it contains: | |
227 | ||
228 | @example | |
229 | <html xml@point{} | |
230 | @end example | |
231 | ||
232 | @noindent | |
233 | Emacs will prompt you in the minibuffer with | |
234 | ||
235 | @example | |
236 | Attribute: xml@point{} | |
237 | @end example | |
238 | ||
239 | @noindent | |
240 | and the buffer showing possible completions will contain | |
241 | ||
242 | @example | |
243 | Possible completions are: | |
b1fbbb32 | 244 | xml:lang xmlns |
8cd39fb3 MH |
245 | @end example |
246 | ||
247 | @noindent | |
248 | If you input @kbd{xmlns}, the result will be: | |
249 | ||
250 | @example | |
251 | <html xmlns="@point{} | |
252 | @end example | |
253 | ||
254 | @noindent | |
255 | (If you do @kbd{C-@key{RET}} again, the namespace URI will | |
256 | be inserted. Should that happen automatically?) | |
257 | @end itemize | |
258 | ||
259 | @node Inserting end-tags | |
260 | @chapter Inserting end-tags | |
261 | ||
262 | The main redundancy in XML syntax is end-tags. nxml-mode provides | |
263 | several ways to make it easier to enter end-tags. You can use all of | |
264 | these without a schema. | |
265 | ||
266 | You can use @kbd{C-@key{RET}} after @samp{</} | |
267 | to complete the rest of the end-tag. | |
268 | ||
269 | @kbd{C-c C-f} inserts an end-tag for the element containing | |
270 | point. This command is useful when you want to input the start-tag, | |
271 | then input the content and finally input the end-tag. The @samp{f} | |
272 | is mnemonic for finish. | |
273 | ||
274 | If you want to keep tags balanced and input the end-tag at the | |
275 | same time as the start-tag, before inputting the content, then you can | |
276 | use @kbd{C-c C-i}. This inserts a @samp{>}, then inserts | |
277 | the end-tag and leaves point before the end-tag. @kbd{C-c C-b} | |
278 | is similar but more convenient for block-level elements: it puts the | |
279 | start-tag, point and the end-tag on successive lines, appropriately | |
280 | indented. The @samp{i} is mnemonic for inline and the | |
281 | @samp{b} is mnemonic for block. | |
282 | ||
283 | Finally, you can customize nxml-mode so that @kbd{/} | |
284 | automatically inserts the rest of the end-tag when it occurs after | |
285 | @samp{<}, by doing | |
286 | ||
287 | @display | |
288 | @kbd{M-x customize-variable @key{RET} nxml-slash-auto-complete-flag @key{RET}} | |
289 | @end display | |
290 | ||
291 | @noindent | |
292 | and then following the instructions in the displayed buffer. | |
293 | ||
294 | @node Paragraphs | |
295 | @chapter Paragraphs | |
296 | ||
297 | Emacs has several commands that operate on paragraphs, most | |
298 | notably @kbd{M-q}. nXML mode redefines these to work in a way | |
299 | that is useful for XML. The exact rules that are used to find the | |
300 | beginning and end of a paragraph are complicated; they are designed | |
301 | mainly to ensure that @kbd{M-q} does the right thing. | |
302 | ||
303 | A paragraph consists of one or more complete, consecutive lines. | |
304 | A group of lines is not considered a paragraph unless it contains some | |
305 | non-whitespace characters between tags or inside comments. A blank | |
306 | line separates paragraphs. A single tag on a line by itself also | |
307 | separates paragraphs. More precisely, if one tag together with any | |
308 | leading and trailing whitespace completely occupy one or more lines, | |
309 | then those lines will not be included in any paragraph. | |
310 | ||
311 | A start-tag at the beginning of the line (possibly indented) may | |
312 | be treated as starting a paragraph. Similarly, an end-tag at the end | |
313 | of the line may be treated as ending a paragraph. The following rules | |
314 | are used to determine whether such a tag is in fact treated as a | |
315 | paragraph boundary: | |
316 | ||
317 | @itemize @bullet | |
318 | @item | |
319 | If the schema does not allow text at that point, then it | |
320 | is a paragraph boundary. | |
321 | @item | |
322 | If the end-tag corresponding to the start-tag is not at | |
323 | the end of its line, or the start-tag corresponding to the end-tag is | |
324 | not at the beginning of its line, then it is not a paragraph | |
325 | boundary. For example, in | |
326 | ||
327 | @example | |
328 | <p>This is a paragraph with an | |
329 | <emph>emphasized</emph> phrase. | |
330 | @end example | |
331 | ||
332 | @noindent | |
333 | the @samp{<emph>} start-tag would not be considered as | |
334 | starting a paragraph, because its corresponding end-tag is not at the | |
335 | end of the line. | |
336 | @item | |
337 | If there is text that is a sibling in element tree, then | |
338 | it is not a paragraph boundary. For example, in | |
339 | ||
340 | @example | |
341 | <p>This is a paragraph with an | |
342 | <emph>emphasized phrase that takes one source line</emph> | |
343 | @end example | |
344 | ||
345 | @noindent | |
346 | the @samp{<emph>} start-tag would not be considered as | |
347 | starting a paragraph, even though its end-tag is at the end of its | |
348 | line, because there the text @samp{This is a paragraph with an} | |
349 | is a sibling of the @samp{emph} element. | |
350 | @item | |
351 | Otherwise, it is a paragraph boundary. | |
352 | @end itemize | |
353 | ||
354 | @node Outlining | |
355 | @chapter Outlining | |
356 | ||
357 | nXML mode allows you to display all or part of a buffer as an | |
358 | outline, in a similar way to Emacs' outline mode. An outline in nXML | |
359 | mode is based on recognizing two kinds of element: sections and | |
360 | headings. There is one heading for every section and one section for | |
361 | every heading. A section contains its heading as or within its first | |
362 | child element. A section also contains its subordinate sections (its | |
363 | subsections). The text content of a section consists of anything in a | |
364 | section that is neither a subsection nor a heading. | |
365 | ||
366 | Note that this is a different model from that used by XHTML. | |
367 | nXML mode's outline support will not be useful for XHTML unless you | |
368 | adopt a convention of adding a @code{div} to enclose each | |
369 | section, rather than having sections implicitly delimited by different | |
370 | @code{h@var{n}} elements. This limitation may be removed | |
371 | in a future version. | |
372 | ||
373 | The variable @code{nxml-section-element-name-regexp} gives | |
374 | a regexp for the local names (i.e. the part of the name following any | |
375 | prefix) of section elements. The variable | |
376 | @code{nxml-heading-element-name-regexp} gives a regexp for the | |
377 | local names of heading elements. For an element to be recognized | |
378 | as a section | |
379 | ||
380 | @itemize @bullet | |
381 | @item | |
382 | its start-tag must occur at the beginning of a line | |
383 | (possibly indented); | |
384 | @item | |
385 | its local name must match | |
386 | @code{nxml-section-element-name-regexp}; | |
387 | @item | |
388 | either its first child element or a descendant of that | |
389 | first child element must have a local name that matches | |
390 | @code{nxml-heading-element-name-regexp}; the first such element | |
391 | is treated as the section's heading. | |
392 | @end itemize | |
393 | ||
394 | @noindent | |
395 | You can customize these variables using @kbd{M-x | |
396 | customize-variable}. | |
397 | ||
398 | There are three possible outline states for a section: | |
399 | ||
400 | @itemize @bullet | |
401 | @item | |
402 | normal, showing everything, including its heading, text | |
403 | content and subsections; each subsection is displayed according to the | |
404 | state of that subsection; | |
405 | @item | |
406 | showing just its heading, with both its text content and | |
407 | its subsections hidden; all subsections are hidden regardless of their | |
408 | state; | |
409 | @item | |
410 | showing its heading and its subsections, with its text | |
411 | content hidden; each subsection is displayed according to the state of | |
412 | that subsection. | |
413 | @end itemize | |
414 | ||
415 | In the last two states, where the text content is hidden, the | |
416 | heading is displayed specially, in an abbreviated form. An element | |
417 | like this: | |
418 | ||
419 | @example | |
420 | <section> | |
421 | <title>Food</title> | |
422 | <para>There are many kinds of food.</para> | |
423 | </section> | |
424 | @end example | |
425 | ||
426 | @noindent | |
427 | would be displayed on a single line like this: | |
428 | ||
429 | @example | |
430 | <-section>Food...</> | |
431 | @end example | |
432 | ||
433 | @noindent | |
434 | If there are hidden subsections, then a @code{+} will be used | |
435 | instead of a @code{-} like this: | |
436 | ||
437 | @example | |
438 | <+section>Food...</> | |
439 | @end example | |
440 | ||
441 | @noindent | |
442 | If there are non-hidden subsections, then the section will instead be | |
443 | displayed like this: | |
444 | ||
445 | @example | |
446 | <-section>Food... | |
447 | <-section>Delicious Food...</> | |
448 | <-section>Distasteful Food...</> | |
449 | </-section> | |
450 | @end example | |
451 | ||
452 | @noindent | |
453 | The heading is always displayed with an indent that corresponds to its | |
454 | depth in the outline, even it is not actually indented in the buffer. | |
455 | The variable @code{nxml-outline-child-indent} controls how much | |
456 | a subheading is indented with respect to its parent heading when the | |
457 | heading is being displayed specially. | |
458 | ||
459 | Commands to change the outline state of sections are bound to | |
460 | key sequences that start with @kbd{C-c C-o} (@kbd{o} is | |
461 | mnemonic for outline). The third and final key has been chosen to be | |
462 | consistent with outline mode. In the following descriptions | |
463 | current section means the section containing point, or, more precisely, | |
464 | the innermost section containing the character immediately following | |
465 | point. | |
466 | ||
467 | @itemize @bullet | |
468 | @item | |
469 | @kbd{C-c C-o C-a} shows all sections in the buffer | |
470 | normally. | |
471 | @item | |
472 | @kbd{C-c C-o C-t} hides the text content | |
473 | of all sections in the buffer. | |
474 | @item | |
475 | @kbd{C-c C-o C-c} hides the text content | |
476 | of the current section. | |
477 | @item | |
478 | @kbd{C-c C-o C-e} shows the text content | |
479 | of the current section. | |
480 | @item | |
481 | @kbd{C-c C-o C-d} hides the text content | |
482 | and subsections of the current section. | |
483 | @item | |
867d4bb3 | 484 | @kbd{C-c C-o C-s} shows the current section |
8cd39fb3 MH |
485 | and all its direct and indirect subsections normally. |
486 | @item | |
487 | @kbd{C-c C-o C-k} shows the headings of the | |
488 | direct and indirect subsections of the current section. | |
489 | @item | |
490 | @kbd{C-c C-o C-l} hides the text content of the | |
491 | current section and of its direct and indirect | |
492 | subsections. | |
493 | @item | |
494 | @kbd{C-c C-o C-i} shows the headings of the | |
495 | direct subsections of the current section. | |
496 | @item | |
497 | @kbd{C-c C-o C-o} hides as much as possible without | |
498 | hiding the current section's text content; the headings of ancestor | |
499 | sections of the current section and their child section sections will | |
500 | not be hidden. | |
501 | @end itemize | |
502 | ||
503 | When a heading is displayed specially, you can use | |
504 | @key{RET} in that heading to show the text content of the section | |
505 | in the same way as @kbd{C-c C-o C-e}. | |
506 | ||
507 | You can also use the mouse to change the outline state: | |
508 | @kbd{S-mouse-2} hides the text content of a section in the same | |
509 | way as@kbd{C-c C-o C-c}; @kbd{mouse-2} on a specially | |
510 | displayed heading shows the text content of the section in the same | |
511 | way as @kbd{C-c C-o C-e}; @kbd{mouse-1} on a specially | |
512 | displayed start-tag toggles the display of subheadings on and | |
513 | off. | |
514 | ||
515 | The outline state for each section is stored with the first | |
516 | character of the section (as a text property). Every command that | |
517 | changes the outline state of any section updates the display of the | |
518 | buffer so that each section is displayed correctly according to its | |
519 | outline state. If the section structure is subsequently changed, then | |
520 | it is possible for the display to no longer correctly reflect the | |
521 | stored outline state. @kbd{C-c C-o C-r} can be used to refresh | |
522 | the display so it is correct again. | |
523 | ||
524 | @node Locating a schema | |
525 | @chapter Locating a schema | |
526 | ||
527 | nXML mode has a configurable set of rules to locate a schema for | |
528 | the file being edited. The rules are contained in one or more schema | |
529 | locating files, which are XML documents. | |
530 | ||
531 | The variable @samp{rng-schema-locating-files} specifies | |
532 | the list of the file-names of schema locating files that nXML mode | |
533 | should use. The order of the list is significant: when file | |
534 | @var{x} occurs in the list before file @var{y} then rules | |
535 | from file @var{x} have precedence over rules from file | |
536 | @var{y}. A filename specified in | |
537 | @samp{rng-schema-locating-files} may be relative. If so, it will | |
538 | be resolved relative to the document for which a schema is being | |
539 | located. It is not an error if relative file-names in | |
867d4bb3 | 540 | @samp{rng-schema-locating-files} do not exist. You can use |
8cd39fb3 MH |
541 | @kbd{M-x customize-variable @key{RET} rng-schema-locating-files |
542 | @key{RET}} to customize the list of schema locating | |
543 | files. | |
544 | ||
545 | By default, @samp{rng-schema-locating-files} list has two | |
546 | members: @samp{schemas.xml}, and | |
547 | @samp{@var{dist-dir}/schema/schemas.xml} where | |
548 | @samp{@var{dist-dir}} is the directory containing the nXML | |
549 | distribution. The first member will cause nXML mode to use a file | |
550 | @samp{schemas.xml} in the same directory as the document being | |
551 | edited if such a file exist. The second member contains rules for the | |
552 | schemas that are included with the nXML distribution. | |
553 | ||
554 | @menu | |
867d4bb3 JB |
555 | * Commands for locating a schema:: |
556 | * Schema locating files:: | |
8cd39fb3 MH |
557 | @end menu |
558 | ||
559 | @node Commands for locating a schema | |
560 | @section Commands for locating a schema | |
561 | ||
562 | The command @kbd{C-c C-s C-w} will tell you what schema | |
563 | is currently being used. | |
564 | ||
565 | The rules for locating a schema are applied automatically when | |
566 | you visit a file in nXML mode. However, if you have just created a new | |
567 | file and the schema cannot be inferred from the file-name, then this | |
568 | will not locate the right schema. In this case, you should insert the | |
40572be6 | 569 | start-tag of the root element and then use the command @kbd{C-c C-s |
8cd39fb3 MH |
570 | C-a}, which reapplies the rules based on the current content of |
571 | the document. It is usually not necessary to insert the complete | |
572 | start-tag; often just @samp{<@var{name}} is | |
573 | enough. | |
574 | ||
575 | If you want to use a schema that has not yet been added to the | |
576 | schema locating files, you can use the command @kbd{C-c C-s C-f} | |
b6f9df0f | 577 | to manually select the file containing the schema for the document in |
8cd39fb3 MH |
578 | current buffer. Emacs will read the file-name of the schema from the |
579 | minibuffer. After reading the file-name, Emacs will ask whether you | |
580 | wish to add a rule to a schema locating file that persistently | |
581 | associates the document with the selected schema. The rule will be | |
582 | added to the first file in the list specified | |
583 | @samp{rng-schema-locating-files}; it will create the file if | |
584 | necessary, but will not create a directory. If the variable | |
585 | @samp{rng-schema-locating-files} has not been customized, this | |
586 | means that the rule will be added to the file @samp{schemas.xml} | |
587 | in the same directory as the document being edited. | |
588 | ||
589 | The command @kbd{C-c C-s C-t} allows you to select a schema by | |
590 | specifying an identifier for the type of the document. The schema | |
591 | locating files determine the available type identifiers and what | |
592 | schema is used for each type identifier. This is useful when it is | |
593 | impossible to infer the right schema from either the file-name or the | |
594 | content of the document, even though the schema is already in the | |
595 | schema locating file. A situation in which this can occur is when | |
596 | there are multiple variants of a schema where all valid documents have | |
597 | the same document element. For example, XHTML has Strict and | |
598 | Transitional variants. In a situation like this, a schema locating file | |
599 | can define a type identifier for each variant. As with @kbd{C-c | |
600 | C-s C-f}, Emacs will ask whether you wish to add a rule to a schema | |
601 | locating file that persistently associates the document with the | |
602 | specified type identifier. | |
603 | ||
604 | The command @kbd{C-c C-s C-l} adds a rule to a schema | |
605 | locating file that persistently associates the document with | |
606 | the schema that is currently being used. | |
607 | ||
608 | @node Schema locating files | |
609 | @section Schema locating files | |
610 | ||
611 | Each schema locating file specifies a list of rules. The rules | |
612 | from each file are appended in order. To locate a schema each rule is | |
613 | applied in turn until a rule matches. The first matching rule is then | |
614 | used to determine the schema. | |
615 | ||
616 | Schema locating files are designed to be useful for other | |
617 | applications that need to locate a schema for a document. In fact, | |
618 | there is nothing specific to locating schemas in the design; it could | |
619 | equally well be used for locating a stylesheet. | |
620 | ||
621 | @menu | |
867d4bb3 JB |
622 | * Schema locating file syntax basics:: |
623 | * Using the document's URI to locate a schema:: | |
624 | * Using the document element to locate a schema:: | |
625 | * Using type identifiers in schema locating files:: | |
626 | * Using multiple schema locating files:: | |
8cd39fb3 MH |
627 | @end menu |
628 | ||
629 | @node Schema locating file syntax basics | |
630 | @subsection Schema locating file syntax basics | |
631 | ||
632 | There is a schema for schema locating files in the file | |
633 | @samp{locate.rnc} in the schema directory. Schema locating | |
634 | files must be valid with respect to this schema. | |
635 | ||
636 | The document element of a schema locating file must be | |
637 | @samp{locatingRules} and the namespace URI must be | |
638 | @samp{http://thaiopensource.com/ns/locating-rules/1.0}. The | |
639 | children of the document element specify rules. The order of the | |
640 | children is the same as the order of the rules. Here's a complete | |
641 | example of a schema locating file: | |
642 | ||
643 | @example | |
644 | <?xml version="1.0"?> | |
645 | <locatingRules xmlns="http://thaiopensource.com/ns/locating-rules/1.0"> | |
646 | <namespace ns="http://www.w3.org/1999/xhtml" uri="xhtml.rnc"/> | |
647 | <documentElement localName="book" uri="docbook.rnc"/> | |
648 | </locatingRules> | |
649 | @end example | |
650 | ||
651 | @noindent | |
652 | This says to use the schema @samp{xhtml.rnc} for a document with | |
653 | namespace @samp{http://www.w3.org/1999/xhtml}, and to use the | |
654 | schema @samp{docbook.rnc} for a document whose local name is | |
655 | @samp{book}. If the document element had both a namespace URI | |
656 | of @samp{http://www.w3.org/1999/xhtml} and a local name of | |
657 | @samp{book}, then the matching rule that comes first will be | |
658 | used and so the schema @samp{xhtml.rnc} would be used. There is | |
659 | no precedence between different types of rule; the first matching rule | |
660 | of any type is used. | |
661 | ||
662 | As usual with XML-related technologies, resources are identified | |
663 | by URIs. The @samp{uri} attribute identifies the schema by | |
664 | specifying the URI. The URI may be relative. If so, it is resolved | |
665 | relative to the URI of the schema locating file that contains | |
666 | attribute. This means that if the value of @samp{uri} attribute | |
667 | does not contain a @samp{/}, then it will refer to a filename in | |
668 | the same directory as the schema locating file. | |
669 | ||
670 | @node Using the document's URI to locate a schema | |
671 | @subsection Using the document's URI to locate a schema | |
672 | ||
673 | A @samp{uri} rule locates a schema based on the URI of the | |
674 | document. The @samp{uri} attribute specifies the URI of the | |
675 | schema. The @samp{resource} attribute can be used to specify | |
676 | the schema for a particular document. For example, | |
677 | ||
678 | @example | |
679 | <uri resource="spec.xml" uri="docbook.rnc"/> | |
680 | @end example | |
681 | ||
682 | @noindent | |
867d4bb3 | 683 | specifies that the schema for @samp{spec.xml} is |
8cd39fb3 MH |
684 | @samp{docbook.rnc}. |
685 | ||
686 | The @samp{pattern} attribute can be used instead of the | |
687 | @samp{resource} attribute to specify the schema for any document | |
688 | whose URI matches a pattern. The pattern has the same syntax as an | |
689 | absolute or relative URI except that the path component of the URI can | |
690 | use a @samp{*} character to stand for zero or more characters | |
691 | within a path segment (i.e. any character other @samp{/}). | |
692 | Typically, the URI pattern looks like a relative URI, but, whereas a | |
693 | relative URI in the @samp{resource} attribute is resolved into a | |
694 | particular absolute URI using the base URI of the schema locating | |
695 | file, a relative URI pattern matches if it matches some number of | |
696 | complete path segments of the document's URI ending with the last path | |
697 | segment of the document's URI. For example, | |
698 | ||
699 | @example | |
700 | <uri pattern="*.xsl" uri="xslt.rnc"/> | |
701 | @end example | |
702 | ||
703 | @noindent | |
704 | specifies that the schema for documents with a URI whose path ends | |
705 | with @samp{.xsl} is @samp{xslt.rnc}. | |
706 | ||
707 | A @samp{transformURI} rule locates a schema by | |
708 | transforming the URI of the document. The @samp{fromPattern} | |
709 | attribute specifies a URI pattern with the same meaning as the | |
710 | @samp{pattern} attribute of the @samp{uri} element. The | |
711 | @samp{toPattern} attribute is a URI pattern that is used to | |
712 | generate the URI of the schema. Each @samp{*} in the | |
713 | @samp{toPattern} is replaced by the string that matched the | |
714 | corresponding @samp{*} in the @samp{fromPattern}. The | |
715 | resulting string is appended to the initial part of the document's URI | |
716 | that was not explicitly matched by the @samp{fromPattern}. The | |
717 | rule matches only if the transformed URI identifies an existing | |
718 | resource. For example, the rule | |
719 | ||
720 | @example | |
721 | <transformURI fromPattern="*.xml" toPattern="*.rnc"/> | |
722 | @end example | |
723 | ||
724 | @noindent | |
725 | would transform the URI @samp{file:///home/jjc/docs/spec.xml} | |
726 | into the URI @samp{file:///home/jjc/docs/spec.rnc}. Thus, this | |
727 | rule specifies that to locate a schema for a document | |
728 | @samp{@var{foo}.xml}, Emacs should test whether a file | |
729 | @samp{@var{foo}.rnc} exists in the same directory as | |
730 | @samp{@var{foo}.xml}, and, if so, should use it as the | |
731 | schema. | |
732 | ||
733 | @node Using the document element to locate a schema | |
734 | @subsection Using the document element to locate a schema | |
735 | ||
736 | A @samp{documentElement} rule locates a schema based on | |
737 | the local name and prefix of the document element. For example, a rule | |
738 | ||
739 | @example | |
740 | <documentElement prefix="xsl" localName="stylesheet" uri="xslt.rnc"/> | |
741 | @end example | |
742 | ||
743 | @noindent | |
744 | specifies that when the name of the document element is | |
745 | @samp{xsl:stylesheet}, then @samp{xslt.rnc} should be used | |
746 | as the schema. Either the @samp{prefix} or | |
747 | @samp{localName} attribute may be omitted to allow any prefix or | |
748 | local name. | |
749 | ||
750 | A @samp{namespace} rule locates a schema based on the | |
751 | namespace URI of the document element. For example, a rule | |
752 | ||
753 | @example | |
754 | <namespace ns="http://www.w3.org/1999/XSL/Transform" uri="xslt.rnc"/> | |
755 | @end example | |
756 | ||
757 | @noindent | |
758 | specifies that when the namespace URI of the document is | |
759 | @samp{http://www.w3.org/1999/XSL/Transform}, then | |
760 | @samp{xslt.rnc} should be used as the schema. | |
761 | ||
762 | @node Using type identifiers in schema locating files | |
763 | @subsection Using type identifiers in schema locating files | |
764 | ||
765 | Type identifiers allow a level of indirection in locating the | |
766 | schema for a document. Instead of associating the document directly | |
767 | with a schema URI, the document is associated with a type identifier, | |
768 | which is in turn associated with a schema URI. nXML mode does not | |
769 | constrain the format of type identifiers. They can be simply strings | |
770 | without any formal structure or they can be public identifiers or | |
771 | URIs. Note that these type identifiers have nothing to do with the | |
772 | DOCTYPE declaration. When comparing type identifiers, whitespace is | |
773 | normalized in the same way as with the @samp{xsd:token} | |
774 | datatype: leading and trailing whitespace is stripped; other sequences | |
775 | of whitespace are normalized to a single space character. | |
776 | ||
777 | Each of the rules described in previous sections that uses a | |
778 | @samp{uri} attribute to specify a schema, can instead use a | |
779 | @samp{typeId} attribute to specify a type identifier. The type | |
780 | identifier can be associated with a URI using a @samp{typeId} | |
781 | element. For example, | |
782 | ||
783 | @example | |
784 | <locatingRules xmlns="http://thaiopensource.com/ns/locating-rules/1.0"> | |
785 | <namespace ns="http://www.w3.org/1999/xhtml" typeId="XHTML"/> | |
786 | <typeId id="XHTML" typeId="XHTML Strict"/> | |
787 | <typeId id="XHTML Strict" uri="xhtml-strict.rnc"/> | |
788 | <typeId id="XHTML Transitional" uri="xhtml-transitional.rnc"/> | |
789 | </locatingRules> | |
790 | @end example | |
791 | ||
792 | @noindent | |
793 | declares three type identifiers @samp{XHTML} (representing the | |
794 | default variant of XHTML to be used), @samp{XHTML Strict} and | |
795 | @samp{XHTML Transitional}. Such a schema locating file would | |
796 | use @samp{xhtml-strict.rnc} for a document whose namespace is | |
797 | @samp{http://www.w3.org/1999/xhtml}. But it is considerably | |
798 | more flexible than a schema locating file that simply specified | |
799 | ||
800 | @example | |
801 | <namespace ns="http://www.w3.org/1999/xhtml" uri="xhtml-strict.rnc"/> | |
802 | @end example | |
803 | ||
804 | @noindent | |
805 | A user can easily use @kbd{C-c C-s C-t} to select between XHTML | |
806 | Strict and XHTML Transitional. Also, a user can easily add a catalog | |
807 | ||
808 | @example | |
809 | <locatingRules xmlns="http://thaiopensource.com/ns/locating-rules/1.0"> | |
810 | <typeId id="XHTML" typeId="XHTML Transitional"/> | |
811 | </locatingRules> | |
812 | @end example | |
813 | ||
814 | @noindent | |
815 | that makes the default variant of XHTML be XHTML Transitional. | |
816 | ||
817 | @node Using multiple schema locating files | |
818 | @subsection Using multiple schema locating files | |
819 | ||
820 | The @samp{include} element includes rules from another | |
821 | schema locating file. The behavior is exactly as if the rules from | |
822 | that file were included in place of the @samp{include} element. | |
823 | Relative URIs are resolved into absolute URIs before the inclusion is | |
824 | performed. For example, | |
825 | ||
826 | @example | |
827 | <include rules="../rules.xml"/> | |
828 | @end example | |
829 | ||
830 | @noindent | |
831 | includes the rules from @samp{rules.xml}. | |
832 | ||
833 | The process of locating a schema takes as input a list of schema | |
834 | locating files. The rules in all these files and in the files they | |
835 | include are resolved into a single list of rules, which are applied | |
836 | strictly in order. Sometimes this order is not what is needed. | |
837 | For example, suppose you have two schema locating files, a private | |
838 | file | |
839 | ||
840 | @example | |
841 | <locatingRules xmlns="http://thaiopensource.com/ns/locating-rules/1.0"> | |
842 | <namespace ns="http://www.w3.org/1999/xhtml" uri="xhtml.rnc"/> | |
843 | </locatingRules> | |
844 | @end example | |
845 | ||
846 | @noindent | |
847 | followed by a public file | |
848 | ||
849 | @example | |
850 | <locatingRules xmlns="http://thaiopensource.com/ns/locating-rules/1.0"> | |
851 | <transformURI pathSuffix=".xml" replacePathSuffix=".rnc"/> | |
852 | <namespace ns="http://www.w3.org/1999/XSL/Transform" typeId="XSLT"/> | |
853 | </locatingRules> | |
854 | @end example | |
855 | ||
856 | @noindent | |
857 | The effect of these two files is that the XHTML @samp{namespace} | |
858 | rule takes precedence over the @samp{transformURI} rule, which | |
859 | is almost certainly not what is needed. This can be solved by adding | |
860 | an @samp{applyFollowingRules} to the private file. | |
861 | ||
862 | @example | |
863 | <locatingRules xmlns="http://thaiopensource.com/ns/locating-rules/1.0"> | |
864 | <applyFollowingRules ruleType="transformURI"/> | |
865 | <namespace ns="http://www.w3.org/1999/xhtml" uri="xhtml.rnc"/> | |
866 | </locatingRules> | |
867 | @end example | |
868 | ||
869 | @node DTDs | |
870 | @chapter DTDs | |
871 | ||
872 | nxml-mode is designed to support the creation of standalone XML | |
873 | documents that do not depend on a DTD. Although it is common practice | |
874 | to insert a DOCTYPE declaration referencing an external DTD, this has | |
875 | undesirable side-effects. It means that the document is no longer | |
876 | self-contained. It also means that different XML parsers may interpret | |
877 | the document in different ways, since the XML Recommendation does not | |
878 | require XML parsers to read the DTD. With DTDs, it was impractical to | |
879 | get validation without using an external DTD or reference to an | |
880 | parameter entity. With RELAX NG and other schema languages, you can | |
9858f6c3 | 881 | simultaneously get the benefits of validation and standalone XML |
8cd39fb3 MH |
882 | documents. Therefore, I recommend that you do not reference an |
883 | external DOCTYPE in your XML documents. | |
884 | ||
885 | One problem is entities for characters. Typically, as well as | |
886 | providing validation, DTDs also provide a set of character entities | |
887 | for documents to use. Schemas cannot provide this functionality, | |
888 | because schema validation happens after XML parsing. The recommended | |
889 | solution is to either use the Unicode characters directly, or, if this | |
890 | is impractical, use character references. nXML mode supports this by | |
891 | providing commands for entering characters and character references | |
892 | using the Unicode names, and can display the glyph corresponding to a | |
893 | character reference. | |
894 | ||
895 | @node Limitations | |
896 | @chapter Limitations | |
897 | ||
898 | nXML mode has some limitations: | |
899 | ||
900 | @itemize @bullet | |
901 | @item | |
902 | DTD support is limited. Internal parsed general entities declared | |
903 | in the internal subset are supported provided they do not contain | |
904 | elements. Other usage of DTDs is ignored. | |
905 | @item | |
906 | The restrictions on RELAX NG schemas in section 7 of the RELAX NG | |
907 | specification are not enforced. | |
8cd39fb3 MH |
908 | @end itemize |
909 | ||
910 | @bye |