2 Common infrastructure............................................................................................................................................................................. 41
2.1 Terminology......................................................................................................................................................................... 41
2.1.1 Resources ...................................................................................................................................................... 41
2.1.2 XML ................................................................................................................................................................ 42
2.1.3 DOM trees ...................................................................................................................................................... 42
2.1.4 Scripting.......................................................................................................................................................... 43
2.1.5 Plugins............................................................................................................................................................ 43
2.1.6 Character encodings ...................................................................................................................................... 44
2.2 Conformance requirements................................................................................................................................................. 44
2.2.1 Conformance classes..................................................................................................................................... 45
2.2.2 Dependencies ................................................................................................................................................ 47
2.2.3 Extensibility..................................................................................................................................................... 55
2.2.4 Interactions with XPath and XSLT.................................................................................................................. 57
2.3 Case-sensitivity and string comparison............................................................................................................................... 58
2.4 Common microsyntaxes...................................................................................................................................................... 58
2.4.1 Common parser idioms .................................................................................................................................. 58
2.4.2 Boolean attributes .......................................................................................................................................... 59
2.4.3 Keywords and enumerated attributes............................................................................................................. 60
2.4.4 Numbers......................................................................................................................................................... 60
2.4.4.1 Signed integers ......................................................................................................................... 60
2.4.4.2 Non-negative integers ............................................................................................................... 61
2.4.4.3 Floating-point numbers.............................................................................................................. 61
2.4.4.4 Percentages and lengths........................................................................................................... 63
2.4.4.5 Lists of integers ......................................................................................................................... 64
2.4.4.6 Lists of dimensions.................................................................................................................... 65
2.4.5 Dates and times.............................................................................................................................................. 66
2.4.5.1 Months....................................................................................................................................... 67
2.4.5.2 Dates ......................................................................................................................................... 67
2.4.5.3 Yearless dates........................................................................................................................... 68
2.4.5.4 Times......................................................................................................................................... 69
2.4.5.5 Local dates and times ............................................................................................................... 70
2.4.5.6 Time zones................................................................................................................................ 71
2.4.5.7 Global dates and times.............................................................................................................. 72
2.4.5.8 Weeks........................................................................................................................................ 73
2.4.5.9 Durations ................................................................................................................................... 74
2.4.5.10 Vaguer moments in time ......................................................................................................... 77
2.4.6 Colours ........................................................................................................................................................... 78
2.4.7 Space-separated tokens ................................................................................................................................ 80
2.4.8 Comma-separated tokens .............................................................................................................................. 80
2.4.9 References ..................................................................................................................................................... 81
2.4.10 Media queries............................................................................................................................................... 81
2.5 URLs.................................................................................................................................................................................... 81
2.5.1 Terminology.................................................................................................................................................... 81
2.5.2 Resolving URLs.............................................................................................................................................. 82
2.5.3 Dynamic changes to base URLs .................................................................................................................... 83
2.6 Fetching resources.............................................................................................................................................................. 83
2.6.1 Terminology.................................................................................................................................................... 83
2.6.2 Processing model........................................................................................................................................... 84
2.6.3 Encrypted HTTP and related security concerns............................................................................................. 86
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