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1 = {{id name="_Toc291503"/}}4 General Notes for Implementers =
2
3 This section discusses a number of topics other than the exchange of data sets in SDMX formats. Supported only in SDMX-ML (and some in SDMX-JSON), these topics include the use of the reference metadata mechanism in SDMX, the use of Structure Sets and Reporting Taxonomies, the use of Processes, a discussion of time and datatyping, and the conventional mechanisms within the SDMX-ML Structure message regarding versioning and referencing.
4
5 == {{id name="_Toc291504"/}}4.1 Representations ==
6
7 This section does not go into great detail on these topics but provides a useful overview of these features to assist implementors in further use of the parts of the specification which are relevant to them.
8
9 There are several different representations in SDMX-ML, taken from XML Schemas and common programming languages. The table below describes the various representations, which are found in SDMX-ML, and their equivalents.
10
11 |SDMX-ML Data Type|XML Schema Data Type|.NET Framework Type|Java Data Type
12 |**String**|**xsd:string**|**System.String**|**java.lang.String**
13 |**Big Integer**|**xsd:integer**|**System.Decimal**|**java.math.BigInteger**
14 |**Integer**|**xsd:int**|**System.Int32**|**int**
15 |**Long**|**xsd.long**|**System.Int64**|**long**
16 |**Short**|**xsd:short**|**System.Int16**|**short**
17 |**Decimal**|**xsd:decimal**|**System.Decimal**|**java.math.BigDecimal**
18 |**Float**|**xsd:float**|**System.Single**|**float**
19 |**Double**|**xsd:double**|**System.Double**|**double**
20 |**Boolean**|**xsd:boolean**|**System.Boolean**|**boolean**
21 |**URI**|**xsd:anyURI**|**System.Uri**|**Java.net.URI or java.lang.String**
22 |**DateTime**|**xsd:dateTime**|**System.DateTime**|**javax.xml.datatype.XMLG regorianCalendar**
23 |**Time**|**xsd:time**|**System.DateTime**|**javax.xml.datatype.XMLG regorianCalendar**
24 |**GregorianYear**|**xsd:gYear**|**System.DateTime**|**javax.xml.datatype.XMLG regorianCalendar**
25 |**GregorianMonth**|**xsd:gYearMonth**|**System.DateTime**|**javax.xml.datatype.XMLG regorianCalendar**
26 |**GregorianDay**|**xsd:date**|**System.DateTime**|**javax.xml.datatype.XMLG regorianCalendar**
27 |**Day, MonthDay, Month**|**xsd:g***|**System.DateTime**|**javax.xml.datatype.XMLG regorianCalendar**
28 |**Duration**|**xsd:duration**|**System.TimeSpan**|**javax.xml.datatype.Dura tion**
29
30 There are also a number of SDMX-ML data types which do not have these direct correspondences, often because they are composite representations or restrictions of a broader data type. For most of these, there are simple types which can be referenced from the SDMX schemas, for others a derived simple type will be necessary:
31
32 • **AlphaNumeric** (**common:AlphaNumericType**, string which only allows A-z and 0-9)
33
34 • **Alpha** (**common:AlphaType**, string which only allows A-z)
35
36 • ,,**Numeric**,, (,,**common:NumericType**,,, string which only allows 0-9, but is not numeric so that is can having leading zeros)
37
38 • ,,**Count**,, (,,**xs:integer**,,, a sequence with an interval of "1")
39
40 • **InclusiveValueRange** (**xs:decimal** with the **minValue** and **maxValue** facets supplying the bounds)
41
42 • **ExclusiveValueRange** (**xs:decimal** with the **minValue** and **maxValue** facets supplying the bounds)
43
44 • **Incremental** (**xs:decimal** with a specified **interval**; the interval is typically enforced outside of the XML validation)
45
46 • **TimeRange** (**common:TimeRangeType**, **startDateTime** + **Duration**)
47
48 • **ObservationalTimePeriod** (**common:ObservationalTimePeriodType**, a union of **StandardTimePeriod** and **TimeRange**).
49
50 • **StandardTimePeriod** (**common:StandardTimePeriodType**, a union of **BasicTimePeriod** and **ReportingTimePeriod**).
51
52 • **BasicTimePeriod** (**common:BasicTimePeriodType**, a union of **GregorianTimePeriod** and **DateTime**)
53
54 • **GregorianTimePeriod** (**common:GregorianTimePeriodType**, a union of **GregorianYear**, **GregorianMonth**, and **GregorianDay**)
55
56 • **ReportingTimePeriod** (**common:ReportingTimePeriodType**, a union of **ReportingYear**, **ReportingSemester**, **ReportingTrimester**, **ReportingQuarter**, **ReportingMonth**, **ReportingWeek**, and **ReportingDay**).
57
58 • **ReportingYear** (**common:ReportingYearType**)
59
60 • **ReportingSemester** (**common:ReportingSemesterType**)
61
62 • **ReportingTrimester** (**common:ReportingTrimesterType**)
63
64 • **ReportingQuarter** (**common:ReportingQuarterType**)
65
66 • **ReportingMonth** (**common:ReportingMonthType**)
67
68 • **ReportingWeek** (**common:ReportingWeekType**)
69
70 • **ReportingDay** (**common:ReportingDayType**)
71
72 • ,,**XHTML**,, (,,**common:StructuredText**,,, allows for multi-lingual text content that has ,,**XHTML**,, markup)
73
74 • **KeyValues** (**common:DataKeyType**)
75
76 • ,,**IdentifiableReference**,, (types for each IdentifiableObject)
77
78 • ,,**GeospatialInformation**,, (a geo feature set, according to the pattern in section 7.2)
79
80 Data types also have a set of facets:
81
82 • ,,**isSequence = true | false**,, (indicates a sequentially increasing value)
83
84 • ,,**minLength = positive integer**,, (# of characters/digits)
85
86 • ,,**maxLength = positive integer**,, (# of characters/digits)
87
88 • ,,**startValue = decimal**,, (for numeric sequence)
89
90 • ,,**endValue = decimal**,, (for numeric sequence)
91
92 • ,,**interval = decimal**,, (for numeric sequence)
93
94 • **timeInterval = duration**
95
96 • **startTime = BasicTimePer,,iod,,** (for time range) ,,**endTime = BasicTimePeriod**,, (for time range)
97
98 * ,,**minValue = decimal**,, (for numeric range)
99 * ,,**maxValue = decimal**,, (for numeric range)
100 * ,,**decimal = Integer**,, (# of digits to right of decimal point)
101 * ,,**pattern =**,, (a regular expression, as per W3C XML Schema)
102 * ,,**isMultiLingual = boolean**,, (for specifying text can occur in more than one language)
103
104 Note that code lists may also have textual representations assigned to them, in addition to their enumeration of codes.
105
106 === {{id name="_Toc291505"/}}4.1.1 Data Types ===
107
108 XML and JSON schemas support a variety of data types that, although rich, are not mapped one-to-one in all cases. This section provides an explanation of the mapping performed in SDMX 3.0, between such cases.
109
110 For identifiers, text fields and Codes there are no restriction from either side, since a generic type (e.g., that of string) accompanied by the proper regular expression works equally well for both XML and JSON.
111
112 For example, for the id type, this is the XML schema definition:
113
114 <xs:simpleType name="IDType">
115
116 <xs:restriction base="NestedIDType">
117
118 <xs:pattern value="[A-Za-z0-9_@$\-]+"/>
119
120 </xs:restriction>
121
122 </xs:simpleType>
123
124 Where the NestedIDType is also a restriction of string.
125
126 The above looks like this, in JSON schema:
127
128 "idType": {
129
130 "type": "string",
131
132 "pattern": "^[A-Za-z0-9_@$-]+$"
133
134 }
135
136 There are also cases, though, that data types cannot be mapped like above. One such case is the array data type, which was introduced in SDMX 3.0 as a new representation. In JSON schema an array is already natively foreseen, while in the XML schema, this has to be defined as a complex type, with an SDMX specific definition (i.e., specific element/attribute names for SDMX). Beyond that, the minimum and/or maximum number of items within an array is possible in both cases.
137
138 Further to the above, the mapping between the non-native data types is presented in the table below:
139
140 |**SDMX Facet**|**XML Schema**|**JSON schema **"**pattern**"^^[[^^1^^>>path:#sdfootnote1sym||name="sdfootnote1anc"]]^^ **for "string" type**
141 |GregorianYear|xsd:gYear|(((
142 "^-?([1-9][0-9]{3,}|0[0-9]{3})(Z|(\+|-)((0[0-
143
144 9]|1[0-3]):[0-5][0-9]|14:00))?$"
145 )))
146 |GregorianMonth|xsd:gYearMonth|(((
147 "^-?([1-9][0-9]{3,}|0[0-9]{3})-(0[1-9]|1[0-
148
149 2])(Z|(\+|-)((0[0-9]|1[0-3]):[0-5][0-
150
151 9]|14:00))?$"
152 )))
153
154 [[image:SDMX 3-0-0 SECTION 6 FINAL-1.0_en_59eee18f.gif||alt="Shape1" height="1" width="192"]]
155
156 |GregorianDay|xsd:date|(((
157 "^-?([1-9][0-9]{3,}|0[0-9]{3})-(0[1-9]|1[0-2])-
158
159 (0[1-9]|[12][0-9]|3[01])(Z|(\+|-)((0[0-9]|1[0-
160
161 3]):[0-5][0-9]|14:00))?$"
162 )))
163 |Day|xsd:gDay|(((
164 "^~-~--(0[1-9]|[12][0-9]|3[01])(Z|(\+|-
165
166 )((0[0-9]|1[0-3]):[0-5][0-9]|14:00))?$"
167 )))
168 |MonthDay|xsd:gMonthDay|(((
169 "^~-~-(0[1-9]|1[0-2])-(0[1-9]|[12][0-
170
171 9]|3[01])(Z|(\+|-)((0[0-9]|1[0-3]):[0-5][0-
172
173 9]|14:00))?$"
174 )))
175 |Month|xsd:Month|(((
176 "^~-~-(0[1-9]|1[0-2])(Z|(\+|-)((0[0-9]|1[0-
177
178 3]):[0-5][0-9]|14:00))?$"
179 )))
180 |Duration|xsd:duration|(((
181 "^-?P[0-9]+Y?([0-9]+M)?([0-9]+D)?(T([0-
182
183 9]+H)?([0-9]+M)?([0-9]+(\.[0-9]+)?S)?)?$"
184 )))
185
186 == {{id name="_Toc291506"/}}4.2 Time and Time Format ==
187
188 This section does not go into great detail on these topics but provides a useful overview of these features to assist implementors in further use of the parts of the specification which are relevant to them.
189
190 === {{id name="_Toc291507"/}}4.2.1 Introduction ===
191
192 First, it is important to recognize that most observation times are a period. SDMX specifies precisely how Time is handled.
193
194 The representation of time is broken into a hierarchical collection of representations. A data structure definition can use of any of the representations in the hierarchy as the representation of time. This allows for the time dimension of a particular data structure definition allow for only a subset of the default representation.
195
196 The hierarchy of time formats is as follows (**bold** indicates a category which is made up of multiple formats, //italic// indicates a distinct format):
197
198 * **Observational Time Period **o **Standard Time Period**
199
200 ▪ **Basic Time Period**
201
202 * **Gregorian Time Period**
203 * //Date Time//
204
205 ▪ **Reporting Time Period**
206
207 o //Time Range//
208
209 The details of these time period categories and of the distinct formats which make them up are detailed in the sections to follow.
210
211 === {{id name="_Toc291508"/}}4.2.2 Observational Time Period ===
212
213 This is the superset of all time representations in SDMX. This allows for time to be expressed as any of the allowable formats.
214
215 === {{id name="_Toc291509"/}}4.2.3 Standard Time Period ===
216
217 This is the superset of any predefined time period or a distinct point in time. A time period consists of a distinct start and end point. If the start and end of a period are expressed as date instead of a complete date time, then it is implied that the start of the period is the beginning of the start day (i.e. 00:00:00) and the end of the period is the end of the end day (i.e. 23:59:59).
218
219 === {{id name="_Toc291510"/}}4.2.4 Gregorian Time Period ===
220
221 A Gregorian time period is always represented by a Gregorian year, year-month, or day. These are all based on ISO 8601 dates. The representation in SDMX-ML messages and the period covered by each of the Gregorian time periods are as follows:
222
223 **Gregorian Year:**
224
225 Representation: xs:gYear (YYYY)
226
227 Period: the start of January 1 to the end of December 31 **Gregorian Year Month**:
228
229 Representation: xs:gYearMonth (YYYY-MM)
230
231 Period: the start of the first day of the month to end of the last day of the month **Gregorian Day**:
232
233 Representation: xs:date (YYYY-MM-DD)
234
235 Period: the start of the day (00:00:00) to the end of the day (23:59:59)
236
237 === {{id name="_Toc291511"/}}4.2.5 Date Time ===
238
239 This is used to unambiguously state that a date-time represents an observation at a single point in time. Therefore, if one wants to use SDMX for data which is measured at a distinct point in time rather than being reported over a period, the date-time representation can be used.
240
241 Representation: xs:dateTime (YYYY-MM-DDThh:mm:ss)^^[[^^2^^>>path:#sdfootnote2sym||name="sdfootnote2anc"]]^^
242
243 === {{id name="_Toc291512"/}}4.2.6 Standard Reporting Period ===
244
245 Standard reporting periods are periods of time in relation to a reporting year. Each of these standard reporting periods has a duration (based on the ISO 8601 definition) associated with it. The general format of a reporting period is as follows:
246
247 [REPORTING_YEAR]-[PERIOD_INDICATOR][PERIOD_VALUE]
248
249 Where:
250
251 REPORTING_YEAR represents the reporting year as four digits (YYYY) PERIOD_INDICATOR identifies the type of period which determines the duration of the period
252
253 PERIOD_VALUE indicates the actual period within the year
254
255 The following section details each of the standard reporting periods defined in SDMX:
256
257 **Reporting Year**:
258
259 Period Indicator: A
260
261 Period Duration: P1Y (one year)
262
263 Limit per year: 1
264
265 Representation: common:ReportingYearType (YYYY-A1, e.g. 2000-A1) **Reporting Semester:**
266
267 Period Indicator: S
268
269 Period Duration: P6M (six months)
270
271 Limit per year: 2
272
273 Representation: common:ReportingSemesterType (YYYY-Ss, e.g. 2000-S2)
274
275 [[image:SDMX 3-0-0 SECTION 6 FINAL-1.0_en_59eee18f.gif||alt="Shape2" height="1" width="192"]]
276
277 **Reporting Trimester:**
278
279 Period Indicator: T
280
281 Period Duration: P4M (four months)
282
283 Limit per year: 3
284
285 Representation: common:ReportingTrimesterType (YYYY-Tt, e.g. 2000-T3) **Reporting Quarter:**
286
287 Period Indicator: Q
288
289 Period Duration: P3M (three months)
290
291 Limit per year: 4
292
293 Representation: common:ReportingQuarterType (YYYY-Qq, e.g. 2000-Q4) **Reporting Month**:
294
295 Period Indicator: M
296
297 Period Duration: P1M (one month)
298
299 Limit per year: 1
300
301 Representation: common:ReportingMonthType (YYYY-Mmm, e.g. 2000-M12)
302
303 Notes: The reporting month is always represented as two digits, therefore 1-9 are 0 padded (e.g. 01). This allows the values to be sorted chronologically using textual sorting methods.
304
305 **Reporting Week**:
306
307 Period Indicator: W
308
309 Period Duration: P7D (seven days)
310
311 Limit per year: 53
312
313 Representation: common:ReportingWeekType (YYYY-Www, e.g. 2000-W53)
314
315 Notes: There are either 52 or 53 weeks in a reporting year. This is based on the ISO 8601 definition of a week (Monday - Saturday), where the first week of a reporting year is defined as the week with the first Thursday on or after the reporting year start day.^^[[^^3^^>>path:#sdfootnote3sym||name="sdfootnote3anc"]]^^ The reporting week is always represented as two digits, therefore 1-9 are 0 padded (e.g. 01). This allows the values to be sorted chronologically using textual sorting methods.
316
317 **Reporting Day**:
318
319 Period Indicator: D
320
321 Period Duration: P1D (one day)
322
323 Limit per year: 366
324
325 Representation: common:ReportingDayType (YYYY-Dddd, e.g. 2000-D366)
326
327 Notes: There are either 365 or 366 days in a reporting year, depending on whether the reporting year includes leap day (February 29). The reporting day is always represented as three digits, therefore 1-99 are 0 padded (e.g. 001). This allows the values to be sorted chronologically using textual sorting methods.
328
329 The meaning of a reporting year is always based on the start day of the year and requires that the reporting year is expressed as the year at the start of the period. This start day is always the same for a reporting year, and is expressed as a day and a month (e.g. July 1). Therefore, the reporting year 2000 with a start day of July 1 begins on July 1, 2000.
330
331 A specialized attribute (reporting year start day) exists for the purpose of communicating the reporting year start day. This attribute has a fixed identifier
332
333 (REPORTING_YEAR_START_DAY) and a fixed representation (xs:gMonthDay) so that it can always be easily identified and processed in a data message. Although this attribute exists in specialized sub-class, it functions the same as any other attribute outside of its identification and representation. It must takes its identity from a concept and state its relationship with other components of the data structure definition. The ability to state this relationship allows this reporting year start day attribute to exist at the appropriate levels of a data message. In the absence of this attribute, the reporting year start date is assumed to be January 1; therefore if the reporting year coincides with the calendar year, this Attribute is not necessary.
334
335 Since the duration and the reporting year start day are known for any reporting period, it is possible to relate any reporting period to a distinct calendar period. The actual
336
337 Gregorian calendar period covered by the reporting period can be computed as follows
338
339 (based on the standard format of [REPROTING_YEAR]-
340
341 [PERIOD_INDICATOR][PERIOD_VALUE] and the reporting year start day as [REPORTING_YEAR_START_DAY]):
342
343 1. **Determine [REPORTING_YEAR_BASE]:**
344
345 Combine [REPORTING_YEAR] of the reporting period value (YYYY) with [REPORTING_YEAR_START_DAY] (MM-DD) to get a date (YYYY-MM-DD).
346
347 This is the [REPORTING_YEAR_START_DATE]
348
349 1.
350 11. **If the [PERIOD_INDICATOR] is W:**
351 111. **If [REPORTING_YEAR_START_DATE] is a Friday, Saturday, or Sunday:**
352
353 Add^^[[^^4^^>>path:#sdfootnote4sym||name="sdfootnote4anc"]]^^ (P3D, P2D, or P1D respectively) to the [REPORTING_YEAR_START_DATE]. The result is the [REPORTING_YEAR_BASE].
354
355 1.
356 11.
357 111. **If [REPORTING_YEAR_START_DATE] is a Monday, Tuesday, Wednesday, or Thursday:**
358
359 Add^^4^^ (P0D, -P1D, -P2D, or -P3D respectively) to the [REPORTING_YEAR_START_DATE]. The result is the [REPORTING_YEAR_BASE].
360
361 1.
362 11. **Else:**
363
364 The [REPORTING_YEAR_START_DATE] is the [REPORTING_YEAR_BASE].
365
366 1. **Determine [PERIOD_DURATION]:**
367 11. If the [PERIOD_INDICATOR] is A, the [PERIOD_DURATION] is P1Y.
368 11. If the [PERIOD_INDICATOR] is S, the [PERIOD_DURATION] is P6M.
369 11. If the [PERIOD_INDICATOR] is T, the [PERIOD_DURATION] is P4M.
370 11. If the [PERIOD_INDICATOR] is Q, the [PERIOD_DURATION] is P3M.
371 11. If the [PERIOD_INDICATOR] is M, the [PERIOD_DURATION] is P1M.
372 11. If the [PERIOD_INDICATOR] is W, the [PERIOD_DURATION] is P7D.
373 11. If the [PERIOD_INDICATOR] is D, the [PERIOD_DURATION] is P1D.
374 1. **Determine [PERIOD_START]:**
375
376 Subtract one from the [PERIOD_VALUE] and multiply this by the [PERIOD_DURATION]. Add^^4^^ this to the [REPORTING_YEAR_BASE]. The result is the [PERIOD_START]. **4. Determine the [PERIOD_END]:**
377
378 Multiply the [PERIOD_VALUE] by the [PERIOD_DURATION]. Add^^4^^ this to the [REPORTING_YEAR_BASE] add^^4^^ -P1D. The result is the [PERIOD_END].
379
380 For all of these ranges, the bounds include the beginning of the [PERIOD_START] (i.e. 00:00:00) and the end of the [PERIOD_END] (i.e. 23:59:59).
381
382 **Examples:**
383
384 **2010-Q2, REPORTING_YEAR_START_DAY = ~-~-07-01 (July 1)**
385
386 1. [REPORTING_YEAR_START_DATE] = 2010-07-01
387
388 b) [REPORTING_YEAR_BASE] = 2010-07-01
389
390 1. [PERIOD_DURATION] = P3M
391 1. (2-1) * P3M = P3M
392
393 2010-07-01 + P3M = 2010-10-01
394
395 [PERIOD_START] = 2010-10-01
396
397 1. 2 * P3M = P6M
398
399 2010-07-01 + P6M = 2010-13-01 = 2011-01-01
400
401 2011-01-01 + -P1D = 2010-12-31
402
403 [PERIOD_END] = 2010-12-31
404
405 The actual calendar range covered by 2010-Q2 (assuming the reporting year begins July 1) is 2010-10-01T00:00:00/2010-12-31T23:59:59
406
407 **2011-W36, REPORTING_YEAR_START_DAY = ~-~-07-01 (July 1)**
408
409 1. [REPORTING_YEAR_START_DATE] = 2010-07-01
410
411 a) 2011-07-01 = Friday
412
413 2011-07-01 + P3D = 2011-07-04
414
415 [REPORTING_YEAR_BASE] = 2011-07-04
416
417 1. [PERIOD_DURATION] = P7D
418 1. (36-1) * P7D = P245D
419
420 2011-07-04 + P245D = 2012-03-05
421
422 [PERIOD_START] = 2012-03-05
423
424 1. 36 * P7D = P252D
425
426 2011-07-04 + P252D =2012-03-12
427
428 2012-03-12 + -P1D = 2012-03-11
429
430 [PERIOD_END] = 2012-03-11
431
432 The actual calendar range covered by 2011-W36 (assuming the reporting year begins July 1) is 2012-03-05T00:00:00/2012-03-11T23:59:59
433
434 === {{id name="_Toc291513"/}}4.2.7 Distinct Range ===
435
436 In the case that the reporting period does not fit into one of the prescribe periods above, a distinct time range can be used. The value of these ranges is based on the ISO 8601 time interval format of start/duration. Start can be expressed as either an ISO 8601 date or a date-time, and duration is expressed as an ISO 8601 duration. However, the duration can only be positive.
437
438 === {{id name="_Toc291514"/}}4.2.8 Time Format ===
439
440 In version 2.0 of SDMX there is a recommendation to use the time format attribute to gives additional information on the way time is represented in the message. Following an appraisal of its usefulness this is no longer required. However, it is still possible, if required , to include the time format attribute in SDMX-ML.
441
442 |Code|Format
443 |OTP|Observational Time Period: Superset of all SDMX time formats (Gregorian Time Period, Reporting Time Period, and Time Range)
444 |STP|Standard Time Period: Superset of Gregorian and Reporting Time Periods
445 |GTP|Superset of all Gregorian Time Periods and date-time
446 |RTP|Superset of all Reporting Time Periods
447 |TR|(((
448 Time Range: Start time and duration (YYYY-MM-
449
450 DD(Thh:mm:ss)?/<duration>)
451 )))
452 |GY|Gregorian Year (YYYY)
453 |GTM|Gregorian Year Month (YYYY-MM)
454 |GD|Gregorian Day (YYYY-MM-DD)
455 |DT|Distinct Point: date-time (YYYY-MM-DDThh:mm:ss)
456 |RY|Reporting Year (YYYY-A1)
457 |RS|Reporting Semester (YYYY-Ss)
458 |RT|Reporting Trimester (YYYY-Tt)
459 |RQ|Reporting Quarter (YYYY-Qq)
460 |RM|Reporting Month (YYYY-Mmm)
461 |RW|Reporting Week (YYYY-Www)
462 |RD|Reporting Day (YYYY-Dddd)
463
464 ==== Table 1: SDMX-ML Time Format Codes ====
465
466 === {{id name="_Toc291515"/}}4.2.9 Time Zones ===
467
468 In alignment with ISO 8601, SDMX allows the specification of a time zone on all time periods and on the reporting year start day. If a time zone is provided on a reporting year start day, then the same time zone (or none) should be reported for each reporting time period. If the reporting year start day and the reporting period time zone differ, the time zone of the reporting period will take precedence. Examples of each format with time zones are as follows (time zone indicated in bold):
469
470 * Time Range (start date): 2006-06-05**-05:00**/P5D
471 * Time Range (start date-time): 2006-06-05T00:00:00**-05:00**/P5D
472 * Gregorian Year: 2006**-05:00**
473 * Gregorian Month: 2006-06**-05:00**
474 * Gregorian Day: 2006-06-05**-05:00**
475 * Distinct Point: 2006-06-05T00:00:00**-05:00**
476 * Reporting Year: 2006-A1**-05:00**
477 * Reporting Semester: 2006-S2**-05:00**
478 * Reporting Trimester: 2006-T2**-05:00**
479 * Reporting Quarter: 2006-Q3**-05:00**
480 * Reporting Month: 2006-M06**-05:00**
481 * Reporting Week: 2006-W23**-05:00**
482 * Reporting Day: 2006-D156**-05:00**
483 * Reporting Year Start Day: ~-~-07-01**-05:00**
484
485 According to ISO 8601, a date without a time-zone is considered "local time". SDMX assumes that local time is that of the sender of the message. In this version of SDMX, an optional field is added to the sender definition in the header for specifying a time zone. This field has a default value of 'Z' (UTC). This determination of local time applies for all dates in a message.
486
487 === {{id name="_Toc291516"/}}4.2.10 Representing Time Spans Elsewhere ===
488
489 It has been possible since SDMX 2.0 for a Component to specify a representation of a time span. Depending on the format of the data message, this resulted in either an element with 2 XML attributes for holding the start time and the duration or two separate XML attributes based on the underlying Component identifier. For example, if REF_PERIOD were given a representation of time span, then in the Compact data format, it would be represented by two XML attributes; REF_PERIODStartTime (holding the start) and REF_PERIOD (holding the duration). If a new simple type is introduced in the SDMX schemas that can hold ISO 8601 time intervals, then this will no longer be necessary. What was represented as this:
490
491 <Series REF_PERIODStartTime="2000-01-01T00:00:00" REF_PERIOD="P2M"/>
492
493 can now be represented with this:
494
495 <Series REF_PERIOD="2000-01-01T00:00:00/P2M"/>
496
497 === {{id name="_Toc291517"/}}4.2.11 Notes on Formats ===
498
499 There is no ambiguity in these formats so that for any given value of time, the category of the period (and thus the intended time period range) is always clear. It should also be noted that by utilizing the ISO 8601 format, and a format loosely based on it for the report periods, the values of time can easily be sorted chronologically without additional parsing.
500
501 === {{id name="_Toc291518"/}}4.2.12 Effect on Time Ranges ===
502
503 All SDMX-ML data messages are capable of functioning in a manner similar to SDMXEDI if the Dimension at the observation level is time: the time period for the first observation can be stated and the rest of the observations can omit the time value as it can be derived from the start time and the frequency. Since the frequency can be determined based on the actual format of the time value for everything but distinct points in time and time ranges, this makes is even simpler to process as the interval between time ranges is known directly from the time value.
504
505 === 4.2.13 Time in Query Messages ===
506
507 When querying for time values, the value of a time parameter can be provided as any of the Observational Time Period formats and must be paired with an operator. This section will detail how systems processing query messages should interpret these parameters.
508
509 Fundamental to processing a time value parameter in a query message is understanding that all time periods should be handled as a distinct range of time. Since the time parameter in the query is paired with an operator, this also effectively represents a distinct range of time. Therefore, a system processing the query must simply match the data where the time period for requested parameter is encompassed by the time period resulting from value of the query parameter. The following table details how the operators should be interpreted for any time period provided as a parameter.
510
511 |**Operator**|**Rule**
512 |Greater Than|Any data after the last moment of the period
513 |Less Than|Any data before the first moment of the period
514 |Greater Than or Equal To|Any data on or after the first moment of the period
515 |Less Than or Equal To|Any data on or before the last moment of the period
516 |Equal To|Any data which falls on or after the first moment of the period and before or on the last moment of the period
517
518 Reporting Time Periods as query parameters are handled like this: any data within the bounds of the reporting period for the year is matched, regardless of the actual start day of the reporting year. In addition, data reported against a normal calendar period is matched if it falls within the bounds of the time parameter based on a reporting year start day of January 1. When determining whether another reporting period falls within the bounds of a report period query parameter, one will have to take into account the actual time period to compare weeks and days to higher order report periods. This will be demonstrated in the examples to follow.
519
520 **Examples:**
521
522 **Gregorian Period**
523
524 Query Parameter: Greater than 2010
525
526 Literal Interpretation: Any data where the start period occurs after 2010-1231T23:59:59.
527
528 Example Matches:
529
530 * 2011 or later
531 * 2011-01 or later
532 * 2011-01-01 or later
533 * 2011-01-01/P[Any Duration] or any later start date
534 * 2011-[Any reporting period] (any reporting year start day)
535 * 2010-S2 (reporting year start day ~-~-07-01 or later)
536 * 2010-T3 (reporting year start day ~-~-07-01 or later)
537 * 2010-Q3 or later (reporting year start day ~-~-07-01 or later)
538 * 2010-M07 or later (reporting year start day ~-~-07-01 or later)
539 * 2010-W28 or later (reporting year start day ~-~-07-01 or later)
540 * 2010-D185 or later (reporting year start day ~-~-07-01 or later)
541
542 **Reporting Period**
543
544 Query Parameter: Greater than or equal to 2010-Q3
545
546 Literal Interpretation: Any data with a reporting period where the start period is on or after the start period of 2010-Q3 for the same reporting year start day, or and data where the start period is on or after 2010-07-01. Example Matches:
547
548 * 2011 or later
549 * 2010-07 or later
550 * 2010-07-01 or later
551 * 2010-07-01/P[Any Duration] or any later start date
552 * 2011-[Any reporting period] (any reporting year start day)
553 * 2010-S2 (any reporting year start day)
554 * 2010-T3 (any reporting year start day)
555 * 2010-Q3 or later (any reporting year start day)
556 * 2010-M07 or later (any reporting year start day)
557 * 2010-W27 or later (reporting year start day ~-~-01-01)^^5^^ • 2010-D182 or later (reporting year start day ~-~-01-01)
558 * 2010-W28 or later (reporting year start day ~-~-07-01)^^6^^
559 * 2010-D185 or later (reporting year start day ~-~-07-01)
560
561 == 4.3 Versioning ==
562
563 Versioning operates at the level of versionable and maintainable objects in the SDMX information model. Within the SDMX Structure and MetadataSet messages, there is a well-defined pattern for artefact versioning and referencing. The artefact identifiers are qualified by their version numbers – that is, an object with an Agency of "A", and ID of "X" and a version of "1.0.0" is a different object than one with an Agency of "A", an ID of "X", and a version of "1.1.0".
564
565 As of SDMX 3.0, the versioning rules are extended to allow for truly versioned artefacts through the implementation of the rules of the well-known practice called "Semantic Versioning" [[(>>url:http://semver.org/]][[__http:~~/~~/semver.org__>>url:http://semver.org/]][[)>>url:http://semver.org/]], in addition to the legacy non-restrictive versioning scheme. In addition, the "isFinal" property is removed from //MaintainableArtefact//. According to the legacy versioning, any artefact defined without a version is equivalent to following the legacy versioning, thus having version ‘1.0’.
566
567 === 4.3.1 Non-versioned artefacts ===
568
569 Indeed, some use cases do not need or are incompatible with versioning for some or all their structural artefacts, such as the Agency, Data Providers, Metadata Providers and Data Consumer Schemes. These artefacts follow the legacy versioning, with a fixed version set to ‘1.0’.
570
571 Many existing organisation’s data management systems work with version-less structures and apply ad-hoc structural metadata governance processes. The new nonversioned artefacts will allow supporting those numerous situations, where organisations do not manage version numbers.
572
573 [[image:SDMX 3-0-0 SECTION 6 FINAL-1.0_en_59eee18f.gif||alt="Shape3" height="1" width="192"]]
574
575 2010-Q3 (with a reporting year start day of ~-~-01-01) starts on 2010-07-01. This is day 4 of week 26, therefore the first week matched is week 27.
576
577 2010-Q3 (with a reporting year start day of ~-~-07-01) starts on 2011-01-01. This is day 6 of week 27, therefore the first week matched is week 28.
578
579 === 4.3.2 Semantically versioned artefacts ===
580
581 Since the purpose of SDMX versioning is to allow communicating the structural artefact changes to data exchange partners and connected systems, SDMX 3.0 offers Semantic Versioning (aka SemVer) with a clear and unambiguous syntax to all semantically versioned SDMX 3.0 structural artefacts. Semantic versioning will thus better respond to situations where the SDMX standard itself is the only structural contract between data providers and data consumers and where changes in structures can only be communicated through the version number increases.
582
583 The semantic version number consists of four parts: MAJOR, MINOR, PATCH and EXTENSION, the first three parts being separated by a dot (.), the last two parts being separated by a hyphen (-): MAJOR.MINOR.PATCH-EXTENSION. All versions are ordered.
584
585 The detailed rules for semantic versioning are listed in chapter 14 in the annex for “Semantic Versioning”. In short, they define:
586
587 Given a version number MAJOR.MINOR.PATCH (without EXTENSION), when making changes to that semantically versioned SDMX artefact, then one must increment the:
588
589 1. MAJOR version when backwards incompatible artefact changes are made,
590 1. MINOR version when artefact elements are added in a backwards compatible manner, or
591 1. PATCH version when backwards compatible artefact property changes are made.
592
593 When incrementing a version part, the right-hand side parts are 0-ed (reset to ‘0’).
594
595 Extensions can be added, changed or dropped.
596
597 iven an extended version number MAJOR.MINOR.PATCH-EXTENSION, when making changes to that versioned artefact, then one is not required to increment the version if those changes are within the allowed scope of the version increment from the previous version (if that existed); otherwise, the above version increment rules apply. EXTENSIONs can be used e.g., for drafting or a pre-release.
598
599 Semantically versioned SDMX artefacts will thus be safe to use. Specific version patterns allow them to become either immutable, i.e., the maintainer commits to never change their content, or changeable only within a well-defined scope. If any further change is required, a new version must be created first. Furthermore, the impact of the further change is communicated using a clear version increment. The built-in version extension facility allows for eased drafting of new SDMX artefact versions.
600
601 The production versions of identifiable artefacts are assumed stable, i.e., they do not have an EXTENSION. This is because once in production, an artefact cannot change in any way, or it must change the version. For cases where an artefact is not static, like during the drafting, the version must indicate this by including an EXTENSION. Draft artefacts should not be used outside of a specific system designed to accommodate them. For most purposes, all artefacts should become stable before being used in production.
602
603 === 4.3.3 Legacy-versioned artefacts ===
604
605 Organisations wishing to keep a maximum of backwards compatibility with existing implementations can continue using the previous 2-digit convention for version numbers (MAJOR.MINOR) as in the past, such as '2.3', but without the ‘isFinal’ property. The new SDMX 3.0 standard does not add any strict rules or guarantees about changes in those artefacts, since the legacy versioning rules were rather loose and non-binding, including the meaning of the ‘isFinal’ property, and their implementations were varying.
606
607 In order to make artefacts immutable or changes truly predictable, a move to the new semantic versioning syntax is required.
608
609 === 4.3.4 Dependency management and references ===
610
611 New flexible dependency specifications with wildcarding allow for easier data model maintenance and enhancements for semantically versioned SDMX artefacts. This allows implementing a smart referencing mechanism, whereby an artefact may reference:
612
613 * a fixed version of another artefact
614 * the **latest available** version of another artefact
615 * the **latest backward compatible** version of another artefact, or the **latest backward and forward** **compatible** version of another artefact.
616
617 References not representing a strict artefact dependency, such as the target artefacts defined in a MetadataProvisionAgreement allow for linking to **all currently available** versions of another artefact. Another illustrative case for such loose referencing is that of Constraints and flows. A Constraint may reference many Dataflows or Metadataflows, the addition of more references to flow objects does not version the Constraint. This is because the Constraints are not properties of the flows – they merely make references to them.
618
619 Semantically versioned artefacts must only reference other semantically versioned artefacts, which may include extended versions. Non-versioned and legacy-versioned artefacts can reference any other non-versioned or versioned (whether semantic or legacy) artefacts. The scope of wildcards in references adapts correspondingly.
620
621 The mechanism named "early binding" refers to a dependency on a stable versioned artefact – everything with a stable versioned identity is a known quantity and will not change. The "late binding" mechanism is based on a wildcarded reference, and it resolves that reference and determines the currently related artefact at runtime.
622
623 One area which is much impacted by this versioning scheme is the ability to reference external objects. With the many dependencies within the various structural objects in SDMX, it is useful to have a scheme for external referencing. This is done at the level of maintainable objects (DSDs, Codelists, Concept Schemes, etc.) In an SDMX Structure Message, whenever an "isExternalReference" attribute is set to true, then the application must resolve the address provided in the associated "uri" attribute and use the SDMX Structure Message stored at that location for the full definition of the object in question. Alternately, if a registry "urn" attribute has been provided, the registry can be used to supply the full details of the object.
624
625 The detailed rules for dependency management and references are listed in chapter 14 in the annex for “Semantic Versioning”.
626
627 In order to allow resolving the described new forms of dependencies, the SDMX 3.0 Rest API supports retrievals legacy-versioned, wildcarded and extended artefact versions:
628
629 * Artefact queries for a **specific** version (X.Y, X.Y.Z or X.Y.Z-EXT).
630 * Artefact queries for **latest available** semantic versions within the wildcard scope (X+.Y.Z, X.Y+.Z or X.Y.Z+).
631 * Queries for **non-versioned** artefacts.
632 * Artefact queries for **all available** semantic versions within the wildcard scope (*, X.* or X.Y.*), where only the first form is required for resolving wildcarded loose references.
633
634 The combination of wildcarded queries with a specific version extension is not permitted.
635
636 Full details can be found in the SDMX RESTful web services specification.
637
638 == 4.4 Structural Metadata Querying Best Practices ==
639
640 When querying for structural metadata, the ability to state how references should be resolved is quite powerful. However, this mechanism is not always necessary and can create an undue burden on the systems processing the queries if it is not used properly.
641
642 Any structural metadata object which contains a reference to an object can be queried based on that reference. For example, a categorisation references both a category and the object is it categorising. As this is the case, one can query for categorisations which categorise a particular object or which categorise against a particular category or category scheme. This mechanism should be used when the referenced object is known.
643
644 When the referenced object is not known, then the reference resolution mechanism could be used. For example, suppose one wanted to find all category schemes and the related categorisations for a given maintenance agency. In this case, one could query for the category scheme by the maintenance agency and specify that parent and sibling references should be resolved. This would result in the categorisations which reference the categories in the matched schemes to be returned, as well as the object which they categorise.