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Helena 1.1 1 {{box title="**Contents**"}}
2 {{toc/}}
3 {{/box}}
4
5 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.
6
7 == 4.1 Representations ==
8
9 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.
10
11 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.
12
13 |SDMX-ML Data Type|XML Schema Data Type|.NET Framework Type|(((
14 Java Data Type
15 )))
16 |**String**|**xsd:string**|**System.String**|**java.lang.String**
17 |**Big Integer**|**xsd:integer**|**System.Decimal**|**java.math.BigInteger**
18 |**Integer**|**xsd:int**|**System.Int32**|**int**
19 |**Long**|**xsd.long**|**System.Int64**|**long**
20 |**Short**|**xsd:short**|**System.Int16**|**short**
21 |**Decimal**|**xsd:decimal**|**System.Decimal**|**java.math.BigDecimal**
22 |**Float**|**xsd:float**|**System.Single**|**float**
23 |**Double**|**xsd:double**|**System.Double**|**double**
24 |**Boolean**|**xsd:boolean**|**System.Boolean**|**boolean**
25 |**URI**|**xsd:anyURI**|**System.Uri**|**Java.net.URI or java.lang.String**
26 |**DateTime**|**xsd:dateTime**|**System.DateTime**|**javax.xml.datatype.XMLG regorianCalendar**
27 |**Time**|**xsd:time**|**System.DateTime**|**javax.xml.datatype.XMLG regorianCalendar**
28 |**GregorianYear**|**xsd:gYear**|**System.DateTime**|**javax.xml.datatype.XMLG regorianCalendar**
29 |**GregorianMonth**|**xsd:gYearMonth**|**System.DateTime**|**javax.xml.datatype.XMLG regorianCalendar**
30 |**GregorianDay**|**xsd:date**|**System.DateTime**|**javax.xml.datatype.XMLG regorianCalendar**
31 |**Day, MonthDay, Month**|**xsd:g***|**System.DateTime**|**javax.xml.datatype.XMLG regorianCalendar**
32 |**Duration**|**xsd:duration**|**System.TimeSpan**|**javax.xml.datatype.Dura tion**
33
34 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:
35
36 * **AlphaNumeric** (**common:AlphaNumericType**, string which only allows A-z and 09)
37 * **Alpha** (**common:AlphaType**, string which only allows A-z)
38 * **Numeric** (**common:NumericType**, string which only allows 0-9, but is not numeric so that is can having leading zeros)
39 * **Count** (**xs:integer**, a sequence with an interval of "1")
40 * **InclusiveValueRange** (**xs:decimal** with the **minValue** and **maxValue** facets supplying the bounds)
41 * **ExclusiveValueRange** (**xs:decimal** with the **minValue** and **maxValue** facets supplying the bounds)
42 * **Incremental** (**xs:decimal** with a specified **interval**; the interval is typically enforced outside of the XML validation)
43 * **TimeRange** (**common:TimeRangeType**, **startDateTime** + **Duration**)
44 * **ObservationalTimePeriod** (**common:ObservationalTimePeriodType**, a union of **StandardTimePeriod** and **TimeRange**).
45 * **StandardTimePeriod** (**common:StandardTimePeriodType**, a union of **BasicTimePeriod** and **ReportingTimePeriod**).
46 * **BasicTimePeriod** (**common:BasicTimePeriodType**, a union of **GregorianTimePeriod** and **DateTime**)
47 * **GregorianTimePeriod** (**common:GregorianTimePeriodType**, a union of **GregorianYear**, **GregorianMonth**, and **GregorianDay**)
48 * **ReportingTimePeriod** (**common:ReportingTimePeriodType**, a union of **ReportingYear**, **ReportingSemester**, **ReportingTrimester**, **ReportingQuarter**, **ReportingMonth**, **ReportingWeek**, and **ReportingDay**).
49 * **ReportingYear** (**common:ReportingYearType**)
50 * **ReportingSemester** (**common:ReportingSemesterType**)
51 * **ReportingTrimester** (**common:ReportingTrimesterType**)
52 * **ReportingQuarter** (**common:ReportingQuarterType**)
53 * **ReportingMonth** (**common:ReportingMonthType**)
54 * **ReportingWeek** (**common:ReportingWeekType**)
55 * **ReportingDay** (**common:ReportingDayType**)
56 * **XHTML** (**common:StructuredText**, allows for multi-lingual text content that has **XHTML** markup)
57 * **KeyValues** (**common:DataKeyType**)
58 * **IdentifiableReference** (types for each IdentifiableObject)
59 * **GeospatialInformation** (a geo feature set, according to the pattern in section 7.2)
60
61 Data types also have a set of facets:
62
63 * **isSequence = true | false** (indicates a sequentially increasing value)
64 * **minLength = positive integer** (# of characters/digits)
65 * **maxLength = positive integer** (# of characters/digits)
66 * **startValue = decimal** (for numeric sequence)
67 * **endValue = decimal** (for numeric sequence)
68 * **interval = decimal** (for numeric sequence) • **timeInterval = duration**
69 * **startTime = BasicTimePeriod** (for time range)
70 * **endTime = BasicTimePeriod** (for time range)
71 * **minValue = decimal** (for numeric range)
72 * **maxValue = decimal** (for numeric range)
73 * **decimal = Integer** (# of digits to right of decimal point)
74 * **pattern =** (a regular expression, as per W3C XML Schema)
75 * **isMultiLingual = boolean** (for specifying text can occur in more than one language)
76
77 Note that code lists may also have textual representations assigned to them, in addition to their enumeration of codes.
78
79 4.1.1 Data Types
80
81 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.
82
83 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.
84
85 For example, for the id type, this is the XML schema definition:
86
87 > <xs:simpleType name="IDType">
88 > <xs:restriction base="NestedIDType">
89 > <xs:pattern value="[A-Za-z0-9_@$\-]+"/>
90 > </xs:restriction>
91 > </xs:simpleType>
92
93 Where the NestedIDType is also a restriction of string.
94
95 The above looks like this, in JSON schema:
96
97 > "idType": {
98 > "type": "string",
99 > "pattern": "^[A-Za-z0-9_@$-]+$"
100 > }
101
102 There are also cases, though, that data types cannot be mapped like above. One such case is the array data type, which was introduced in SDMX 3.0 as a new representation. In JSON schema an array is already natively foreseen, while in the XML schema, this has to be defined as a complex type, with an SDMX specific definition (i.e., specific element/attribute names for SDMX). Beyond that, the minimum and/or maximum number of items within an array is possible in both cases.
103
104 Further to the above, the mapping between the non-native data types is presented in the table below:
105
106 |**SDMX Facet**|**XML Schema**|**JSON schema **"**pattern**"[[^^~[1~]^^>>path:#_ftn1]] **for "string" type**
107 |GregorianYear|xsd:gYear|(((
108 "^-?([1-9][0-9]{3,}|0[0-9]{3})(Z|(\+|-)((0[0-
109
110 9]|1[0-3]):[0-5][0-9]|14:00))?$"
111 )))
112 |GregorianMonth|xsd:gYearMonth|(((
113 "^-?([1-9][0-9]{3,}|0[0-9]{3})-(0[1-9]|1[0-
114
115 2])(Z|(\+|-)((0[0-9]|1[0-3]):[0-5][0-
116
117 9]|14:00))?$"
118 )))
119 |GregorianDay|xsd:date|(((
120 "^-?([1-9][0-9]{3,}|0[0-9]{3})-(0[1-9]|1[0-2])-
121
122 (0[1-9]|[12][0-9]|3[01])(Z|(\+|-)((0[0-9]|1[0-
123
124 3]):[0-5][0-9]|14:00))?$"
125 )))
126 |Day|xsd:gDay|(((
127 "^~-~--(0[1-9]|[12][0-9]|3[01])(Z|(\+|-
128
129 )((0[0-9]|1[0-3]):[0-5][0-9]|14:00))?$"
130 )))
131 |MonthDay|xsd:gMonthDay|(((
132 "^~-~-(0[1-9]|1[0-2])-(0[1-9]|[12][0-
133
134 9]|3[01])(Z|(\+|-)((0[0-9]|1[0-3]):[0-5][0-
135
136 9]|14:00))?$"
137 )))
138 |Month|xsd:Month|(((
139 "^~-~-(0[1-9]|1[0-2])(Z|(\+|-)((0[0-9]|1[0-
140
141 3]):[0-5][0-9]|14:00))?$"
142 )))
143 |Duration|xsd:duration|(((
144 "^-?P[0-9]+Y?([0-9]+M)?([0-9]+D)?(T([0-
145
146 9]+H)?([0-9]+M)?([0-9]+(\.[0-9]+)?S)?)?$"
147 )))
148
Helena 1.2 149 == 4.2 Time and Time Format ==
Helena 1.1 150
151 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.
152
Helena 1.2 153 === 4.2.1 Introduction ===
Helena 1.1 154
155 First, it is important to recognize that most observation times are a period. SDMX specifies precisely how Time is handled.
156
157 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.
158
159 The hierarchy of time formats is as follows (**bold** indicates a category which is made up of multiple formats, //italic// indicates a distinct format):
160
161 * **Observational Time Period **o **Standard Time Period**
162
163 § **Basic Time Period**
164
165 * **Gregorian Time Period**
166 * //Date Time//
167
168 § **Reporting Time Period **o //Time Range//
169
170 The details of these time period categories and of the distinct formats which make them up are detailed in the sections to follow.
171
Helena 1.2 172 === 4.2.2 Observational Time Period ===
Helena 1.1 173
174 This is the superset of all time representations in SDMX. This allows for time to be expressed as any of the allowable formats.
175
Helena 1.2 176 === 4.2.3 Standard Time Period ===
Helena 1.1 177
178 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).
179
Helena 1.2 180 === 4.2.4 Gregorian Time Period ===
Helena 1.1 181
182 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:
183
184 **Gregorian Year:**
185
186 Representation: xs:gYear (YYYY)
187 Period: the start of January 1 to the end of December 31 **Gregorian Year Month**:
188 Representation: xs:gYearMonth (YYYY-MM)
189 Period: the start of the first day of the month to end of the last day of the month **Gregorian Day**:
190 Representation: xs:date (YYYY-MM-DD)
191 Period: the start of the day (00:00:00) to the end of the day (23:59:59)
192
Helena 1.3 193 === 4.2.5 Date Time ===
Helena 1.1 194
195 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.
196
197 Representation: xs:dateTime (YYYY-MM-DDThh:mm:ss)[[^^~[2~]^^>>path:#_ftn2]]
198
Helena 1.3 199 === 4.2.6 Standard Reporting Period ===
Helena 1.1 200
201 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:
202
203 [REPORTING_YEAR]-[PERIOD_INDICATOR][PERIOD_VALUE]
204
205 Where:
206
207 REPORTING_YEAR represents the reporting year as four digits (YYYY) PERIOD_INDICATOR identifies the type of period which determines the duration of the period
208 PERIOD_VALUE indicates the actual period within the year
209
210 The following section details each of the standard reporting periods defined in SDMX:
211
212 **Reporting Year**:
213
214 Period Indicator: A
215
216 Period Duration: P1Y (one year)
217
218 Limit per year: 1
219
220 Representation: common:ReportingYearType (YYYY-A1, e.g. 2000-A1) **Reporting Semester:**
221
222 Period Indicator: S
223
224 Period Duration: P6M (six months)
225
226 Limit per year: 2
227
228 Representation: common:ReportingSemesterType (YYYY-Ss, e.g. 2000-S2)
229
230 **Reporting Trimester:**
231
232 Period Indicator: T
233
234 Period Duration: P4M (four months)
235
236 Limit per year: 3
237
238 Representation: common:ReportingTrimesterType (YYYY-Tt, e.g. 2000-T3) **Reporting Quarter:**
239
240 Period Indicator: Q
241
242 Period Duration: P3M (three months)
243
244 Limit per year: 4
245
246 Representation: common:ReportingQuarterType (YYYY-Qq, e.g. 2000-Q4) **Reporting Month**:
247
248 Period Indicator: M
249
250 Period Duration: P1M (one month)
251
252 Limit per year: 1
253
254 Representation: common:ReportingMonthType (YYYY-Mmm, e.g. 2000-M12) 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.
255
256 **Reporting Week**:
257
258 Period Indicator: W
259
260 Period Duration: P7D (seven days)
261
262 Limit per year: 53
263
264 Representation: common:ReportingWeekType (YYYY-Www, e.g. 2000-W53)
265
266 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:#_ftn3]] 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.
267
268 **Reporting Day**:
269
270 Period Indicator: D
271
272 Period Duration: P1D (one day)
273
274 Limit per year: 366
275
276 Representation: common:ReportingDayType (YYYY-Dddd, e.g. 2000-D366) 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.
277
278 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.
279
280 A specialized attribute (reporting year start day) exists for the purpose of communicating the reporting year start day. This attribute has a fixed identifier
281
282 (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.
283
284 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 Gregorian calendar period covered by the reporting period can be computed as follows (based on the standard format of [REPROTING_YEAR]-
285
286 [PERIOD_INDICATOR][PERIOD_VALUE] and the reporting year start day as [REPORTING_YEAR_START_DAY]):
287
288 1. **Determine [REPORTING_YEAR_BASE]:**
289
290 Combine [REPORTING_YEAR] of the reporting period value (YYYY) with [REPORTING_YEAR_START_DAY] (MM-DD) to get a date (YYYY-MM-DD).
291
292 This is the [REPORTING_YEAR_START_DATE]
293
294 1.
295 11. **If the [PERIOD_INDICATOR] is W:**
296 111. **If [REPORTING_YEAR_START_DATE] is a Friday, Saturday, or Sunday:**
297
298 Add[[^^~[4~]^^>>path:#_ftn4]] (P3D, P2D, or P1D respectively) to the [REPORTING_YEAR_START_DATE]. The result is the [REPORTING_YEAR_BASE].
299
300 1.
301 11.
302 111. **If [REPORTING_YEAR_START_DATE] is a Monday, Tuesday, Wednesday, or Thursday:**
303
304 Add^^4^^ (P0D, -P1D, -P2D, or -P3D respectively) to the [REPORTING_YEAR_START_DATE]. The result is the [REPORTING_YEAR_BASE].
305
306 1.
307 11. **Else:**
308
309 The [REPORTING_YEAR_START_DATE] is the [REPORTING_YEAR_BASE].
310
311 1. **Determine [PERIOD_DURATION]:**
312 11. If the [PERIOD_INDICATOR] is A, the [PERIOD_DURATION] is P1Y.
313 11. If the [PERIOD_INDICATOR] is S, the [PERIOD_DURATION] is P6M.
314 11. If the [PERIOD_INDICATOR] is T, the [PERIOD_DURATION] is P4M.
315 11. If the [PERIOD_INDICATOR] is Q, the [PERIOD_DURATION] is P3M.
316 11. If the [PERIOD_INDICATOR] is M, the [PERIOD_DURATION] is P1M.
317 11. If the [PERIOD_INDICATOR] is W, the [PERIOD_DURATION] is P7D.
318 11. If the [PERIOD_INDICATOR] is D, the [PERIOD_DURATION] is P1D.
319 1. **Determine [PERIOD_START]:**
320
321 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].
322
323 1. **Determine the [PERIOD_END]:**
324
325 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].
326
327 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).
328
329 **Examples:**
330
331 **2010-Q2, REPORTING_YEAR_START_DAY = ~-~-07-01 (July 1)**
332
333 1. [REPORTING_YEAR_START_DATE] = 2010-07-01
334
335 b) [REPORTING_YEAR_BASE] = 2010-07-01
336
337 1. [PERIOD_DURATION] = P3M 3. (2-1) * P3M = P3M
338
339 2010-07-01 + P3M = 2010-10-01
340
341 [PERIOD_START] = 2010-10-01
342
343 4. 2 * P3M = P6M
344
345 2010-07-01 + P6M = 2010-13-01 = 2011-01-01
346
347 2011-01-01 + -P1D = 2010-12-31
348
349 [PERIOD_END] = 2010-12-31
350
351 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
352
353 **2011-W36, REPORTING_YEAR_START_DAY = ~-~-07-01 (July 1)**
354
355 1. [REPORTING_YEAR_START_DATE] = 2010-07-01
356
357 a) 2011-07-01 = Friday
358
359 2011-07-01 + P3D = 2011-07-04
360
361 [REPORTING_YEAR_BASE] = 2011-07-04
362
363 1. [PERIOD_DURATION] = P7D 3. (36-1) * P7D = P245D
364
365 2011-07-04 + P245D = 2012-03-05
366
367 [PERIOD_START] = 2012-03-05
368
369 4. 36 * P7D = P252D
370
371 2011-07-04 + P252D =2012-03-12
372
373 2012-03-12 + -P1D = 2012-03-11
374
375 [PERIOD_END] = 2012-03-11
376
377 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
378
Helena 1.3 379 === 4.2.7 Distinct Range ===
Helena 1.1 380
381 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.
382
Helena 1.3 383 === 4.2.8 Time Format ===
Helena 1.1 384
385 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.
386
387 |Code|Format
388 |OTP|Observational Time Period: Superset of all SDMX time formats (Gregorian Time Period, Reporting Time Period, and Time Range)
389 |STP|Standard Time Period: Superset of Gregorian and Reporting Time Periods
390 |GTP|Superset of all Gregorian Time Periods and date-time
391 |RTP|Superset of all Reporting Time Periods
392 |TR|(((
393 Time Range: Start time and duration (YYYY-MM-
394
395 DD(Thh:mm:ss)?/<duration>)
396 )))
397 |GY|Gregorian Year (YYYY)
398 |GTM|Gregorian Year Month (YYYY-MM)
399 |GD|Gregorian Day (YYYY-MM-DD)
400 |DT|Distinct Point: date-time (YYYY-MM-DDThh:mm:ss)
401 |RY|Reporting Year (YYYY-A1)
402 |RS|Reporting Semester (YYYY-Ss)
403 |RT|Reporting Trimester (YYYY-Tt)
404 |RQ|Reporting Quarter (YYYY-Qq)
405 |RM|Reporting Month (YYYY-Mmm)
406 |RW|Reporting Week (YYYY-Www)
407 |RD|Reporting Day (YYYY-Dddd)
408
409 ==== Table 1: SDMX-ML Time Format Codes ====
410
Helena 1.3 411 === 4.2.9 Time Zones ===
Helena 1.1 412
413 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):
414
415 * Time Range (start date): 2006-06-05**-05:00**/P5D
416 * Time Range (start date-time): 2006-06-05T00:00:00**-05:00**/P5D
417 * Gregorian Year: 2006**-05:00**
418 * Gregorian Month: 2006-06**-05:00**
419 * Gregorian Day: 2006-06-05**-05:00**
420 * Distinct Point: 2006-06-05T00:00:00**-05:00**
421 * Reporting Year: 2006-A1**-05:00**
422 * Reporting Semester: 2006-S2**-05:00**
423 * Reporting Trimester: 2006-T2**-05:00**
424 * Reporting Quarter: 2006-Q3**-05:00**
425 * Reporting Month: 2006-M06**-05:00**
426 * Reporting Week: 2006-W23**-05:00**
427 * Reporting Day: 2006-D156**-05:00**
428 * Reporting Year Start Day: ~-~-07-01**-05:00**
429
430 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.
431
Helena 1.3 432 === 4.2.10 Representing Time Spans Elsewhere ===
Helena 1.1 433
434 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:
435
436 <Series REF_PERIODStartTime="2000-01-01T00:00:00" REF_PERIOD="P2M"/>
437
438 can now be represented with this:
439
440 <Series REF_PERIOD="2000-01-01T00:00:00/P2M"/>
441
Helena 1.3 442 === 4.2.11 Notes on Formats ===
Helena 1.1 443
444 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.
445
Helena 1.4 446 === 4.2.12 Effect on Time Ranges ===
Helena 1.1 447
448 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.
449
Helena 1.4 450 === 4.2.13 Time in Query Messages ===
Helena 1.1 451
452 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.
453
454 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.
455
456 |**Operator**|**Rule**
457 |Greater Than|Any data after the last moment of the period
458 |Less Than|Any data before the first moment of the period
459 |Greater Than or Equal To|Any data on or after the first moment of the period
460 |Less Than or Equal To|Any data on or before the last moment of the period
461 |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
462
463 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.
464
465 **Examples:**
466
467 **Gregorian Period**
468
469 Query Parameter: Greater than 2010
470
471 Literal Interpretation: Any data where the start period occurs after 2010-1231T23:59:59.
472
473 Example Matches:
474
475 * 2011 or later
476 * 2011-01 or later
477 * 2011-01-01 or later
478 * 2011-01-01/P[Any Duration] or any later start date
479 * 2011-[Any reporting period] (any reporting year start day)
480 * 2010-S2 (reporting year start day ~-~-07-01 or later)
481 * 2010-T3 (reporting year start day ~-~-07-01 or later)
482 * 2010-Q3 or later (reporting year start day ~-~-07-01 or later)
483 * 2010-M07 or later (reporting year start day ~-~-07-01 or later)
484 * 2010-W28 or later (reporting year start day ~-~-07-01 or later)
485 * 2010-D185 or later (reporting year start day ~-~-07-01 or later)
486
487 **Reporting Period**
488
489 Query Parameter: Greater than or equal to 2010-Q3
490
491 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:
492
493 * 2011 or later
494 * 2010-07 or later
495 * 2010-07-01 or later
496 * 2010-07-01/P[Any Duration] or any later start date
497 * 2011-[Any reporting period] (any reporting year start day)
498 * 2010-S2 (any reporting year start day)
499 * 2010-T3 (any reporting year start day)
500 * 2010-Q3 or later (any reporting year start day)
501 * 2010-M07 or later (any reporting year start day)
502 * 2010-W27 or later (reporting year start day ~-~-01-01)^^5^^
503 * 2010-D182 or later (reporting year start day ~-~-01-01)
Helena 1.5 504 * 2010-W28 or later (reporting year start day ~-~-07-01)^^6^^
505 * 2010-D185 or later (reporting year start day ~-~-07-01)
Helena 1.1 506
Helena 1.5 507 = 4.3 Versioning ==
508
Helena 1.1 509 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".
510
511 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
512
513 //MaintainableArtefact//. According to the legacy versioning, any artefact defined without a version is equivalent to following the legacy versioning, thus having version
514
515 ‘1.0’.
516
Helena 1.7 517 === 4.3.1 Non-versioned artefacts ===
Helena 1.1 518
519 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’.
520
521 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.
522
Helena 1.6 523 === 4.3.2 Semantically versioned artefacts ===
Helena 1.1 524
525 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.
526
527 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.
528
529 The detailed rules for semantic versioning are listed in chapter 14 in the annex for “Semantic Versioning”. In short, they define:
530
531 Given a version number MAJOR.MINOR.PATCH (without EXTENSION), when making changes to that semantically versioned SDMX artefact, then one must increment the:
532
533 1. MAJOR version when backwards incompatible artefact changes are made,
534 1. MINOR version when artefact elements are added in a backwards compatible manner, or
535 1. PATCH version when backwards compatible artefact property changes are made.
536
537 When incrementing a version part, the right-hand side parts are 0-ed (reset to ‘0’).
538
539 Extensions can be added, changed or dropped.
540
541 Given 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.
542
543 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.
544
545 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.
546
Helena 1.8 547 === 4.3.3 Legacy-versioned artefacts ===
Helena 1.1 548
549 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.
550
551 In order to make artefacts immutable or changes truly predictable, a move to the new semantic versioning syntax is required.
552
Helena 1.8 553 === 4.3.4 Dependency management and references ===
Helena 1.1 554
555 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:
556
557 * a fixed version of another artefact
558 * the **latest available** version of another artefact
559 * the **latest backward compatible** version of another artefact, or the **latest backward and forward** **compatible** version of another artefact.
560
561 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.
562
563 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.
564
565 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.
566
567 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.
568
569 The detailed rules for dependency management and references are listed in chapter 14 in the annex for “Semantic Versioning”.
570
571 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:
572
573 * Artefact queries for a **specific** version (X.Y, X.Y.Z or X.Y.Z-EXT).
574 * Artefact queries for **latest available** semantic versions within the wildcard scope (X+.Y.Z, X.Y+.Z or X.Y.Z+).
575 * Queries for **non-versioned** artefacts.
576 * 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.
577
578 The combination of wildcarded queries with a specific version extension is not permitted.
579
580 Full details can be found in the SDMX RESTful web services specification.
581
582 1.
583 11. Structural Metadata Querying Best Practices
584
585 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.
586
587 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.
588
589 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.
590
591
592 ----
593
594 [[~[1~]>>path:#_ftnref1]] Regular expressions, as specified in [[W3C XML Schema Definition Language (XSD)>>url:https://www.w3.org/TR/xmlschema11-2/]][[ >>url:https://www.w3.org/TR/xmlschema11-2/]][[1.1 Part 2: Datatypes>>url:https://www.w3.org/TR/xmlschema11-2/]][[.>>url:https://www.w3.org/TR/xmlschema11-2/]]
595
596 [[~[2~]>>path:#_ftnref2]] The seconds can be reported fractionally
597
598 [[~[3~]>>path:#_ftnref3]] ISO 8601 defines alternative definitions for the first week, all of which produce equivalent results. Any of these definitions could be substituted so long as they are in relation to the reporting year start day.
599
600 [[~[4~]>>path:#_ftnref4]] The rules for adding durations to a date time are described in the W3C XML Schema specification. See [[http:~~/~~/www.w3.org/TR/xmlschema>>url:http://www.w3.org/TR/xmlschema-2/#adding-durations-to-dateTimes]][[->>url:http://www.w3.org/TR/xmlschema-2/#adding-durations-to-dateTimes]][[2/#adding>>url:http://www.w3.org/TR/xmlschema-2/#adding-durations-to-dateTimes]][[->>url:http://www.w3.org/TR/xmlschema-2/#adding-durations-to-dateTimes]][[durations>>url:http://www.w3.org/TR/xmlschema-2/#adding-durations-to-dateTimes]][[->>url:http://www.w3.org/TR/xmlschema-2/#adding-durations-to-dateTimes]][[to>>url:http://www.w3.org/TR/xmlschema-2/#adding-durations-to-dateTimes]][[dateTimes>>url:http://www.w3.org/TR/xmlschema-2/#adding-durations-to-dateTimes]][[ >>url:http://www.w3.org/TR/xmlschema-2/#adding-durations-to-dateTimes]]for further details.
601
602