Changes for page 4 General Notes for Implementers

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edited by Helena
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@@ -146,11 +146,14 @@
 ]+H)?([0-9]+M)?([0-9]+(\.[0-9]+)?S)?)?$"
  )))
--== 4.2 Time and Time Format ==
++1.
++11. Time and Time Format
  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.
--=== 4.2.1 Introduction ===
++1.
++11.
++111. Introduction
  First, it is important to recognize that most observation times are a period. SDMX specifies precisely how Time is handled.
@@ -169,34 +169,50 @@
  The details of these time period categories and of the distinct formats which make them up are detailed in the sections to follow.
--=== 4.2.2 Observational Time Period ===
++1.
++11.
++111. Observational Time Period
  This is the superset of all time representations in SDMX. This allows for time to be expressed as any of the allowable formats.
--=== 4.2.3 Standard Time Period ===
++1.
++11.
++111. Standard Time Period
  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).
--=== 4.2.4 Gregorian Time Period ===
++1.
++11.
++111. Gregorian Time Period
  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:
++
  **Gregorian Year:**
  Representation: xs:gYear (YYYY)
++
  Period: the start of January 1 to the end of December 31 **Gregorian Year Month**:
++
  Representation: xs:gYearMonth (YYYY-MM)
++
  Period: the start of the first day of the month to end of the last day of the month **Gregorian Day**:
++
  Representation: xs:date (YYYY-MM-DD)
++
  Period: the start of the day (00:00:00) to the end of the day (23:59:59)
--=== 4.2.5 Date Time ===
++1.
++11.
++111. Date Time
  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.
  Representation: xs:dateTime (YYYY-MM-DDThh:mm:ss)[[^^~[2~]^^>>path:#_ftn2]]
--=== 4.2.6 Standard Reporting Period ===
++1.
++11.
++111. Standard Reporting Period
  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:
@@ -205,6 +205,7 @@
  Where:
  REPORTING_YEAR represents the reporting year as four digits (YYYY) PERIOD_INDICATOR identifies the type of period which determines the duration of the period
++
  PERIOD_VALUE indicates the actual period within the year
  The following section details each of the standard reporting periods defined in SDMX:
@@ -376,11 +376,15 @@
  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
--=== 4.2.7 Distinct Range ===
++1.
++11.
++111. Distinct Range
  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.
--=== 4.2.8 Time Format ===
++1.
++11.
++111. Time Format
  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.
@@ -408,7 +408,9 @@
  ==== Table 1: SDMX-ML Time Format Codes ====
--=== 4.2.9 Time Zones ===
++1.
++11.
++111. Time Zones
  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):
@@ -429,7 +429,9 @@
  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.
--=== 4.2.10 Representing Time Spans Elsewhere ===
++1.
++11.
++111. Representing Time Spans Elsewhere
  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:
@@ -439,15 +439,21 @@
  <Series REF_PERIOD="2000-01-01T00:00:00/P2M"/>
--=== 4.2.11 Notes on Formats ===
++1.
++11.
++111. Notes on Formats
  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.
--=== 4.2.12 Effect on Time Ranges ===
++1.
++11.
++111. Effect on Time Ranges
  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.
--=== 4.2.13 Time in Query Messages ===
++1.
++11.
++111. Time in Query Messages
  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.
@@ -501,11 +501,9 @@
  * 2010-M07 or later (any reporting year start day)
  * 2010-W27 or later (reporting year start day ~-~-01-01)^^5^^
  * 2010-D182 or later (reporting year start day ~-~-01-01)
--* 2010-W28 or later (reporting year start day ~-~-07-01)^^6^^
--* 2010-D185 or later (reporting year start day ~-~-07-01)
++* 2010-W28 or later (reporting year start day ~-~-07-01)^^6^^ •    2010-D185 or later (reporting year start day ~-~-07-01)
++*1. Versioning
--= 4.3 Versioning ==
--
  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".
  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
@@ -514,13 +514,17 @@
  ‘1.0’.
--=== 4.3.1 Non-versioned artefacts ===
++1.
++11.
++111. Non-versioned artefacts
  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’.
  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.
--=== 4.3.2 Semantically versioned artefacts ===
++1.
++11.
++111. Semantically versioned artefacts
  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.
@@ -544,13 +544,17 @@
  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.
--=== 4.3.3 Legacy-versioned artefacts ===
++1.
++11.
++111. Legacy-versioned artefacts
  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.
  In order to make artefacts immutable or changes truly predictable, a move to the new semantic versioning syntax is required.
--=== 4.3.4 Dependency management and references ===
++1.
++11.
++111. Dependency management and references
  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:
@@ -579,7 +579,8 @@
  Full details can be found in the SDMX RESTful web services specification.
--== 4.4 Structural Metadata Querying Best Practices ==
++1.
++11. Structural Metadata Querying Best Practices
  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.
@@ -587,6 +587,7 @@
  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.
++
  ----
  [[~[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/]]