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Muldis-DB-0.2.0
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/ Muldis::DB::Language::Ext::Temporal

NAME

Muldis::DB::Language::Ext::Temporal - Muldis D extension for temporal data types and operators

VERSION

This document is Muldis::DB::Language::Ext::Temporal version 0.1.0.

PREFACE

This document is part of the Muldis D language specification, whose root document is Muldis::DB::Language; you should read that root document before you read this one, which provides subservient details.

DESCRIPTION

Muldis D has a mandatory core set of system-defined (eternally available) entities, which is referred to as the Muldis D core or the core; they are the minimal entities that all Muldis D implementations need to provide; they are mutually self-describing and are used to bootstrap the language; any entities outside the core, called Muldis D extensions, are non-mandatory and are defined in terms of the core or each other, but the reverse isn't true.

This current Temporal document describes the system-defined Muldis D Temporal Extension, which consists of temporal data types and operators, particularly durations and dates or times.

This current document does not describe the polymorphic operators that all types, or some types including core types, have defined over them; said operators are defined once for all types in Muldis::DB::Language::Core.

This documentation is pending.

TYPE SUMMARY

Following are all the data types described in this document, arranged in a type graph according to their proper sub|supertype relationships (but that the first 4 just reappear from the core set to provide a similar context, and aren't re-described here):

sys.type.Universal

    sys.type.Empty

    sys.type.Scalar
        sys.type.Ordinal

            # The following are all regular ordinal scalar types.

            sys.type.Temporal.Duration
            sys.type.Temporal.DurationOfDays
            sys.type.Temporal.DateTime
            sys.type.Temporal.DateTimeNoTZ
            sys.type.Temporal.Date
            sys.type.Temporal.DateNoTZ
            sys.type.Temporal.Time
            sys.type.Temporal.TimeNoTZ

This documentation is pending.

SYSTEM-DEFINED TEMPORAL SCALAR DATA TYPES

These non-core scalar data types describe common kinds of temporal artifacts according to modern calendars. They come in a variety of precisions and epochs so that users can pick one that most accurately represents what they actually know about their data. Of course, dealing with these types in general isn't a perfect science; they stand to be revised or rewritten.

sys.type.Temporal.Duration

A Temporal.Duration is a single amount of time, with precision to arbitrary fractions of a second. It is not fixed to any date or time and is agnostic to both the calendar and whether or not a time-zone offset is known. Its default value is zero. The cardinality of this type is infinity; to define a most-generalized finite Temporal.Duration subtype, you must specify the maximum amount of time that its values may be.

sys.type.Temporal.DurationOfDays

A Temporal.DurationOfDays is the same as Temporal.Duration in all respects but that its precision is only to the whole terrestrial day. The cardinality of this type is infinity; to define a most-generalized finite Temporal.DurationOfDays subtype, you must specify the maximum amount of time that its values may be.

sys.type.Temporal.DateTime

A Temporal.DateTime is a single specific time on a specific date, with precision to arbitrary fractions of a second. It does incorporate an explicit terrestrial time-zone offset (relative to UTC), so you use it when you do know the time-zone and it is significant (which is usually). It is conceptually calendar-agnostic. The default value of Temporal.DateTime is the Perl 6 epoch, namely 2000-1-1T0:0:0 in the Gregorian calendar, with a time-zone offset of zero. The cardinality of this type is infinity; to define a most-generalized finite Temporal.DateTime subtype, you must specify the earliest and latest datetimes it includes, and also its least magnitude fraction of a second.

sys.type.Temporal.DateTimeNoTZ

A Temporal.DateTimeNoTZ is the same as Temporal.DateTime in its precision, but it does not incorporate an explicit terrestrial time-zone offset interval, and so it is conceptually ambiguous within an interval of about 25 hours; you use it when you do not know the time-zone or it is not significant (which is not usually). Its default value is 2000-1-1T0:0:0 in the Gregorian calendar. Matters of its cardinality are the same as for Temporal.DateTime.

sys.type.Temporal.Date

A Temporal.Date is the same as Temporal.DateTime in all respects but that its precision is only to the whole terrestrial day. Its default value is 2000-1-1 in the Gregorian calendar. The cardinality of this type is infinity; to define a most-generalized finite Temporal.Date subtype, you must specify the earliest and latest dates it includes.

sys.type.Temporal.DateNoTZ

A Temporal.DateNoTZ is the same as Temporal.Date in all respects but that its differences correspond to the differences between Temporal.DateTime and Temporal.DateTimeNoTZ. Matters of its cardinality are the same as for Temporal.Date.

sys.type.Temporal.Time

A Temporal.Time is a single specific time that isn't on any day in particular, and isn't part of any calendar in particular, with a precision to arbitrary fractions of a second; its allowed range is between zero seconds (inclusive) and 1 terrestrial day (exclusive). It does incorporate an explicit time-zone offset interval as per Temporal.DateTime. Its default value is 0:0:0. The cardinality of this type is infinity; to define a most-generalized finite Temporal.Time subtype, you must specify its least magnitude fraction of a second.

sys.type.Temporal.TimeNoTZ

A Temporal.TimeNoTZ is the same as Temporal.Time in all respects but that its differences correspond to the differences between Temporal.DateTime and Temporal.DateTimeNoTZ. Matters of its cardinality are the same as for Temporal.Time.

SEE ALSO

Go to Muldis::DB for the majority of distribution-internal references, and Muldis::DB::SeeAlso for the majority of distribution-external references.

AUTHOR

Darren Duncan (perl@DarrenDuncan.net)

LICENSE AND COPYRIGHT

This file is part of the Muldis::DB framework.

Muldis::DB is Copyright © 2002-2007, Darren Duncan.

See the LICENSE AND COPYRIGHT of Muldis::DB for details.

ACKNOWLEDGEMENTS

The ACKNOWLEDGEMENTS in Muldis::DB apply to this file too.