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| <h1>The Asterix Data Model (ADM)</h1> |
| <div class="section"> |
| <h2><a name="Table_of_Contents"></a><a name="toc" id="toc">Table of Contents</a></h2> |
| <ul> |
| |
| <li><a href="#PrimitiveTypes">Primitive Types</a> |
| <ul> |
| |
| <li><a href="#PrimitiveTypesBoolean">Boolean</a></li> |
| <li><a href="#PrimitiveTypesString">String</a></li> |
| <li><a href="#PrimitiveTypesInt">Tinyint / Smallint / Integer (Int) / Bigint</a></li> |
| <li><a href="#PrimitiveTypesFloat">Float</a></li> |
| <li><a href="#PrimitiveTypesDouble">Double (Double Precision)</a></li> |
| <li><a href="#PrimitiveTypesBinary">Binary</a></li> |
| <li><a href="#PrimitiveTypesPoint">Point</a></li> |
| <li><a href="#PrimitiveTypesLine">Line</a></li> |
| <li><a href="#PrimitiveTypesRectangle">Rectangle</a></li> |
| <li><a href="#PrimitiveTypesCircle">Circle</a></li> |
| <li><a href="#PrimitiveTypesPolygon">Polygon</a></li> |
| <li><a href="#PrimitiveTypesDate">Date</a></li> |
| <li><a href="#PrimitiveTypesTime">Time</a></li> |
| <li><a href="#PrimitiveTypesDateTime">Datetime (Timestamp)</a></li> |
| <li><a href="#PrimitiveTypesDuration">Duration/Year_month_duration/Day_time_duration</a></li> |
| <li><a href="#PrimitiveTypesInterval">Interval</a></li> |
| <li><a href="#PrimitiveTypesUUID">UUID</a></li> |
| </ul> |
| </li> |
| <li>[Incomplete Information Types] (#IncompleteInformationTypes) |
| <ul> |
| |
| <li><a href="#IncompleteInformationTypesNull">Null</a></li> |
| <li><a href="#IncompleteInformationTypesMissing">Missing</a></li> |
| </ul> |
| </li> |
| <li><a href="#DerivedTypes">Derived Types</a> |
| <ul> |
| |
| <li><a href="#DerivedTypesObject">Object</a></li> |
| <li><a href="#DerivedTypesArray">Array</a></li> |
| <li><a href="#DerivedTypesMultiset">Multiset</a></li> |
| </ul> |
| </li> |
| </ul> |
| <p>An instance of Asterix data model (ADM) can be a <i><i>primitive type</i></i> (<tt>boolean</tt>, <tt>tinyint</tt>, <tt>smallint</tt>, <tt>integer</tt>, <tt>bigint</tt>, <tt>string</tt>, <tt>float</tt>, <tt>double</tt>, <tt>date</tt>, <tt>time</tt>, <tt>datetime</tt>, etc.), a <i><i>special type</i></i> (<tt>null</tt> or <tt>missing</tt>), or a <i><i>derived type</i></i>.</p> |
| <p>The type names are case-insensitive, e.g., both <tt>BIGINT</tt> and <tt>bigint</tt> are acceptable.</p><!-- |
| ! Licensed to the Apache Software Foundation (ASF) under one |
| ! or more contributor license agreements. See the NOTICE file |
| ! distributed with this work for additional information |
| ! regarding copyright ownership. The ASF licenses this file |
| ! to you under the Apache License, Version 2.0 (the |
| ! "License"); you may not use this file except in compliance |
| ! with the License. You may obtain a copy of the License at |
| ! |
| ! http://www.apache.org/licenses/LICENSE-2.0 |
| ! |
| ! Unless required by applicable law or agreed to in writing, |
| ! software distributed under the License is distributed on an |
| ! "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| ! KIND, either express or implied. See the License for the |
| ! specific language governing permissions and limitations |
| ! under the License. |
| !--> |
| </div> |
| <div class="section"> |
| <h2><a name="Primitive_Types"></a><a name="PrimitiveTypes" id="PrimitiveTypes">Primitive Types</a></h2> |
| <div class="section"> |
| <h3><a name="Boolean"></a><a name="PrimitiveTypesBoolean" id="PrimitiveTypesBoolean">Boolean</a></h3> |
| <p><tt>boolean</tt> data type can have one of the two values: <i><i>true</i></i> or <i><i>false</i></i>.</p> |
| <ul> |
| |
| <li> |
| |
| <p>Example:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "true": true, "false": false }; |
| </pre></div></div> |
| </li> |
| <li> |
| |
| <p>The expected result is:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "true": true, "false": false } |
| </pre></div></div> |
| </li> |
| </ul></div> |
| <div class="section"> |
| <h3><a name="String"></a><a name="PrimitiveTypesString" id="PrimitiveTypesString">String</a></h3> |
| <p><tt>string</tt> represents a sequence of characters. The total length of the sequence can be up to 2,147,483,648.</p> |
| <ul> |
| |
| <li> |
| |
| <p>Example:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "v1": string("This is a string."), "v2": string("\"This is a quoted string\"") }; |
| </pre></div></div> |
| </li> |
| <li> |
| |
| <p>The expected result is:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "v1": "This is a string.", "v2": "\"This is a quoted string\"" } |
| </pre></div></div> |
| </li> |
| </ul><!-- |
| ! Licensed to the Apache Software Foundation (ASF) under one |
| ! or more contributor license agreements. See the NOTICE file |
| ! distributed with this work for additional information |
| ! regarding copyright ownership. The ASF licenses this file |
| ! to you under the Apache License, Version 2.0 (the |
| ! "License"); you may not use this file except in compliance |
| ! with the License. You may obtain a copy of the License at |
| ! |
| ! http://www.apache.org/licenses/LICENSE-2.0 |
| ! |
| ! Unless required by applicable law or agreed to in writing, |
| ! software distributed under the License is distributed on an |
| ! "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| ! KIND, either express or implied. See the License for the |
| ! specific language governing permissions and limitations |
| ! under the License. |
| !--> |
| </div> |
| <div class="section"> |
| <h3><a name="Tinyint_.2F_Smallint_.2F_Integer_.28Int.29_.2F_Bigint"></a><a name="PrimitiveTypesInt" id="PrimitiveTypesInt">Tinyint / Smallint / Integer (Int) / Bigint</a></h3> |
| <p>Integer types using 8, 16, 32, or 64 bits. The ranges of these types are:</p> |
| <ul> |
| |
| <li><tt>tinyint</tt>: -128 to 127</li> |
| <li><tt>smallint</tt>: -32768 to 32767</li> |
| <li><tt>integer</tt>: -2147483648 to 2147483647</li> |
| <li><tt>bigint</tt>: -9223372036854775808 to 9223372036854775807</li> |
| </ul> |
| <p><tt>int</tt> is an abbreviated alias for integer.</p> |
| <ul> |
| |
| <li> |
| |
| <p>Example:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "tinyint": tiny("125"), "smallint": smallint("32765"), "integer": 294967295, "bigint": bigint("1700000000000000000")}; |
| </pre></div></div> |
| </li> |
| <li> |
| |
| <p>The expected result is:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "tinyint": 125, "smallint": 32765, "integer": 294967295, "bigint": 1700000000000000000 } |
| </pre></div></div> |
| </li> |
| </ul></div> |
| <div class="section"> |
| <h3><a name="Float"></a><a name="PrimitiveTypesFloat" id="PrimitiveTypesFloat">Float</a></h3> |
| <p><tt>float</tt> represents approximate numeric data values using 4 bytes. The range of a float value can be from 2^(-149) to (2-2^(-23)·2^(127) for both positive and negative. Beyond these ranges will get <tt>INF</tt> or <tt>-INF</tt>.</p> |
| <ul> |
| |
| <li> |
| |
| <p>Example:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "v1": float("NaN"), "v2": float("INF"), "v3": float("-INF"), "v4": float("-2013.5") }; |
| </pre></div></div> |
| </li> |
| <li> |
| |
| <p>The expected result is:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "v1": "NaN", "v2": "INF", "v3": "-INF", "v4": -2013.5 } |
| </pre></div></div> |
| </li> |
| </ul></div> |
| <div class="section"> |
| <h3><a name="Double_.28double_precision.29"></a><a name="PrimitiveTypesDouble" id="PrimitiveTypesDouble">Double (double precision)</a></h3> |
| <p><tt>double</tt> represents approximate numeric data values using 8 bytes. The range of a double value can be from (2^(-1022)) to (2-2^(-52))·2^(1023) for both positive and negative. Beyond these ranges will get <tt>INF</tt> or <tt>-INF</tt>.</p> |
| <ul> |
| |
| <li> |
| |
| <p>Example:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "v1": double("NaN"), "v2": double("INF"), "v3": double("-INF"), "v4": "-2013.593823748327284" }; |
| </pre></div></div> |
| </li> |
| <li> |
| |
| <p>The expected result is:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "v1": "NaN", "v2": "INF", "v3": "-INF", "v4": -2013.5938237483274 } |
| </pre></div></div> |
| </li> |
| </ul> |
| <p><tt>Double precision</tt> is an alias of <tt>double</tt>.</p></div> |
| <div class="section"> |
| <h3><a name="Binary"></a><a name="PrimitiveTypesBinary" id="PrimitiveTypesBinary">Binary</a></h3> |
| <p><tt>binary</tt> represents a sequence of bytes. It can be constructed from a <tt>hex</tt> or a <tt>base64</tt> string sequence. The total length of the byte sequence can be up to 2,147,483,648.</p> |
| <ul> |
| |
| <li> |
| |
| <p>Example:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ |
| "hex1" : hex("ABCDEF0123456789"), |
| "hex2": hex("abcdef0123456789"), |
| "base64_1" : base64("0123456789qwertyui+/"), |
| "base64_2" : base64('QXN0ZXJpeA==') |
| }; |
| </pre></div></div> |
| </li> |
| <li> |
| |
| <p>The default output format is in <tt>hex</tt> format. Thus, the expected result is:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ |
| "hex1": hex("ABCDEF0123456789"), |
| "hex2": hex("ABCDEF0123456789"), |
| "base64_1": hex("D35DB7E39EBBF3DAB07ABB72BA2FBF"), |
| "base64_2": hex("41737465726978") |
| } |
| </pre></div></div> |
| </li> |
| </ul></div> |
| <div class="section"> |
| <h3><a name="Point"></a><a name="PrimitiveTypesPoint" id="PrimitiveTypesPoint">Point</a></h3> |
| <p><tt>point</tt> is the fundamental two-dimensional building block for spatial types. It consists of two <tt>double</tt> coordinates x and y.</p> |
| <ul> |
| |
| <li> |
| |
| <p>Example:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "v1": point("80.10d, -10E5"), "v2": point("5.10E-10d, -10E5") }; |
| </pre></div></div> |
| </li> |
| <li> |
| |
| <p>The expected result is:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "v1": point("80.1,-1000000.0"), "v2": point("5.1E-10,-1000000.0") } |
| </pre></div></div> |
| </li> |
| </ul></div> |
| <div class="section"> |
| <h3><a name="Line"></a><a name="PrimitiveTypesLine" id="PrimitiveTypesLine">Line</a></h3> |
| <p><tt>line</tt> consists of two points that represent the start and the end points of a line segment.</p> |
| <ul> |
| |
| <li> |
| |
| <p>Example:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "v1": line("10.1234,11.1e-1 +10.2E-2,-11.22"), "v2": line("0.1234,-1.00e-10 +10.5E-2,-01.02") }; |
| </pre></div></div> |
| </li> |
| <li> |
| |
| <p>The expected result is:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "v1": line("10.1234,1.11 0.102,-11.22"), "v2": line("0.1234,-1.0E-10 0.105,-1.02") } |
| </pre></div></div> |
| </li> |
| </ul></div> |
| <div class="section"> |
| <h3><a name="Rectangle"></a><a name="PrimitiveTypesRectangle" id="PrimitiveTypesRectangle">Rectangle</a></h3> |
| <p><tt>rectangle</tt> consists of two points that represent the <i><i>bottom left</i></i> and <i><i>upper right</i></i> corners of a rectangle.</p> |
| <ul> |
| |
| <li> |
| |
| <p>Example:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "v1": rectangle("5.1,11.8 87.6,15.6548"), "v2": rectangle("0.1234,-1.00e-10 5.5487,0.48765") }; |
| </pre></div></div> |
| </li> |
| <li> |
| |
| <p>The expected result is:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "v1": rectangle("5.1,11.8 87.6,15.6548"), "v2": rectangle("0.1234,-1.0E-10 5.5487,0.48765") } |
| </pre></div></div> |
| </li> |
| </ul></div> |
| <div class="section"> |
| <h3><a name="Circle"></a><a name="PrimitiveTypesCircle" id="PrimitiveTypesCircle">Circle</a></h3> |
| <p><tt>circle</tt> consists of one point that represents the center of the circle and a radius of type <tt>double</tt>.</p> |
| <ul> |
| |
| <li> |
| |
| <p>Example:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "v1": circle("10.1234,11.1e-1 +10.2E-2"), "v2": circle("0.1234,-1.00e-10 +10.5E-2") }; |
| </pre></div></div> |
| </li> |
| <li> |
| |
| <p>The expected result is:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "v1": circle("10.1234,1.11 0.102"), "v2": circle("0.1234,-1.0E-10 0.105") } |
| </pre></div></div> |
| </li> |
| </ul></div> |
| <div class="section"> |
| <h3><a name="Polygon"></a><a name="PrimitiveTypesPolygon" id="PrimitiveTypesPolygon">Polygon</a></h3> |
| <p><tt>polygon</tt> consists of <i><i>n</i></i> points that represent the vertices of a <i><i>simple closed</i></i> polygon.</p> |
| <ul> |
| |
| <li> |
| |
| <p>Example:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ |
| "v1": polygon("-1.2,+1.3e2 -2.14E+5,2.15 -3.5e+2,03.6 -4.6E-3,+4.81"), |
| "v2": polygon("-1.0,+10.5e2 -02.15E+50,2.5 -1.0,+3.3e3 -2.50E+05,20.15 +3.5e+2,03.6 -4.60E-3,+4.75 -2,+1.0e2 -2.00E+5,20.10 30.5,03.25 -4.33E-3,+4.75") |
| }; |
| </pre></div></div> |
| </li> |
| <li> |
| |
| <p>The expected result is:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ |
| "v1": polygon("-1.2,130.0 -214000.0,2.15 -350.0,3.6 -0.0046,4.81"), |
| "v2": polygon("-1.0,1050.0 -2.15E50,2.5 -1.0,3300.0 -250000.0,20.15 350.0,3.6 -0.0046,4.75 -2.0,100.0 -200000.0,20.1 30.5,3.25 -0.00433,4.75") } |
| } |
| </pre></div></div> |
| </li> |
| </ul></div> |
| <div class="section"> |
| <h3><a name="Date"></a><a name="PrimitiveTypesDate" id="PrimitiveTypesDate">Date</a></h3> |
| <p><tt>date</tt> represents a time point along the Gregorian calendar system specified by the year, month and day. ASTERIX supports the date from <tt>-9999-01-01</tt> to <tt>9999-12-31</tt>.</p> |
| <p>A date value can be represented in two formats, extended format and basic format.</p> |
| <ul> |
| |
| <li>Extended format is represented as <tt>[-]yyyy-mm-dd</tt> for <tt>year-month-day</tt>. Each field should be padded if there are less digits than the format specified.</li> |
| <li>Basic format is in the format of <tt>[-]yyyymmdd</tt>.</li> |
| <li> |
| |
| <p>Example:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "v1": date("2013-01-01"), "v2": date("-19700101") }; |
| </pre></div></div> |
| </li> |
| <li> |
| |
| <p>The expected result is:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "v1": date("2013-01-01"), "v2": date("-1970-01-01") } |
| </pre></div></div> |
| </li> |
| </ul></div> |
| <div class="section"> |
| <h3><a name="Time"></a><a name="PrimitiveTypesTime" id="PrimitiveTypesTime">Time</a></h3> |
| <p><tt>time</tt> type describes the time within the range of a day. It is represented by three fields: hour, minute and second. Millisecond field is optional as the fraction of the second field. Its extended format is as <tt>hh:mm:ss[.mmm]</tt> and the basic format is <tt>hhmmss[mmm]</tt>. The value domain is from <tt>00:00:00.000</tt> to <tt>23:59:59.999</tt>.</p> |
| <p>Timezone field is optional for a time value. Timezone is represented as <tt>[+|-]hh:mm</tt> for extended format or <tt>[+|-]hhmm</tt> for basic format. Note that the sign designators cannot be omitted. <tt>Z</tt> can also be used to represent the UTC local time. If no timezone information is given, it is UTC by default.</p> |
| <ul> |
| |
| <li> |
| |
| <p>Example:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "v1": time("12:12:12.039Z"), "v2": time("000000000-0800") }; |
| </pre></div></div> |
| </li> |
| <li> |
| |
| <p>The expected result is:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "v1": time("12:12:12.039Z"), "v2": time("08:00:00.000Z") } |
| </pre></div></div> |
| </li> |
| </ul></div> |
| <div class="section"> |
| <h3><a name="Datetime_.28Timestamp.29"></a><a name="PrimitiveTypesDateTime" id="PrimitiveTypesDateTime">Datetime (Timestamp)</a></h3> |
| <p>A <tt>datetime</tt> value is a combination of an <tt>date</tt> and <tt>time</tt>, representing a fixed time point along the Gregorian calendar system. The value is among <tt>-9999-01-01 00:00:00.000</tt> and <tt>9999-12-31 23:59:59.999</tt>.</p> |
| <p>A <tt>datetime</tt> value is represented as a combination of the representation of its <tt>date</tt> part and <tt>time</tt> part, separated by a separator <tt>T</tt>. Either extended or basic format can be used, and the two parts should be the same format.</p> |
| <p>Millisecond field and timezone field are optional, as specified in the <tt>time</tt> type.</p> |
| <ul> |
| |
| <li> |
| |
| <p>Example:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "v1": datetime("2013-01-01T12:12:12.039Z"), "v2": datetime("-19700101T000000000-0800") }; |
| </pre></div></div> |
| </li> |
| <li> |
| |
| <p>The expected result is:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "v1": datetime("2013-01-01T12:12:12.039Z"), "v2": datetime("-1970-01-01T08:00:00.000Z") } |
| </pre></div></div> |
| </li> |
| </ul> |
| <p><tt>timestamp</tt> is an alias of <tt>datetime</tt>.</p></div> |
| <div class="section"> |
| <h3><a name="Duration.2FYear_month_duration.2FDay_time_duration"></a><a name="PrimitiveTypesDuration" id="PrimitiveTypesDuration">Duration/Year_month_duration/Day_time_duration</a></h3> |
| <p><tt>duration</tt> represents a duration of time. A duration value is specified by integers on at least one of the following fields: year, month, day, hour, minute, second, and millisecond.</p> |
| <p>A duration value is in the format of <tt>[-]PnYnMnDTnHnMn.mmmS</tt>. The millisecond part (as the fraction of the second field) is optional, and when no millisecond field is used, the decimal point should also be absent.</p> |
| <p>Negative durations are also supported for the arithmetic operations between time instance types (<tt>date</tt>, <tt>time</tt> and <tt>datetime</tt>), and is used to roll the time back for the given duration. For example <tt>date("2012-01-01") + duration("-P3D")</tt> will return <tt>date("2011-12-29")</tt>.</p> |
| <p>There are also two sub-duration types, namely <tt>year_month_duration</tt> and <tt>day_time_duration</tt>. <tt>year_month_duration</tt> represents only the years and months of a duration, while <tt>day_time_duration</tt> represents only the day to millisecond fields. Different from the <tt>duration</tt> type, both these two subtypes are totally ordered, so they can be used for comparison and index construction.</p> |
| <p>Note that a canonical representation of the duration is always returned, regardless whether the duration is in the canonical representation or not from the user’s input. More information about canonical representation can be found from <a class="externalLink" href="http://www.w3.org/TR/xpath-functions/#canonical-dayTimeDuration">XPath dayTimeDuration Canonical Representation</a> and <a class="externalLink" href="http://www.w3.org/TR/xpath-functions/#canonical-yearMonthDuration">yearMonthDuration Canonical Representation</a>.</p> |
| <ul> |
| |
| <li> |
| |
| <p>Example:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "v1": duration("P100Y12MT12M"), "v2": duration("-PT20.943S") }; |
| </pre></div></div> |
| </li> |
| <li> |
| |
| <p>The expected result is:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "v1": duration("P101YT12M"), "v2": duration("-PT20.943S") } |
| </pre></div></div> |
| </li> |
| </ul></div> |
| <div class="section"> |
| <h3><a name="Interval"></a><a name="PrimitiveTypesInterval" id="PrimitiveTypesInterval">Interval</a></h3> |
| <p><tt>interval</tt> represents inclusive-exclusive ranges of time. It is defined by two time point values with the same temporal type(<tt>date</tt>, <tt>time</tt> or <tt>datetime</tt>).</p> |
| <ul> |
| |
| <li> |
| |
| <p>Example:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ |
| "v1": interval(date("2013-01-01"), date("20130505")), |
| "v2": interval(time("00:01:01"), time("213901049+0800")), |
| "v3": interval(datetime("2013-01-01T00:01:01"), datetime("20130505T213901049+0800")) |
| }; |
| </pre></div></div> |
| </li> |
| <li> |
| |
| <p>The expected result is:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ |
| "v1": interval(date("2013-01-01"), date("2013-05-05")), |
| "v2": interval(time("00:01:01.000Z"), time("13:39:01.049Z")), |
| "v3": interval(datetime("2013-01-01T00:01:01.000Z"), datetime("2013-05-05T13:39:01.049Z")) |
| } |
| </pre></div></div> |
| </li> |
| </ul></div> |
| <div class="section"> |
| <h3><a name="UUID"></a><a name="PrimitiveTypesUUID" id="PrimitiveTypesUUID">UUID</a></h3> |
| <p><tt>uuid</tt> represents a UUID value, which stands for Universally unique identifier. It is defined by a canonical format using hexadecimal text with inserted hyphen characters. (E.g.: 5a28ce1e-6a74-4201-9e8f-683256e5706f). This type is generally used to store auto-generated primary key values.</p> |
| <ul> |
| |
| <li> |
| |
| <p>Example:</p> |
| |
| <div> |
| <div> |
| <pre class="source">return { "v1":uuid("5c848e5c-6b6a-498f-8452-8847a2957421") } |
| </pre></div></div> |
| </li> |
| <li> |
| |
| <p>The expected result is:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "v1": uuid("5c848e5c-6b6a-498f-8452-8847a2957421") } |
| </pre></div></div> |
| </li> |
| </ul><!-- |
| ! Licensed to the Apache Software Foundation (ASF) under one |
| ! or more contributor license agreements. See the NOTICE file |
| ! distributed with this work for additional information |
| ! regarding copyright ownership. The ASF licenses this file |
| ! to you under the Apache License, Version 2.0 (the |
| ! "License"); you may not use this file except in compliance |
| ! with the License. You may obtain a copy of the License at |
| ! |
| ! http://www.apache.org/licenses/LICENSE-2.0 |
| ! |
| ! Unless required by applicable law or agreed to in writing, |
| ! software distributed under the License is distributed on an |
| ! "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| ! KIND, either express or implied. See the License for the |
| ! specific language governing permissions and limitations |
| ! under the License. |
| !--> |
| </div></div> |
| <div class="section"> |
| <h2><a name="Incomplete_Information_Types"></a><a name="IncompleteInformationTypes" id="IncompleteInformationTypes">Incomplete Information Types</a></h2> |
| <div class="section"> |
| <h3><a name="Null"></a><a name="IncompleteInformationTypesNull" id="IncompleteInformationTypesNull">Null</a></h3> |
| <p><tt>null</tt> is a special value that is often used to represent an unknown value. For example, a user might not be able to know the value of a field and let it be <tt>null</tt>.</p> |
| <ul> |
| |
| <li> |
| |
| <p>Example:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "field": null }; |
| </pre></div></div> |
| </li> |
| <li> |
| |
| <p>The expected result is:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "field": null } |
| </pre></div></div> |
| </li> |
| </ul></div> |
| <div class="section"> |
| <h3><a name="Missing"></a><a name="IncompleteInformationTypesMissing" id="IncompleteInformationTypesMissing">Missing</a></h3> |
| <p><tt>missing</tt> indicates that a name-value pair is missing from an object. If a missing name-value pair is accessed, an empty result value is returned by the query.</p> |
| <p>As neither the data model nor the system enforces homogeneity for datasets or collections, items in a dataset or collection can be of heterogeneous types and so a field can be present in one object and <tt>missing</tt> in another.</p> |
| <ul> |
| |
| <li> |
| |
| <p>Example:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ "field": missing }; |
| </pre></div></div> |
| </li> |
| <li> |
| |
| <p>The expected result is:</p> |
| |
| <div> |
| <div> |
| <pre class="source">{ } |
| </pre></div></div> |
| </li> |
| </ul> |
| <p>Since a field with value <tt>missing</tt> means the field is absent, we get an empty object.</p><!-- |
| ! Licensed to the Apache Software Foundation (ASF) under one |
| ! or more contributor license agreements. See the NOTICE file |
| ! distributed with this work for additional information |
| ! regarding copyright ownership. The ASF licenses this file |
| ! to you under the Apache License, Version 2.0 (the |
| ! "License"); you may not use this file except in compliance |
| ! with the License. You may obtain a copy of the License at |
| ! |
| ! http://www.apache.org/licenses/LICENSE-2.0 |
| ! |
| ! Unless required by applicable law or agreed to in writing, |
| ! software distributed under the License is distributed on an |
| ! "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| ! KIND, either express or implied. See the License for the |
| ! specific language governing permissions and limitations |
| ! under the License. |
| !--> |
| </div></div> |
| <div class="section"> |
| <h2><a name="Derived_Types"></a><a name="DerivedTypes" id="DerivedTypes">Derived Types</a></h2> |
| <div class="section"> |
| <h3><a name="Object"></a><a name="DerivedTypesObject" id="DerivedTypesObject">Object</a></h3> |
| <p>An <tt>object</tt> contains a set of fields, where each field is described by its name and type. An object type may be defined as either open or closed. Open objects (instances of open object types) are permitted to contain fields that are not part of the type definition, while closed objects do not permit their instances to carry extra fields. An example type definition for an object is:</p> |
| |
| <div> |
| <div> |
| <pre class="source"> create type SoldierType as open { |
| name: string?, |
| rank: string, |
| serialno: int |
| }; |
| </pre></div></div> |
| |
| <p>Syntactically, object constructors are surrounded by curly braces “{…}”. Some examples of legitimate instances of the above type include:</p> |
| |
| <div> |
| <div> |
| <pre class="source"> { "name": "Joe Blow", "rank": "Sergeant", "serialno": 1234567 } |
| { "rank": "Private", "serialno": 9876543 } |
| { "name": "Sally Forth", "rank": "Major", "serialno": 2345678, "gender": "F" } |
| </pre></div></div> |
| |
| <p>The first instance has all of the type’s prescribed content. The second instance is missing the name field, which is fine because it is optional (due to the ?). The third instance has an extra field; that is fine because the type definition specifies that it is open (which is also true by default, if open is not specified). To more tightly control object content, specifying closed instead of open in the type definition for SoldierType would have made the third example instance an invalid instance of the type.</p></div> |
| <div class="section"> |
| <h3><a name="Array"></a><a name="DerivedTypesArray" id="DerivedTypesArray">Array</a></h3> |
| <p>An <tt>array</tt> is a container that holds a fixed number of values. Array constructors are denoted by brackets: “[…]”.</p> |
| <p>An example would be</p> |
| |
| <div> |
| <div> |
| <pre class="source"> ["alice", 123, "bob", null] |
| </pre></div></div> |
| </div> |
| <div class="section"> |
| <h3><a name="Multiset"></a><a name="DerivedTypesMultiset" id="DerivedTypesMultiset">Multiset</a></h3> |
| <p>A <tt>multiset</tt> is a generalization of the concept of a set that, unlike a set, allows multiple instances of the multiset’s elements. Multiset constructors are denoted by two opening curly braces followed by data and two closing curly braces, like “{{…}}”.</p> |
| <p>An example would be</p> |
| |
| <div> |
| <div> |
| <pre class="source"> {{"hello", 9328, "world", [1, 2, null]}} |
| </pre></div></div></div></div> |
| </div> |
| </div> |
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