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				29	<li id="publishDate">Last Published: 2019-03-07</li>
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				93	<h1>The Asterix Data Model (ADM)</h1>
				94	<div class="section">
				95	<h2><a name="Table_of_Contents"></a><a name="toc" id="toc">Table of Contents</a></h2>
				96	<ul>
				97
				98	<li><a href="#PrimitiveTypes">Primitive Types</a>
				99	<ul>
				100
				101	<li><a href="#PrimitiveTypesBoolean">Boolean</a></li>
				102	<li><a href="#PrimitiveTypesString">String</a></li>
				103	<li><a href="#PrimitiveTypesInt">Tinyint / Smallint / Integer (Int) / Bigint</a></li>
				104	<li><a href="#PrimitiveTypesFloat">Float</a></li>
				105	<li><a href="#PrimitiveTypesDouble">Double (Double Precision)</a></li>
				106	<li><a href="#PrimitiveTypesBinary">Binary</a></li>
				107	<li><a href="#PrimitiveTypesPoint">Point</a></li>
				108	<li><a href="#PrimitiveTypesLine">Line</a></li>
				109	<li><a href="#PrimitiveTypesRectangle">Rectangle</a></li>
				110	<li><a href="#PrimitiveTypesCircle">Circle</a></li>
				111	<li><a href="#PrimitiveTypesPolygon">Polygon</a></li>
				112	<li><a href="#PrimitiveTypesDate">Date</a></li>
				113	<li><a href="#PrimitiveTypesTime">Time</a></li>
				114	<li><a href="#PrimitiveTypesDateTime">Datetime (Timestamp)</a></li>
				115	<li><a href="#PrimitiveTypesDuration">Duration/Year_month_duration/Day_time_duration</a></li>
				116	<li><a href="#PrimitiveTypesInterval">Interval</a></li>
				117	<li><a href="#PrimitiveTypesUUID">UUID</a></li>
				118	</ul>
				119	</li>
				120	<li>[Incomplete Information Types] (#IncompleteInformationTypes)
				121	<ul>
				122
				123	<li><a href="#IncompleteInformationTypesNull">Null</a></li>
				124	<li><a href="#IncompleteInformationTypesMissing">Missing</a></li>
				125	</ul>
				126	</li>
				127	<li><a href="#DerivedTypes">Derived Types</a>
				128	<ul>
				129
				130	<li><a href="#DerivedTypesObject">Object</a></li>
				131	<li><a href="#DerivedTypesArray">Array</a></li>
				132	<li><a href="#DerivedTypesMultiset">Multiset</a></li>
				133	</ul>
				134	</li>
				135	</ul>
				136	<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>
				137	<p>The type names are case-insensitive, e.g., both <tt>BIGINT</tt> and <tt>bigint</tt> are acceptable.</p><!--
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				139	! or more contributor license agreements. See the NOTICE file
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				143	! "License"); you may not use this file except in compliance
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				146	! http://www.apache.org/licenses/LICENSE-2.0
				147	!
				148	! Unless required by applicable law or agreed to in writing,
				149	! software distributed under the License is distributed on an
				150	! "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
				151	! KIND, either express or implied. See the License for the
				152	! specific language governing permissions and limitations
				153	! under the License.
				154	!-->
				155	</div>
				156	<div class="section">
				157	<h2><a name="Primitive_Types"></a><a name="PrimitiveTypes" id="PrimitiveTypes">Primitive Types</a></h2>
				158	<div class="section">
				159	<h3><a name="Boolean"></a><a name="PrimitiveTypesBoolean" id="PrimitiveTypesBoolean">Boolean</a></h3>
				160	<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>
				161	<ul>
				162
				163	<li>
				164
				165	<p>Example:</p>
				166
				167	<div>
				168	<div>
				169	<pre class="source">{ "true": true, "false": false };
				170	</pre></div></div>
				171	</li>
				172	<li>
				173
				174	<p>The expected result is:</p>
				175
				176	<div>
				177	<div>
				178	<pre class="source">{ "true": true, "false": false }
				179	</pre></div></div>
				180	</li>
				181	</ul></div>
				182	<div class="section">
				183	<h3><a name="String"></a><a name="PrimitiveTypesString" id="PrimitiveTypesString">String</a></h3>
				184	<p><tt>string</tt> represents a sequence of characters. The total length of the sequence can be up to 2,147,483,648.</p>
				185	<ul>
				186
				187	<li>
				188
				189	<p>Example:</p>
				190
				191	<div>
				192	<div>
				193	<pre class="source">{ "v1": string("This is a string."), "v2": string("\"This is a quoted string\"") };
				194	</pre></div></div>
				195	</li>
				196	<li>
				197
				198	<p>The expected result is:</p>
				199
				200	<div>
				201	<div>
				202	<pre class="source">{ "v1": "This is a string.", "v2": "\"This is a quoted string\"" }
				203	</pre></div></div>
				204	</li>
				205	</ul><!--
				206	! Licensed to the Apache Software Foundation (ASF) under one
				207	! or more contributor license agreements. See the NOTICE file
				208	! distributed with this work for additional information
				209	! regarding copyright ownership. The ASF licenses this file
				210	! to you under the Apache License, Version 2.0 (the
				211	! "License"); you may not use this file except in compliance
				212	! with the License. You may obtain a copy of the License at
				213	!
				214	! http://www.apache.org/licenses/LICENSE-2.0
				215	!
				216	! Unless required by applicable law or agreed to in writing,
				217	! software distributed under the License is distributed on an
				218	! "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
				219	! KIND, either express or implied. See the License for the
				220	! specific language governing permissions and limitations
				221	! under the License.
				222	!-->
				223	</div>
				224	<div class="section">
				225	<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>
				226	<p>Integer types using 8, 16, 32, or 64 bits. The ranges of these types are:</p>
				227	<ul>
				228
				229	<li><tt>tinyint</tt>: -128 to 127</li>
				230	<li><tt>smallint</tt>: -32768 to 32767</li>
				231	<li><tt>integer</tt>: -2147483648 to 2147483647</li>
				232	<li><tt>bigint</tt>: -9223372036854775808 to 9223372036854775807</li>
				233	</ul>
				234	<p><tt>int</tt> is an abbreviated alias for integer.</p>
				235	<ul>
				236
				237	<li>
				238
				239	<p>Example:</p>
				240
				241	<div>
				242	<div>
				243	<pre class="source">{ "tinyint": tiny("125"), "smallint": smallint("32765"), "integer": 294967295, "bigint": bigint("1700000000000000000")};
				244	</pre></div></div>
				245	</li>
				246	<li>
				247
				248	<p>The expected result is:</p>
				249
				250	<div>
				251	<div>
				252	<pre class="source">{ "tinyint": 125, "smallint": 32765, "integer": 294967295, "bigint": 1700000000000000000 }
				253	</pre></div></div>
				254	</li>
				255	</ul></div>
				256	<div class="section">
				257	<h3><a name="Float"></a><a name="PrimitiveTypesFloat" id="PrimitiveTypesFloat">Float</a></h3>
				258	<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>
				259	<ul>
				260
				261	<li>
				262
				263	<p>Example:</p>
				264
				265	<div>
				266	<div>
				267	<pre class="source">{ "v1": float("NaN"), "v2": float("INF"), "v3": float("-INF"), "v4": float("-2013.5") };
				268	</pre></div></div>
				269	</li>
				270	<li>
				271
				272	<p>The expected result is:</p>
				273
				274	<div>
				275	<div>
				276	<pre class="source">{ "v1": "NaN", "v2": "INF", "v3": "-INF", "v4": -2013.5 }
				277	</pre></div></div>
				278	</li>
				279	</ul></div>
				280	<div class="section">
				281	<h3><a name="Double_.28double_precision.29"></a><a name="PrimitiveTypesDouble" id="PrimitiveTypesDouble">Double (double precision)</a></h3>
				282	<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>
				283	<ul>
				284
				285	<li>
				286
				287	<p>Example:</p>
				288
				289	<div>
				290	<div>
				291	<pre class="source">{ "v1": double("NaN"), "v2": double("INF"), "v3": double("-INF"), "v4": "-2013.593823748327284" };
				292	</pre></div></div>
				293	</li>
				294	<li>
				295
				296	<p>The expected result is:</p>
				297
				298	<div>
				299	<div>
				300	<pre class="source">{ "v1": "NaN", "v2": "INF", "v3": "-INF", "v4": -2013.5938237483274 }
				301	</pre></div></div>
				302	</li>
				303	</ul>
				304	<p><tt>Double precision</tt> is an alias of <tt>double</tt>.</p></div>
				305	<div class="section">
				306	<h3><a name="Binary"></a><a name="PrimitiveTypesBinary" id="PrimitiveTypesBinary">Binary</a></h3>
				307	<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>
				308	<ul>
				309
				310	<li>
				311
				312	<p>Example:</p>
				313
				314	<div>
				315	<div>
				316	<pre class="source">{
				317	"hex1" : hex("ABCDEF0123456789"),
				318	"hex2": hex("abcdef0123456789"),
				319	"base64_1" : base64("0123456789qwertyui+/"),
				320	"base64_2" : base64('QXN0ZXJpeA==')
				321	};
				322	</pre></div></div>
				323	</li>
				324	<li>
				325
				326	<p>The default output format is in <tt>hex</tt> format. Thus, the expected result is:</p>
				327
				328	<div>
				329	<div>
				330	<pre class="source">{
				331	"hex1": hex("ABCDEF0123456789"),
				332	"hex2": hex("ABCDEF0123456789"),
				333	"base64_1": hex("D35DB7E39EBBF3DAB07ABB72BA2FBF"),
				334	"base64_2": hex("41737465726978")
				335	}
				336	</pre></div></div>
				337	</li>
				338	</ul></div>
				339	<div class="section">
				340	<h3><a name="Point"></a><a name="PrimitiveTypesPoint" id="PrimitiveTypesPoint">Point</a></h3>
				341	<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>
				342	<ul>
				343
				344	<li>
				345
				346	<p>Example:</p>
				347
				348	<div>
				349	<div>
				350	<pre class="source">{ "v1": point("80.10d, -10E5"), "v2": point("5.10E-10d, -10E5") };
				351	</pre></div></div>
				352	</li>
				353	<li>
				354
				355	<p>The expected result is:</p>
				356
				357	<div>
				358	<div>
				359	<pre class="source">{ "v1": point("80.1,-1000000.0"), "v2": point("5.1E-10,-1000000.0") }
				360	</pre></div></div>
				361	</li>
				362	</ul></div>
				363	<div class="section">
				364	<h3><a name="Line"></a><a name="PrimitiveTypesLine" id="PrimitiveTypesLine">Line</a></h3>
				365	<p><tt>line</tt> consists of two points that represent the start and the end points of a line segment.</p>
				366	<ul>
				367
				368	<li>
				369
				370	<p>Example:</p>
				371
				372	<div>
				373	<div>
				374	<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") };
				375	</pre></div></div>
				376	</li>
				377	<li>
				378
				379	<p>The expected result is:</p>
				380
				381	<div>
				382	<div>
				383	<pre class="source">{ "v1": line("10.1234,1.11 0.102,-11.22"), "v2": line("0.1234,-1.0E-10 0.105,-1.02") }
				384	</pre></div></div>
				385	</li>
				386	</ul></div>
				387	<div class="section">
				388	<h3><a name="Rectangle"></a><a name="PrimitiveTypesRectangle" id="PrimitiveTypesRectangle">Rectangle</a></h3>
				389	<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>
				390	<ul>
				391
				392	<li>
				393
				394	<p>Example:</p>
				395
				396	<div>
				397	<div>
				398	<pre class="source">{ "v1": rectangle("5.1,11.8 87.6,15.6548"), "v2": rectangle("0.1234,-1.00e-10 5.5487,0.48765") };
				399	</pre></div></div>
				400	</li>
				401	<li>
				402
				403	<p>The expected result is:</p>
				404
				405	<div>
				406	<div>
				407	<pre class="source">{ "v1": rectangle("5.1,11.8 87.6,15.6548"), "v2": rectangle("0.1234,-1.0E-10 5.5487,0.48765") }
				408	</pre></div></div>
				409	</li>
				410	</ul></div>
				411	<div class="section">
				412	<h3><a name="Circle"></a><a name="PrimitiveTypesCircle" id="PrimitiveTypesCircle">Circle</a></h3>
				413	<p><tt>circle</tt> consists of one point that represents the center of the circle and a radius of type <tt>double</tt>.</p>
				414	<ul>
				415
				416	<li>
				417
				418	<p>Example:</p>
				419
				420	<div>
				421	<div>
				422	<pre class="source">{ "v1": circle("10.1234,11.1e-1 +10.2E-2"), "v2": circle("0.1234,-1.00e-10 +10.5E-2") };
				423	</pre></div></div>
				424	</li>
				425	<li>
				426
				427	<p>The expected result is:</p>
				428
				429	<div>
				430	<div>
				431	<pre class="source">{ "v1": circle("10.1234,1.11 0.102"), "v2": circle("0.1234,-1.0E-10 0.105") }
				432	</pre></div></div>
				433	</li>
				434	</ul></div>
				435	<div class="section">
				436	<h3><a name="Polygon"></a><a name="PrimitiveTypesPolygon" id="PrimitiveTypesPolygon">Polygon</a></h3>
				437	<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>
				438	<ul>
				439
				440	<li>
				441
				442	<p>Example:</p>
				443
				444	<div>
				445	<div>
				446	<pre class="source">{
				447	"v1": polygon("-1.2,+1.3e2 -2.14E+5,2.15 -3.5e+2,03.6 -4.6E-3,+4.81"),
				448	"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")
				449	};
				450	</pre></div></div>
				451	</li>
				452	<li>
				453
				454	<p>The expected result is:</p>
				455
				456	<div>
				457	<div>
				458	<pre class="source">{
				459	"v1": polygon("-1.2,130.0 -214000.0,2.15 -350.0,3.6 -0.0046,4.81"),
				460	"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") }
				461	}
				462	</pre></div></div>
				463	</li>
				464	</ul></div>
				465	<div class="section">
				466	<h3><a name="Date"></a><a name="PrimitiveTypesDate" id="PrimitiveTypesDate">Date</a></h3>
				467	<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>
				468	<p>A date value can be represented in two formats, extended format and basic format.</p>
				469	<ul>
				470
				471	<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>
				472	<li>Basic format is in the format of <tt>[-]yyyymmdd</tt>.</li>
				473	<li>
				474
				475	<p>Example:</p>
				476
				477	<div>
				478	<div>
				479	<pre class="source">{ "v1": date("2013-01-01"), "v2": date("-19700101") };
				480	</pre></div></div>
				481	</li>
				482	<li>
				483
				484	<p>The expected result is:</p>
				485
				486	<div>
				487	<div>
				488	<pre class="source">{ "v1": date("2013-01-01"), "v2": date("-1970-01-01") }
				489	</pre></div></div>
				490	</li>
				491	</ul></div>
				492	<div class="section">
				493	<h3><a name="Time"></a><a name="PrimitiveTypesTime" id="PrimitiveTypesTime">Time</a></h3>
				494	<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>
				495	<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>
				496	<ul>
				497
				498	<li>
				499
				500	<p>Example:</p>
				501
				502	<div>
				503	<div>
				504	<pre class="source">{ "v1": time("12:12:12.039Z"), "v2": time("000000000-0800") };
				505	</pre></div></div>
				506	</li>
				507	<li>
				508
				509	<p>The expected result is:</p>
				510
				511	<div>
				512	<div>
				513	<pre class="source">{ "v1": time("12:12:12.039Z"), "v2": time("08:00:00.000Z") }
				514	</pre></div></div>
				515	</li>
				516	</ul></div>
				517	<div class="section">
				518	<h3><a name="Datetime_.28Timestamp.29"></a><a name="PrimitiveTypesDateTime" id="PrimitiveTypesDateTime">Datetime (Timestamp)</a></h3>
				519	<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>
				520	<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>
				521	<p>Millisecond field and timezone field are optional, as specified in the <tt>time</tt> type.</p>
				522	<ul>
				523
				524	<li>
				525
				526	<p>Example:</p>
				527
				528	<div>
				529	<div>
				530	<pre class="source">{ "v1": datetime("2013-01-01T12:12:12.039Z"), "v2": datetime("-19700101T000000000-0800") };
				531	</pre></div></div>
				532	</li>
				533	<li>
				534
				535	<p>The expected result is:</p>
				536
				537	<div>
				538	<div>
				539	<pre class="source">{ "v1": datetime("2013-01-01T12:12:12.039Z"), "v2": datetime("-1970-01-01T08:00:00.000Z") }
				540	</pre></div></div>
				541	</li>
				542	</ul>
				543	<p><tt>timestamp</tt> is an alias of <tt>datetime</tt>.</p></div>
				544	<div class="section">
				545	<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>
				546	<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>
				547	<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>
				548	<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>
				549	<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>
				550	<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>
				551	<ul>
				552
				553	<li>
				554
				555	<p>Example:</p>
				556
				557	<div>
				558	<div>
				559	<pre class="source">{ "v1": duration("P100Y12MT12M"), "v2": duration("-PT20.943S") };
				560	</pre></div></div>
				561	</li>
				562	<li>
				563
				564	<p>The expected result is:</p>
				565
				566	<div>
				567	<div>
				568	<pre class="source">{ "v1": duration("P101YT12M"), "v2": duration("-PT20.943S") }
				569	</pre></div></div>
				570	</li>
				571	</ul></div>
				572	<div class="section">
				573	<h3><a name="Interval"></a><a name="PrimitiveTypesInterval" id="PrimitiveTypesInterval">Interval</a></h3>
				574	<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>
				575	<ul>
				576
				577	<li>
				578
				579	<p>Example:</p>
				580
				581	<div>
				582	<div>
				583	<pre class="source">{
				584	"v1": interval(date("2013-01-01"), date("20130505")),
				585	"v2": interval(time("00:01:01"), time("213901049+0800")),
				586	"v3": interval(datetime("2013-01-01T00:01:01"), datetime("20130505T213901049+0800"))
				587	};
				588	</pre></div></div>
				589	</li>
				590	<li>
				591
				592	<p>The expected result is:</p>
				593
				594	<div>
				595	<div>
				596	<pre class="source">{
				597	"v1": interval(date("2013-01-01"), date("2013-05-05")),
				598	"v2": interval(time("00:01:01.000Z"), time("13:39:01.049Z")),
				599	"v3": interval(datetime("2013-01-01T00:01:01.000Z"), datetime("2013-05-05T13:39:01.049Z"))
				600	}
				601	</pre></div></div>
				602	</li>
				603	</ul></div>
				604	<div class="section">
				605	<h3><a name="UUID"></a><a name="PrimitiveTypesUUID" id="PrimitiveTypesUUID">UUID</a></h3>
				606	<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>
				607	<ul>
				608
				609	<li>
				610
				611	<p>Example:</p>
				612
				613	<div>
				614	<div>
				615	<pre class="source">return { "v1":uuid("5c848e5c-6b6a-498f-8452-8847a2957421") }
				616	</pre></div></div>
				617	</li>
				618	<li>
				619
				620	<p>The expected result is:</p>
				621
				622	<div>
				623	<div>
				624	<pre class="source">{ "v1": uuid("5c848e5c-6b6a-498f-8452-8847a2957421") }
				625	</pre></div></div>
				626	</li>
				627	</ul><!--
				628	! Licensed to the Apache Software Foundation (ASF) under one
				629	! or more contributor license agreements. See the NOTICE file
				630	! distributed with this work for additional information
				631	! regarding copyright ownership. The ASF licenses this file
				632	! to you under the Apache License, Version 2.0 (the
				633	! "License"); you may not use this file except in compliance
				634	! with the License. You may obtain a copy of the License at
				635	!
				636	! http://www.apache.org/licenses/LICENSE-2.0
				637	!
				638	! Unless required by applicable law or agreed to in writing,
				639	! software distributed under the License is distributed on an
				640	! "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
				641	! KIND, either express or implied. See the License for the
				642	! specific language governing permissions and limitations
				643	! under the License.
				644	!-->
				645	</div></div>
				646	<div class="section">
				647	<h2><a name="Incomplete_Information_Types"></a><a name="IncompleteInformationTypes" id="IncompleteInformationTypes">Incomplete Information Types</a></h2>
				648	<div class="section">
				649	<h3><a name="Null"></a><a name="IncompleteInformationTypesNull" id="IncompleteInformationTypesNull">Null</a></h3>
				650	<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>
				651	<ul>
				652
				653	<li>
				654
				655	<p>Example:</p>
				656
				657	<div>
				658	<div>
				659	<pre class="source">{ "field": null };
				660	</pre></div></div>
				661	</li>
				662	<li>
				663
				664	<p>The expected result is:</p>
				665
				666	<div>
				667	<div>
				668	<pre class="source">{ "field": null }
				669	</pre></div></div>
				670	</li>
				671	</ul></div>
				672	<div class="section">
				673	<h3><a name="Missing"></a><a name="IncompleteInformationTypesMissing" id="IncompleteInformationTypesMissing">Missing</a></h3>
				674	<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>
				675	<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>
				676	<ul>
				677
				678	<li>
				679
				680	<p>Example:</p>
				681
				682	<div>
				683	<div>
				684	<pre class="source">{ "field": missing };
				685	</pre></div></div>
				686	</li>
				687	<li>
				688
				689	<p>The expected result is:</p>
				690
				691	<div>
				692	<div>
				693	<pre class="source">{ }
				694	</pre></div></div>
				695	</li>
				696	</ul>
				697	<p>Since a field with value <tt>missing</tt> means the field is absent, we get an empty object.</p><!--
				698	! Licensed to the Apache Software Foundation (ASF) under one
				699	! or more contributor license agreements. See the NOTICE file
				700	! distributed with this work for additional information
				701	! regarding copyright ownership. The ASF licenses this file
				702	! to you under the Apache License, Version 2.0 (the
				703	! "License"); you may not use this file except in compliance
				704	! with the License. You may obtain a copy of the License at
				705	!
				706	! http://www.apache.org/licenses/LICENSE-2.0
				707	!
				708	! Unless required by applicable law or agreed to in writing,
				709	! software distributed under the License is distributed on an
				710	! "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
				711	! KIND, either express or implied. See the License for the
				712	! specific language governing permissions and limitations
				713	! under the License.
				714	!-->
				715	</div></div>
				716	<div class="section">
				717	<h2><a name="Derived_Types"></a><a name="DerivedTypes" id="DerivedTypes">Derived Types</a></h2>
				718	<div class="section">
				719	<h3><a name="Object"></a><a name="DerivedTypesObject" id="DerivedTypesObject">Object</a></h3>
				720	<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>
				721
				722	<div>
				723	<div>
				724	<pre class="source"> create type SoldierType as open {
				725	name: string?,
				726	rank: string,
				727	serialno: int
				728	};
				729	</pre></div></div>
				730
				731	<p>Syntactically, object constructors are surrounded by curly braces “{…}”. Some examples of legitimate instances of the above type include:</p>
				732
				733	<div>
				734	<div>
				735	<pre class="source"> { "name": "Joe Blow", "rank": "Sergeant", "serialno": 1234567 }
				736	{ "rank": "Private", "serialno": 9876543 }
				737	{ "name": "Sally Forth", "rank": "Major", "serialno": 2345678, "gender": "F" }
				738	</pre></div></div>
				739
				740	<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>
				741	<div class="section">
				742	<h3><a name="Array"></a><a name="DerivedTypesArray" id="DerivedTypesArray">Array</a></h3>
				743	<p>An <tt>array</tt> is a container that holds a fixed number of values. Array constructors are denoted by brackets: “[…]”.</p>
				744	<p>An example would be</p>
				745
				746	<div>
				747	<div>
				748	<pre class="source"> ["alice", 123, "bob", null]
				749	</pre></div></div>
				750	</div>
				751	<div class="section">
				752	<h3><a name="Multiset"></a><a name="DerivedTypesMultiset" id="DerivedTypesMultiset">Multiset</a></h3>
				753	<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>
				754	<p>An example would be</p>
				755
				756	<div>
				757	<div>
				758	<pre class="source"> {{"hello", 9328, "world", [1, 2, null]}}
				759	</pre></div></div></div></div>
				760	</div>
				761	</div>
				762	</div>
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