Creating Schemas

Simple types

This is an element that can contain only text strings

In a DTD, we used <#PCDATA> to represent a text string as the content of an element

The content could take any number of forms (numbers, letters, dates...)

In schemas, simple types can use a predefined set of datatypes to specify text or numeric content

There are also facets that can be used to further restrict these elements

Two examples are 9 digit zip codes or telephone numbers

The generic form of a simple type is:

<xsd:element name="somename" type="datatype"/>

In an XML document, the corresponding element would look like this:

<somename>content</somename>

Here is a subset of the available datatypes that can be used

Datatype		Meaning
xsd:string		Alphanumeric characters
xsd:decimal		Numbers with decimal points
xsd:boolean		Contains conditional stratement (true/false; 0/1)
xsd:uri-reference		Contains a URL
xsd:date		Year, month, day
xsd:time		Hours, minutes, seconds
xsd:language		Two character ISO language code
custom		One you make up

The <xsd:time> datatype can be broken down to include more specific content

Time datatype		Meaning		Format		Schema example		As XML
xsd:time		Greenwich mean time: EST is UTC-5		hh:mm:ss.sssUTC_time_zone		<xsd:element name="alien_visit" type="xsd:time"/>		<alien_visit>22:15-35-14</alien_visit>
xsd:duration		A bounded period of time		PYrMoDTHrMmSs		<xsd:element name="alien_visit" type="xsd:duration"/>		<alien_visit>P4D</alien_visit>
xsd:timeinstant		A specific moment		Full_yr-Mo-DTHrMmSs		<xsd:element name="alien_visit" type="xsd:timeinstant"/>		<alien_visit>1960-07-08T-519:22:45.32</alien_visit>
xsd:date		A specific date		Full_yr-Mo-D		<xsd:element name="alien_visit" type="xsd:date"/>		<alien_visit>1960-07-08</alien_visit>
xsd:gYearMonth		A specific month		Full_yr-Mo		<xsd:element name="alien_visit" type="xsd:gYearMonth"/>		<alien_visit>1960-07</alien_visit>
xsd:gYear		A specific year		Full_yr		<xsd:element name="alien_visit" type="xsd:gYear"/>		<alien_visit>1960</alien_visit>
xsd:recurringDate		A specific day in a specific month without the year		--Mo-D		<xsd:element name="alien_visit" type="xsd:recurringDate"/>		<alien_visit>--08-23</alien_visit>
xsd:recurringDay		A specific day without the year and month		---D		<xsd:element name="alien_visit" type="xsd:recurringDay"/>		<alien_visit>---15</alien_visitt>

There is also a set of datatypes for working with numbers

Number datatype		Meaning		Format		Schema example		As XML
xsd:decimal		Positive or negative numbers		#, -#, #.##		<xsd:element name="alien_visit" type="xsd:decimal"/>		<alien_visit>45.3</alien_visit>
xsd:integer		Positive or negative whole numbers		#, -#		<xsd:element name="alien_visit" type="xsd:integer"/>		<alien_visit>62</alien_visit>
xsd:positiveInteger		Only positive whole numbers		#		<xsd:element name="alien_visit" type="xsd:positiveInteger"/>		<alien_visit>165</alien_visit>
xsd:negativeInteger		Only negative whole numbers		-#		<xsd:element name="alien_visit" type="xsd:negativeInteger"/>		<alien_visit>-13</alien_visit>
xsd:nonNegativeInteger		Only positive whole numbers (not "0")		#		<xsd:element name="alien_visit" type="xsd:nonNegativeInteger"/>		<alien_visit>45</alien_visit>
xsd:nonPositiveIntegers		Only negative numbers (not "0")		-#		<xsd:element name="alien_visit" type="xsd:nonPositiveIntegers"/>		<alien_visit>-35</alien_visit>

It is also possible to create custom simple datatypes