XML

Overview

XML or Extensible Markup Language is a common format used by enterprises for data exchange. Haxall supports a standardized translation of Grid into XML. Note this format is not standardized by Project Haystack, but rather is specific to Haxall.

Usage

Fantom APIs:

• XParser to decode into DOM
• XDoc in-memory DOM model and writing
• OutStream has many methods for XML escape sequences

Axon APIs:

• ioWriteXml() to encode Grids

REST APIs:

• content negotiation for "text/xml" MIME type

Grid Format

SkySpark defines a standard mapping of Grid into XML which is used by the REST API and ioWriteXml() function. The XML representation maintains full fidelity with the Haystack data model - all meta-data and type information is maintained. However the downside is that XML is much more verbose than Zinc.

The Grid to XML mapping is as follows:

• Top level <grid ver="3.0"> element which contains:
  • An optional <meta> element with grid meta
  • One <cols> element with column definitions
  • Zero or more <row> elements with row definitions
• A column definition is <{name}> with an optional dis attribute and optional <meta> child element (dis meta is always skipped)
• Rows are encoded in <row> elements which contain values elements
• Meta data and row values are encoded into <{name}> elements
• Value cells always define a kind attribute with the kind name or "null" if the value is null
• If the value is a scalar, then the val attribute maps to the Fantom toStr representation of the value. If the value is null, Marker, or Remove then the val tag is omitted
• Ref values may include an optional dis attribute
• Values which are nested collections are encoded to a tree of children elements as illustrated in the examples below

Example:

// Zinc
ver:"3.0" projName:"test"
dis dis: "Equip Name" primaryCol:M,equip,siteRef,installed
"RTU-1",M,@153c600e-699a1886 "HQ",2005-06-01
"RTU-2",M,@153c600e-699a1886 "HQ",1999-07-12

// XML
<grid ver='3.0'>
<meta>
  <projName kind='Str' val='test'/>
</meta>
<cols>
  <dis dis='Equip Name'>
  <meta>
    <primaryCol kind='Marker'/>
  </meta>
  </dis>
  <equip/>
  <siteRef/>
  <installed/>
</cols>
<row>
  <dis kind='Str' val='RTU-1'/>
  <equip kind='Marker'/>
  <siteRef kind='Ref' dis='HQ' val='153c600e-699a1886'/>
  <installed kind='Date' val='2005-06-01'/>
</row>
<row>
  <dis kind='Str' val='RTU-2'/>
  <equip kind='Marker'/>
  <siteRef kind='Ref' dis='HQ' val='153c600e-699a1886'/>
  <installed kind='Date' val='1999-07-12'/>
</row>
</grid>

Nested list values:

// Zinc
ver:"3.0"
list
[1,2,3]

// XML
<grid ver='3.0'>
<cols>
  <list/>
</cols>
<row>
  <list kind='List'>
    <item kind='Number' val='1'/>
    <item kind='Number' val='2'/>
    <item kind='Number' val='3'/>
  </list>
</row>
</grid>

Nested dict values:

// Zinc
ver:"3.0"
dict
{dis:"hello!", foo}

// XML
<grid ver='3.0'>
<cols>
  <dict/>
</cols>
<row>
  <dict kind='Dict'>
    <dis kind='Str' val='hello!'/>
    <foo kind='Marker'/>
  </dict>
</row>
</grid>

Nested grid values:

// Zinc
ver:"3.0"
grid
<<
ver:"3.0"
dis
"Grid"

>>

// XML
<grid ver='3.0'>
<cols>
  <grid/>
</cols>
<row>
  <grid kind='Grid'>
    <cols>
      <dis/>
    </cols>
    <row>
      <dis kind='Str' val='Grid'/>
    </row>
  </grid>
</row>
</grid>

You can also access SkySpark data via oBIX which is an alternate XML format.