As discussed in this
morning's meeting, here are a few possibilities for XML encoding of the HCE
protocol. Obviously, we can mix and match things we like about each group.
What do you think?
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Option 1: Heavily SOAP influenced
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This is basically what I sent out yesterday. The command header is represented
as an element with attributes, and the command itself is a single element within
the command header. The command uses an XML namespace to fill the role of identifying
the interface.
The primary advantage of this representation is that if you strip off the
command header your left with something that is exactly SOAP-compatible. Thus,
it is a known solution that will be familiar to those who know SOAP.
On the other hand, it is a bit verbose.
Definition
-----------
<xsd:complexType name="CommandType">
<xsd:sequence>
<xsd:any minOccurs="1" maxOccurs="1">
</xsd:sequence>
<xsd:attribute name="headerID" type="xsd:int">
<xsd:attribute name="destination" type="xsd:int">
<xsd:attribute name="source" type="xsd:int">
<xsd:attribute name="session" type="xsd:int">
<xsd:attribute name="context" type="xsd:int">
</xsdComplexType>
<xsd:complexType name="RegisterAgentType">
<xsd:element name="agentID" type="xsd:int>
<xsd:element name="processID" type="xsd:int>
<xsd:element name="agentName" type="xsd:string>
</xsd:complexType>
Example
-----------
<Command
headerID="1"
destination="101"
source="100"
session="1"
context="10001">
<agentMgr:registerAgent xmlns:agentMgr="org.eclipse.hyades.agentMgr">
<agentID>100</agentID>
<processID>4067</processID>
<agentName>org.eclipse.hyades.processControllerAgent</agentName>
</agentMgr:registerAgent>
</Command>
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Option 2: Interface and command IDs as attributes
--------------------------------------------------
This second variation moves the command ID and interface ID into the command
header (as pure IDs, no longer names). The command header then contains a
standardized element, parameters. The contents of the "parameters"
element are command-specific, and continue to use standard XML Schema type
definitions.
Definition
-----------
<xsd:complexType name="CommandType">
<xsd:sequence>
<xsd:element name="parameters" type="ParamListType"
minOccurs="1" maxOccurs="1">
</xsd:sequence>
<xsd:attribute name="headerID" type="xsd:int">
<xsd:attribute name="destination" type="xsd:int">
<xsd:attribute name="source" type="xsd:int">
<xsd:attribute name="session" type="xsd:int">
<xsd:attribute name="context" type="xsd:int">
<xsd:attribute name="interfaceID" type="xsd:int">
<xsd:attribute name="comandID" type="xsd:int">
</xsdComplexType>
<xsd:complexType name="ParamListType">
<xsd:any minOccurs="0" maxOccurs="unbound">
</xsd:complexType>
Example
-----------
<Command
headerID="1"
destination="101"
source="100"
session="1"
context="10001"
interfaceID="1001"
commandID="1">
<parameters>
<agentID>100</agentID>
<processID>4067</processID>
<agentName>org.eclipse.hyades.processControllerAgent</agentName>
</parameters>
</Command>
--------------------------------------------------
Option 3: Element-oriented command header
--------------------------------------------------
This option moves the command header members into the position of elements rather
than attributes of the command element. This adds some flexibility in the
command header format.
Definition
-----------
<xsd:complexType name="CommandType">
<xsd:sequence>
<xsd:element name="headerID" type="xsd:int">
<xsd:element name="destination" type="xsd:int">
<xsd:element name="source" type="xsd:int">
<xsd:element name="session" type="xsd:int">
<xsd:element name="context" type="xsd:int">
<xsd:element name="interfaceID" type="xsd:int">
<xsd:element name="comandID" type="xsd:int">
<xsd:element name="parameters" type="ParamListType"
minOccurs="1" maxOccurs="1">
</xsd:sequence>
</xsdComplexType>
<xsd:complexType name="ParamListType">
<xsd:any minOccurs="0" maxOccurs="unbound">
</xsd:complexType>
Example
-----------
<Command
<headerID>1<headerID>
<destination>101<destination>
<source>100<source>
<session>1<session>
<context>10001<context>
<interfaceID>1001<interfaceID>
<commandID>1<commandID>
<parameters>
<agentID>100</agentID>
<processID>4067</processID>
<agentName>org.eclipse.hyades.processControllerAgent</agentName>
</parameters>
</Command>
--------------------------------------------------
Option 4: Short names
--------------------------------------------------
Finally, this option follows the format in Option 3 (though it could be done
with any of the above options) but shortens all the names to reduce the size of
the data on the wire. The tradeoff is that it becomes significantly less
human-readable.
Definition
-----------
<xsd:complexType name="CommandType">
<xsd:sequence>
<xsd:element name="HID" type="xsd:int">
<xsd:element name="dest" type="xsd:int">
<xsd:element name="src" type="xsd:int">
<xsd:element name="ses" type="xsd:int">
<xsd:element name="ctxt" type="xsd:int">
<xsd:element name="IID" type="xsd:int">
<xsd:element name="CID" type="xsd:int">
<xsd:element name="parms" type="ParamListType"
minOccurs="1" maxOccurs="1">
</xsd:sequence>
</xsdComplexType>
<xsd:complexType name="ParamListType">
<xsd:any minOccurs="0" maxOccurs="unbound">
</xsd:complexType>
Example
-----------
<Command
<HID>1</HID>
<dest>101</dest>
<src>100</src>
<sess>1</sess>
<ctxt>10001</ctxt>
<IID>1001</IID>
<CID>1</CID>
<parms>
<AID>100</AID>
<PID>4067</PID>
<name>org.eclipse.hyades.processControllerAgent</name>
</parms>
</Command>
