Express Interface (Xi) Technical Overview

© 2009 OPC Express Interface Slide 1

EXPRESS interfaceEXPRESS interface

Technical OverviewTechnical Overview


What is Xi?What is Xi?A simple Microsoft.NET interface for securely wrapping industrial automation systems, for both local and remote access.

Xi Client Xi Client

Xi ClientExistingClient

Xi Client

OPC COM Server

Xi InterfaceXi SecureMessaging

Xi SecureMessaging


Why was Xi developed?Why was Xi developed?New Microsoft-based client developments have moved to .NET => These application need a native .NET interface to talk to OPC COM servers, instead of each having to develop its own.

Before Xi (need a custom adapter for each type of OPC server)

OPC COMServer

.NET

Interface “A”

.NET Client Application “A”COM/DCOM

.NET

Interface “B”.NET Client Application “B”

COM/DCOM

Custom Adapter

Custom Adapter

Custom Adapter.NET

Interface “C”.NET Client Application “C”

COM/DCOM

With Xi (Xi Wrapper is common to all types of OPC Servers)

OPC COM Server

.NET Client Application “A”

.NET Client Application “B”COM/

DCOM

Xi Wrapper

.NET Client Application “C”

Xi .NET

Interface


Is Xi a common interface?Is Xi a common interface?Yes - Xi provides access to runtime and historical data, events, and alarms, all in one interface

Xi Alarm Client

Xi Interface

Xi DA Client

OPC DAServer

OPC HDAServer

OPC A&EServer

Xi History Client

Xi Integrated Client

Xi Integrated Client


Security modelSecurity model

Full Access

Limited Access (e.g. no Writes)

Full Access


Performance modelPerformance model

Higher Performance

Remote Access Performance

Highest Performance


Platform modelPlatform model

Open – Generally Windows

Open – Any platform using web services

Windows


Xi Interface ArchitectureXi Interface ArchitectureMulti-layer architecture to reduce interoperability problems

Client Interface

Client App

Client Base

Server Base

OPC Wrapper

OPC COM Server

Server Interface

WCF

Alternate Server Implementation

Developer-specific code

Standard code for the client

Standard code for the server

Developer-specific code

Standard code for OPC Wrappers


Xi Functional ArchitectureXi Functional ArchitectureClients select resources (data/alarms/events) into lists, and add lists to endpoints for access

Client App

System Resources

Client-specific Context

HistoricalData

Alarms & Events

Historical Alarms & Events

Runtime.Data

Common to all clients

filterfilter

Read

Write

Subscribe

Manage


Security conceptsSecurity concepts Base user privileges defined by access

control list Base encryption and authentication

provided by .NET WCF Read, write, and subscribe privileges for

the user can be restricted based on location of the user and the client application being used (e.g. only approved client apps can write).

Patent pending (royalty-free license for use with Xi)


Read Endpoint

Resource Management

Endpoint

Security architectureSecurity architecture

List of Resource Discovery Endpoints

Server Discovery Endpoint

List of Resources

Write Endpoint

Secure

One per server

One per system

•Dynamically opened

•Multiple endpoints per client

•Multiple lists per endpoint

•Known only to the client

Only if authorized

List of Resources

List of Resources

Subscribe Endpoint

List of Resources

Poll or Callback

(may be redundant)

Access Controls

ClientApplication


Server and endpoint discoveryServer and endpoint discovery

PNRP Enabled Servers

Non-PNRP Enabled Servers

PNRP Enabled Clients

Non-PNRP Enabled Clients

Xi Discovery

Server

Manual Configuration of Discovery Server

Address

Manual Configuration of Server Address

PNRP Discovery of Servers

Xi Discovery of Server Endpoints Xi Discovery of Xi

Server Endpoints

PNRP Discovery of Discovery

Servers

PNRP = Peer Name Resolution Protocol (Microsoft)


Endpoint interfacesEndpoint interfaces

ServerDiscovery

ResourceManagement

Callback Poll

Read

Write

Used to locate servers

Used to: discover resources of a server, create lists of resources, create endpoints, and assign lists to endpoints

Used to get the value of list entries

Used to update the value of list entries

Subscribe


Obtaining information about the serverObtaining information about the server

Standard MIB Objects

Vendor MIB Objects

(optional)

Server Management Info Base (MIB)

Server capabilities and settings

Server-specific management object values

Vendor MIB Object descriptions


Finding objects (filtered browsing)Finding objects (filtered browsing)

A

B C

D E F G

Object Hierarchy

Objects located by their path (e.g. A/C/G)

Object Attributes

InstanceId

Name

Description

IsLeaf

ObjectTypeIdDataTypeIdListDimensions

IsReadable

IsWritable

FastestScanRateRoles

IsCollectingHistory

Flags


Data listsData lists

Data Lists

A

B C

E F G

Object Hierarchy

data objects

D

• Data lists select data objects that are to be accessed via read/write/subscribe

• Data lists can be created by the client or the server


Historical data listsHistorical data lists

Historical Data Lists

A

B C

E F G

Object Hierarchy

Historical values

D

• Historical data lists are data lists that contain historical values

• Historical lists are updated as new values are received into the Data Journal


Alarm and event listsAlarm and event lists

Event/Alarm List

Filter Criteria

Alarms and

Events

Alarm/Event Sources

AreaHierarchy

• Alarms and events, like data, are accessed via lists, but membership in the list is defined by filters

• Events are in lists only long enough for them to be reported via a subscription

• Alarms stay in lists until they are acked/inactive• Alarms and event lists can be created by the client or the server

Areas


Historical alarm and event listsHistorical alarm and event lists

Historical Event/Alarm

ListFilter

Criteria

Historical Alarms and Events

Alarm/Event Sources

Event Journal

• Historical alarm/event list membership is defined by filters

• Historical lists are updated as new alarms/events are received into the Event Journal

Areas


Interface summaryInterface summary


Example specification pageExample specification page


ConclusionConclusion Open Additional security layered on top of traditional

security mechanisms Supports runtime and historical data, events, and

alarms. Additionally supports passthroughs Provides:

– Local access via NamedPipe bindings– LAN access via NetTcp bindings– Web access and off-platform access via REST

interface & Http bindings

Business

Express Interface (Xi) Technical Overview