OPC UA与REST.pdf

1、Randy Armstrongrandy.armstrongopcfoundation.org2Statelessness Each request from the client to the server must contain all the necessary information to understand and process the request.Client-Server Architecture The system is divided into client(user interface)and server(data storage and processing

2、)components.Uniform Interface RESTful APIs have a uniform and consistent interface that is defined by a set of constraints.Cacheability Responses must,implicitly or explicitly,define themselves as either cacheable or non-cacheable to prevent clients from providing stale or inappropriate data in resp

3、onse to further requests.Decoupled A client cannot ordinarily tell whether it is connected directly to the end server or to an intermediary along the way.3Many web programmers need a simple HTTP based API to access data;Numerous standard tools exist facilitate development with REST based APIsClientS

4、erverHTTP POST alpha:1,beta:hello,gamma:red,yellow HTTP RESPONSE result:1,delta:force4HTTPS transport has been supported for years;OPC UA Services can be invoked sending binary,XML or JSON encoded Service message via HTTPS POST.Allows firewall and proxy transversal(two requirements of REST)5Services

5、 that can be invoked without creating a Session.Authentication is done on call(i.e.by passing a user token).Only Browse,Translate,Read,Write,HistoryRead,HistoryWrite and Call support Session-less operation.https:/reference.opcfoundation.org/Core/Part4/v105/docs/6.36Open API 3.0.0 schema definition.N

6、o Server side sessions.No webhooks and no subscriptions.Mandatory support for OAuth2Tooling to generate Open API definitions from types defined in a NodeSet.7OPC UA NodeIds are qualified by NamespaceUris to ensure co-existence between information models.Normally,a NamespaceIndex is used to optimize