Midlleware and EAI

Some distributed system

Human designed more samrt system in mobile system, such as smart card.

Mobile computing

Most of mobile system are forcused on networking. Wire connection is slow and not stable.

Sesor networks

Generaly make more memory into sensors. Kep them simple to makek them small.

  • All data is stored in a operator’s site and sensor only conveys the signal.
  • Each sensor stores part of data. Some integration ssytem drops some signals without losing key information.

Architectural system

Layer organization (your free to design layers)

  • broadcast. One layer to one layer, they can exchange messages
  • Web. Send request to split to storage system and do check , one transacion combines two subtransactions.
  • One layer responses to request by doing multible jobs.

Example: communication protocols

RBC model: A classic architecture

Socket: write something to the end of pipe, server listen in the other end.

Application layer(server) in the middle between : cacheing layer. Query generator stores index of all pages.

Objext-based style: Less popular

Put user interface to machine 1, put server to machine 2, put other method to machine 3, looks good to distributed system, but actually not good because of too many machines result to latency.

CORBA: （Common Object Request Broker Architecture公共对象请求代理体系结构）是由OMG组织制订的一种标准的面向对象应用程序体系规范。

RESTful architectures: more popular

全称是 Resource Representational State Transfer：通俗来讲就是：资源在网络中以某种表现形式进行状态转移。分解开来：Resource：资源，即数据（前面说过网络的核心）。比如 newsfeed，friends等；Representational：某种表现形式，比如用JSON，XML，JPEG等；State Transfer：状态变化。通过HTTP动词实现。

Basic operation: PUT(update), GET, DELETE, POST

Hard to state transaction. Example: Amazon’s Simple Storage Service(operation is simple), Amazon S3 SOAP interface (call can come back, you can see what is wrong).

Cordination

Temporal and referential coupling

  • Temporal coupling
    • Phone call system. You must know location and phone number.
  • Temporally decoupled.
    • Email system. You must know location and email address. You should be upon running all the time but the reciever doesn’t need to upon running all the time.

Event based and Shared space

  • don’t need to know address, because this meassage will be distributed
  • don’t need to know both

Build middleware (some popluar mechanism)

my4

Reference material:
Book: Distributed Systems, Third edition, Version 3.02(2018), Maarten van Steen and Andrew S. Tanenbaum.
Lectures: University of Waterloo, CS 454/654 (Distributed System), 2020 winter term, Professor Khuzaima Daudjee.