The Research And Implementation Of Medicine Storehouse System Based On Windows DNA

Hospital Information System is the most complicated one in existingenterprise systems in the world. It is designed to manage hospital and itsevery departments and subsidiary units used computer technology. TheMedicine Storehouse System is a subsystem of Hospital Information Systemfor Sanjiu hospital of Shenzhen.Traditional application is based on Customer/Server structure whichcan greatly reduce the LAN transmission and the difficulty of data control.It's greatest advantage is simple and easy to realize. But it has manyproblems when it is used in a large-scale application, such as badlyperformance in scalability and security, and it also has difficult onmaintainability. Two layers mode has already far from been meeting thedemands of modern enterprise systems.Three layers system is improved from two layers system. It separatesthe business logic from customer GUI and makes it as an intermediate layer.Three layers is the combine of User Service, Business Service and DataService. User Service is the customer GUI. All of the business logic areimplemented in Business Service layer. Data Service layer is used forstoring user data and it is usually a relational database. Using intermediatelayer to implement business logic can reduce the pressure of the customerand make the system more flexibility. Windows DNA is the frame which isused by Microsoft to establish a generation of commercial solution withhigh adaptability. It is the simple case of three layer structure. And it is thefirst application structure designed for distributed calculation system whichis the combine of Internet, Customer/Server and Calculated PC model.Windows DNA structure uses COM+ to implement intermediate layerwhich is based on Component Object Model. COM is a better C++ and itimplements the binary software reuse. We can look COM+ as the combineof COM and MTS. It inherits and develops the advantage of COM and MTS.It uses component service explorer to manage COM+ component and itsimples the development of component by component service.The Medicine Storehouse is the implement of Windows DNA based onCOM+. It is designed and implemented as a three layers system. We usedVisual Basic to develop the Customer Service layer and ATL to implementCOM+. The system uses SQL Server 2000 as Data Service layer.The Medicine Storehouse uses ADO to access database. ADO is aCOM based on OLE DB. It encapsulates the interfaces of OLE DB to agroup of objects. Record set is one of the ADO objects and it is widely usedin the system. We use record set to transmit data between different layers ofthe system.Transaction processing is an important concept in MIS (ManagementInformation System). It is used for complicated business logic and to makesure the consistency of the system. There are three transaction types: localtransaction, distributed transaction and declarative transaction. Localtransaction is for the simple transaction with one COM+ object and oneresource. Distributed transaction is for the more complicated transactionwith several COM+ objects and COM+ uses DTC and two steps submitprotocol to implement distributed transaction. Declarative transaction is asimple way to implement distributed transaction by combining DTC andobject context to hide the complicate of distributed transaction.There are many other COM+ services used by the system to improvethe performance. Using constructor string to transmit the DSN to theinstance of the COM+ object and make the system more flexibility. Usingobject pool to optimize the COM+ object which's used frequently and notcheap to create. Using JITA to optimize the COM+ object which will have alarge number of resources when it is activated. All of the COM+ servicesused can improve the expansibility and scalability of the system.