Page 815 - ExtendSim User Guide
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Data Management and Exchange 789
Technologies for communication
☞ Since Microsoft constantly updates and replaces these protocols, it is best practice to use the ExtendSim blocks for DDE communication. See the ExtendSim blocks starting on page 772.
ODBC/SQL
Open DataBase Connectivity (ODBC) provides a standard application programming interface (API) method for accessing database data independent of programming language, operating system, and database system. The goal is to enable access to data from any application, regard- less of which database management system (DBMS) is handling the data. It does this by insert- ing a middle layer between an application and the DBMS that translates data queries into commands understandable by the DBMS.
The ODBC API allows applications to access data in DBMS using SAG SQL (SAG = SQL Access Group; SQL - Structured Query Language) as the standard for requesting information from a database. SQL allows a single application to access different database management sys- tems.
ODBC offers connectivity to a wide variety of data sources, including relational databases and non-relational data sources such as spreadsheets and text files.
☞ Since Microsoft constantly updates and replaces these protocols, it is best practice to use the ExtendSim blocks for ODBC communication. See the ExtendSim blocks starting on page 772.
FTP
File Transfer Protocol (FTP) is used to connect two computers over the Internet or an intranet for the purpose of transferring data and commands. In an FTP environment, one computer acts as a server and the other acts as a client.
As a client, ExtendSim initiates a connection to the server. Once connected, ExtendSim accesses a specified file on the server and either imports data from it or exports data to it.
ExtendSim implements FTP by:
• The Data Import Export block (Value library) can open a file on a remote computer and access the data for use in an ExtendSim model.
• InternetAccessfunctionsprovidemoreflexibilitythanusingtheDataImportExportblock. See the Developer Reference.
DLLs and Shared Libraries
Dynamic-Link Libraries (DLLs on Windows) and Shared Libraries (Mac OS) are segments of code written in a language other than ExtendSim's ModL. This standardized interface provides a method for linking between ModL and other languages. When and if a DLL or Shared Library file is needed, it is loaded into memory and run by ExtendSim.
DLLs and Shared Libraries can contain code, data, and resources. They are used to provide access to functions that are already written in another language or to solve problems that might be difficult or impossible to solve in ModL. Use a DLL or Shared Library to calculate some function, perform a task, access application programming interface (API) calls, or even control external hardware devices.
ExtendSim implements DLLs and Shared Libraries by:
• TheRatelibraryusestheLPSolveDLLorSharedLibrary.
• ExtendSim functions allow you to call the external code segments from within a block's ModL code and perform operations. For example, a block can pass data to the DLL or
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