Tags Defined

The basis of the Visual Tag System software is a group of components called "tags" (sometimes referred to as "points"), which represent the various equipment processes that make up your system, and enable you to create a chain of communications from VTS to your physical equipment. A typical VTS application based on the VTS layer will include a series of tag types, of which you can make almost infinite copies (known as "instances"). Each instance or copy of a tag type is a tag. For example, the Analog Input tag type can be used to generate thousands of analog input tags.

Tag instances and their unique configuration data are stored in an ODBC-compliant database. By default, this is a Microsoft Access database file that is named, "Points.mdb". This "tag properties database" consists of a series of tables, each of which represents a specific tag type. The records held within a table define individual tags, and the fields within a table define the properties of each tag. The fields within a table in the tag properties database correspond one-to-one with the parameters of a tag template.

The diagram below illustrates the structure of some of the tables in the tag properties database.

VTS has its own interface to the tag properties database, so that users need not directly edit the "Points.mdb" Microsoft Access database file. The built-in interface to the tag properties database is the Tag Browser and tag properties folders.

When creating your own tags, it may be helpful to refer to the tag template files with commented source code that are included with VTS. Further information on these template files can be found in Template.src Template File.

Terms and Abbreviations Related to Custom Tag Type Development

The following terms and abbreviations are used throughout this document:

 

Tag Template A module that defines the generic instance of a tag. An example of a typical tag template module would be "AnalogInput". The tag template has formal parameters that correspond one-for-one with the fields in the tag properties database (i.e. "Points.mdb"). Note: Tag template files with commented source code are included when you install VTS to assist you in the creation of custom tag types. Information is provided in Tag Template Modules.

 

Tag For the purposes of this section, a tag is defined as a named value (or variable) that is the instance of a tag template. For example, an instance of the DigitalInput tag template is a digital input tag.

 (Another definition to describe a tag is "a software component that can communicate with objects in the outside world. A tag can be used to accept input or generate output, and works with either analog (continuous) values or digital (discrete) values.")

 

Database The "Database" module is at the highest scope in a VTS application, and is the location where all of the tags for the application are defined.

 

Library The "Library" module is the location in a VTS application where most of the modules and non-tag related variables are defined. The Library module is at the scope level just under the Database module. This module's instance goes by the name of "\Code" when referenced within a VTS application.

 

ODBC  ODBC (Open DataBase Connectivity) is a standard interface provided by Microsoft that allows access to a variety of commercial databases using one set of code. ODBC enables support of Microsoft Excel, Microsoft Access, SyBase, Interbase, Paradox, FoxPro, Dbase, Microsoft SQL, and other databases. An ODBC driver for the specific database must be installed in the appropriate Windows control panel (e.g. Databases (ODBC)) prior to use.

 

Points.mdb The Microsoft Access database file that defines all of the tags for your application; also referred to as the "tag properties database".

 

Tag Properties Folder  A file folder style dialog with a series of tabs, each of which contains a set of tag properties of a specific category and is appropriately labeled according to the property fields it contains (e.g. the "ID" tab contains properties that identify the tag.) The tag properties folder is a convenient method of enabling users to enter data into the tag properties database without having to modify the database manually.

 

The section that follows provides an introduction to the organization of modules within a VTS application.