It is not necessary to understand how EDDL works in order to enjoy the benefits. However, understanding the technology may be helpful when choosing EDDL over inferior technology. EDDL is a structured textual declaration similar to an XML, HTML web page, or SGML document. EDDL is not like the printer driver concept in the Windows operating system.
The purpose of EDDL is decoupling the device developers from the software developers. Device developers need not worry about configuration tools, and software developers need not worry about each individual device type.
EDDL can theoretically be used with any protocol. EDDL declares device parameters and their dependencies, visual representations, user interactions, and how system accesses information etc. EDDL hides complex logic and decisions such as Bayesian networks and conditionals using method scripts.
Semantics described through EDDL automatically make cryptic codes and complex data structures human readable. Different menu hierarchies can be defined, one for large-screen computer software and another for small display handheld communicator included in the same DD.
EDDL is a precise declaration of data available in the device; it is not a device driver software. The declaration is based on keywords similar to XML or HTML web page tags and includes data type, label, and help text in many languages, classification, unit, range, and other aspects. EDDL also includes interactive methods, which are scripts based on a subset of ANSI C to guide the technician through steps requiring interaction.
The Electronic Device Description file is distributed in either plain text or compressed text format depending on what the chosen software requires.
Figure 32 EDDL can be used in plain text form or compressed text form
The broad categorird of EDD contents are:
- Device Definition: which includes blocks and parameters
- Business Logic: which includes wizards (methods) and conditionals
- User Interface Description: which includes menus and graphics
Plain Text EDD
Plain text EDDL is verified using a checker tool before it is distributed for use.
Compressed Text EDD
For compressed text EDDL, the source EDDL "tokenized" to a compressed formatto prevent tampering and subsequent problems. The compilation process also includes checking of EDDL syntax etc. The tokenized files are relatively small and therefore files for many types and versions of devices can be stored also in the limited flash memory of a handheld communicator or in the device itself from where it can be uploaded by the software.
EDDL applications render the display based on EDDL keywords and interactive method scripts - just like a web browser renders a display from an HTML web page or like a reader.
Plain text EDD are interpreted by EDDI (Electronic Device Description Interpreter) in the software whenever the data is used, to render the display or when it is printed, just like a web browser.
Compressed text EDD are decoded by DD services, just like a reader for PDF files.
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