Application Design is where you build an APPX application. You describe the data, the screens, the reports and the rules, and APPX produces a working application from that description.
Describe it, and APPX builds it
APPX uses a specification approach. Instead of writing every step in a procedural language, you fill in the specifications for each part of the application: its files and fields, menus, input screens and reports. APPX turns those specifications into the menus, screens and reports your users work with.
Where a business rule needs more than a specification, you add a routine in ILF, the Integrated Language Facility, APPX’s own procedural language. Some applications are built from specifications alone. Others use ILF wherever they need exact control over records, calculations, or the order in which things happen.
The parts of an application
The data dictionary
Each field and file is defined once, in the data dictionary: domains, fields, file structures and keys. The dictionary is active, so what you set there applies everywhere the field is used, on every screen and in every report. Its tools also create and restructure the files and tables, whether the data lives in APPXIO or in Oracle, Microsoft SQL Server, PostgreSQL or MySQL.
Nine kinds of process
An application is built from processes. Four of them have a screen or printed layout, which you paint in the Image Editor:
- Menus list the options a user can choose.
- Inputs enter, change, view and delete records.
- Inquiries look up one record and can print it.
- Outputs produce reports and lists, on screen or on paper.
The other five work without a layout. Queries select and sort records, Updates change data under program control, Subroutines hold routines that any other process can call, Job Streams run a series of processes in order, and Status Checks do error checking. You connect the processes to one another to form the application.
The Image Editor
Screens and reports are painted in the Image Editor, which places fields and text exactly where they should appear. Its GUI tools add graphical controls such as buttons.
ILF and the debugger
ILF routines are attached to event points in each process, so each one runs at the right moment. The ILF Editor is where you write them. The statement debugger steps through a routine one statement at a time and shows how each field’s value changes; you can change a value on the spot to see what a fix would do.
Documentation as you go
Each part of an application carries its own documentation, written in the same place it is designed, so when the application is finished, so is its documentation. The same screens can also hold a requirements specification before anything is built.
Prototype with your users
Screens and reports are quick to specify and quick to change, which makes APPX a good prototyping tool. Build sample screens and reports, review them with the people who will use them, adjust them, and repeat. The prototype then grows into the application, with ILF added where the rules call for it.
More than one version
Application Design keeps more than one version of an application, for example a production version, a test version and a development version, or a version for each company in your organization.