nDP will run any number of tasks in parallel. Each task is represented by an icon on the nDP desktop which depicts the processing status of that task. A task is effectively a single nDP program and can be edited to reveal the functional network that describes its actions.
Data is processed as a stream. Data streams flow through functional blocks which are responsible for all the data processing activities. All data processing occurs in parallel (as far as is possible) - and as the data flows are driven by demand, any unwanted results are simply not computed. Where functions must ask the user for input - this occurs when the demand exists for the result - and the resulting effect is somewhat like a wizard. Some functions will wait for external events such as the arrival of a file or operator input or even the completion of another program.
The element headers (with their attributes) are the main target for data processing operations, the data component of elements being carried by the header. To operate on the data itself, fields must be extracted and added to an elements attributes. Most nDP processing functions make extensive use of attribute values.
The dialogue called the "Director" is used to organise the activity.
Edit an existing task by choosing "Edit" from the right-clicking the task icon, or use "New" from
the file menu of the Director.
Add functional blocks from the bar at the top of the Director. Link them by dragging between the input and output arrows on the blocks. Set up constant data using right-click popup menu, either to change the properties or just feed literal data into an input. Shift-click directly starts either properties or constant input as appropriate.
The technique for constructing or editing the flow networks is to make use of nDP's ability to
stop and restart a task very easily. The display function called "View" is the most useful
block when developing a network. Starting with example data, you can build up the network one
step at a time, each time running the task and viewing the flow leaving the final block. By this means
you can quickly identify problems and ensure each step is correct before adding the next. Because
nDP is a functional processor the only way that one function can impact on another is where they
are both interacting with the external environment (e.g. accessing files).
When construction a network to process files you can simplify directory specifications by using the special function "Dir" which associates a name with a directory path that can then be referenced by other functions using its name followed by "::" wherever a filename would be written. This allows you to quickly change the directories used from a testing to a production environment without having to look through the whole processing network.
Functional blocks are grouped into 7 groups by their nature, and this is shown by their colour coding. You can click the coloured buttons at the left of the toolbar to move to/though the groups. The functional blocks have been given different shapes to aid recognition. The functions are documented in the nDP Reference manual which you will probably need open while editing a flow network - this manual is the primary guide to the specifications of the functions and is always issued with each new release of nDP.
Warning: you can edit while the task is actually running! The status icon is repeated from the desktop in the corner of the Director so you can see it's state. A running task will only be reset if your changes have compromised the data flow. You can change the state of a task by clicking its status icon - use right-click for menu of commands or just click for nDP to change it to a likely next state.
<TASK NAME="Task-Identifier" [ INSTANCES="count" ] >
Each task is specified by a TASK element. When the task installer finishes reading the element the task will be installed and set into the required initial state.
The INSTANCES count specifies how the task behaves when activated. A zero count means the task deletes itself on completion. Positive counts indicate how many copies of the task may run in parallel.
Inside the TASK element is the complete specification of the functional processing that the task is to perform. Each functional block is represented by an element, and these link together in various possible ways.
There are very few limits on the sizes that data can be. The main one is that the maximumm length of names for elements and attributes is currently set to 64 characters (unless Unicode characters >FF are encountered). There is no particular limit to the size of an attribute string value or of data content or the number of levels of nesting but some functions may perform with sub-optimal speed if unusually structured data of massive scale is encountered. Most processing limits will be set by the PC platform being used.
Note that nDP makes use of itself to load and save task descriptions.