IBM SG24-7368-00 manual Joint realization tables, DRF1 PRF1

more is learned over the course of the system development effort. Eventually the entire model comes together.

This is also true when deciding whether to reason about distribution issues first with sequence diagrams, or with joint realization tables. In all likelihood, we should perform both activities in parallel—we can use joint realization tables to get a view of multiple dimensions, and we can use sequence diagrams to focus on and reason about functionality in the viewpoint. We now turn to joint realization tables, which we have actually used before and partially filled in, as we did operation analysis in the logical viewpoint (refer to “Operation analysis” on page 72).

Joint realization tables

In MDSD, we distinguish between functional requirements and nonfunctional requirements (NFRs). Functional requirements describe the system behavior as well as the collaboration among system components to accomplish the system behavior. NFRs pertain to how a system performs its functions and include concerns such as quality, quantity, and timeliness.

Joint realization tables (JRTs) decompose the system behavior in the context of the logical and distribution architectures and, at the same time, assign nonfunctional requirements to these system behavior steps (services/operations). In a real sense, this is the missing link—the item that was needed to connect object-oriented development models to the needs of the engineering community developing large-scale systems.

A JRT example that decomposes the task of printing a page is shown in

Table 5-1.

Table 5-1 Partial joint realization table for printing a page

White	Action Performed	White-box	Distribution	Process
-box		Budgeted	Reference	Reference
Step		Requirements	(Locality)
1	LRF1: I/O Services	SUP1: 10 ms	DRF1:	PRF1:
	WSB1: receives the block and stores in an		Printer	Data_rec
	available data buffer in memory.		Control Unit
2	LRF2: I/O Services	SUP2: 2 ms	DRF2:	PRF2:
	WSB2: updates the input data buffer queue		Printer	Input_data
	with the address of the received block and		Control Unit	_buff_mgt
	sends the awaiting process input data buffer
	queue address list to the Raster Image
	Processing subsystem.

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