White

Action Performed

White-box

Distribution

Process

-box

 

Budgeted

Reference

Reference

Step

 

Requirements

(Locality)

 

 

 

 

 

 

3

LRF3: Raster Image Processing

 

DRF3:

PRF3:

 

WSB3: reads the buffer queue address list and

 

Printer

Page_RIP

 

begins reading the data blocks. As the block

 

Control Unit

 

 

are processed, one or more page bitmaps are

 

 

 

 

rendered to memory and stored in available

 

 

 

 

page bitmap buffers.

 

 

 

 

 

 

 

 

4

LRF4: Raster Image Processing

 

DRF4:

PRF4:

 

WSB4: indicates the input data block is

 

Printer

Input_data

 

available for reuse after the block is read and

 

Control Unit

_buff_mgt

 

processed.

 

 

 

 

 

 

 

 

The header material for the Build Page operation provides context for elaborating the JRT. This JRT decomposition allocates the functionality of the single black-box operation to white-box printer entities:

￿The Action Performed column captures both the logical entity performing the action and the logical step performed. In this example, two logical entities, I/O Services and Raster Image Processing, collaborate to print a page.

￿NFRs are allocated to the logical white-box steps in the White-box Budgeted Requirements column—for example, 10 milliseconds are allocated to the I/O Services’ operation that receives and stores an available data block in memory.

￿The last two columns provide the distribution and process references. In this example the Printer Control Unit locality and Data_rec process must perform the operation of receiving a block and putting it into memory within the same 10 millisecond budget.

The JRT maintains context, captures the logical and distribution decomposition, and provides for the allocation of nonfunctional requirements. With the JRT in place, (or, as noted before, developing it in parallel), it is useful to represent the content in SysML as a coupled set of sequence diagrams showing the same flow in the different viewpoints. Figure 5-5shows the sequence diagrams for the print page service.

Chapter 5. Understanding distribution of responsibility

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IBM SG24-7368-00 manual LRF4 Raster Image Processing