TROST: Open-System Trustworthiness

i050803 TROST InfoNote
 Pattern Templates
Description Approach 0.31

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 0.31 2006-08-08 -22:19 -0700

A. Organization of TROST Pattern Descriptions
B. Pattlet Summary Structure
C. TROST Pattern Description Template (at i050803c)

A. Organization of TROST Pattern Descriptions

A.1 TROST pattern descriptions are based on a detailed template that is designed to be consistent with the variety of other pattern templates in common usage. 

A.2 The minimal TROST pattern description consists of a Pattlet Summary that provides a compact summary of the essential characteristics of a pattern.  The principles of the overall template are honored but the content is abbreviated as a form of digest.

A.3 For pattern descriptions with extensive content, a pattlet summary is used as a cover, with detailed description and supporting materials on supplemental pages.  In these cases, the pattern description will provide detailed coverage of topics and subtopics.  Variations will be introduced to accommodate the special circumstances that apply to individual pattern cases.

A.4 There is provision for patterns being specialized variations of more general patterns.  It is also possible for patterns that are focused on realization in concrete implementations to be based on more-abstract patterns.  The differences are in placement of emphasis and detail.  The same pattern description structure is applied throughout.

see also:
i050803c: Detailed Pattern Template
i050803d: Pattern Comparisons
i050901: TROST Pattern Language

B. Pattlet Summary Structure

B.1 Pattlets are summaries of TROST pattern descriptions (Trowbridge et.al. 2003).  The ten key topics of the full TROST pattern template are addressed briefly and selectively.

B.2 The pattlet format is convenient for determining whether it is promising to examine the complete pattern description.  In the TROST pattern language, pattlets are commonly provided as cover sheets to the expanded material that follows.

B.3 Pattlets are also convenient as summaries of patterns having detailed descriptions provided elsewhere.  In that case, the summary saves the reader from having to track down additional sources simply to see how the pattern is being applied in an immediate situation.  The pattlet is a summary-level stand-in and connection to further detail.

B.4 The TROST pattern-description topics:

  1. Identification - how the pattern is known
  2. Situation - the setting in which the pattern can occur or be desired
  3. Intention - what is to be accomplished
  4. Concerns - issues to be balanced and addressed
  5. Approach - how to satisfy the intention - what to do
  6. Realization - strategy for aspecific implementations of the approach
  7. Considerations - additional matters to be aware of
  8. Consequences - the result of achieving the pattern: benefits and limitations
  9. Usage - actual cases, related patterns involved in completing the approach
10. Sources - acknowledgment of source materials and contributions

B.5 The elements in the summary outline, below, are linked to the corresponding detailed descriptions in the complete TROST Pattern Template description.  Specific sources are provided there and in the Pattern Comparisons which are the basis for the TROST Pattern Template.


1. Identification

The Identification topic covers how the pattern is known.   The elements are usually presented without any introductory heading.  There are important subordinate elements that situate the pattern description, even in summary forms.

  • Name: a simple title that is appropriate to the intention and approach, reflecting the situation as necessary

  • Version: version and date as needed to differentiate variations in the description and the pattern over time

  • Summary: one-sentence or less descriptive summary

  • Also Known As: any aliases important for identifying the pattern with any known ones

  • Archetype: image that evokes the essential quality of the pattern

2. Situation

The situation is the setting in which the pattern may occur.  The description establishes context and assists the reader in understanding where the pattern comes into play.

3. Intention

The intention is a simple declaration of what is accomplished with the pattern.

4. Concerns

Concerns are issues that must be explicitly acknowledged and accounted for.  The concerns must be addressed but will not necessarily be resolved.  The approach will balance them in a particular way.  

5. Approach

The approach is written in the form of instructions for achieving the intention.  The statements may be simple, with accompanying diagrams or models for illustrating the manifestation of the pattern in the prescribed situation.

6. Realization

Realizations are specific implementations shown in design form or as a template, especially for realizations in software.  When a realization is summarized, it will provide a reference to the detailed version.  In other cases there may simply be a brief statement of the strategy for carrying out a realization.

7. Considerations

There are important non-functional considerations that apply to approaches and their realizations, especially in software-engineering and information-technology situations.  This topic is unusual in summary pattlets unless there is a major consideration that it is important for readers to know about.  The fact of the consideration might then be noted in the pattlet so that it is not overlooked.

8. Consequences

The consequences of establishing a pattern are the results that are achieved with its presence, including limitations as well as benefits.  Summary pattlets may omit any reference to the consequences, although ones that are critical to recognize might be identified with simple statements.

9. Usage

Usage provides identification of known cases and of patterns that are related.  In summary pattlets there may be limited usage information to assist the reader in appraising the desirability of making deeper examination of the pattern.  Typical elements are:

  • Known Examples: specific actual cases in which the pattern is applied or apparent

  • Variants: similar patterns of possible interest that address different situations, intentions, and approaches

  • Related Patterns: ones used in conjunction with this one and that may be required in completing the details of the approach

10. Sources

It is important to acknowledge the sources for the current pattern, especially when the current pattern replicates or summarizes material published elsewhere.  In a summary pattlet, only main sources are identified:

  • References: citations to source materials with enough information so they can be located and used

  • Contributors: identification of those who provided material contribution to the development of the pattern

  • Attribution: information on how to make attribution to the summary, and any intellectual-property notices that apply to it.
Revision History:
0.31 2005-12-21-20:54 Incorporate Errata and Link to Next Version
Simple errata and improvements noticed while working on the version in the thesis are edited back into this version.
0.30 2005-09-23-21:07 Provide initial Pattlet Summary Format
The 0.30 i050803c document is summarized.  Any insights in doing that are applied back to the full template description before these two are published together.  This version is the basis for thesis Appendix A.
0.00 2005-09-23-14:11 Create Initial Placeholder
Make a copy of an i050803c 0.30 draft for distilling down to the initial pattlet format.
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created 2005-08-21-16:31 -0700 (pdt) by orcmid
$$Author: Orcmid $
$$Date: 06-08-08 22:19 $
$$Revision: 12 $
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