J.D. Meier's Blog : Process

Patterns and Practices of Lean Software Development

J.D. Meier — Mon, 22 Jun 2009 12:31:40 GMT

I have a guest post on Shaping Software from Corey Ladas on Patterns and Practices of Lean Software Development. This is a follow up to Corey's previous post, Introduction to Lean Software Development. Several readers had ask for more information on the principles, patterns, and practices of Lean Software Development. Corey's latest guest post is in response to this request and provides a map and narrative of how some key principles, patterns, and practices can help support Lean Software Development.

Read Corey's post, Patterns and Practices of Lean Software Development.

Lean Software Development

J.D. Meier — Mon, 15 Jun 2009 16:51:44 GMT

I'm honored to have a guest post on Shaping Software from Corey Ladas on Introduction to Lean Software Development. Corey is a product development methodologist and the author of Scrumban: Essays on Kanban Systems for Lean Software Development.

In the post, Corey explains the principles of Lean Thinking, the origins of Lean Thinking, the metaphor school of Lean Software Development and the workflow school of Lean Software Development.

Read Corey's post Introduction to Lean Software Development.

Agile Architecture Method

J.D. Meier — Thu, 06 Nov 2008 07:31:03 GMT

I presented our new patterns & practices Agile Architecture Method for the first time at the patterns & practices Summit. Our Agile Architecture Method is an iterative and incremental approach for designing architectures.

To summarize, it’s a technique that:

Scopes and focuses your architecture exercise.
Uses scenarios to drive the design and evaluate potential solutions.
Helps you think through your choice of application type, deployment, architectural style and technologies.
Helps you quickly iterate through potential solutions.
Helps you map potential patterns.

I’ve summarized the approach below, and we’ve posted a step-step how to on CodePlex:

How To Design Using Agile Architecture

Input
Here’s the key input into the process:

Use cases and usage scenarios
Functional requirements
Non-functional requirements (quality attributes such as performance, security, and reliability)
Technological requirements
Target deployment environment
Constraints

Output
Here’s the key output of the process:

Architecturally significant use cases
Architecture hot spots
Candidate architectures
Architectural spikes

Summary of Steps

Step 1. Identify Architecture Objectives.
Step 2. Identify Key Scenarios.
Step 3. Create an Application Overview.
Step 4. Analyze Key Hot Spots.
Step 5. Create Candidate Solutions.

Step 1. Identify Architecture Objectives
This is a scoping exercise. The purpose of this step is to figure out how much time and energy to spend on subsequent steps as well as guide your overall effort. You should know what you want in terms of outcomes. Here’s an example of potential goals:

Build a prototype
Identify key technical risks
Test potential paths
Share models and understanding

Step 2. Identify Key Scenarios
Identify relevant scenarios to focus your design on what matters most, and to evaluate your candidate solutions. In this case, you want to identify architecturally significant use cases. Architecturally significant use cases are those that meet the following criteria:

They are important for the success and acceptance of the deployed application.
They exercise enough of the design to be useful in evaluating the architecture.

You can draw key scenarios from your user stories, business stories and system stories.

Step 3. Create an Application Overview
Create an application overview. The application overview serves to make your architecture more real, connecting it to real-world constraints and decisions.

An application overview consists of the following steps:

Determine your application type. First, determine what type of application you are building. Is it a mobile application, a rich client, a rich internet application, a service, a Web application, or some combination?
Understand your deployment constraints. Next, understand your targeted deployment environment and determine what impact this will have on your architecture.
Identify important architectural styles. Determine which architectural styles you will be using in your design. Will you build a service oriented architecture, client/server, layered, a message bus, or some combination?
Determine relevant technologies. Finally, identify the relevant technology choices based on your application type, architectural styles and deployment constraints.

A good test of an application overview is whether you can whiteboard it.

Step 4. Analyze Key Hot Spots
Identify key hotspots based on quality attributes and the architecture frame. These are the areas where mistakes are most often made when designing an application.

Quality Attributes Frame
Understand the quality attributes that are important for your application and scenarios. For instance, most applications need to address security and performance and will be traded against usability, flexibility and other attributes that may be more or less important to you depending on your scenarios and requirements. You can use the following frame to identify key quality attributes to consider:

Category	Considerations
Availability	How to design for failover support How to design a redundant site How to plan for backup and recovery How to design for runtime upgrades
Conceptual Integrity	How to isolate from external dependencies How to create a migration path from legacy technologies How evolve the system without breaking clients
Flexibility	How to handle dynamic business rules How to handle dynamic UI How to handle changes in data and logic processing How to handle changes in business requirements
Interoperability	How to allow applications to interoperate while still evolving separately How to isolate systems through the use of service interfaces How to isolate systems through the use of mapping layers
Maintainability	How to reduce dependencies between layers and components How to implement a pluggable architecture How to choose an appropriate communication model
Manageability	How to understand the key types of failure How to monitor system operation and health How to modify system behavior based on load
Performance	How to determine a caching strategy How to design high performance communication between layers How to design high performance data access How to manage resources effectively
Reliability	How to handle unreliable external systems How to audit requests and jobs How to redirect load How to handle failed communication How to handle failed transactions How to handle exceptions
Reusability	How to reduce duplication between components and layers How to share functionality across systems How to share functionality across components and layers
Scalability	How to design layers and tiers for scalability How to scale-up or scale-out How to handle spikes in traffic and load
Security	How to address authentication and authorization. How to protect against malicious input. How to protect sensitive data
Supportability	How to design auditing and logging How to design usable error messages
Testability	How to design for testability How to design unit tests How to design for UI automation
Usability	How to design for user empowerment How to improve responsiveness How to avoid common user experience pitfalls

Architecture Frame
The architecture frame represents cross cutting concerns that will impact your design across layers and tiers. These are also the areas in which high impact design mistakes are most often made. Use the architecture frame to identify hot spots in your design that require additional attention to get right. You can use the following architecture frame to identify cross cutting concerns in your design:

Category	Considerations
Authentication and Authorization	How to choose an authentication strategy. How to choose an authorization strategy. How to flow identity across layers and tiers. How to store user identities when not using Active Directory.
Caching and State	How to choose an appropriate caching technology. How to determine what data to cache. How to determine where to cache the data. How to determine the expiration policy.
Communication	How to choose appropriate protocols for communication across layers and tiers. How to design loose coupling across layers. How to perform asynchronous communication. How to pass sensitive data.
Composition	How to choose a composition pattern for the user interface (UI). How to avoid dependencies between modules in the UI. How to handle communication between modules in the UI.
Concurrency and Transactions	How to handle concurrency between threads. How to choose between optimistic and pessimistic concurrency. How to handle distributed transactions. How to handle long running transactions.
Configuration Management	How to determine what information needs to be configurable. How to determine where and how to store configuration information. How to protect sensitive configuration information. How to handle configuration information in a farm/cluster.
Coupling and Cohesion	How to choose an appropriate layering strategy for separation of concerns. How to design highly cohesive components and group them within layers. How to determine when loose coupling is appropriate between components within a layer.
Data Access	How to manage database connections. How to handle exceptions. How to improve performance. How to handle binary large objects (blobs).
Exception Management	How to handle exceptions. How to log exceptions. How to provide notification when required.
Logging and Instrumentation	How to determine which information to log. How to make the logging configurable. How to determine what level of instrumentation is required.
User Experience	How to improve task efficiency and effectiveness. How to improve responsiveness. How to improve user empowerment. How to improve look and feel. </>
Validation	How to determine where and how to perform validation. How to validate for length, range, format, and type. How to constrain and reject input. How to sanitize output.
Workflow	How to choose the appropriate workflow technology. How to handle concurrency issues within a workflow. How to handle task failure within a workflow. How to orchestrate processes within a workflow.

Step 5. Create Candidate Solutions
Create a candidate architecture and along with architectural spikes and evaluate it against your key scenarios, hot spots, and deployment constraints. The outcomes of this step are:

Baseline / Candidate Architectures
Architectural Spikes

Iterative and Incremental Design
You can iteratively flesh out your architecture as you work through your design and discover more details that impact your architecture. You don’t have to design your architecture in a single iteration. Do not get lost in the details; focus on the big steps and build a framework on which you can base your architecture and design.

My Related Posts

New Release: patterns & practices App Arch Guide 2.0 Beta 1

patterns & practices App Arch Guide 2.0 Project

App Arch Guide 2.0 Overview Slides

Abstract for Application Architecture Guide 2.0

Layers and Components

Key Software Trends

Cheat Sheet: patterns & practices Catalog at a Glance Posted to CodePlex

Cheat Sheet: patterns & practices Pattern Catalog Posted to CodePlex

Software Methodologies at a Glance

J.D. Meier — Mon, 18 Aug 2008 09:14:01 GMT

I like to draw from a variety of sources for software engineering principles, patterns, and practices. To be able to do this, I usually need to create information models that let me quickly scan bodies of knowledge. Once I can frame out a space, it's a lot easier to drill into areas looking for gold. I can also step back and see across approaches and this helps me see underlying principles or key distinctions between approaches.

XP, MSF Agile, RUP, and Microsoft Solution Framework
To compare process methodologies, here are some skeletal information models I've used:

While the frames aren't entirely consistent, I can still quickly scan the methodologies and get a good sense of what the key ideas, activities, artifacts, and practices are.

My Related Posts

MSF Agile Frame (Workstreams and Activities)

MSF Agile Frame (Workstreams and Key Activities)

J.D. Meier — Sun, 01 Jul 2007 02:33:00 GMT

When I review an approach, I find it helpful to distill it to a simple frame so I can get a bird's-eye view. For MSF Agile, I found the most useful frame to be the workstreams and key activities. According to MSF, workstreams are simply groups of activities that flow logically together and are usually associated with a particular role. I couldn't find this view in MSF Agile, so I created one:

Workstream	Role	Key Activities
Capture Project Vision	Business Analyst	Write Vision Statement; Define Personas; Refine Personas
Create a Quality of Service Requirement	Business Analyst	Brainstorm quality of Service Requirements; Develop Lifestyle Snapshot; Prioritize Quality of Service Requirements List; Write Quality of Service Requirements; Identify Security Objectives
Create a Scenario	Business Analyst	Brainstorm Scenarios; Develop Lifestyle Snapshot; Prioritize Scenario List; Write Scenario Description; Storyboard a Scenario
Guide Project	Project Manager	Review Objectives; Assess Progress; Evaluate Test Metric Thresholds; Triage Bugs; Identify Risk
Plan an Iteration	Project Manager	Determine Iteration Length; Estimate Scenario; Estimate Quality of Service Requirements; Schedule Scenario; Schedule Quality of Service Requirement; Schedule bug Fixing Allotment; Divide Scenarios into Tasks; Divide Quality of Service Requirements into Tasks
Guide Iteration	Project Manager	Monitor Iteration; Mitigate a Risk; Conduct Retrospectives
Create a Solution Architecture	Architect	Partition the System; Determine Interfaces; Develop Threat Model; Develop Performance Model; Create Architectural Prototype; Create Infrastructure Architecture
Build a Product	Developer	Start a Build; Verify a Build; Fix a Build; Accept Build
Fix a Bug	Developer	Reproduce the Bug; Locate the Cause of a Bug; Reassign a Bug; Decide on a Bug Fix Strategy; Code the Fix for a Bug; Create or Update a Unit Test; Perform a Unit Test; Refactor Code; Review Code
Implement a Development Task	Developer	Cost a Development Task; Create or Update a Unit Test; Write Code for a Development Task; Perform Code Analysis; Perform a Unit Test; Refactor Code; Review Code; Integrate Code Changes
Close a Bug	Tester	Verify a Fix; Close the Bug
Test a Quality of Service Requirement	Tester	Define Test Approach; Write Performance Tests; Write Security Tests; Write Stress Tests; Write Load Tests; Select and Run a Test Case; Open a Bug; Conduct Exploratory Testing
Test a Scenario	Tester	Define Test Approach; Write Validation Tests; Select and Run a Test Case; Open a Bug; Conduct Exploratory Testing
Release a Product	Release Manager	Execute a Release Plan; Validate a Release; Create Release Notes; Deploy the Product

MSF Agile Persona Template

J.D. Meier — Mon, 05 Feb 2007 01:01:00 GMT

I was looking for examples of persona templates, and I came across Personas: Moving Beyond Role-Based Requirements Engineering by Randy Miller and Laurie Williams. I found it to be insightful and practical. I also like the fact they included a snapshot of a persona template example from MSF Agile ...

MSF Agile Persona Template

Name - Enter a respectful, fictitious name for the persona.
Status and Trust Level - Favored or disfavored and level of credentials.
Role - Place the user group in which the persona belongs.
Demographics - Age and personal details optional Goals, motives and concerns.
Knowledge, skills and abilities - Group real but generalized information about the capabilities of the persona.
Goals, motives, and concerns - Describe the real needs of the users in the user group represented by the persona. If multiple groupings exist, write a persona for each grouping.
Usage Patterns - Write the frequency and usage patterns of the system by the persona. Develop a detailed understanding of what functions would be most used. Look for any challenges that the system must help the persona overcome. Note the learning and interaction style if the system is new. Does the persona explore the system to find new functionality or need guidance? Keep this area brief but accurate.