Software Architecture VO/KU (707.023/707.024) Denis Helickti.tugraz.at/staff/denis/courses/sa/slides_ia.pdf · 2012. 11. 29. · Often an infrastructure component acts as a \container"

$Page 1: Software Architecture VO/KU (707.023/707.024) Denis Helickti.tugraz.at/staff/denis/courses/sa/slides_ia.pdf · 2012. 11. 29. · Often an infrastructure component acts as a \container"$
Implementation ArchitectureSoftware Architecture VO/KU (707.023/707.024)

Denis Helic

KMI, TU Graz

Nov 7, 2012

Denis Helic (KMI, TU Graz) Implementation Architecture Nov 7, 2012 1 / 41

Outline

1 Definition

2 Design

3 Behavior

4 Quality attributes

5 Prototype


Definition

Implementation Architecture

Focuses on how the system is built

Which technological elements are needed to implement the system

Software packages, libraries, frameworks, classes, ...

Addresses non-runtime quality attributes: configurability, testability,reusability, ...

Comprised of components and connectors


Definition

Implementation Architecture

Components and connectors reflect software entities and theirrelationships at the level of source and binary code

Typically a number of implementation models

Each model focuses on one of the concurrent subsystems or processesfrom the execution view


Definition

Components

Two types of components: application and infrastructure components

Application components are responsible for implementingdomain-level responsibilities

These are responsibilities found in a detailed conceptual architecture

Application components might be realized as binary packages, sourcepackages, and files


Definition

Components

Infrastructure components are needed to make the system run but arenot related to the application functionality

E.g. HTTP Connection Handler in our sample is a typicalinfrastructure component

Whether a particular component is an application or an infrastructurecomponent depends on the application

E.g. if we are building a Web application server then HTTPConnection Handler is an application component


Definition

Components

Often an infrastructure component acts as a “container” forapplication components

A container component provides an execution environment for thecontained components

Typically, the container executes within a process and creates threadsfor application components

E.g. a Web application server which runs multiple applications, eachof them in their own threads


Definition

Component stereotypes

Figure: Implementation stereotypes from Software Architecture Primer


Definition

Connectors

In implementation architecture connectors represent a “uses” relation

The arrow depicts the direction of this relation

The nature of communication is depicted through the connector styles


Definition

Connectors

API call: A component calls a method in another component(possibly only if both components are in the same process)

Callback: The caller passes a reference of an object to the callee. Thecallee invokes a method on that object later.

Network protocol: Needed when implementation components reside indifferent processes on networked machines. Components need toagree on a common protocol or use a standardized protocol

OS signals: Communication between processes running on the samemachine


Definition

Connectors

Figure: Implementation connectors from Software Architecture Primer


Definition

Connectors

In some cases we depict ports as endpoints of connectors betweencomponents

Ports are used to identify a particular component interface

E.g. a component might be quite complex but it provides a simpleinterface for communication

E.g. the standard Java library provides an API


Definition

Example

Figure: Example of implementation architecture from Software ArchitecturePrimer


Definition

Conceptual vs. Implementation

Element Conceptual Implementation

Components Domain-level responsibilities Implementation module

Connectors Information flow “Uses” relationship

Views Single Split


Definition

Conceptual vs. Execution vs. Implementation

Figure: Conceptual vs. execution vs. implementation from Software ArchitecturePrimer


Design

Implementation architecture design

1 Find application components

2 Find infrastructure components

3 Interface design

4 Behavior design and verification


Design

Application components

Ideal 1-to-1 mapping of conceptual components onto applicationcomponents is typically not possible

Some conceptual components will become infrastructure components

E.g. persistent storage (databases) are typically infrastructurecomponents

Some conceptual components are spread over a number of applicationcomponents

E.g. conceptual components have complex responsibilities


Design

Application components

A number of conceptual components can be mapped onto a singleapplication component

E.g. small number and simple responsibilities

Complex conceptual components might map on additional applicationcompinents

UI components map onto one application component (i.e. HTML UI)

All other map onto a single application component on the server


Design

Infrastructure components

Off-the-shelf components

Frameworks (e.g. application framework)

Servers (web, application, database, file)

Generic clients (browser)

In our sample at least two infrastructure components: browser,application server


Design

Sample infrastructure components

Web browser

Web application server

Apache Tomcat: http://tomcat.apache.org/

Reference implementation of the Servlet API

Servlet API abstracts the HTTP protocol from programmers andallows to write Java classes that handle HTTP requests


http://tomcat.apache.org/

http://tomcat.apache.org/

Design


public class SomeServlet extends HttpServlet {

public void doGet(HttpServletRequest request,

HttpServletResponse response)

throws ServletException, IOException {

...

PrintWriter out = response.getWriter();

...

}

}


Design


With a servlet we can read parameters from the user

E.g. dataset name, dataset file

We can respond with HTML

E.g a new input form for uploading a dataset


Design


Servlets are still very low level

We want to operate on a higher level of abstraction thanreading/handling user parameters

There are frameworks which abstract e.g. HTTP request/responsecycle

For example, for general UI applications MVC frameworks

Component-based frameworks such as GWT

Also, Java servlets are just one possibility (Python, PHP, etc..)


Design

Infrastructure selection

Research

Conceptual issues, e.g. MVC, component-based, service-based, ...

Execution issues, e.g. spawning of external processes

Implementation issues, e.g. programming language

Contextual issues, e.g. commercial products, open source, etc.

Organizational issues, e.g. know-how, team, ...


Design

Infrastructure selection

Trough research you will obtain a list of several infrastructures

Identification of criteria set (what is important)

Weighting of criteria (to what extent is some feature important)

Evaluation of modules

Selection


Design

Weighted Scoring Method

There are n alternatives A1,A2, ...,An

There are m different criteria C1,C2, ...,Cm

Each alternative is for each criterion with score Sij

Each criterion has a weight relative to its importance W1,W2, ...,Wm

The final score for the alternative Ai :

S(Ai ) =m∑j=1

SijWj (1)


Design


For uniform distribution of weights:

S(Ai ) =1

m

m∑j=1

Sij (2)


Design

Weighted Scoring Method78 10. Solution Evaluation and Selection

Criteria group Criterion CodeFunctionality Login and access system1 F0Functionality Access rights and permission management1 F1Functionality Content management system1 F2Functionality ’Product basket’ feature1 F3Functionality Product catalogue management1 F4Functionality Product comparison feature1 F5Functionality Product management1 F6Functionality Product tagging feature1 F7Functionality Search feature1 F8Functionality Reporting feature1 F9Quality Adaptability/Source code quality1 Q0Quality Reliability1 Q1Quality Security1 Q2Quality Technology/Programming language1 Q3Usability Error reporting1 U0Usability User interface/Ease of use1 U1Vendor References2 V0Cost Installation and implementation cost1 C0

Table 10.3: Final evaluation criteria set.1 Very poor, poor, fair, good, very good - corresponding to numericalvalues 1 to 5.

2 Very poor (<3), poor (4-10), fair (11-20), good (21-30), very good(>30) - corresponding to numerical values 1 to 5.

problem because the complexity of the decision, that is the number of criteria and options, israther low.

10.4 Weighted Scoring Method (WSM)

In the first step each software package needs to be numerically evaluated for each criterion. Todo so the software is installed, executed, tested and its source code analysed. The results of thedetailed analysis of each software package for each criterion can be found in the appendix insection A.1, in table A.1 for Magento, in table A.2 for OSCommerce, in table A.3 for Zen Cartand in table A.4 for PHPB2B. The detailed analysis justifies the score for each package andeach criterion.

Secondly, the individual weighting for each criterion needs to be determined in order to calculatethe weighted sum, which is the score for each package. In the simplest approach each criterionhas the same weighting (i.e. averaging criteria scores). With more sophistication the weightingis adapted to the specific needs of this project in correspondence with the weighted scoringmethod.

Table 10.4 summarises the results for the WSM evaluation. Column two represents the simpleaverage weightings, column three the more sophisticated relative weightings tailored to this pro-ject and column 4 normalises them to serve as basis for the weighted scoring method. Columns

Figure: Example of WSMDenis Helic (KMI, TU Graz) Implementation Architecture Nov 7, 2012 28 / 41

Design


80 10. Solution Evaluation and Selection

Criteria Weighting SW Package ScoreCode AVG1 RW2 WSM3 Magento OSCommerce Zen Cart PHPB2BF0 6% 3 8% 5 3 2 5F1 6% 3 8% 2 1 1 5F2 6% 1 3% 5 1 1 3F3 6% 1 3% 4 3 3 4F4 6% 3 8% 4 3 3 5F5 6% 1 3% 5 1 1 1F6 6% 3 8% 5 3 3 3F7 6% 1 3% 5 1 1 1F8 6% 2 5% 4 4 4 4F9 6% 1 3% 4 3 3 3Q0 6% 5 13% 5 3 3 1Q1 6% 2 5% 5 5 5 1Q2 6% 1 3% 5 5 5 2Q3 6% 4 10% 5 3 3 1U0 6% 1 3% 4 3 3 2U1 6% 2 5% 5 5 5 2V0 6% 1 3% 5 5 4 3C0 6% 5 13% 3 3 3 2

AVG Score 4,44 3,06 2,94 2,67Norm. AVG Score 34% 23% 22% 20%

WSM 4,33 3,05 2,95 2,65Norm. WSM 33% 24% 23% 20%

Table 10.4: Scores of software packages based on WSM.1 Simple average weighting (AVG) for all criteria.2 Relative weighting (RW) for each criterion with 1 to 5, low to high importance.3 Normalised weights derived from RW for the weighted scoring method (WSM).

The WSM’s clear winner is Magento, whereas OSCommerce and Zen Cart have not onlyvery similar overall score but also similar scores for each criterion. The reason is that ZenCart is based on OSCommerce and has thus very similar properties and functionalities.One at first rather surprising finding is the fact that differences between the score based onaverage weights and the WSM weights are almost negligible. Since the distribution betweenthe scores for each criterion and the distribution between the relative weightings is rathersmall (1-5), with the number of criteria high (18), small changes in the weighting of thecriteria do not have a significant effect on the total score.Figure 10.1 illustrates the normalised and weighted scores for each criterion and softwarepackage. Criteria Q0 (adaptability/source code quality) and C0 (installation and imple-menation cost) with a weighting of 12,5%, together with Q3 (technology/programminglanguage) at 10% were rated as most important criteria. Magento scored at the top forall criteria, except for F1 where it was strongly outperformed by PHPB2B. Overall all thefigure shows clearly why Magento is to be chosen.

Figure: Example of WSMDenis Helic (KMI, TU Graz) Implementation Architecture Nov 7, 2012 29 / 41

Design

Sample infrastructure selection

Apply the same methodology for your projects

We select Open Source Java with Tomcat

We select component-based framework

Apache Wicket as a Web application framework

We select SNAP library for network analysis

We select gnuplot for diagrams


Design

Interface design

For all application and infrastructure components we need to defineinterfaces (ports)

Helps in clarifying the responsibilities of a component

Some interfaces are also standardized

E.g. HTTP, SQL, File I/O


Design

Sample interface design

UI: Combination of HTML/HTTP

It is standardized!

Web application server: HTTP/Servlet API

It is standardized

Component separation

Wicket components are specified by the framework


Design


We need to specify interface between Wicket and our application logic

A new interface is needed

We need to tell to the application logic that there is a request for ane.g. calculation

e.g. executeCalculation(user, dataset)


Design


We should also tell to the system where to write calculations,datasets, users, etc.

Typically these are only files

We can store users in an e.g. XML file

e.g. users.storeUser(user);

calcs.storeCalc(calc);


Behavior

Behavior design

Now we need to go into details

Use-case maps are not enough anymore

We need to investigate behavior at the operation level

Thus, we need a sequence diagram


Behavior

Sample implementation Architecture

Figure: Detailed sample implementation architecture


Behavior

Sample implementation Architecture

Figure: Sample implementation architecture


Behavior

Sample interface Sequence Diagram

Figure: Sample sequence diagram


Quality attributes

Non-runtime quality attributes

Since implementation view addresses build structure

It is the right place to consider non-runtime quality attributes

E.g. maintainability, extensibility, reusability, ...

We can use a mechanism similar to use-case maps

Impact-maps: try to investigate what parts of the system need tochange if “something” happens


Quality attributes

Impact-maps

Map 1: new external system - interface to external system needs tobe changed

Map 2: new calculation - network analysis application componentneeds to be changed

Map 3: new UI - UI component needs to be changed

Goal: as few component changes as possible


Prototype

Prototype

To show that the architectural solution is feasible we implementprototypes

For each identified application component we provide implementation

Deploy it within the infrastructure components

Test it and check correctness, functionality, quality-attributes


Documents

Software Architecture VO/KU (707.023/707.024) Denis Helickti.tugraz.at/staff/denis/courses/sa/slides_ia.pdf · 2012. 11. 29. · Often an infrastructure component acts as a \container"