Essential software architecture 2011 pdf

If you design, develop, or manage large software systems or plan to do so , you will find this book to be a valuable resource for getting up to speed on the state of the art. Totally new material covers Contexts of software architecture: technical, project, business, and professional Architecture competence: what this means both for individuals and organizations The origins of business goals and how this affects architecture Architecturally significant requirements, and how to determine them Architecture in the life cycle, including generate-and-test as a design philosophy; architecture conformance during implementation; architecture and testing; and architecture and agile development Architecture and current technologie.

It is both a readily accessible introduction to software architecture and an invaluable handbook of well-established best practices. A supporting Web site containing further information can be found at www. Without an architecture that is appropriate for the problem being solved, a project will stumble along or, most likely, fail. Even with a superb architecture, if that architecture is not well understood or well communicated the project is unlikely to succeed.

Documenting Software Architectures, Second Edition, provides the most complete and current guidance, independent of language or notation, on how to capture an architecture in a commonly understandable form. Drawing on their extensive experience, the authors first help you decide what information to document, and then, with guidelines and examples in various notations, including UML , show you how to express an architecture so that others can successfully build, use, and maintain a system from it.

The book features rules for sound documentation, the goals and strategies of documentation, architectural views and styles, documentation for software interfaces and software behavior, and templates for capturing and organizing information to generate a coherent package. New and improved in this second edition: Coverage of architectural styles such as service-oriented architectures, multi-tier architectures, and data models Guidance for documentation in an Agile development environment Deeper treatment of documentation of rationale, reflecting best industrial practices Improved templates, reflecting years of use and feedback, and more documentation layout options A new, comprehensive example available online , featuring documentation of a Web-based service-oriented system Reference guides for three important architecture documentation languages: UML, AADL, and SySML.

Software Architecture for Busy Developers Author : Stephane Eyskens Publisher : Packt Publishing Ltd Release Date : Genre: Computers Pages : ISBN 10 : GET BOOK Software Architecture for Busy Developers Book Description : A quick start guide to learning essential software architecture tools, frameworks, design patterns, and best practices Key Features Apply critical thinking to your software development and architecture practices and bring structure to your approach using well-known IT standards Understand the impact of cloud-native approaches on software architecture Integrate the latest technology trends into your architectural designs Book Description Are you a seasoned developer who likes to add value to a project beyond just writing code?

Have you realized that good development practices are not enough to make a project successful, and you now want to embrace the bigger picture in the IT landscape? If so, you're ready to become a software architect; someone who can deal with any IT stakeholder as well as add value to the numerous dimensions of software development. The sheer volume of content on software architecture can be overwhelming, however. Software Architecture for Busy Developers is here to help.

Written by Stephane Eyskens, author of The Azure Cloud Native Mapbook, this book guides you through your software architecture journey in a pragmatic way using real-world scenarios. By drawing on over 20 years of consulting experience, Stephane will help you understand the role of a software architect, without the fluff or unnecessarily complex theory.

You'll begin by understanding what non-functional requirements mean and how they concretely impact target architecture. The book then covers different frameworks used across the entire enterprise landscape with the help of use cases and examples.

Finally, you'll discover ways in which the cloud is becoming a game changer in the world of software architecture. By the end of this book, you'll have gained a holistic understanding of the architectural landscape, as well as more specific software architecture skills. You'll also be ready to pursue your software architecture journey on your own - and in just one weekend!

What you will l. Over the past few years, incremental developments in core engineering practices for software development have created the foundations for rethinking how architecture changes over time, along with ways to protect important architectural characteristics as it evolves.

This practical guide ties those parts together with a new way to think about architecture and time. Popular Books. End of Days by Brad Taylor. The Summer Proposal by Vi Keeland. Field of Prey by John Sandford. It Ends with Us by Colleen Hoover. For example, a message broker application, perhaps a chat room, may be designed to process messages of an expected average size. How well will the architecture react if the size of messages grows significantly?

In a slightly different vein, an information management solution may be designed to search and retrieve data from a repository of a specified size.

This would include effort for distribution, configuration and updating with new versions. An ideal solution would provide automated mechanisms that can dynamically deploy and configure an application to a new user, capturing registration information in the process. This is in fact exactly how many applications are today distributed on the Internet.

It takes a savvy and attentive architect to ensure inherently nonscalable approaches are not introduced as core architectural components.

The requirements specify this as approximately users. The more flexibility that can be built into a design upfront, then the less painful and expensive subsequent changes will be. The modifiability quality attribute is a measure of how easy it may be to change an application to cater for new functional and nonfunctional requirements.

You only know for sure what a change will cost after it has been made. Then you find out how good your estimate was. Modifiability measures are only relevant in the context of a given architectural solution. This solution must be expressed at least structurally as a collection of components, the component relationships and a description of how the components interact with the environment.

Then, assessing modifiability requires the architect to assert likely change scenarios that capture how the requirements may evolve. Sometimes these will be known with a fair degree of certainty. In fact the changes may even be specified in the project plan for subsequent releases. For each change scenario, the impact of the anticipated change on the architec- ture can be assessed.

This impact is rarely easy to quantify, as more often than not the solution under assessment does not exist. In many cases, the best that can be achieved is a convincing impact analysis of the components in the architecture that will need modification, or a demonstration of how the solution can accommodate the modification without change.

Finally, based on cost, size or effort estimates for the affected components, some useful quantification of the cost of a change can be made. Changes isolated to single components or loosely coupled subsystems are likely to be less expensive to make than those that cause ripple effects across the architecture. If a likely change appears difficult and complex to make, this may highlight a weakness in the architecture that might justify further consideration and redesign.

A word of caution should be issued here. Highly modular architectures can become overly com- plex, incur additional performance overheads and require significantly more design and construction effort. That sounds reasonable, but requires a reliable crystal ball.

If the predictions are wrong, much time and money can be wasted. I recently was on the peripheral of such a project. The technical lead spent 5 months establishing a carefully designed messaging-based architecture based on the dependency injection pattern. With these in place, the theory was that the architecture could be reused over and over again with minimal effort, and it would be straightforward to inject new processing components due to the flexibility offered by dependency injection.

The word theory in the previous sentence was carefully chosen however. The system stakeholders became impatient, wondering why so much effort was being expended on such a sophisticated solution, and asked to see some demonstrable progress.

The technical lead resisted, insisting his team should not be diverted and continued to espouse the long term benefits of the architecture. Just as this initial solution was close to completion, the stakeholders lost patience and replaced the technical lead with someone who was promoting a much simpler, Web server based solution as sufficient.

This was a classic case of overengineering. While the original solution was elegant and could have reaped great benefits in the long term, such arguments are essentially impossible to win unless you can show demonstrable, concrete evidence of this along the way. Adopting agile approaches is the key to success here. The demonstration would have involved some prototypical elements in the architecture, would not be fully tested, and no doubt required some throw-away code to implement the use case — all unfortunately distasteful things to the technical lead.

The key then is to not let design purity drive a design. Rather, concentrating on known requirements and evolving and refactoring the architecture through regular iterations, while producing running code, makes eminent sense in almost all circumstances. As part of this process, you can continually analyze your design to see what future enhancements it can accommodate or not. Working closely with stakeholders can help elicit highly likely future requirements, and eliminate those which seem highly unlikely.

Let these drive the architecture strategy by all means, but never lose sight of known requirements and short term outcomes. A likely requirement would be for the range of events trapped and stored by the ICDE client to be expanded. Another would be for third party tools to want to communicate new message types. This would have implications on the message exchange mechanisms that the ICDE server supported.

Hence both these modifiability scenarios could be used to test the resulting design for ease of modification. At the architectural level, security boils down to understanding the precise security requirements for an application, and devising mechanisms to support them.

The most common security-related requirements are: l Authentication: Applications can verify the identity of their users and other applications with which they communicate. This means neither can subsequently refute their participation in the message exchange. There are well known and widely used technologies that support these elements of application security.

Operating systems and databases provide login-based security for authentication and authorization. There are many ways, in fact sometimes too many, to support the required security attributes for an application. Databases want to impose their security model on the world.

NET designers happily leverage the Windows operating security features. Java applications can leverage JAAS without any great problems. If an application only needs to execute in one of these security domains, then solutions are readily available. In v1. This gives them access to the data in the data store associated with their activities.

ICDE v2. Also, as third party tools may be executing remotely and access the ICDE data over an insecure network, the in-transit data should be encrypted. Availability is relatively easy to specify and measure. In terms of specification, many IT applications must be available at least during normal business hours. For a live system, availability can be measured by the proportion of the required time it is useable. Failures in applications cause them to be unavailable.

The length of time any period of unavailability lasts is determined by the amount of time it takes to detect failure and restart the system. Consequently, applications that require high availability minimize or preferably eliminate single points of failure, and institute mechanisms that automatically detect failure and restart the failed components.

Replicating components is a tried and tested strategy for high availability. When a replicated component fails, the application can continue executing using replicas that are still functioning. This may lead to degraded performance while the failed component is down, but availability is not compromised. Recoverability is closely related to availability. An application is recoverable if it has the capability to reestablish required performance levels and recover affected data after an application or system failure.

A database system is the classic example of a recoverable system. When a database server fails, it is unavailable until it has recovered. This means restarting the server application, and resolving any transac- tions that were in-flight when the failure occurred.

Interesting issues for recoverable applications are how failures are detected and recovery commences preferably automatically , and how long it takes to recover before full service is reestablished. This leaves plenty of scope for downtime for such needs as system upgrade, backup and maintenance.

The value of an application or com- ponent can frequently be greatly increased if its functionality or data can be used in ways that the designer did not originally anticipate. The most widespread strategies for providing integration are through data integration or providing an API.

Data integration involves storing the data an application manipulates in ways that other applications can access. This may be as simple as using a standard relational database for data storage, or perhaps implementing mechanisms to extract the data into a known format such as XML or a comma-separated text file that other applications can ingest. With data integration, the ways in which the data is used or abused by other applications is pretty much out of control of the original data owner.

This is because the data integrity and business rules imposed by the application logic are by-passed. The alternative is for interoperability to be achieved through an API see Fig.

In this case, the raw data the application owns is hidden behind a set of functions that facilitate controlled external access to the data. In this manner, business rules and security can be enforced in the API implementation. The only way to access the data and integrate with the application is by using the supplied API. Data integration is flexible and simple.

Applications written in any language can process text, or access relational databases using SQL. Building an API requires more effort, but provides a much more controlled environment, in terms of correctness and security, for integration. It is also much more robust from an integration perspective, as the API clients are insulated from many of the changes in the underlying data structures.

As always, the best choice of strategy depends on what you want to achieve, and what constraints exist. There must be a well-defined and understood mechanism for third party tools to access data in the ICDE data store. As third party tools will often execute remotely from an ICDE data store, integration at the data level, by allowing tools direct access to the data store, seems unlikely to be viable.

Portability depends on the choices of software technology used to implement the application, and the characteristics of the platforms that it needs to execute on.

Easily portable code bases will have their platform dependencies isolated and encapsulated in a small set of components that can be replaced without affecting the rest of the application. Early design decisions can greatly affect the amount of test cases that are required. As a rule of thumb, the more complex a design, the more difficult it is to thoroughly test.

Simplicity tends to promote ease of testing. Supportable systems tend to provide explicit facilities for diagnosis, such as application error logs that record the causes of failures. They are also built in a modular fashion so that code fixes can be deployed without severely inconveniencing application use. Pick a required quality attribute, and provide mechanisms to support it.

Quality attributes are not orthogonal. They interact in subtle ways, meaning a design that satisfies one quality attribute require- ment may have a detrimental effect on another. For example, a highly secure system may be difficult or impossible to integrate in an open environment. A highly available application may trade-off lower performance for greater availability. An application that requires high performance may be tied to a particular platform, and hence not be easily portable.

Understanding trade-offs between quality attribute requirements, and designing a solution that makes sensible compromises is one of the toughest parts of the architect role.

Does this sound easy? If only this were the case. Part of the difficultly is that quality attributes are not always explicitly stated in the requirements, or adequately cap- tured by the requirements engineering team. Of course, understanding the quality attribute requirements is merely a necessary prerequisite to designing a solution to satisfy them.

Conflicting quality attributes are a reality in every application of even mediocre complexity. Creating solutions that choose a point in the design space that adequately satisfies these requirements is remarkably difficult, both technically and socially. Chung, B. Nixon, E. Yu, J. Mylopoulos, Editors.

An excellent general reference on security and the techniques and technologies an architect needs to consider is: J. Designing Security Architecture Solutions. An interesting and practical approach to assessing the modifiability of an architecture using architecture reconstruction tools and impact analysis metrics is described in: I.

Gorton, L. There are similarities, but also lots of profound differences. When an architect designs a building, they create drawings, essentially a design that shows, from various angles, the structure and geometric properties of the building. These drawings are an abstract representation of the intended concrete sic artifact. And as each of these elements of a building is designed in detail, suitable materials and components for constructing each are selected.

These materials and components are the basic construction blocks for buildings. The reasons are: l Middleware provides proven ways to connect the various software components in an application so they can exchange information using relatively easy-to-use mechanisms.

Middleware provides the pipes for shipping data between compo- nents, and can be used in a wide range of different application domains. Baragry and K.

Connections can be one-to-one, one-to-many or many- to-many. As long as it works, and works well, middleware is invisible infrastructure.

This is of course very like real plumbing and wiring systems. But hopefully it has served its purpose. Middleware provides ready-to-use infrastructure for connecting software components. It can be used in a whole variety of different application domains, as it has been designed to be general and configurable to meet the common needs of software applications.

Of course in reality middleware is much more complex than plumbing or a simple layer insulating an application from the underlying operating system services. Different application domains tend to regard different technologies as middle- ware.

Figure 4. These pipes provide simple facilities and mechanisms that make exchanging data straightforward in distributed applica- tion architectures. They provide additional capabilities such as transaction, security and directory services. They also support a programming model for building multithreaded server-based applications that exploit these additional services.

This engine provides features for fast message transformation and high-level programming features for defining how to exchange, manipulate and route messages between the various components of an application. In such applications, business processes may take many hours or days to complete due to the need for people to perform certain tasks.

BPOs provide the tools to describe such business processes, execute them and manage the intermediate states while each step in the process is executed. Best characterized by CORBA,2 distributed object-based middleware has been in use since the earlier s. As many readers will be familiar with CORBA and the like, only the basics are briefly covered in this section for completeness.

A simple scenario of a client sending a request to a server across an object request broker ORB is shown in Fig. IDL interfaces define the methods that a server object supports, along with the parameter and return types. An IDL compiler is used to process interface definitions. The programmer must then write the code to implement each servant method in a native programming language: The server process must create an instance of the servant and make it callable through the ORB: A client process can now initialize a client ORB and get a reference to the servant that resides within the server process.

Servants typically store a reference to themselves in a directory. Clients query the directory using a simple logical name, and it returns a reference to a servant that includes its network location and process identity.

The servant call looks like a synchronous call to a local object. However, the ORB mechanisms transmit, or marshal, the request and associated parameters across the network to the servant. The method code executes, and the result is marshaled back to the waiting client. This has a performance impact. Applications need strategies to cope with failure and mechanisms to restart failed servers.

Mechan- isms for state recovery must consequently be designed. It is the glue that binds together otherwise indepen- dent and autonomous applications and turns them into a single, integrated system. These applications can be built using diverse technologies and run on different platforms. Users are not required to rewrite their existing applications or make substantial and risky changes just to have them play a part in an enterprise-wide application. This is achieved by placing a queue between senders and receivers, providing a level of indirection during communications.

How MOM can be used within an organization is illustrated in Fig. This means the sender and receiver of a message are not tightly coupled, unlike synchronous middleware technologies such as CORBA. Synchronous middleware technologies have many strengths, but can lead to fragile designs if all of the components and network links always have to be working at the same time for the whole system to successfully operate.

A messaging infrastructure decouples senders and receivers using an intermedi- ate message queue. The sender can send a message to a receiver and know that it will be eventually delivered, even if the network link is down or the receiver is not available.

The sender just tells the MOM technology to deliver the message and then continues on with its work. Senders are unaware of which application or process eventually processes the request. MOM is often implemented as a server that can handle messages from multiple concurrent clients.

A MOM server can create and manage multiple messages queues, and can handle multiple messages being sent from queues simultaneously using threads organized in a thread pool. One or more processes can send messages to a message queue, and each queue can have one or many receivers.

Each queue has a name which senders and receivers specify when they perform send and receive opera- tions. This architecture is illustrated in Fig. A MOM server has a number of basic responsibilities. First, it must accept a message from the sending application, and send an acknowledgement that the message has been received.

Next, it must place the message at the end of the queue that was specified by the sender. Hence the MOM must be prepared to hold messages in a queue for an extended period of time.

When a receiver requests a message, the message at the head of the queue is delivered to the receiver, and upon successful receipt, the message is deleted from the queue. The asynchronous, decoupled nature of messaging technology makes it an extremely useful tool for solving many common application design problems. It just wants to send the message to another application and continue on with its own work.

This is known as send- and-forget messaging. The receiver may take perhaps several minutes to process a request and the sender can be doing useful work in the meantime rather than just waiting. The sender relies on the MOM to deliver the message when a connection is next established.

The MOM layer must be capable of storing messages for later delivery, and possibly recovering unsent messages after system failures. Mission critical systems need much stronger guarantees of message delivery and performance than can be provided by a basic MOM server. These features are explained in the following sections. In many enterprise applications, this delivery must be done reliably, giving the sender guarantees that the message will eventually be processed.

If this message is lost due the MOM server crashing — such things do happen — then the customer may be happy, but the store where the purchase was made and the credit card company will lose money. Such scenarios obviously cannot tolerate message loss, and must ensure reliable delivery of messages.

Reliable message delivery however comes at the expense of performance. MOM servers normally offer a range of quality of service QoS options that let an architect balance performance against the possibility of losing messages. Three levels of delivery guarantee or QoS are typically available, with higher reliability levels always coming at the cost of reduced performance. Undelivered messages are only kept in memory on the server and can be lost if a system fails before a message is delivered.

Network outages or unavailable receiving appli- cations may also cause messages to time out and be discarded. Undelivered messages are logged to disk as well as being kept in memory and so can be recovered and subsequently delivered after a system failure.

This is depicted in Fig. Messages are kept in a disk log for the queue until they have been delivered to a receiver. Also, message delivery can be coordinated with an external resource manager such as a database. More on transactional delivery is explained in the following sections. Various studies have been undertaken to explore the performance differences between these three QoS levels. All of these by their very nature are specific to a particular benchmark application, test environment and MOM product.

Transactional will be slower than persistent, but often not by a great deal, as this depends mostly on how many transaction participants are involved. See the further reading section at the end of this chapter for some pointers to these studies. It tightly inte- grates messaging operations with application code, not allowing transactional mes- sages to be sent until the sending application commits their enclosing transaction. Basic MOM transactional functionality allows applications to construct batches of messages that are sent as a single atomic unit when the application commits.

Receivers must also create a transaction scope and ask to receive complete batches of messages. If the transaction is committed by the receivers, these transac- tional messages will be received together in the order they were sent, and then removed from the queue. If the receiver aborts the transaction, any messages already read will be put back on the queue, ready for the next attempt to handle the same transaction.

In addition, consecutive transactions sent from the same system to the same queue will arrive in the order they were committed, and each message will be delivered to the application exactly once for each committed transaction. Transactional messaging also allows message sends and receives to be coordi- nated with other transactional operations, such as database updates.

For example, an application can start a transaction, send a message, update a database and then commit the transaction. The MOM layer will not make the message available on the queue until the transaction commits, ensuring either that the message is sent and the database is updated, or that both operations are rolled back and appear never to have happened.

A pseudocode example of integrating messaging and database updates is shown in Fig. The sender application code uses transaction demarcation statements the exact form varies between MOM systems to specify the scope of the transac- tion. All statements between the begin and commit transaction statements are considered to be part of the transaction. Note we have two, independent transactions occurring in this example.

The sender and receiver transactions are separate and commit or abort individually. Not surprisingly then, industrial strength MOM technologies make it possible to cluster MOM servers, running instances of the server on multiple machines see Fig.

However, the scheme in Fig. Multiple instances of MOM servers are configured in a logical cluster. Each server supports the same set of queues, and the distribution of these queues across servers is transparent to the MOM clients. MOM clients behave exactly the same as if there was one physical server and queue instance. When a client sends a message, one of the queue instances is selected and the message stored on the queue. Likewise, when a receiver requests a message, one of the queue instances is selected and a message removed.

The MOM server clustering implementation is responsible for directing client requests to individual queue instances. This may be done statically, when a client opens a connection to the server, or dynamically, for every request. First, if one MOM server fails, the other queue instances are still available for clients to use. Applications can consequently keep communicating. Second, the request load from the clients can be spread across the individual servers. This helps distribute the messaging load across multiple machines, and can provide much higher application performance.

In this case, the sender simply uses the MOM layer to send a request message to a receiver on a request queue. The message contains the name of the queue to which a reply message should be sent. The sender then waits until the receiver sends back a reply message on a reply queue, as shown in Fig.

There are a number of pragmatic reasons why architects might choose to use messaging technology in this way, including: l Messaging technology can be used with existing applications at low cost and with minimal risk.

Adapters are available, or can be easily written to interface between commonly used messaging technologies and applications. Applications do not have to be rewritten or ported before they can be integrated into a larger system. But, like everything, it has its limitations. The major one is that MOM is inherently a one-to-one technology. One sender sends a single message to a single queue, and one receiver retrieves that message for the queue.

Not all problems are so easily solved by a 1—1 messaging style. This is where publish—subscribe archi- tectures enter the picture. Publish—subscribe messaging extends the basic MOM mechanisms to support 1 to many, many to many, and many to 1 style communications.

Publishers send a single copy of a message addressed to a named topic, or subject. Topics are a logical name for the publish—subscribe equivalent of a queue in basic MOM technology. Subscribers listen for messages that are sent to topics that interest them.

The publish—subscribe server then distributes each message sent on a topic to every subscriber who is listening on that topic. This basic scheme is depicted in Fig.

In terms of loose coupling, publish—subscribe has some attractive properties. Senders and receivers are decoupled, each respectively unaware of which applica- tions will receive a message, and who actually sent the message. Each topic may also have more than one publisher, and the publishers may appear and disappear dynamically. This gives considerable flexibility over static configuration regimes.

Likewise, subscribers can dynamically subscribe and unsubscribe to a topic. Hence the subscriber set for a topic can change at any time, and this is transparent to the application code. In publish—subscribe technologies, the messaging layer has the responsibility for managing topics, and knowing which subscribers are listening to which topics. It also has the responsibility for delivering every message sent to all active current sub- scribers. Topics can be persistent or nonpersistent, with the same effects on reliable message delivery as in basic point-to-point MOM explained in the previous section.

This tells the publish—subscribe server to attempt to deliver a message to all active subscribers for the time-to-live period, and after that delete the message from the queue. The underlying protocol a MOM technology uses for message delivery can profoundly affect performance.

Implementations of publish—subscribe built on point-to-point messaging technology duplicate each message send operation from the server for every subscriber.

In contrast, some MOM technologies support multicast or broad- cast protocols, which send each message only once on the wire, and the network layer handles delivery to multiple destinations. Each node in the publish—subscribe network runs a daemon process known as rvd. When a new topic is created, it is assigned a multicast IP address.

When a publisher sends a message, its local rvd daemon intercepts the message and multicasts a single copy of the message on the network to the address associated with the topic. If so, it delivers the message to the subscriber s , otherwise it ignores the message. If a message has subscribers on a remote network,5 an rvrd daemon intercepts the message and sends a copy to each remote network using standard IP protocols. Each receiving rvrd daemon then multicasts the message to all subscribers on its local network.

Not surprisingly, solutions based on multicast tend to provide much better raw performance and scalability for best effort messaging. Of Subscribers Fig. We investigated this by writing and running some benchmarks to compare the relative performance of three publish—subscribe technologies, and Fig. It shows the average time for delivery from a single publisher to between 10 and 50 concurrent subscribers when the publisher outputs a burst of messages as fast as possible.

The results clearly show that multicast publish—subscribe is ideally suited to applications with demands for low message latencies and hence very high throughput. Topic names are simply strings, and are specified administratively or programmatically when the topic is created.

Each topic has a logical name which is specified by all applications which wish to publish or subscribe using the topic. Some publish—subscribe technologies support hierarchical topic naming. The details of exactly how the mechanisms explained below work are product depen- dent, but the concepts are generic and work similarly across implementations.

Each box represents a topic name that can be used to publish messages. Subscribers can use wildcards to receive messages from more than one topic when they subscribe. Such a wildcard is powerful as it is naturally extensible.

If new topics are added within this branch of the topic hierarchy, subscribers do not have to change the topic name in their subscription request in order to receive messages on the new topics. Carefully crafted topic name hierarchies combined with wildcarding make it possible to create some very flexible messaging infrastructures.

Consider how applications might want to subscribe to multiple topics, and organize your design to support these. Namely, an application server is a component-based server technol- ogy that resides in the middle-tier of an N-tier architecture, and provides distributed communications, security, transactions and persistence. Application servers are widely used to build internet-facing applications. This is commodity technology, not an element of the application server.

The incoming request identifies the exact web component to call. This component processes the request parameters, and uses these to call the business logic tier to get the required information to satisfy the request.

The web component then formats the results for return to the user as HTML via the web server. The business components receive requests from the web tier, and satisfy requests usually by accessing one or more databases, returning the results to the web tier. The container supplies a number of services to the components it hosts. These varying depending on the container type e. Job titles like Technical Architect and Chief Architect nowadays abound in software industry, yet many people suspect that architecture is one of the most.

Henry Pedersen rated it liked it Oct 05, Just a moment while we sign you in to your Goodreads account. You may also like. Sftware — Oustanding Academic Title in The volume is organized in three main parts, the first of which provides a comprehensive but clear definition of software architecture.

A case study is used to illustrate concepts throughout those chapters. People who bought this also bought. Published April 1st by Springer first woftware January 1st Therefore a more traditional textbook with helpful educational aspects like key words, review questions, homework assignments and a glossary would be more beneficial to students.

The second edition is starting to show its age though. Zbigniew rated it really liked it Feb 04, architectuure Packaging should be the same as what is found in a retail store, unless the item is handmade or was packaged by the manufacturer in non-retail packaging, such as an unprinted box or plastic bag. I had selected this book for several reasons: To see what your friends thought of this book, please sign up. Cesar rated it architecturr was amazing Jan 24, All approaches are illustrated by an ongoing real-world example.

The volume is organized in three main parts, the first of which provides a comprehensive but clear definition of software architecture.