Business Logic PDF

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Business Logic...

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What Is Business Logic? Business logic is the custom rules or algorithms that handle the exchange of information between a database and user interface. Business logic is essentially the part of a computer program that contains the information (in the form of business rules) that defines or constrains how a business operates. Such business rules are operational policies that are usually expressed in true or false binaries. Business logic can be seen in the workflows that they support, such as in sequences or steps that specify in detail the proper flow of information or data, and therefore decision-making. Business logic is also known as "domain logic." Key Takeaways   

Business logic refers to the logic and algorithms serving as the foundation of code in business software. Business logic can be seen in the workflows that they support, such as in sequences or steps that specify in detail the proper flow of information or data Business logic exists at a higher level than the type of code that is used to maintain basic computer infrastructure.

Understanding Business Logic Put another way, business logic is real-world business rules put into computer code and shown in a computer program via a user interface. Business logic is most evident in its role in creating workflows that pass data between users and software systems. Business logic determines how data may be shown, stored, created, and altered. It provides a system of rules that guides how business objects (parts of software that control how data is transported) work with one another. Business logic also guides how business objects within software are accessed and updated. It exists at a higher level than the type of code that is used to maintain basic computer infrastructure, such as how a database is displayed to a user or as basic system infrastructure. The algorithms involved in business logic perform behind-the-scenes data processing that is invisible to the user but is critical to keeping things running smoothly in a modern economy. Business Logic vs. Business Rules Business rules are useless without business logic to determine how data is calculated, changed, and transmitted to users and software. But without business rules to create a framework, business logic cannot exist. Business logic is any part of a business enterprise that makes up a system of processes and procedures, whereas anything else is an example of a business rule. Business Logic Example A credit card issuer's business logic may specify that out-of-state credit card transactions above a certain limit, say $500, be flagged as suspicious and the issuer contacted as soon as possible to confirm the authenticity of the transaction. The policy of flagging such a transaction is an example of a business rule; the actual process of flagging the transaction is an example of business logic. Given that millions of credit card transactions are conducted every single day, business logic enables such transactions to be checked and processed in an efficient and timely manner. In computer software, business logic or domain logic is the part of the program that encodes the realworld business rules that determine how data can be created, stored, and changed. It is contrasted with the remainder of the software that might be concerned with lower-level details of managing a database or displaying the user interface, system infrastructure, or Business logic: Prescribes how business objects interact with one another Enforces the routes and the methods by which business objects are accessed and updated Business rules:

Model real-life business objects (such as accounts, loans, itineraries, and inventories) Business logic comprises. Workflows that are the ordered tasks of passing documents or data from one participant (a person or a software system) to another. Business logic should be distinguished from business rules.[2] Business logic is the portion of an enterprise system which determines how data is transformed or calculated, and how it is routed to people or software (workflow). Business rules are formal expressions of business policy. Anything that is a process or procedure is business logic, and anything that is neither a process nor a procedure is a business rule. Welcoming a new visitor is a process (workflow) consisting of steps to be taken, whereas saying every new visitor must be welcomed is a business rule. Further, business logic is procedural whereas business rules are declarative.[3] For example, an e-commerce website might allow visitors to add items to a shopping cart, specify a shipping address, and supply payment information. The business logic of the website might include a workflow such as: 

The sequence of events that happens during checkout, for example a multi-page form which first asks for the shipping address, then for the billing address, next page will contain the payment method, and last page will show congratulations.

There will be also business rules of the website:   

Adding an item more than once from the item description page increments the quantity for that item. Specific formats that the visitor's address, email address, and credit card information must follow. A specific communication protocol for talking to the credit card network

The web site software also contains other code which is not considered part of business logic nor business rules:     

Peripheral content not related to the core business data, such as the HTML that defines the colors, appearance, background image, and navigational structure of the site Generic error-handling code (e.g. which displays the HTTP Error Code 500 page) Initialization code that runs when the web server starts up the site, which sets up the system Monitoring infrastructure to make sure all the parts of the site are working properly (e.g. the billing system is available) Generic code for making network connections, transmitting objects to the database, parsing user input via HTTP POST events, etc.

Business logic could be anywhere in a program. For example, given a certain format for an address, a database table could be created which has columns that correspond exactly to the fields specified in the business logic, and type checks added to make sure that no invalid data is added. Business logic often changes. For example, the set of allowable address formats might change when an online retailer starts shipping products to a new country. Thus it is often seen as desirable to make the code that implements the business logic relatively isolated, or loosely coupled. This makes it more likely that changes to business logic will require a small set of code changes, in only one part of the code. Distant but strongly coupled code also creates more of a risk that the programmer will only make some of the necessary changes and miss part of the system, leading to incorrect operation.[4] A multitier architecture formalizes this decoupling by creating a business logic layer which is separate from other tiers or layers, such as the data access layer or service layer. Each layer "knows" only a minimal amount about the code in the other layers - just enough to accomplish necessary tasks. For example, in a model–view–controller paradigm, the controller and view layers, might be made as small as possible, with all the business logic concentrated in the model. In the e-commerce example, the controller determines the sequence of web pages in the checkout sequence, and is also responsible for validating that email, address, and payment information satisfy the business rules (rather than leaving any of that up to the database itself or lower-level database access code).

Alternative paradigms are possible. For example, with relatively simple business entities, a generic view and controller could access database objects which themselves contain all the relevant business logic about what formats they accept and what changes are possible (known as the database model). Some tiered schemes use either a distinct application layer or a service layer, or consider the business logic layer to be the same as one of those. Business logic can be extracted from procedural code using a business rule management system (BRMS). The business rules approach of software development uses BRMSs and enforces a very strong separation of business logic from other code. User interface management systems are another technology used to enforce a strong separation between business logic and other code. The magic pushbutton is considered an "anti-pattern": a technique that in this case creates undesirable constraints which make it difficult to code business logic in an easy-to-maintain way. A domain model is an abstract representation of the data storage types required by business rules....