Overview of Formal Methods - Foundation for analysis methods

Want to learn more about what are formal methods, used as the basis for analysis methods ? Well, you can get the complete article at the 'Learn Software Process' (link to article):

Formal methods provide a foundation for specification environments leading to analysis models that are more complete, consistent, and unambiguous than those produced using conventional or object-oriented methods. The descriptive facilities of set theory and logic notation enable a software engineer to create a clear statement of facts.
A decision to use formal methods should consider startup costs as well as the cultural changes associated with a radically different technology. In most instances, formal methods have highest payoff for safety-critical and business-critical systems.

Learn software concepts - Restructuring Concepts

Software restructuring modifies source code and/or data in an effort to make it amenable to future changes. In general, restructuring does not modify the overall program architecture. It tends to focus on the design details of individual modules and on local data structures defined within modules. Reasons for restructuring :

1. The current code would have reached a stage where it is impossible to do any more modifications without breaking something else.
2. The requirements have changed so much that the current architecture/design cannot handle it without a redesign.
3. The current application doesn’t/will not scale, perform well enough as it wasn’t designed to handle the current load/anticipated growth.
4. The folks who worked on the code are no longer there and nobody knows what the code really does.
5. You don’t really like the current way it is implemented and think that there is a better way to do it using framework X or library Y.

Code Restructuring :
It is performed to yield a design that produces the same function as the original program but with higher quality. In general, code restructuring techniques model program logic using Boolean algebra and then apply a series of transformation rules that yield restructured logic. A resource exchange diagram maps each program module and the resources that are exchanged between it and other modules. By creating representations of resource flow, the program architecture can be restructured to achieve minimum coupling among modules.

Data Restructuring :
Before data restructuring begins, a reverse engineering activity called analysis of source code must be conducted. Once the data analysis is done, data redesign commences. A data record standardization step clarifies data definitions to achieve consistency among the data item names or physical record formats within an existing data structure or file format. Another form of redesign, called data name rationalization ensures that all data naming conventions conform to local standards and that aliases are eliminated as data flow through the system. When restructuring moves beyond standardization and rationalization, physical modifications to existing data structures are made to make the data design more effective.

Learn software concepts - Introduction to Data Binding

Data binding is the process that establishes a connection between the application UI and business logic. If the binding has the correct settings and the data provides the proper notifications, then, when the data changes its value, the elements that are bound to the data reflect changes automatically. Data binding can also mean that if an outer representation of the data in an element changes, then the underlying data can be automatically updated to reflect the change. A typical use of data binding is to place server or local configuration data into forms or other UI controls.

Basic Data Binding Concepts :
Data binding is based on a component architecture that consists of four major pieces : the data source object (DSO), data consumers, the binding agent, and the table repetition agent. Data source objects provide the data to a page, data-consuming HTML elements display the data, and the agents ensure that both the provider and the consumer are synchronized.

Direction of the Data Flow :
The data flow of a binding can go from the binding target to the binding source and/or from the binding source to the binding target.
- One Way binding causes changes to the source property to automatically update the target property, but changes to the target property are not propagated back to the source property. This type of binding is appropriate if the control being bound is implicitly read-only.
- Two Way binding causes changes to either the source property or the target property to automatically update the other. This type of binding is appropriate for editable forms or other fully-interactive UI scenarios. Most properties default to One Way binding, but some dependency properties default to Two Way binding.
- OneWayToSource is the reverse of OneWay binding; it updates the source property when the target property changes. One example scenario is if you only need to re-evaluate the source value from the UI.

Data Source Objects
To bind data to the elements of an HTML page in Windows Internet Explorer, a DSO must be present on that page. DSOs implement an open specification that leaves it up to the DSO developer to determine the following:
- How the data is transmitted to the page. A DSO can use any transport protocol it chooses. This might be a standard Internet protocol, such as HTTP or simple file I/O. A DSO also determines whether the transmission occurs synchronously or asynchronously. Asynchronous transmission is preferred, because it provides the most immediate interactivity to the user.
- How the data set is specified. A DSO might require an Open Database Connectivity (ODBC) connection string and an Structured Query Language (SQL) statement, or it might accept a simple URL.
- How the data is manipulated through scripts. Since the DSO maintains the data on the client, it also manages how the data is sorted and filtered.
- Whether updates are allowed.

Data Consumers
Data consumers are elements on the HTML page that are capable of rendering the data supplied by a DSO. Elements include many of those intrinsic to HTML, as well as custom objects implemented as Java applets or Microsoft ActiveX Controls.
A DSO typically exposes this functionality through an object model that is accessible to scripts.

Binding Agents
The binding and repetition agents are implemented by MSHTML.dll, the HTML viewer for Internet Explorer, and they work completely behind the scenes. When a page is first loaded, the binding agent finds the DSOs and the data consumers among those elements on the page. Once the binding agent recognizes all DSOs and data consumers, it maintains the synchronization of the data that flows between them.

Introduction To Data Warehousing

A data warehouse is a type of computer database that is responsible for collecting and storing the information of a particular organization. The goal of using a data warehouse is to have an efficient way of managing information and analyzing data.
In addition to a relational database, a data warehouse environment includes an extraction, transportation, transformation, and loading (ETL) solution, an online analytical processing (OLAP) engine, client analysis tools, and other applications that manage the process of gathering data and delivering it to business users.

Despite the fact that data warehouses can be designed in a number of different ways, they all share a number of important concepts.
A data warehouse is a :
- Subject-oriented : This means that the information that is in the data warehouse is stored in a way that allows it to be connected to objects or events which occur in reality.
- Integrated : Data warehouses must put data from disparate sources into a consistent format. They must resolve such problems as naming conflicts and inconsistencies among units of measure. When they achieve this, they are said to be integrated.
- Time-variant : A time variant will allow changes in the information to be monitored and recorded over time.
- Non-volatile : This means that it cannot be deleted, and must be held to be analyzed in the future. All of the programs that are used by a particular institution will be stored in the data warehouse, and it will be integrated together.



CHARACTERISTICS OF DATA WAREHOUSES :
- Multi-dimensional conceptual view.
- Generic dimensionality.
- Unlimited dimensions and aggression levels.
- Unrestricted cross-dimensional operations.
- Dynamic sparse matrix handling.
- Client-server architecture.
- Multi-user support.
- Accessibility.
- Transparency.
- Intuitive data manipulation.
- Consistent reporting performance.
- Flexible reporting.

Introduction to Firewalls

A firewall is a hardware or software system that prevents unauthorized access to or from a network. They can be implemented in both hardware and software, or a combination of both. Firewalls are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet. All data entering or leaving the Intranet pass through the firewall, which examines each packet and blocks those that do not meet the specified security criteria.

Firewalls can greatly enhance the security of a host or a network. They can be used to do one or more of the following things:
* To protect and insulate the applications, services and machines of your internal network from unwanted traffic coming in from the public Internet.
* To limit or disable access from hosts of the internal network to services of the public Internet.
* To support network address translation (NAT), which allows your internal network to use private IP addresses and share a single connection to the public Internet (either with a single IP address or by a shared pool of automatically assigned public addresses).



FIREWALL CONCEPTS
There are two basic ways to create firewall rulesets: “inclusive” or “exclusive”. An exclusive firewall allows all traffic through except for the traffic matching the ruleset. An inclusive firewall offers much better control of the outgoing traffic, making it a better choice for systems that offer services to the public Internet. It also controls the type of traffic originating from the public Internet that can gain access to your private network. All traffic that does not match the rules, is blocked and logged by design.
Inclusive firewalls are generally safer than exclusive firewalls because they significantly reduce the risk of allowing unwanted traffic to pass through them.

HOW FIREWALLS WORK ?
A firewall, working closely with a router program, examines each network packet to determine whether to forward it toward its destination. A firewall also includes or works with a proxy server that makes network requests on behalf of workstation users. A firewall is often installed in a specially designated computer separate from the rest of the network so that no incoming request can get directly at private network resources.
Firewalls use one or more of three methods to control traffic flowing in and out of the network:
* Packet filtering - Packets are analyzed against a set of filters. Packets that make it through the filters are sent to the requesting system and all others are discarded.
* Proxy service - Information from the Internet is retrieved by the firewall and then sent to the requesting system and vice versa.
* Stateful inspection - It compares certain key parts of the packet to a database of trusted information. Information traveling from inside the firewall to the outside is monitored for specific defining characteristics, then incoming information is compared to these characteristics. If the comparison yields a reasonable match, the information is allowed through. Otherwise it is discarded.