XSL: Extensible Stylesheet Language. Allows structural changes of XML documents -- such as: changing the order of content, removing content etc. (Therefore, also called XSLT -- XSL Transformations)
XSLT files are typically declarative, since documents are static.
XPath: In order to make these structural changes, we need some way to reference XML nodes. This can be done using the XPath standard.
RDF: Resource Description Framework: A metadata data model. Used in Firefox to manage a number of internal data structures. Implemented as XML-formatted files.
The focal length of a camera lens is the distance between the center of the lens and the film when an in-focus image is formed of an object very far away. The focal length of a camera lens is displayed on the barrel of the lens along with the measurement of the largest aperture and the maker. The focal length of a lens establishes the field of view of the camera. The shorter the focal length is, the larger the field of view. The magnification factor of the picture of an object and the object's actual size can be found by dividing the focal length of the camera lens used by the focal length of a standard lens.
There are three general types of lenses for a camera: normal or standard, wide angle, and telephoto. The focal length of a normal lens for a 35 mm SLR camera is approximately 50 mm. A standard or normal lens produces a picture with a perspective similar to the human eye. The focal length of a wide angle lens is any measurement less than 50 mm, but is typically 28 mm. A wide angle lens makes things appear smaller and distorts the view if the object is too close to the camera. The focal length of a telephoto lens ranges from 60 to 1000 mm. A telephoto lens magnifies the subject while at the same time narrowing the field of vision. These lenses create an image that looks flatter than that produced by a standard lens.
Miriam Janove -- 2002
Source: http://hypertextbook.com/facts/2002/MiriamJanove.shtml
If there are x numbers to be encoded in binary, then I need to have log2x bits.
For eg: 8 = 23
By multiplication principle, 3 bits can hold 8 values (0 to 7)
And log28 = 3.
Benford's law states that the leading digit d (d ∈ {1, …, b − 1} ) in base b (b ≥ 2) occurs with probability proportional to logb(d + 1) − logbd = logb((d + 1)/d). This quantity is exactly the space between d and d + 1 in a log scale.
In base 10, the leading digits have the following distribution by Benford's law, where d is the leading digit and p the probability:
| d | p |
| 1 | 30.1% |
| 2 | 17.6% |
| 3 | 12.5% |
| 4 | 9.7% |
| 5 | 7.9% |
| 6 | 6.7% |
| 7 | 5.8% |
| 8 | 5.1% |
| 9 | 4.6% |
Using the example given is the TCP/IP guide, I made a comparison of normal PPP and Multilink PPP (just to have some fun).
Original frame size = 32 bytes = 256 bits
Stripped down frame size = 24 bytes = 192 bits
MP Frame size = 158 bits X 3
Size difference = |256 bits - 474 bits| = 218 bits
Time to transfer orginal on 64,000bps = 0.004s .....(1)
Time to transfer MP in 64,000bps X 2 = [(158X2)bits over 128kbps = 0.00246875s] + [158bits over 64,000bps = 0.00246875s] = 0.0049375s .....(2)
From (1) and (2), time taken my MP is more.
However, the Information field of PPP frames is variable. So when a larger amount of data is to be carried, MP is obviously more efficient.
A PPP frame starts and ends with a Flag with value 0x7E. The Flag (start) is followed by Address and Control fields, with are not needed for PPP, but are present for compatibility with High Level Data Link Control Protocol (HDLC). Default values are 0xFF for Address (broadcast) and 3 for Control. The fields are suppressed when using Field compression. (0xFF03 is not a valid Protocol field, and thus the difference is made).
The Protocol field ranges from 0x0000 to 0xFFFF, each used for a particular protocol. Some values are not used (see above). The first octet is even and the second octet is odd. The value when encapsulating an IP packet is 0x0021. When using IPCP, the value is 0x8021. (Add 8 to first digit for getting corresponding NCP value).
The Information Field has the Network Layer data encapsulated. It may be followed by Padding.
This is followed by FSC (Frame Check Sequence), which is a CRC code of the data. It is 2(default) or 4 bytes in size.
The last byte is, ofcourse, the Flag, 0x7E.
Link dead -> Link Establishment -> (Authentication) -> Network Layer Protocol -> Link Open -> Link Termination.