# String Item

A String Item is a tuple of items (string members) from a finite alphabet.

**AKA:**Finite String.**Context:**- It can range from being an Empty String to being a Non-Empty String (such as a short string or a long string).
- It can be an input to a String Item Operation (such as string length, string item probability).
- It can be represented by a String Data Structure.

**Example(s):**- Language Character String, (where the alphabet is a character set).
- [
*A*]; [*12*]; [*1 milllllion monkeys typing.*]; [*10fa23*]

- [
- an Organic Molecule String (DNA, Protein).
- a Terminal Word String, such as:
- ([I] [bought] [a] [real time] [operating system]),
- ([日文] [章魚] [怎麼] [說]).

- a Text Item.
- a Formal String (if it satisfies a formal language).
- a Linguistic Expression (if it can be understood by a linguistic agent).

- Language Character String, (where the alphabet is a character set).
**Counter-Example(s):**- an Infinite Sequence, such as the Integer Sequence.
- a Partially Ordered Set.

**See:**List, String Kernel, Abstract Entity.

## References

### 2011

- (Wikipedia, 2011) ⇒ http://en.wikipedia.org/wiki/String_(computer_science)
- In formal languages, which are used in mathematical logic and theoretical computer science, a
**string**is a finite sequence of symbols that are chosen from a set or alphabet.In computer programming, a string is traditionally a sequence of characters, either as a literal constant or as some kind of variable. The latter may allow its elements to be mutated and/or the length changed, or it may be fixed (after creation). A string is generally understood as a data type and is often implemented as a byte (or word) array that stores a sequence of elements, typically characters, using some character encoding. A string may also denote more general array data types and/or other sequential data types and structures; terms such as byte string, or more general,

**string of***datatype*, or*datatype*-**string**, are sometimes used to denote strings in which the stored data does not (necessarily) represent text.Depending on programming language and/or precise datatype used, a variable declared to be a string may either cause storage in memory to be statically allocated for a predetermined

*max length*or employ dynamic allocation to allow it to hold*chronologically*variable number of elements.When a string appears literally in source code, it is known as a string literal and has a representation that denotes it as such.

Let Σ be an

*alphabet*, a non-empty finite set. Elements of Σ are called*symbols*or*characters*. A string (or**word**) over Σ is any finite sequence of characters from Σ. For example, if Σ = {0, 1}, then*0101*is a string over Σ.The

*length*of a string is the number of characters in the string (the length of the sequence) and can be any non-negative integer. The*empty string*is the unique string over Σ of length 0, and is denoted*ε*or*λ*.The set of all strings over Σ of length

*n*is denoted Σ^{n}. For example, if Σ = {0, 1}, then Σ^{2}= {00, 01, 10, 11}. Note that Σ^{0}= {ε} for any alphabet Σ.

- In formal languages, which are used in mathematical logic and theoretical computer science, a

### 2009

- http://www.csee.umbc.edu/help/theory/lang_def.shtml
- String also called a Word
- A finite sequence of symbols from an alphabet.
- 01110 and 111 are strings from the alphabet B above.
- aaabccc and b are strings from the alphabet C above.
- A null string is a string with no symbols, usually denoted by epsilon.
- The null string has length zero.
- The null string is usually denoted epsilon.
- Vertical bars around a string indicate the length of a string expressed as a natural number. For example |00100| = 5, |aab| = 3, | epsilon | = 0

- String also called a Word

### 2007

- (Kakkonen, 2007) ⇒ Tuomo Kakkonen. (2007). “Framework and Resources for Natural Language Evaluation." Academic Dissertation. University of Joensuu.
- Let [math]\Sigma[/math] be an alphabet.
- A finite sequence of symbols [math]S=(x_1 x_2 … x_n), n≥0, x \in \Sigma[/math] is called a
*string*in alphabet [math]\Sigma[/math]. - The
*length*|S| of string S is*n*. - The
*empty string*is the sequence of length 0; written [math]\varepsilon[/math]. - [math]\Sigma^*[/math] is the set of all strings in [math]\Sigma[/math].