Sooner or later, any person working in the field of development meets with the concept of "data parsing". The term has another name: syntactic analysis. In simple terms, this is the process of converting one data format into another, more readable format.
At a more technical level, a parser is a software component that uses input data (for example, HTML) to create a structured, human–readable representation of this input data.
Analyzers break down the input data they receive into parts such as nouns (objects), verbs (methods) and their attributes or parameters. Then they are controlled by other programs, compiler components. The parser can also check whether all the necessary input data has been provided.
How does parsing work?
A parser is a program that is part of the compiler, and parsing is part of the compilation process. Parsing occurs at the stage of compilation analysis.
In parsing, the code is taken from the preprocessor, broken into smaller parts and analyzed so that other software can understand it. The parser does this by creating a data structure from the input data.
In particular, a person writes code in an understandable human language, such as C++ or Java, and saves it as a set of text files. The parser takes these text files as input and splits them so that they can be translated to the target platform.
Parsers are used for many technologies, including:
- Java and other programming languages
- HTML and XML
- Interactive data language and object definition language
- SQL and other database languages
- Modeling languages
- Scripting languages
- HTTP and other Internet protocols
Stages of parsing
The parser consists of three components, each of which handles different stages of the parsing process. Three stages:
1. Lexical analysis
A lexical analyzer or scanner takes the code from the preprocessor and breaks it into smaller parts. It groups the input code into sequences of characters called tokens, each of which corresponds to a token. Tokens are units of programming language grammar that are understandable to the compiler.
Lexical analyzers also remove whitespace characters, comments, and errors from the input.
2. Syntactic analysis
At this stage, the syntactic structure of the input is checked using a data structure called a parsing tree or an output tree. The syntax analyzer uses markers to build a parsing tree that combines a predefined programming language grammar with input string markers. The parser reports a syntax error if the syntax is incorrect.
3. Semantic analysis
Semantic analysis checks the parsing tree against the symbol table and determines whether it is semantically consistent. This process is also known as context-sensitive analysis. It includes data type checking, label checking, and flow control checking.
In some sources, only the second stage is called parsing because it generates a parsing tree. They do not take into account lexical and semantic analysis.
Types of parsers
The parser simplifies the "understanding" of the information array by a computer program and there are two types:
- dependency tree – this structure consists of components that are in hierarchical relationships to each other;
- the tree of components – in the structure of this type, the components are closely related to each other, but without hierarchical relationships.
Also, the result of the parser can be a combination of models. The program operates according to one of two algorithms:
Top-down parsing. The analysis is carried out from the general to the particular, and the syntactic tree grows downwards.
Ascending parsing. The analysis and construction of the syntactic tree are carried out from the bottom up
The choice of a particular parsing method depends on the ultimate goal. In any case, the parser should be able to isolate only the necessary data from the general array, as well as convert them into a format convenient for solving the problem.
Creating or buying a parser?
When it comes to the business side, you can ask a great question: "Should my technical team create their own parser or should we just outsource it?"
As a rule, your own parser is cheaper than a ready-made solution. However, it is not easy to answer this question, and when making a decision about creating or buying, several things should be taken into account.
Creation
Making a decision to create a parser gives several clear advantages:
- The parser can be anything. It can be adapted for any required work (analysis).
- Creating your own parser will be cheaper.
- You can control any decisions that need to be made when updating and maintaining the parser.
But, as with everything, there is always a downside to creating your own parser:
- You will need to hire and train an entire internal team to create a parser.
- Parser support is necessary, which means more internal costs and time resources used.
- You will need to buy and build a server that will be fast enough to analyze data at the right speed.
- It is necessary to work closely with the technical team to make the right decisions to create something good, spending a lot of time on planning and testing.
Self-creation has its advantages, but requires a lot of resources and time. Especially if you need to develop a complex parser for parsing large volumes. It will require more maintenance and human resources, as well as valuable human resources, because it will require a highly qualified development team to create it.
Purchase
Advantages
- There will be no need to spend money on human resources, as everything will be done for you, including the maintenance of the parser and servers.
- The problems that arise will be solved much faster, because the people from whom the tools are purchased have extensive know-how and are familiar with their technologies.
- It is unlikely that the parser will fail or there will be any problems in general, as it will be tested and improved in accordance with the requirements of the market.
- You will significantly save on human resources and your own time, since the decision on how to create the best parser will be made by outsourcing.
Of course, buying a parser has several disadvantages:
- A third-party parser will come out a little more expensive.
- There won't be a full control.
It may seem that buying a parse has more advantages. There is only one thing that will simplify the choice – you need to understand which parser you will need. An experienced developer can make a simple parser in about a week. But if it is difficult, it may take months. And this is the time and resources spent.
ТAlso, the choice depends on whether you have a large business or a small one. The first one has a lot of time and resources available to create and maintain a parser. For the second (small business), you need to do something to be able to grow in the market.
Syntactic analysis is a fundamental concept of software development and computational theory. However, most IT professionals can do without a deep understanding of parsing, using low-code platforms that allow users to create programs without writing thousands of lines of code.