SD Times Issue 204 by BZ Media

Author:BZ Media
Language: eng
Format: epub
Tags: SD Times;
Published: 2008-08-14T16:00:00+00:00

XMLs ease of use is not great, although it's better than it once was due to the fact that there are many good parsers available. Even so, the requirement to translate certain characters, and the consequent need for CCDATA, mean encoding can at times be complex. Finally, XML expressivity is abysmal. Data must be structured, items can at times be categorized only in one specific hierarchy, and each hierarchy level must encompass all lower levels. What's more, repeating patterns of fields, such as a list of employee records, must repeat all the field names and hierarchy for every instance.

I could go on about XML limitations, but the key objection is performance. Google, intensely focused on performance, examined XML and deemed it too slow for the company's high-speed requirements. In true Google tradition, rather than use an alternative existing protocol, it crafted its own: Protocol Buffers, (code.google.com/p/proto-buf) a new format for serializing data that the company open-sourced in July.

The data structure for Protocol Buffers data items is described using a simple data description language, remi-

niscent of CORBA's Interface Description Language. This description is saved in a .proto file, which is then compiled into C++, Java or Python.

The Protocol Buffers meta-language is surprisingly extensive. Both sequential and hierarchical data structures can be defined. And data items, covering all the standard string and integral types, can be marked required or optional. Fields can include enums, which is a common mechanism for tightly associating a specific value to a variable name.

Protocol Buffers is a binary format. This is a crucial dimension for performance; it means long text strings and field names do not have to be parsed for each item. Also, marshalling and unmarshalling functions are built directly into the code, via the .proto compiler—guaranteeing every aspect is optimized for speed.

Unlike earlier technologies released by Google that still had an experimental feel to them, Google has been using Protocol Buffers for years and in almost all aspects of the services they provide. So, this is a technology that has been extensively tested ... and optimized. If you need to transfer data in C++, Java or Python and want a fast, simple solution that avoids the penalties imposed by XML, try Protocol Buffers. I think you'll like what you find. I

Andrew Binstock is the principal analyst at Pacific Data Works. Read his hlog at binstock. hlogspot. com.

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