Patent Publication Number: US-11663244-B2

Title: Segmenting machine data into events to identify matching events

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit as a CON of U.S. Ser. No. 15/885753, filed Jan. 31, 2018, which claims benefit as a CON of U.S. Ser. No. 14/611,189, filed Jan. 31, 2015, now U.S. Pat. No. 10,318,553, issued Jun. 11, 2019, which claims benefit as a CON of U.S. Ser. No. 14/170,228, filed Jan. 31, 2014, now U.S. Pat. No. 9,128,916, issued Sep. 8, 2015, which claims benefit as a CON of U.S. Ser. No. 13/664,109, filed Oct. 30, 2012, now U.S. Pat. 8,694,450, issued Apr. 8, 2014, which claims benefit as a CON of U.S. Ser. No. 13/099,268, filed May 2, 2011, now U.S. Pat. 8,589,321, issued Nov. 19, 2013, which claims benefit as a CON of U.S. Ser. No. 11/459,632, filed Jul. 24, 2006, now U.S. Pat. 7,937,344, issued May 3, 2011, which claims benefit of U.S. PRO Ser. No. 60/702,496, filed Jul. 25, 2005, contents of the aforementioned are hereby incorporated by reference as if fully set forth herein, under 35 U.S.C. § 120. The applicant(s) hereby rescind any disclaimer of claim scope in the parent application(s) or the prosecution history thereof and advise the USPTO that claims in this application may be broader than any claim in the parent application(s). 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to information organization and understanding, and more particularly to the organization and understanding of machine data. 
     2. Description of the Related Art 
     Information systems invariably generate vast amounts and wide varieties of machine data (e.g., activity logs, configuration files, messages, database records) whose value is widespread. Troubleshooting systems, detecting operational trends, catching security problems and measuring business performance, for example, typically require the organization and understanding of machine data. But the overwhelming volume, different and changing formats, and overall complexity of machine data create substantial difficulty for software developers, system administrators and business people who want to make sense of it and gain insight into information system behavior. The problem is compounded by the fact that information systems, and the machine data they generate, continue to grow in complexity and size. 
     Consider for example an information system environment for web-based applications consisting of web servers, application servers, databases and networks. Each information system component is constantly logging its own machine data documenting its activities. System administrators need to access and comprehend the machine data from one or more components to find and fix problems during operations. Security analysts want to understand patterns of machine data behavior from network devices to identify potential security threats. Business people are interested in tracing the machine data across components to follow the paths and activities customers perform when purchasing products or services. 
     Today, people generally attempt to comprehend information system behavior by manually looking at and trying to piece together machine data using the knowledge from one or more individuals about one or more systems. Individuals typically have specific technology domain expertise like networking, operating systems, databases, web servers or security. This expertise can also be in specific application domains like finance, healthcare, or communications. Manual approaches can be effective when considering small amounts of machine data in a single domain, but humans are easily overwhelmed as the size, variety and dynamic nature of the machine data grows. 
     Automated approaches, like homegrown scripts, data analysis programs, and data warehousing software, by contrast, can work with large amounts of machine data. But organizing different types of frequently changing data and formats can be troublesome, generally requiring specific methods for each type of data and necessitating modification of methods when the data formats change or new types of data are encountered. Automated approaches to building understanding from machine data are typically limited to finding simple, predefined relationships between known data elements. 
     Generally machine data is organized today by relying on predefined data schemas and predetermined algorithms for parsing and categorizing data. In current approaches, what data elements exist in a machine data set and how the data elements are classified generally must be known ahead of time. How the data is cleansed, parsed and categorized is defined algorithmically in advance for different types of data formats resulting in systems that are brittle, expensive to implement, and have numerous functional shortcomings. For example, unexpected types of data are typically ignored. As a result, data categorization usefulness degrades quickly and unexpected data and behaviors are not observed or recorded. Given the inherent dynamic nature of information systems and the machine data they generate, current organization methods have limited applicability. 
     Building understanding from machine data is inherently subjective and depends on the task, scope of data and skill level of people using a solution. Deriving specific, useful meanings from large quantities of machine data can require expertise in one or more domains and knowledge of how data from one domain relates to data from another domain. Current methods of deriving meaning from machine data are generally based on building simple pair-wise relationships (A-&gt;B) between predetermined data elements using data values. More advanced techniques may be able to find predetermined multi-data element relationships (A-&gt;B-&gt;C), provided the data elements are described in advance, requiring the availability of multiple domain experts to configure and continuously manage a solution. 
     Conventional methods, whether human or automated, of organizing and understanding machine data across multiple information systems and domains suffer from an inability to effectively keep up with changing machine data and are constrained by limited data relationships, making these methods difficult, time consuming, expensive and often ineffective. 
     There exists, therefore, a need to develop other techniques for organizing and deriving understanding from machine data. 
     SUMMARY OF THE INVENTION 
     Methods and apparatus consistent with the invention address these and other needs by turning machine data (MD) into a machine data web (MDW). A MDW is created by organizing MD into events representing discrete activities, and dynamically linking events together representing larger, more complex activities. Much like the World Wide Web is a hyperlinked information space of documents and web sites. A MDW is an interconnected information space of information system events and activities. The MDW can be searched, browsed, navigated, and analyzed as a proxy for the information-processing environment itself. Unlike the WWW&#39;s HTML documents and hyperlinks, however, the events organized from machine data, and the links between these events, do not generally exist and must be manufactured through the processing and analysis of MD. 
     In one implementation, MD is organized into events using a collection of techniques including, but not limited to, aggregating a MD collection into discrete events, extracting important entities from an event&#39;s data, segmenting an event&#39;s data into tokens, and classifying events into like categories. An important aspect is the ability to continuously learn and adapt, keeping up with changes in the MD. In the example of a web-based application information system environment, data sources and data formats can be constantly changing. For example, new web servers and network components can be added and old ones removed as the application requires more capacity or reconfiguration. 
     In another aspect, knowledge or understanding is built from the organized MD as events are connected to one another by dynamically constructing links using a number of techniques, including but not limited to the analysis of event data values, timing, patterns, and statistics. One advantage of the MDW is that it can learn new types of links as they occur and build paths by chaining multiple links together. Another advantage is the ability to preserve integrity by reconstructing the original MD from the MDW events. Dynamic construction of links and paths through multiple machine data sources enables a system administrator working on a web-based application information system to follow the sequence of activities from the web server to the application and eventually the database in order to locate the source of a problem. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention has other advantages and features which will be more readily apparent from the following detailed description, when taken in conjunction with the accompanying drawings: 
         FIG.  1    is a diagram an example information-processing environment suitable for use with an MDW. 
         FIG.  2    is a flow diagram of one example of creation of an MDW according to the invention. 
         FIG.  3    is a flow diagram of one example of MD organization according to the invention. 
         FIG.  4    is a flow diagram of one example of MD understanding according to the invention. 
         FIG.  5    is a diagram illustrating access to an MDW. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the example of  FIG.  1   , the information-processing environment includes hardware and software components such as computers, routers, databases, operating systems and applications in a distributed configuration for processing information. Each component may be producing MD  110 , and there may be many MD sources and large quantities of MD across multiple technology and application domains. For example, a computer may be logging operating system events, a router may be auditing network traffic events, a database may be cataloging database reads and writes or schema changes, and an application may be sending the results of one application call to another across a message queue. In this embodiment, individual IT personnel —who may reside in different data centers, companies, or even geographies—typically manage specific technology and application domains. Aspects of the invention will be described with respect to the information-processing environments in  FIG.  1   , but the invention can also be used with other information-processing environments. 
       FIG.  2    represents one approach  200  to building a MDW  290  from MD  110 . This approach includes an organization process  235  and an understanding process  275 . During the organization process  235 , the MD  110  is organized into collections of discrete events  250 , referred to herein as event data (ED). Events  250  represent units of system activity. Examples of events  250  include, for example, a web server servicing an HTTP “get” request from a web browser, an application server servicing an API call, or a database updating records in a table. Collections of events  250  can describe larger system activities, such as an attempt to update a customer record or submit an order. One of the challenges in organizing  235  MD  110  into events  250  is that MD generally has little formal structure and typically includes not much more than a time stamp common across different sources of MD and different types of events. MD  110  is also subject to changes in environment configurations. For example, changing the verbosity level in a web server configuration file can dramatically increase or decrease the amount of information included in an HTTP “get” event found in the web server&#39;s log file. 
     During the understanding process  275 , ED  250  is analyzed to create dynamic links between events and build the MDW  290 . As an example, consider that a log from a web server may contain specific types of events  250  with specific event data, but a log from an application server or database may contain different events  250  and event data specific to its own domain. A system administrator may, for example, locate the web server event by looking for a session ID found in a web server log, locate the application server event by finding a process ID in the message queue, and locate a database table update event by searching for a transaction ID in the database audit trail. All three sources may contain events  250  that are part of a larger system activity, yet there is no obvious or explicit common structure or data shared among the MD  110  produced by each system. Common structure is manufactured across the three sources by analyzing the event data  250  so that connections between events can be identified. In one implementation, patterns of event behavior are recorded in real-time and identified, for example, as frequently occurring or infrequently occurring. Frequent patterns identify typical system processes and well-known links. Infrequent patterns identify deviations or anomalies and less well-known links. Contrast this with the world of the web, where hyperlinks are part of the formal, common structure of HTML—the language for building most web pages. Building links by hand for large volumes of ED  250  is not an option for complex information-processing environments. 
     Machine Data Organization Process 
       FIG.  3    is a flow diagram of one implementation  235  of the MD organization process of  FIG.  2   . In this implementation, there are several steps including collection  305 , source identification  315 , aggregation  325 , extraction  335 , segmentation  345 , and classification  355 . Through these steps, MD  110  is collected from the information-processing environment and organized into ED  250  for the MD understanding process. For convenience, the technology that implements each step will be referred to as a module. That is, the “collection module” is the technology that collects MD. In one implementation, the modules are all implemented as software. 
     Collection 
     In the collection step  305 , the MD  110  may be collected directly from its original source or consolidated over a number of sources. Machine data  110  can, and often does, arrive out of order. Collection  305  of MD  110  can be performed based on standard approaches to data access, for example, reading log files, examining message bus traffic, becoming a sync for logging systems like Syslog, or connecting to database auditing systems. Parts of the collection module can be situated in different locations, preferably with access to the MD  110 . 
     Source Identification—Classification into Domains 
     Given the repetitive, yet dynamic, nature of MD  110 , an effective organization process  235  (such as shown in  FIG.  3   ) preferably will learn about data formats and structure automatically. In one implementation, learning is separated into different domains based on the source of MD  110 . Domains can be general system types, such as log files, message bus traffic, and network management data, or specific types, such as output of a given application or technology—Sendmail logging data, Oracle database audit data, and J2EE messaging. An MDW can include a mix of general domains and specific domains. 
     In this example organization process  235 , the domain for a given source of MD is identified  315  so that domain specific organization methods can be applied. Domains are determined through a learning process. The learning process uses collections of MD from well-known domains as input and creates a source signature  312  for each domain. In one implementation, source signatures  312  are generated from representative samples of MD  110  by creating a hash table mapping punctuation characters to their frequency. While the tokens and token values can change in a MD collection, in this particular implementation, the signature  312  generated by the frequency of punctuation is quite stable, and reliable within a specific domain. Other implementations could use functions of the punctuation and tokens, such as the frequencies of the first punctuation character on a line, or the first capitalized term on a line. Given that source signatures  312  can be large and hard to read, signatures can have a corresponding label in the form of a number or text that can be machine generated or human assigned. For example, the source signature  312  for an Apache web server log might be programmatically assigned the label “ 205 ”, or a user can assign the label “Apache Server Log”. 
     In one embodiment, clustering is used to classify  315  collected MD  110  into domains according to their source signatures  312 . As collections of MD  110  are encountered, each collection&#39;s signature is matched to the set of known source signatures  312  by performing a nearest-neighbor search. If the distance of the closest matching signature  312  is within a threshold, the closest matching signature  320 &#39;s domain is assumed to be the domain of the source. If no best match can be found, a new source signature  312  can be created from the sample signature and a new source domain created. Alternatively, a default source domain can be used. In one implementation, the distance between two signatures is calculated by iterating over the union of attributes of the two signatures, with the total signature distance being the average of distances for each attribute. For each attribute A, the value of A on Signature1 and Signature2, V1 and V2, are compared and a distance is calculated. The distance for attribute A is the square of (V1−V2)*IDF, where IDF is the log(N/|A|), where N is the number of signatures, and |A| is the number of signatures with attribute A. 
     Source Identification—Classification as Text/Binary 
     Some MD  110  sources are non-textual or binary and cannot be easily processed unless a known process is available to convert the binary MD into textual form. To classify a source as textual or binary, a sample MD collection is analyzed. Textual MD can also have embedded binary MD, such as a memory dump, and the classification preferably identifies it as such. In one implementation, the textual/binary classification works as follows. The sample is a set of lines of data, where a line is defined as the data between new lines (i.e., ‘\n’), carriage-returns (i.e., ‘\r’), or their combination (i.e., ‘\r\n’). For each line, if the line&#39;s length is larger than some large threshold, such as 2 k characters, or if the line contains a character with an ASCII value of zero (0), a count of Binary-looking lines is incremented. Otherwise, if the line&#39;s length is shorter than a length that one would expect most text lines to be below, such as 256 characters, a count of Text-looking lines is incremented. If the number of Text-looking lines is twice as numerous as the Binary-looking lines (other ratios can be used depending on the context), the source is classified as text. Otherwise, the source is classified as binary. 
     Aggregation of Machine Data into Raw Events 
     When the source signature  320  for a collection of MD has been identified  315 , the corresponding aggregation rules are applied  325  to the MD collection. Aggregation rules describe the manner in which MD  110 , from a particular domain, is organized  325  into event data  330  by identifying the boundaries of events within a collection of MD, for example, how to locate a discrete event by finding its beginning and ending. In one implementation, the method of aggregation  325  learns, without prior knowledge, by grouping together multiple lines from a sample of MD  110 . Often MD  110  contains events  330  that are anywhere from one to hundreds of lines long that are somehow logically grouped together. 
     The MD collection may be known a priori, or may be classified, as single-line type (i.e., containing only single-line events) or multi-line type (i.e., possibly containing multi-line events) prior to performing aggregation. For those MD collections that are classified as single-line type, aggregation  325  is simple—single-line type MD collections are broken on each line as a separate event. Multi-line type MD collections are processed  325  for aggregation. In one implementation, a MD collection is classified as a multi-line type if 1) there is a large percentage of lines that start with spaces or are blank (e.g., if more than 5% of the lines start with spaces or are blank), or 2) there are too many varieties of punctuation characters in the first N punctuation characters. For example, if the set of the first three punctuation characters found on each line has more than five patterns (e.g., ‘:::’, ‘!:!’, ‘,,,’, ‘:..’, ‘( )*’), the collection might be classified as multi-line. 
     Another aspect of aggregation methods  325  is the ability to learn, and codify into rules, what constitutes a break between lines and therefore the boundary between events, by analyzing a sample of MD. For example, in one implementation, an aggregation method  325  compares every two-line pair looking for statistically similar structures (e.g., use of white space, indentation, and time-stamps) to quickly learn which two belong together and which two are independent. In one implementation, aggregation  325  works as follows. For each line, first check if the line starts with a time-stamp. If so, then break. Typically, lines starting with a time-stamp are the start of a new event. For lines that do not start with a time-stamp, combine the current line with the prior line to see how often the pair of lines occurs, one before the other, as a percentage of total pairs in the MD sample. Line signatures are used in place of lines, where a line signature is a more stable version of a line, immune to simple numeric and textual changes. In this implementation, signatures can be created by converting a line into a string that is the concatenation of leading white space, any punctuation on the line, and the first word on the line. The line “10:29:03 Host 191.168.0.1 rebooting:normally” is converted to“::..:Host.” 
     Now this current line signature can be concatenated with the previous line signature (i.e., signature1 combined with signature2) and used as a combined key into a table of break rules. The break rule table maps the combined key to a break rule, which determines whether there should be a ‘break’, or not, between the two lines (i.e., whether they are part of different events or not). Break rules can have confidence levels, and a more confident rule can override a less confident rule. Break rules can be created automatically by analyzing the co-occurrence data of the two lines and what percent of the time their signatures occur adjacently. If the two line signatures highly co-occur, a new rule would recommend no break between them. Alternatively, if they rarely co-occur, a new rule would recommend a break between them. For example, if line signature A is followed by line signature B greater than 20% of the time A is seen, then a break rule might be created to recommend no break between them. Rules can also be created based on the raw number of line signatures that follow/proceed another line signature. For example, if a line signature is followed by say, ten different line signatures, create a rule that recommends a break between them. If there is no break rule in the break rule table, the default behavior is to break and assume the two lines are from different events. Processing proceeds by processing each two-line pair, updating line signature and co-occurrence statistics, and applying and learning corresponding break rules. At regular intervals, the break rule table is written out to the hard disk or permanent storage. 
     Extraction of Entities 
     Following aggregation  325  and before event segmentation  345 , various extraction methods  335  can be applied to identify semantic entities  340  within the data. In one implementation, search trees or regular expressions can be applied to extract and validate, for example, IP addresses or email addresses. The goal of extraction  335  is to assist the segmentation process  345  and provide semantic value to the data. 
     Segmentation of Events 
     Segmentation  345  rules describe how to divide event data  330  into segments (also known as tokens  350 ). It is important to note at this point that segments  350  have little semantic value, unless an extracted entity  340  has been applied. In one implementation a segmentation rule  345  examines possible separators or punctuation within the event  330 , for example, commas, spaces or semicolons. An important aspect of segmentation  345  is the ability to not only identify individual segments  350 , but also to identify overlapping segments  350 . For example, the text of an email address, “bob.smith@corp.com”, can be broken  345  into individual and overlapping segments  350 ; &lt;bob.smith&gt;, &lt;@&gt; and &lt;corp.com&gt; can be identified as individual segments, and bob.smith&gt;&lt;@&gt;&lt;corp.com&gt;&gt; can also be identified as an overlapping segment. In one implementation, segmentation  345  uses a two-tier system of major and minor breaks. Major breaks are separators or punctuation that bound the outer most segment  350 . Examples include spaces, tabs, and new lines. Minor breaks are separators or punctuation that break larger segments  350  into sub segments  350 , for example periods, commas, and equal signs. In one implementation, more complex separators and punctuation combinations are used to handle complex segmentation tasks  345 , for example handling Java exceptions in an application server log file. 
     Classification of Event Types 
     In the embodiment of  FIG.  3   , the final step of the organization process  235  is the classification  355  of events  350  into event types. Examples of event types include a web server HTTP “get,” an application server database “connect,” or an email server “send mail attempt.” In one implementation, an event signature  352  is generated for each event type. One method for generating an event signature  352  is to build a hierarchical scheme for identifying particular types of events based on the overall event structure  330 , segmentation  350 , segment values  350 , and extracted entities  340 . The purpose of the event signature  352  is to identify a type of event regardless of the situation. In this way a particular type of event can have the same signature  352  in multiple MDWs. For example, a mail server&#39;s send mail attempt generally has the same signature  352  in every MDW regardless of the information-processing environment. 
     In one implementation a hierarchical event signature {v1, v2, v3, . . . vn}  352  is constructed from a list of successively more specific hash functions {f1( ), f2( ), f3( ), . . . fn( )}, where each fn( ) produces a value representing a level of the hierarchy. The event signature  352  is most useful when each successive function is more specific. For example, in one embodiment, the following function list represents a 9 level event signature  352 , from most general to most specific:
         f1( ): firstCharType—returns alpha, numeric, white space, other, depending on the type of the first character of the event.   f2( ): headwhitespace—returns the number of spaces/tabs at the beginning of the event.   f3( ): firstpunc—returns the first punctuation character of the event.   f4( ): firstImportantKeywords—returns a hash value of first word in the event that is an important keyword, where there is a list of known important terms.   f5( ): firstKnownWord—returns the first word in the event that is a known keyword, where there is a list of known terms.   f6( ): importantKeywords—returns the list of all hash values of important keywords that are found in the event.   f7( ): firstUnknownWord—returns the first word in event that is not a known keyword.   f8( ): headPunc—returns the first 10 punctuation characters in the event, removing duplicates.   f9( ): allPunc—returns all punctuation in event.       

     In this implementation, the event signature  352  is a traversal through a hierarchy of possible values. Given that event signatures  352  can be large and hard to read, an event signature can have a corresponding label in the form of a number or text that can be machine generated or human assigned. For example, an email server “send mail attempt” event might be programmatically assigned the label “500”, but a user can assign the label “send mail attempt”. 
     Machine Data Understanding Process 
       FIG.  4    is a flow diagram of one implementation  275  of the MD understanding process shown in  FIG.  2   . During the understanding process  275 , knowledge about how events relate to one another is discovered from the event data  250 . This knowledge is valuable in understanding the behavior of the underlying information-processing environment. Links  410 , representing relationships between events  250  are useful, among other things, for finding connections and causality where little or no common structure exists. For example, in an email-messaging information-processing environment, an event  250  may exist in the message transfer agent (MTA) indicating the receipt of a message from a sender, another event  250  may exist in the spam filtering software documenting that the sender is known and the message is safe to forward to a user&#39;s mailbox, and finally the mailbox authentication may contain an event  250  showing that the user attempted to login to their mailbox and retrieve their mail. These three events  250  may contain no common structure other than a timestamp. However, the three events  250  are connected as part of a larger email messaging activity. In one implementation of the understanding process  275 , several techniques are applied including linking  405 , which creates connections  410  between events  250 ; path construction  415 , to build more complex, multi-link connections  420 ; and analysis  425 , which records historical data  492  and generates statistics  494  about the MDW. 
     Linking Events 
     By analyzing event data  250  and possible link hints  402  from external systems or human input, links  410  can be created  405 . An important feature of the MDW approach is the ability to create  405  link relationships  410  dynamically and learn new possible link relationships on the fly. A number of methods can be used in the analysis of ED  250  to create  405  links  410 , including, but not limited to, value analysis, statistical analysis, timing analysis, and the evaluation of link hints  402 . These methods can be used individually or in combination with one another. From our previous example, perhaps the link  410  between the MTA and the spam filter events  250  is a value association between the MTA message ID and the spam filter article ID, or the link  410  between the spam filter and the user email retrieval  250  is an associative mail box name. All three events  250  might be tied together, for example by observing a timing pattern that occurs over and over again with statistically relevant frequency. 
     In one implementation, link analysis  405  takes place by creating a co-occurrence table with an entry for pairs of event types or event data values that occur within a predetermined window of each other. In one aspect, windows are bounded by a window threshold taking the form of time (e.g. 10 minutes), event types (e.g. 50 unique event types), or event instances (e.g.  1000  events). The value of the co-occurrence table entry is the distance between the pair (time, event types, or event instances). Pairs that co-occur often enough, and meet a distance standard deviation threshold are deemed relevant and reliable links. For example, assume that an event  250  of type A occurred 50 times, an event of type B occurred 40 times, an event of type A was followed by an event of type B 20% of the time, and the standard deviation of their distance was less than 5.0 (a predetermined threshold), then a link  410  is created between events  250  of type A and type B (represented as A-&gt;B). Standard deviation thresholds are based on a function of window thresholds and may change based on the time to complete analysis or the number of desired results. Window thresholds may change based on data density and time available to complete the analysis. 
     Path Construction by Chaining Linked Events 
     Paths  420  are multi-link collections representing a chain of linked events  410 . Paths  420  often represent a higher level of information system behavior, possibly spanning multiple systems, applications or data centers. Paths  420  are useful, for example, for following more complex activities or transactions through one or more systems. In our email example, a path  420  could be the receiving or sending of an email including three or more events  250  and two or more links  410 . Similar to links  410 , paths  420  are created  415  by analyzing event data  250 , 410  and possible path hints  412  from external systems or human input. An important feature is the ability to create paths  420  dynamically and team new possible paths on the fly. 
     Paths  420  are built by chaining together  415  event links  410 , using a number of methods. In one implementation, paths  420  are discovered as chains of transitive links  410 . For example, given previously discovered links  410  A-&gt;B, B-&gt;C, A-&gt;C, and C-&gt;A, transitively composition yields the following three event paths  420 : A-&gt;B-&gt;C, B-&gt;C-&gt;A, A-&gt;C-&gt;A, C-&gt;A-&gt;B and C-&gt;A-&gt;C. These paths  420  can also be combined to make larger and larger path chains. In one aspect, certain restrictions are applied  415  to reduce combinatorial explosion. One restriction might involve the elimination of cycles and repetitions. For example, one rule  415  might be that A-&gt;C and C-&gt;A cannot be combined to create A-&gt;C-&gt;A. In a second possible restriction  415 , for A-&gt;B and B-&gt;C to be combined there must be an A-&gt;C link  410 , with the average distance of A-&gt;C being approximately equal to the sum of the average distances between A-&gt;B and B-&gt;C. In addition, the standard deviation of the distance for A-&gt;C must be approximately equal to the standard deviations of A-&gt;B and B-&gt;C. Finally, paths  420  that are rotations of other paths can be removed, keeping the most reliable path. For example, given paths  420  A-&gt;B-&gt;C and C-&gt;A-&gt;B, if the standard deviation of the distance between C-&gt;A is greater than the standard deviation of the distance between B-&gt;C then A-&gt;B-&gt;C would be kept and C-&gt;A-&gt;B removed. 
     Like the WWW and HTML hyperlinks, event links  410  and paths  420  can be represented as a uniform resource locator (URL). In one implementation a link  410  from one event  250  to another is represented by the following URL “mdw://&lt;name of MDW&gt;/&lt;link type&gt;/&lt;link value&gt;/&lt;event 1&gt;/event &lt;2&gt;.” A link  410  can resolve to one of several destinations including, but not limited to an event type, an event instance or an event segment within an event instance. 
     Analysis of the MDW 
     In addition to links  410  and paths  420 , another aspect of the MDW understanding process  275  is the ability to generate  425  historical information  492  about itself, for example, statistics  494  for event, event type, link or path occurrences. One aspect of historical data  492  regarding the MDW is that it can reveal historical behavior of the information-processing environment itself. 
     Accessing the MDW 
       FIG.  5    refers to one approach to access the elements of the machine data web  290 , including its data and dynamic relationships, through an application-programming interface (API). In one embodiment, the MDW  290  and corresponding technology infrastructure is Internet-based. The API includes commands to post data  510  to the MDW infrastructure  290  including, but not limited to, MD, events, segments, source signatures, link hints, and path hints. In the same embodiment, the API also includes commands to get data  520  from the MDW  290  including, but not limited to, the original MD, events, segments, source signatures, links, and paths. Utilizing the MDW API, a variety of applications and systems can take advantage of an advanced organization and understanding of machine data. 
     The MDW can be implemented in many different ways. In one approach, each box in  FIGS.  2 ,  3  and  4    is implemented in software as a separate process. All of the processes can run on a single machine or they can be divided up to run on separate logical or physical machines. In alternate embodiments, the invention is implemented in computer hardware, firmware, software, and/or combinations thereof. Apparatus of the invention can be implemented in a computer program product tangibly embodied in a machine-readable storage device for execution by a programmable processor. Method steps of the invention can be performed by a programmable processor executing a program of instructions to perform functions of the invention by operating on input data and generating output. The invention can be implemented advantageously in one or more computer programs. Each computer program can be implemented in a high-level procedural or object-oriented programming language or in assembly or machine language if desired; in any case, the language can be a compiled or interpreted language. Any of the foregoing can be supplemented by, or incorporated in, ASICs (application-specific integrated circuits) and other forms of hardware. 
     Although the detailed description contains many specifics, these should not be construed as limiting the scope of the invention but merely as illustrating different examples and aspects of the invention. It should be appreciated that the scope of the invention includes other embodiments not discussed in detail above. For example, not all of the steps shown are required in every implementation, and they may be implemented in ways other than the examples given above. The order of the steps may also be changed in certain cases. Various other modifications, changes and variations which will be apparent to those skilled in the art may be made in the arrangement, operation and details of the method and apparatus of the present invention disclosed herein without departing from the spirit and scope of the invention.