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The following terminology are some of the key terms related to XML and data submission to the EIS.

Key XML Terms

Namespace	A namespace uniquely identifies a set of names such that there is no ambiguity when objects having different origin but the same names are mixed together.
Markup Language	A way to combine text and extra information to show the structure and layout of a document. This information is expressed using markup, which is typically intermingled with the primary text. A commonly known markup language is HTML.
Tuple	An ordered list of objects, each of a specific type. The CERS uses valued pairs consisting of a parameter name and a parameter value to report optional data elements to the EIS.
XML	A markup language for documents containing structured information. The XML specification defines a standard way to add markup to documents. Its primary purpose is to facilitate the sharing of structured data across different information systems, particularly via the internet.
XML Schema	An XML schema describes the structure of an XML document. An XML schema defines the set of rules to which the XML document must conform in order to be considered "valid" according to its schema. An instance of an XML schema is an XML schema document and is a file with the extension .xsd.
XML Document	An XML document is a file containing data organized into a structured document using XML markup. An XML document is considered to be "well-formed" if it conforms to all XML syntax rules. An XML document is considered to be "valid" if it conforms to all the semantic rules defined by an associated XML schema. An XML document cannot be processed if it is not well-formed or valid. XML documents have the file extension .xml.
XML Element	An XML element is a unit of the XML document that is expressed as tags in the form "<tagname>". XML elements must have either a start and end tag as in <FacilitySite> </FacilitySite> or a single empty tag name as in </FacilitySite>. XML elements may be nested within one another in a structured hierarchy and sequence specified in an XML schema.
XML Attribute	An XML attribute contains additional information about an XML element placed at the start tag of the XML element. XML attributes have the form attributeName = "attributeValue," as in <StateCode="CA">. EIS will use XML attributes to report identifying information or to help the EIS process the data being reported within the EIS elements
XML Simple Type	An XML element which has no attributes or nested elements.
XML Complex Type	An XML element which has attributes or nested elements. All EIS components described in other section of this document are XML complex types comprised of XML simple types and other complex types.

Key Terms Relating to EIS Data Submission

CDX	The Central Data Exchange (CDX) serves as the EPA node on the Exchange Network and is the gateway for receiving environmental information through the Web.
Component	A component is a group of XML elements. This term is used in other sections of this document to be synonymous with "complex type."
Content Type	Denotes the particular form of content. For the purposes of this document, the content types referenced in the EIS schema are elements, attributes, complex types, and attachments.
Data Block	A logical grouping of data elements and other data blocks defined for the purposes of reporting data.
Data Category	The category of emissions inventory data to be reported. For the EIS, these are: Facility Inventory; Point emissions; Nonpoint emissions; Onroad/nonroad activity; Onroad/nonroad emissions; and Event emissions.
Data Element	The smallest discrete unit of information that can be reported and still have meaning between systems. Examples of data elements are Agency identifiers, State codes and stack height measure. The EIS will process data elements as part of XML complex types corresponding to complex types defined as part of the reporting instructions.
Data Type	The data format defined for a given data element. Common data types include string, integer, and date. EIS requires that all data elements reported in the XML document have a data type of string. These data will be converted by the EIS to the data types defined for each data element in the reporting instructions. For example, the data element EndDate must be reported in XML as a string, but will be converted by the EIS to a date as defined in the various sections of the reporting instructions.
Exchange Network	A secure Internet - and standards-based approach for exchanging data.
Major Data Group	A logical grouping of related Data Blocks that fully describe business area, functions, and entities.
Node	A web server that facilitates the interface between database systems and the Exchange Network. It is a partners "point of presence" on the Exchange Network.
Node Client	A type of node that can submit, request, and receive data on the Network, but cannot respond to data queries from other Nodes.
Submittal Data Block	The set of data blocks that can be submitted together for a category of data. These submittal data blocks are defined for each data category and contain the minimal complex types necessary to report data such that the EIS can successfully process and integrate the data into the inventory.
Web Client	A web-based submission tool that sends data to the CDX Node over the Exchange Network. It cannot receive data on the network or respond to data queries from other nodes.

An XML schema is the definition that constrains the structure and content of an XML document written in XML Schema language as defined by the World Wide Web Consortium (W3C). An XML schema defines:

• The elements and attributes that are expected;
• The allowable data types for each element;
• The hierarchy and order in which elements must appear;
• Which elements are optional and which are required; and
• The maximum number of occurrences allowed for each element.

Like the architectural blueprint that describes the structural design of a house, an XML schema describes the structural design of an XML file.

Files submitted to the EIS are accepted or rejected based on their conformity to the EIS XML schema.

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The domain model views show the associations between entities and therefore may resemble a relational model, similar to how a database may be represented. In comparison, the CERS structure is hierarchical, though it is possible to see a partial representation of the relational aspects of the EIS domain model in the schema complex types. The complex types themselves loosely correspond to tables; each complex type has elements that describe identity and contains data values.

Within the CERS, the hierarchical structure is a partial representation of the relational aspects of the complex types. This can be seen in the way that each complex type nests within another complex type. The nesting of that complex type in the schema demonstrates that the data in that complex type is likely to be stored in a table joined to another table in a relational database.

XML elements are individual pieces of data that correspond to columns in a table in a database. Complex types have only XML elements. These complex types contain data that is related to the owning entity by virtue of the nesting hierarchy in the XML schema.