Over a decade ago, we worked with Charles Perfetti to create a framework (Britt, Perfetti, Sandak, & Rouet, 1999; Perfetti, Rouet, & Britt, 1999; Rouet, 2006) that extends the situation model theory of text comprehension (Kintsch, 1988; Zwaan, Langston, & Graesser, 1995) to encompass multiple document learning situations. Our efforts were motivated by three observations. First, when engaging in in-depth learning, students read multiple accounts of the same situation and must reconcile agreements and discrepancies in those accounts. Reading multiple texts requires integration mechanisms that go beyond the construction of a model of a single author’s description of a situation. The documents might provide discrepant accounts of a particular event. To maintain a coherent representation, a reader must either dismiss one of the accounts (i.e., purposefully ignore some information) or somehow represent the discrepancies and account for why two sources would provide different explanations (i.e., generate inferences about authors’ knowledge or motives). Neither of these mechanisms is accounted for in coherence-based models of comprehension (Lorch & O’Brien, 1995; Zwaan & Singer, 2003). Our second observation was that authors can be both sources of documents and actors in a described situation. For example, in U.S. President Roosevelt’s memoirs, he is both an author and an actor. Additionally, authors themselves may be explicitly mentioned in a document. For example, historians cite Roosevelt’s memoirs when writing about the events during his presidency. Thus, a reader must be able to representationally distinguish between authors as sources and authors as agents and deal with their various levels of knowledge and trustworthiness. By their very nature, documents present a situation from the perspectives of its authors. Content often cannot be simply added to a representation withouttaking the author information into account. Finally, our third observation was that there is more to a source than the identity of the author. Other parameters that characterize the origin of the docu ment (e.g., date, publisher, context during writing) can also affect one’s comprehension of the message. We subsume all of these parameters under the construct of “source” (e.g., author and document parameters). These observations led us to propose the Documents Model framework, to describe additional representational structures (and later mechanisms) that account for comprehension in a multiple document learning situation. The Documents Model framework extends the situation model theory by adding knowledge structures that represent sources of information and links them to situation model content, other sources and, through them, representations of alternative situations. In addition to representing content (e.g., spatiotemporal events and causal-temporal relations), the framework describes an Intertext Model in which sources may be explicitly represented as Document Nodes and connected through intertext links to situation model content or to other Document Nodes. For example, the most salient information about the source of Web Text 1 (Figure 11.1) may be that it is an article about the benefits of Global Warming obtained from a website named foodstuff.org. In the reader’s representation, a Document Node for this Web Text might include document characteristics (Web article from foodstuff.org, posted December 2010) and author characteristics (author named “admin,” National ConsumerResource for Agriculture). It may also include evaluations of the document or author (e.g., includes a scientific-looking illustration, corporate author name seems like an industry-sponsored “grass-roots” organization). The Document Node may be related to salient content information provided on the Web page, through source-to-content links, such as “According to foodstuff.org, global warming entails some benefits.” In addition to Document Nodes and source-to-content links, the Intertext Model also allows for source-to-source links. For example, the reader may link their Document Node for Web Text 1 (“benefits of global warming”) to their Document Node for Web Text 2 (in Figure 11.2) (“threats of global warming”) with an “opposes” link. See Figure 11.3 for a schematic of a Documents Model for these two Web Texts. Document Nodes may also link to other situation models. When learning from multiple documents on the same topic, readers are trying to understand the situation described across the various sources. In most cases, however, the authors present varying or partial accounts that one might not fully accept. Sometimes these accounts may be dismissed and ignored. There are other occasions when such alternatives must be represented and related to each other.Secondary history texts, for example, frequently present alternative explanations for an event by attributing them to specific historians. Intertext links provide a way to relate alternative models of a situation. We originally referred to this meta-level representation as the Situations Model to highlight the fact that multiple situations were represented in the history texts we studied (Perfetti et al., 1999). However, in an effort to extend the framework to science texts that describe natural phenomena, we now refer to one’s understanding of the unique, overlapping, and conflicting information mentioned in all the texts as the Integrated Mental Model (Britt & Rouet, 2012; Wiley, Britt, Griffin, Steffens, & Project READi, 2012). During the past decade, there has been a growing interest in multiple text comprehension and frameworks such as the Documents Model (see e.g., Braten, Britt, Stromso, & Rouet, 2011; Rouet, 2006). The view that, when deeply engaged in document-based learning tasks, readers need to represent source features and integrate across sources has received an increasing amount of empirical support (Britt & Aglinskas, 2002; Britt et al., 1999; Kobayashi, 2009; Rouet, Favart, Britt, & Perfetti, 1997; Stahl, Hynd, Britton, McNish, & Bosquet, 1996; Stadtler & Bromme, 2007; Stromso, Braten, & Britt, 2010; Wiley & Voss, 1999; Wineburg, 1991). Yet the Documents Model framework, as initially proposed, was a rather general and descriptive framework. In this chapter we seek to examine in greater detail one of its key assumptions, the document-as-entity assumption. Our purpose is to demonstrate the heuristic value of this assumption and how it may provide explanatory mechanisms for a range of observations that